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1. 3 3 31 5 Ending Clustering coser ba eta se onam OP s Ra Rdn ON asa Eu Duas au tip ecu aos 3 3 Soler WOISMOUTON B ESSO TET T m 3 3 3 2 Elliptic PDE Solver Control Functions sessessssssssss 3 3 3 2 1 Background Control FUNCION sc2zscse 2esceseceobedecexebossedeewasaedivencedaebendeedeeeiwenss 3 3 3 2 2 Foreground Control Function cccoocccocccnnccccnonononeconononanononcnnonanonenanononos 3 3 3 3 Unstructured Grid Attributes cit esta Des ds d eese Ca edo ade 3 4 Snow DOMAINS E 3 4 dixe A eae oe hes eaten at oon Cu c Sto io ast acea ao 3 4 3 4 Domain Topology Controls oooccccoonnccoccnocccnnococnnononononnononannnonacnnonannnnns 3 5 o MP Me 3 5 om NOMI PAS eR 3 5 3 5 Database Parameterization sss eene nnn 3 6 3 6 QuickSave File Name m tese onda aM ect 3 6 UNA E 3 6 Sdt Node Tolerant E crpiti T T c 3 6 9d GONMECION FolerariGe ei a is 3 6 32 20 GUA PON TOCA NC Erana a TM 3 6 o A N N a NC dE 3 7 9 8 DB Pik MaSK os citadas 3 7 3 9 Other Informatio uii ideas 3 7 4 Importing and Exporting Files lt 00 0 0 4 1 4T Import GIdgen FUC ds 4 1 4 1 1 Gridgen File Database Associativity coocccconnonocnononnonnnnnonononanonnannos 4 2 21 2 0verwrnte VS APPENA iut divat uaa oM nva bot oa iv eds d idi edis 4 3 4 1 3 Gridgen File
2. occccoccccocncconncoccncconoconnnononononoss 4 19 4 8 Export Glyph Initial FUNC er rr i eto hued Macatee eden 4 19 4 9 EXDOIL Analysis BGS oae big o irs taedet Unda t Ecos Goto bats 4 19 4 10 Export Analysis Grid o NE Ra drea 4 19 4 11 Export Analysis DATA a Dad ud tid 4 19 4 12 Export FIELDVIEW Boundary Surface File ooooooooonoooommoo 4 19 4 13 Incorporate Volume Grid ooocccooccccocccococnncnoonononononononononononannonanononos 4 20 4 14 Block Ell Solver GIVDIIL e ec cei hele ete eee 4 20 osLayer Mana Olmeca A E qn ears beast E 5 1 Dil QVCIVIOW sai a a a E aoa eas 5 1 5 2 Database Groups and the Layer Manager ooooccoococonoconicocncconcconnnos 5 1 5 3 Scripting and the Layer Manager sss enne 5 1 5 4 Layer Assignment ooo ee DOO ipod E AA A 5 1 5 41 Database rie IMPON usan 5 1 5 4 2 The Assign Layer Comimallde sido poo eod exte or iii 5 1 5 4 3 The Layer Move Combine Commands seccceececseeeeeseeceecseeeeseeeeees 5 3 5 5 The Layer Manager Panel ccccccccccccseecseecneeccsuensuessueenssessuseauensusssnessanes 5 3 5 5 1 Opening the Layer Manager Panel eese 5 3 9 9 2 Layer BFOWSOLr dui dites quitus but ad A 5 5 D500 HIST PINMGRS 2 35 20 tsar anaes Da quio RN De STILO M a ined 5 5 3 94 Layer OSO rro 5 6 5 0adVed Layer els atest Mourne emite deste etie talas 5 7 5 0 6 SPeclaliFe alles tesi eti
3. The two buttons labeled Graphics Prec let you specify the numerical precision of the graphics calculations By default Gridgen s graphics are Single precision 4 byte real numbers However if the Display window image seems to vibrate when you zoom in very closely on a grid with a large range of length scales for example very tight grid point spacing on a very large body you will benefit from enabling Double preci sion graphics 8 byte real numbers However keep in mind that double precision graphics also doubles the size of Gridgen s graphical objects and the memory used by them The Reset Colors button in this menu will re initialize the color map to the proper Gridgen settings if it 2 21 Graphical User Interface should become corrupted by another application perhaps Mous Glide This toggle button controls whether or not the Display window image will continue to move glide even after mouse motion has stopped as long as the mouse button is pressed By default this toggle is on See Section 2 7 2 Mous LeftPk This toggle button allows you to change which mouse button Gridgen uses for Display win dow item picking Gridgen uses the right mouse button for picking by default Turning on the LeftPk tog gle causes the left mouse button to be used for picking the right mouse button is then used for image panning Mous Demote If the value of Demote is non zero the Display window image is drawn in a sparse mode demoted duri
4. sessi eene 1 4 1 6 Gridgen s History ooooccooncccconccccccnnccconononnnononononannnnnnnnonannnnnannnnnnnnnnannnonannnnnos 1 5 1 7 Document Conventions csi 1 5 2 Graphical User Interface oooocococconoconocconocoroccrconoronnoronaronnoso 2 1 2 1 Th Gridg n SOIC CIN cias 2 1 22 MO MOUSE 2 2 2 3 Menu Buttons ooooocccocccocccoononoconocnnncncnononononnnnonononcnnn anna nn nn enhn nans snas naa nena nns 2 3 al DONNA RR TRE 2 3 RCM TOE Cy E 2 3 2d OOS BUONO rta 2 4 2 9 4 Radio BUTONS viviste 2 4 2 9 5 VOBRPBHUOPIS eee ee sae nee EE eee ee ene near ioda 2 4 20 0 QUIER C c E 2 5 2 3 7 Quick Menu llsseessssssssssseen enn nnn nennen nnns nan nnns aas n ss se nnn ssa a sanas aa sa sana 2 6 2 9 0 VIS CCAM OS enira este magnx UR En y MAN eM MES 2 8 2 4 Entity Selection isses essen a nnns n anna snas a sona 2 8 2 4 1 Selecting From The Display WiNdOW oooccccooccccocccccocononocononoconnnnononnoos 2 8 2 4 2 Selecting From The BroOWSel cccccseccccseeeceececseeeseeeeeeseeesseeeseeeessaeees 2 9 2 2 9 PIOR MASKO sit vt a tb ai 2 10 2 4 4 Special Picking CONTFO S ooccccoccccconnccoconononononocononannnnonononononononononannnnos 2 10 2 5 Selecting File Names oooooooocccconccocooncccoononocononononononnnnonnnonnnnonanononannonaninonanos 2 12 20 TOX INDU A 2 13 2 7 Image Mani
5. 3 6 DB Pick Mask Model Size 3 7 4 Model Size The model size is the basis for all tolerances used for Gridgen s geometric computations such as intersec tions projections and the triangular surface mesher The default value for the model size is 1000 Other tolerances are then computed from the model size as shown in the table below Gridgen s Model Size and Geometric Tolerances type of tolerance default value surface fit 3 8 DB Pick Mask DB Pick Mask is a very useful tool in Gridgen for filtering large Browser lists of database entities The DB PICK MASK MENU provides a toggle list of database entity types that may be toggled On or Off individu ally or in groups Once an entity type is toggled Off all instances of that entity type in the Browser will become darkly shaded and the user will no longer be able to pick that entity type in either the Browser or the Display window 3 9 Other Information Even though it is not a user setable default value the Blackboard in the Defaults menu displays a value called the Grid DB Leng This value is the approximate size of the largest dimension of the current grid and database and is useful for gauging the size of your grid relative to other lengths such as the model size or average spacing default 3 7 Setting Defaults 3 8 4 Importing and Exporting Files Gridgen can import and export many different types of files via the INPUT OUTPUT COMMANDS menu The file types
6. Other commands of interest during segment editing include Store CP by Picking pad via Keybrd pad Original Location o Edit New Seqment Ae Prev o p e padije pad3 Akima h Cnurt to Movement Restrictions m Sensi t Move Rotation Pt To t Done Editing ent Store CP O by Picking Store CP O via Keybrd These commands allow you to save a control point in a new location by picking an existing point or by typing in a value via the keyboard A button for storing the control point at the current cursor location is not present because the control point 1s implicitly being stored at the cursor location as you edit the segment and move the cursor Original O Location The edit point will be returned to the location it occupied before it was selected for editing Remove LI This command will remove the edit point from the segment definition Naturally this com mand will become available only when the resulting segment definition will remain viable without the deleted point For example it is not possible to remove any of the three non sliding control points on a Cir cular Arc segment since exactly three are needed to define the segment Also the removal of a control point on a surface segment could force an additional point to be removed if only one point remains on the current surface after the edit point is removed Insert L1 This command will add a control point equidistant from the cur
7. Structured Grid Point Export Gum Y o Y mos Y Y mmm Y Y wemw Y Y n n n n lt lt wwe Ix AAA zZ Z Z z Z K 4 18 Export Glyph Initial File Exporting Unstructured Grid Points 4 7 5 Exporting Unstructured Grid Points The Grid Pts Export command allows you to export the following unstructured grid types Unstructured Grid Point Export VRML 1 0 FV UNS XPATCH Structured surface grids are exported in the unstructured form if the STL VRML or NASTRAN style attribute is chosen and their cells are converted to triangles during grid point export 48 Export Glyph Initial File The Export Glyph Init File command is used to export from Gridgen a Glyph file suitable for use as a run commands or rc file Section of the Glyph Reference Manual containing the current settings of the Defaults command and the display states in the DISPLAY COMMANDS menu 4 9 Export Analysis BCs The Export Analysis BCs command allows you to write to a file the current analysis software boundary conditions volume conditions and other data formatted for the current analysis software package It is only available if the current analysis software package allows for separate boundary condition and grid files See Section 17 8 for more information on Analysis Software BCs 4 10 Export Analysis Grid The Export Analysis Grid command allows you to write to a file the current grid formatted for the current analysi
8. 1 Youcreate a new connector Section 7 2 If neither the Dimension Section 3 1 1 nor Average Spacing Section 3 1 2 defaults are set the pro cess is complete and the connector has no grid points 3 If either the Dimension Section 3 1 1 or Average Spacing Section 3 1 2 default is set it is applied to the connector 4 Ifthe Maximum Chord Height Deviation default is set grid points are added to the connector until the specified limit is satisfied The initial value for this default is 0 it is not enabled To set this default press the Con Dim Max Dev but ton and type in the new value 3 1 5 Beginning Clustering The beginning clustering default is the spacing constraint Section 11 3 2 1 that will be applied to the begin ning of new connectors The initial value of this default is O 0 the spacing will be unconstrained To change the value of this default press the Con Dist Bgn As button and type the new value in the Text Input window 3 1 6 Ending Clustering The ending clustering default is the spacing constraint Section 11 3 2 1 that will be applied to the ending of new connectors The initial value of this default is 0 0 the spacing will be unconstrained To change the value of this default press the Con Dist End As button and type the new value in the Text Input window 3 1 7 Distribution Function The distribution function default is the function Section 11 3 2 2 that will be applied to distribute grid po
9. By default p is set to 0 5 Adjust Conic Value i Adjust Conic p Value Pressing this button brings up the following menu allowing you to graphically adjust p using the mouse or to enter a p value via the keyboard ADJUST CONIC e VALUE Enter amp via Keyboard pad Done Editing Y value ent To adjust the p value move the mouse horizontally while pressing the right mouse key Moving the mouse to the right increases the p value upper limit is 1 and moving the mouse to the left decreases the p value lower limit is 0 The mathematical nature of the conic section is defined by the p value as shown in the fol lowing table Effect of p value on conic section p value conic section type 0 p 0 5 elliptic 0 5 parabola 0 5 p 1 hyperbolic 7 5 Creating Connectors An exact p value may be typed in with the Enter p via Keyboard menu button and control can be passed back to the tangent intersection point with the Done Editing p Value menu button Further editing of the tangent intersection point will not change the value of p input earlier It will not be possible to edit the p value unless the current edit point 1s the tangent intersection point If one of the other control points is being edited use one of the Edit buttons to edit the tangent intersection point then select the Adjust Conic p Value menu button 7 2 3 2 Circular Arc The circle segment allows you to define a circular arc of not m
10. Home of the VRML Consortium 3D Systems Inc StereoLithography Interface Specification October 1989 Intelligent Light FIELDVIEW User s Manual Software Release Version 5 5 November 1996 E von Lavante Elliptic Generation of Two Dimensional Grids for Internal Flow Calculations Texas Engine ering Experiment Station TEES Technical Report No 12415 82 01 25 March 1982 19 3 References 19 4 20 Index ABCDEFGHIJKLMNOPQRSTUVWXYZ Numerics 2 Point Connectors 7 0 A ACIS SAT import as database 4 7 Add Segment 7 2 ADPAC asw 17 6 algebraic solver 2 automatic initialization blocks 70 8 domains 9 3 Align LJ K 75 8 Analysis Software ADPAC 17 8 CFD 7 6 CFDSHIP Iowa 7 6 CFX 4 17 9 CFX 5 17 9 CGNS structured 77 9 CGNS unstructured 7 9 CNSFV 17 9 Cobalt 17 9 COMO 17 9 CRUNCH 7 9 current 2 data file export 7 7 DTNS 17 10 Exodus II 7 0 export boundary conditions 4 9 data 4 9 grid 4 19 Falcon 17 10 FANS 7 10 FDNS UNIC 7 10 FLUENT v4 7 10 FLUENT v5 17 10 GASP 17 10 generic 17 8 GUST 77 11 INCA v2 17 11 INCA v3 17 11 mirror for export 7 7 NCC 7 12 NPARC 7 12 OVERFLOW 7 13 PHOENICS 17 13 requirements of 4 SCRYU 17 13 SCRYU Tetra 17 153 selection 7 1 setting boundary conditions 7 3 17 5 SPLITFLOW 17 13 STAR CD 7 14 TACOMA 17 14 TASCflow 17 14 TEAM 17 14 TETREX 7 14 VSAERO 7 15 WIND 7 15 Analysis Software Commands 7 anchor
11. Importing and Exporting Files Sample of Gridgen Version 8 Database Import When Gridgen imports this GRIDBLOCK file the only mechanism it has to associate the grid with the data base is references to entities numbered 1 4 However when Gridgen imports these same files the entity numbering is different because of the group entities that Gridgen creates automatically as shown on the fol lowing page Sample of Gridgen Database Import eet veatea arco It should be apparent that when Gridgen tries to associate the grid to entity 3 the first surface in aft net it 18 really looking at the group entity for fore net and when it looks for entity 4 it is looking at the first network in aft net instead of the second The solution is to use Gridgen s UnGroup command Section 15 2 in the DATABASE COMMANDS menu to delete entities 4 and 6 the automatically created groups After the UnGroup command is applied Gridgen will automatically renumber the remaining database entities so that they appear as expected by the GRIDBLOCK file At this point the Gridgen database is topologically equivalent to the database references in the GRIDBLOCK file and the GRIDBLOCK file may be imported 4 5 Export Database File The Export command in the DATABASE COMMANDS menu allows you to write selected database enti ties from Gridgen into a file Only Gridgen network segment and composite file types may be exported Gridgen composite files can be used to s
12. ReSelect Group A a ReSelect Group B b Set Tolerance Ag Done ent Commands of interest during intersection include Run ReRun The Run command starts the intersection process and is available only after both Groups A and B have been selected The ReRun command allows you to restart the intersection process by deleting 15 16 Feature Extraction Topological Filter Commands any current intersections and re computing intersections starting with the first entity of group A and the first entity of group B You would use the ReRun command if you started the intersection process but then paused it after realizing you forgot to set the appropriate tolerance for example Continue After the intersection process has been paused pressing the Continue button will re start the process from where it was stopped If you change the intersection tolerance and then press continue the new tolerance will only be applied to intersections computed after the Continue button was pressed Pause Pressing this button will stop the intersection process Select Group A Pressing this button allows you to select or re select the first group of entities to be inter sected All entities of Group A are intersected with all entities of Group B Group A entities are colored orange Select Group B Pressing this button allows you to select or re select the second group of entities to be intersected All entities of Group A are intersected with all entities o
13. User Manual Version 15 SSA fw Copyright 1997 2003 Pointwise Inc All rights reserved This document contains proprietary information of Pointwise Inc The contents of this document may not be disclosed to third parties copied or duplicated in any form in whole or in part without the prior written permission of Pointwise Inc Pointwise Inc reserves the right to make changes in specifications and other information contained in this document without prior notice ALTHOUGH DUE CARE HAS BEEN TAKEN TO PRESENT ACCURATE INFORMATION POINTWISE INC DIS CLAIMS ALL WARRANTIES WITH RESPECT TO THE CONTENTS OF THIS DOCUMENT INLUDING WITH OUT LIMITATION WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE EITHER EXPRESSED OR IMPLIED POINTWISE INC SHALL NOT BE LIABLE FOR DAMAGES RESULTING FROM ANY ERROR CONTAINED HEREIN INCLUDING BUT NOT LIMITED TO FOR ANY SPECIAL INCI DENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF OR IN CONNECTION WITH THE USE OF THIS DOCUMENT Pointwise Inc 213 S Jennings Ave Forth Worth Texas 76104 1107 USA phone 817 377 2807 toll free 588 GRIDGEN fax 817 377 2799 email gridgen pointwise com URL http www pointwise com Notice The terms of the agreement under which you are acquiring the right to use the software include the Right to Use License attached hereto or accompanying the software Your purchase license receipt or use of the softwrae constitu
14. mae Angle s Join Angle l DB Coord Coord lt IJ i e Uv v QuickSave Filename Tolerances t DB Pick Mask k Done ent Help 3 1 3 Maximum Angular Deviation The maximum angular deviation default is the maximum turning angle in degrees allowed between succes sive grid points on a connector If you set a value here it is applied as follows 1 You create a new connector Section 7 2 If neither the Dimension Section 3 1 1 nor Average Spacing Section 3 1 2 defaults are set the process is complete and the connector has no grid points 3 If either the Dimension Section 3 1 1 or Average Spacing Section 3 1 2 default is set it is applied to the connector 4 If the Maximum Angular Deviation default is set grid points are added to the connector until the speci fied limit is satisfied The initial value for this default is 0 meaning it is not enabled To set this default press the Con Dim Max Ang button and type in the new value in degrees 3 2 Elliptic PDE Solver Control Functions Maximum Chord Height Deviation 3 1 4 Maximum Chord Height Deviation The maximum chord height deviation default is the maximum distance allowed between a connector s ana lytical shape defined by its segments and its discrete shape defined by its grid points The deviation is computed between the segment s analytical definition and the midpoint of the line between two successive grid points This default is applied as follows
15. set a different VC to each block to avoid automatic merge Alternatively setting block VC s to No Volume Condition will cause the blocks to be exported separately under their block names Wherever Gridgen detects a singularity in a structured grid it will convert the cell from a hex quad to a wedge triangle when exporting it for use with STAR CD 17 8 32 TACOMA TACOMA export supports 2D and 3D structured grids only 17 8 33 TASCflow TASCflow export supports 3D structured grids only Gridgen writes two files TASCflow s grd and bcf files You are given a choice as to whether these files will be ASCII or unformatted A TASCflow name lun file must exist in order for Gridgen to export files for TASCflow Gridgen first checks for a name Lun file in the current directory and then in the directory pointed to by the TASC UTILITY environment variable If Gridgen does not find a name Lun file in either of these loca tions it will create one in the current directory TASCflow unformatted export is not supported under Linux Glyph requests for unformatted export under Linux will automatically be converted to ASCII 17 8 84 TEAM TEAM export supports 2D and 3D structured grids only Please note the following e The first line of boundary condition data for each block always has the strings INITIAL FLOW set to FREE and EQUATION_SET setto EULER e The additional line of data for the SOLID V boundary condition i
16. to the database Otherwise lines are created On DB Entities Many connectors are created at one time by selecting database entities A connector will be created on each selected curve database entity Four connectors one on each boundary will be created on each selected surface database entity Connectors will be created on each trimming curve of selected trimmed surface database entities Each of these connector creation methods is described in the following sections 7 2 Add Segment You may create many different types of segments as shown in the menu below 3D Space Line d Curve e Ak i ma h DB cnstr Line c Curve e Ak i ma h Rational Conic a Circle b others Copy m Import n Gridgen s segment types are grouped into four categories 1 3D Space These segments are free to be created anywhere in three dimensional space 2 DB cnstr These segments are constrained to lie on the database 3 Rational This category covers curves that are mathematically rational such as circles and conics 4 Others These are segments created by copying other connectors or importing data from a file The Don t Add Segment button ends the segment adding process and returns you to the Create menu There are other segment types that cannot be created directly The available segment types are described in the following sections 7 2 1 3D Space Segments The 3D Space segments are simple polynomial curves created betw
17. 1 Enter As at Picked t Begin A The spacing constraint you enter will be applied to the break point at the beginning of the sub connector The beginning break point is orange Ending A The spacing constraint you enter will be applied to the break point at the end of the subconnec tor The end break point is blue Enter As at Picked A The spacing constraint you enter will be applied to both sides of the break point on which the cursor is currently positioned This command will guarantee grid point spacing continuity at the break point but may not be used at the beginning or ending of the connector since only one spacing con straint exists at each of those points This command will always enforce a constraint on the arc length even if the spline variable Section 11 3 2 3 is selected to be x y or z To specify a Ax Ay or Az constraint on both sides of a break point set the spline variable to the appropriate value and then select the Begin A and Ending A menu buttons successively on the two subconnectors touching the break point 11 3 2 2 Distribution Function Select Distrib Func d The spacing constraints are the primary control in determining the distribution of grid points along the sub connector but it 1s the distribution function a mathematical equation that determines how the points are distributed between the constraints Gridgen s distribution functions can be selected by pressing the Select Distrib Func bu
18. 6 The true pyramid height is then limited by the user specified minimum and maximum 13 8 Grid Point Insertion on Boundaries Minimum Pyramid Height 13 7 1 Minimum Pyramid Height The Pyramid Min Height attribute specifies the minimum height allowed for any pyramid cell By default this limiter is disabled 13 7 2 Maximum Pyramid Height The Pyramid Max Height attribute specifies the maximum height allowed for any pyramid cell By default this limiter is disabled 13 7 3 Pyramid Aspect Ratio The Pyramid Aspect Ratio attribute specifies the aspect ratio that is used to scale the nominal pyramid height to obtain the true pyramid height By default this value is 1 13 7 4 Pyramid Display Whether or not the Pyramid Display toggle button is enabled controls whether or not pyramid cells will be drawn in the Display window when running the unstructured solver The pyramids are drawn using the same display attributes as the structured domain from which they are extruded 13 8 Grid Point Insertion on Boundaries 13 8 1 Domains Grid points are not inserted onto a domain s boundary by the unstructured solver 13 8 2 Blocks Grid points are not inserted onto a block s boundary by the unstructured solver 13 9 Grid Methods for Unstructured Domains and Blocks 13 10 14 Modifying Entities 14 1 Overview Gridgen provides a variety of tools for modifying database and grid entities The Modify command can be accessed from t
19. After choosing the extrusion basis you select the connector s or domain s that will form the initial grid for the extrusion Then the Extrusion menu appears as shown below Type Hyp Nrmi Rot Tran Path Run s Back a Run 1 l Back 141 Run M n Back MN n Restart Aq Set Attributes Ag Set Stop Criteria c Done ent Abort esc You specify one of five extrusion methods from the radio buttons labeled Type on the Extrusion menu Note that several extrusion types may be employed in a single extrusion session For example you can use a translational extrusion to create a straight section and then switch to a rotational extrusion to add a curved section before saving the final grid with the Done button Hyp The hyperbolic extrusion is based on the solution to a set of partial differential equations Reference 4 Reference 26 The PDEs prescribe a trajectory for the extruded grid lines that is orthogonal to the initial grid that follow a prescribed marching step size variation in the extrusion direction and that is very smooth Because the hyperbolic method is PDE based it 1s not applicable to the extrusion of prism blocks from trian gular unstructured domains Nrml The normal extrusion is an algebraic method with results that mimic the hyperbolic PDE method orthogonality and prescribed marching step sizes but which is applicable to extrusion of both structured and prismatic grids Rot The rotational extru
20. CONSEQUENTIAL DAMAGES WHATSO EVER INCLUDING WITHOUT LIMITA TION DAMAGES FOR LOSS OF BUSINESS INFORMATION OR ANY OTHER PECUNIARY LOSS ARISING OUT OF THE USE OF OR INABILITY TO USE THE LICENSED PRODUCTS EVEN IF PWI HAS BEEN ADVISED OF THE POSSI BILITY OF SUCH DAMAGES AND REGARDLESS OF THE FAULT OR NEGLI GENCE OF PWI PWI s liability to Licensee for damages shall not exceed the amount of the license fee paid by Licensee to PWI 9 MAINTENANCE AND SUPPORT a PWI will be responsible for providing corrections for programming errors and peri odic software updates only during the Mainte nance Period and during any period when the Licensee is covered by a Maintenance Agree ment from PWI or an authorized representative of PWI The specific policy for software updates and enhancement varies on a per prod uct basis PWI warrants that during the term of this License it will use reasonable efforts to remedy defects in the unaltered Licensed Soft ware made known to it by Licensee PWI does not warrant that the Licensed Products will meet all requirements of Licensee or that the operation of the Licensed Software will be uninterrupted or error free or that all software defects will be corrected b During the Maintenance Period PWI agrees to telephone hot line support available to Licensee These services may be provided by PWI or a designated third party 10 TERMINATION Licensee may terminate this License upon thirty
21. Create GridCon GridStr GridUnstr odi fy Examine ASW GCL Tutor Bump Tutor Sweep Tutor_ Pipes Tutor _ 747 Tutor Elbow 2 References File Formats 747 redim gg exam ine memor y gg pipe gg dquicksave gg 0UTPUT Gr idgen FILE Name k Dir d Go to Dir s origh Display All Files a Abor t esc Disp Only ext Files This command will list in the Browser only the files with extensions that match the string ext where ext is chosen by Gridgen based on the file type being read or written For example the default extension for Gridgen files is gg When working with database files the Browser will list all files with the default extensions of all database file types 2 12 Text Input Special Picking Controls Disp All Files This command will list in the Browser all files in the current directory regardless of their extension When the correct file name is queued you press the Open button in the menu window If the file is to be read reading commences If the file is to be written the file name is checked against those in the current directory If Gridgen determines that you will over write an existing file it will present a new menu and ask you to confirm the choice of file name CONF IRM Yes overwrite file y Abort Do not write filesc 2 6 Text Input You will need to communicate with Gridgen at times by entering data directly through the keyboard For
22. DATABASE COMMANDS Import i Export o Create n Modify m Copy c Delete d Intersect 2 F Hame 3lAssign Layer ci Group 4 A5 Examine e En Disable t Done ent Cons C Doms D B1ks B DB F Dflt T I o E AS W A Glyph Quit Q Save S Disp a Help Activation of this command puts you into Browser mode with a list of all available database entities This list only shows entities that can be assigned to a layer Entities currently in a layer whose status is off are not available to be reassigned and are not shown in the Browser Likewise this list is also subject to the enable state of each entity in the currently displayed layer set disabled entities are not available to be reassigned An example of the Browser list is shown below ASSIGN DB ENTITY LAYER Each line of the Browser represents a database entity with the entity number current layer and entity name Once you select the entities from this list you wish to reassign and press Done you are put into a second Browser list of all 1024 layers 5 2 The Layer Manager Panel The Layer Move Combine Commands ASSIGN DB ENTITY LAYER In this Browser you see each layer listed by number in the second column The dash in the first column indi cates that particular layer is currently off The third column contains a plus and or minus symbol indi cating the layer contains either enabled plus and or disabled minus database entities Absence of eith
23. For example if blocks 1 2 and 4 were selected in the list below shown in bold their alphabetized sort is as follows Example of alphabetic block sorting wing a 18x29x11 axle CLOXTOX LO E fuselage 21x18x45 fuselage 21x18x45 aileron 21x31x19 aileron 21x31x19 a axle 10x10x10 wing_a 18x29x11 Reverse the Order This will reverse the order of the picked blocks relative to one another keeping all non queued blocks in their original position For example if blocks 1 2 and 4 were queued in the list below their new arrangement is as follows Example of reversing the sort order wing a 18x29x11 axle 10x10x10 fuselage 21x18x45 fuselage 21x18x45 aileron 21x31x19 aileron 21x31x19 nm axle 10x10x10 wing_a 183x29x11 Sort By Block Dimens This will rearrange the order of the selected blocks relative to one another from the largest block size to the smallest size leaving all non selected blocks in their original position Once a sorting criterion is picked the blocks will be rearranged in the Blackboard display as dictated You may then select a new set of blocks to sort and repeat this process accept the new arrangement with the Done Selecting menu button or revert back to the original order with the Abort menu button 15 6 Enable Disable Database Entities 15 6 Enable Disable The En Disable command is used to temporarily turn off entities There are two reasons for disabling
24. Nodes and Connectors used in structured domains are not candidates for merging if they have different dimensions Consider the example shown below with four connectors A B C and D Each connector is 1 unit long con nectors A and B are vertically separated by 0 1 units as are connectors C and D Note that all connectors have 11 points except for B which has 7 Imagine for example connectors A and B are supposed to be coincident as are C and D but they were created on a sloppy database resulting in the vertical gap we want to eliminate After pressing the Merge Conns button you enter the connector merge tolerance In this example we use a value of 0 2 Enter a tolerance for which connector pair merger candidates will be listed 1 node tol 2 con tol default 0 200000 The Browser then lists all connector pairs that match within the tolerance of 0 2 Pairs A B and C D are can didates and Gridgen recognizes A and B do not have the same dimension MERGE CONNECTORS Pick the connector pairs to merge 1 A Mig lilt Gi 1 2 A 0 316228 B D After you select both pairs for merging Gridgen eliminates connector B in favor of connector A and elimi nates connector D in favor of connector C as shown below 15 10 38 Nodes and Connectors The Merge Nod Con command combines the Merge Nodes command with a pre processing steps that splits overlapping connectors After pressing the Merge Nod Con button you enter the dis
25. O ruled surface Llsurface of revolution O tabulated cylinder MB spline surface Lloffset surface O trimmed surface i Li shell j Curves On c Off c lcircular are lconic arc copious data Oline O parametric curve B spline curve Lloffset curve Others n ojoff o plane v Opoint w O group x Linote y Done ent Help Abort esc w tes Oe fe ee 2 a 2 i mx If any database entities are being filtered with DB Pick Mask the word Active will appear on the DB Pick Mask button as shown below DB Pick Mask CActive k 2 4 4 opecial Picking Controls Several menu buttons are available for use in selecting multiple entities 2 10 Entity Selection Special Picking Controls Scroll x v v A A Pick All a None n Tog AT Page in Box on Box ByText Bget 1st O last Set to O off O on tog num2 typ3 0 reva o nam Pick by Expression 5 DB Pick Mask k Done ent Help Abor t esc Scroll The VCR buttons are described in Section 2 3 5 Pick All All pickable entities are picked Pick None AII pickable entities are un picked Pick Tog The status either picked or not picked of each pickable entity is reversed Page All items on the current page of the Browser are toggled in Box Use of the pick in box for picking multiple entities at a time from the Display window is described in Section 2 4 1 2 on Box Use of the pick on bo
26. This will allow editing of control points to proceed as in the strict Line or Curve case In the figure below the lower right connector has been converted to Bezier form and the slope points blue and red filled circles are being manually edited 14 22 Connector Least Squares Fit Edit LIN YI Done Editing The segment editor will be exited 14 10 Connector Least Squares Fit Lst Sq Fit 1 A dimensioned connector can be modified by replacing its shape with a least squares fit of its grid points This command is most useful for converting the connectors that are created by the extrusion methods Sec tion 8 into forms that are more easily editable After pressing the Lst Sq Fit button you are prompted for the tolerance to use when fitting the grid points For example consider the case shown below The grid on the left was extruded hyperbolically from the hor izontal straight line on the bottom The resulting arc connector on the top is consists of a line segment with 11 control points each of which corresponds to a grid point Suppose you wanted to edit the shape of this connector Each control point would have to be moved individually and the resulting curve would lack smoothness since the segment is linear The same grid is shown on the right after the arc connector on the top has been run through the Lst Sq Fit command Note that there are only two control points the begin ning and the ending Furthermore the segment is a Bezier cur
27. amp Midd A Anal Next n Prev An O Focus All s TFI Attributes Methods T interp i E i Elliptic Attributes interp the i surface Shape Params 1 ae e i Relaxation Parameter 2 Floating Background Cont Funcs 3 Floating F Floating oreground Cont Funcs 4 ch Solver Bound Conds Done Setting Attributes esc Focus Next Moves focus to the next grid in numerical order of the grids selected for the solver The focus grid is the grid whose attributes are listed in the Browser and whose image is highlighted in the Display win dow Focus Prev Moves focus to the previous grid in numerical order of the grids selected for the solver The focus grid is the grid whose attributes are listed in the Browser and whose image is highlighted in the Dis play window Apply to Focus This toggle button specifies that the selected attributes are to be applied to the focus grid only When enabled this toggle gives you access to the individual boundaries of the focus grid for setting foreground control functions and boundary conditions Apply to All This toggle button specifies that the selected attributes are to be applied to all grids currently selected for the solver When enabled this toggle applies foreground control function and boundary condi tion attributes to all boundaries of all selected grids 12 6 Elliptic PDE Methods Relaxation Parameter TFI Methods The TFI methods are used to establish an initial grid
28. command 2 projection Section 14 4 Domains grid points become linked to a database entity either by 1 assembling them using connectors that are database constrained Section 9 2 and Section 9 3 14 2 Linkages Database Linkages 2 creating them using the On DB Ents Section 9 6 command 3 projection either via the Modify menu Section 14 4 one of the structured solvers Section 12 1 5 Sec tion 12 1 6 Section 12 2 6 the unstructured solver Section 13 3 or one of the extrusion methods Section 8 2 2 For purposes of demonstration assume that in the sample grid shown above we are modifying the database by translating the square database surface pink left to the left Gridgen detects the following linkages between that database entity and the grid the domain lies entirely on the modified database entity the vertical connectors emanating from the domain are attached to the square database entity at their lower nodes one edge of the block is shared with the domain and therefore 1s on the database entity Because of the linkages Gridgen displays the following menu when the database surface is modified Unlink From Grid y Maintain Linkage esc If you choose Unlink from Grid Gridgen does the following Converts each segment in the affected connectors into a general segment Section 7 2 5 e Removes the database link from each connector grid point The point s x y z coordinates do not change bu
29. example when translating a domain you may choose to type in the translation offset In these cases the Text Input window will be highlighted and the Message window will prompt you for a response You may type in the desired response which may be either a character string real number s integer number s or a Tcl expression In each case you terminate your input by pressing the enter key Gridgen stores previous text entries They can be accessed and reused or edited using the hot keys described below ENTER TRANSLATION OFFSET Enter the x and z translation offsets default 0 0 0 3 PR Hot keys of interest during text input include u erase the entire entry escape abort from text entry enter terminate text entry gt right arrow key scroll to the right through existing text left arrow key scroll to the left through existing text T up arrow key scroll backward through the list of previous text entries V down arrow key scroll forward through the list of previous text entries Tab automatically complete partially typed variable name Text input that consists of multiple words for example entering a point s x y z coordinates can be delimited using either spaces or commas For example the point 1 2 3 may be entered by typing either 1 2 3 or1 2 3or1 2 3 Note that decimal points do not have to be entered when typing real num bers in other words 1 is the same as 1 0 Furtherm
30. instead The DB cnstr Akima segment above bottom is a cubic polynomial between successive control points The segment will not necessarily be cubic and slope continuous in x y z space The cubic polynomial is constructed using a stencil of five adjacent control points to account for possible linear slopes Akima seg ment generally have fewer wiggles than Curve segments and should be used when a smooth curve with minimal overshoot is needed Do not use this segment type if your intent is to trace a constant parameter line for example a surface s boundary or a curve entity Use a database constrained Line instead Any of the database constrained segments may span more than one database entity However at least two control points must be defined on each entity When adjacent control points lie on different entities the seg ment between the points is drawn as a dashed line called a branch segment There are two instances when 7 3 Creating Connectors this occurs 1 If this is not the first segment in the connector then a branch segment will be inserted between the pre vious segment end point and the current segment beginning point to maintain the point wise continuity of the connector 2 lfasingle database constrained segment spans two entities then the portion of the segment that crosses between the two entities will be a branch segment Keep in mind that branch segments are straight lines between the two control poi
31. integer ni nmax nj nmax real x imax jmax nmax amp y imax jmax nmax amp z imax jmax nmax do 10 n 1 nmax write 1 ni n nj n weite l t X 21 73 1 1 1 nzi n l Wu amp C yj i l ni n J ala d amp z2 1 7 8 i 1 51 n y nj n 10 continue A code fragment for exporting a network file in PLOT3D style is shown below Note this is PLOT3D s 3D multi grid format with kmax 1 and no i blanking This is the only PLOT3D format used by Gridgen Cn wee nmax is number of networks a PES ni n number of points in the i direction for the nth network E aca Es nj n number of points in the j direction for the nth network integer ni nmax nj nmax real x imax jmax nmax amp y imax jmax nmax amp z imax jmax nmax write 1 nmax write 1 nam nym 1 n l nmax do 10 n 1 nmax wrltell 1 4 X 1l J9 n i cl ntr n Jz jel nyjg in Jy amp y i j n i l ni n j 1 nj n D amp A m lg melnmim PO 2 10 continue 18 5 Segment File The segment file default extension dat consists of one or more discrete linear curves segments Seg ments can be imported Section 4 4 and exported Section 4 5 as database curves imported Section 4 6 and exported Section 4 7 as connector grid points and imported as a connector segment type Section 18 2 Composite Database File 7 2 4 When importing a segment file Gridgen reads until the end of file is
32. not begin until all connectors that will lie on that domain s edges have been created Keep in mind each structured domain requires four edges even if an edge or a portion of that edge is collapsed to a point a point singularity or pole Section 7 2 5 1 If a domain connects to itself one connector can be used twice in the same domain Connectors can be added to the edges in any order during domain assembly without regard for the eventual computational n C axis system Section 15 7 of any blocks which will use this domain Gridgen only refers to the computational axes at the block level so you do not have to worry about that while creating connectors or domains Creating Domains Domain assembly can be thought of as the selection of the closed loop of connectors that form the domain s perimeter In addition to defining the perimeter you also designate where on the perimeter the four corners of the structured domain are located This permits the connector s grid points to be mapped into a four sided region of I x J grid points There are eight different ways to select the connectors on a structured domain s perimeter you can start in any of the four corners and proceed either clockwise or counterclock wise Each of these eight permutations is the same to Gridgen Before beginning to create a domain you must choose 1 the corner node from which the domain s perimeter will begin and end 2 the direction in which the connector loop wil
33. the relation of subconnectors and other components relative to each other Gridgen s convention is to use the terms beginning and ending in reference to the direction in which the connector was drawn In addition the break points are color coded orange for beginning and blue for ending to aid in identifying the connector s direction 11 3 2 Distribution Parameters 11 3 2 1 Spacing Constraint Spacing constraint in the discussion to follow refers to the distance between the two grid points at the end of the subconnector By default this distance will be the total arc length s between the two points However the spacing constraint may also be set to refer to the distance in a single Cartesian coordinate direction x y or z Section 11 3 2 3 Initially the spacing constraints are set to the type specified by the Defaults com mand Section 3 which is originally set to zero unconstrained There are three valid entries for the spacing constraint 11 6 Distributing Grid Points on Connectors Distribution Parameters 1 Entering a value of 1 will insure grid point spacing continuity with the adjacent connector or subcon nector For an adjacent subconnector an internal break point the spacing constraint stored at the common break point will be copied into the current subconnector The result will be a continuous distribution of grid point spacing across the break point For an adjacent connector a break point at either end of a con
34. 1 Inflow 1 2 5olid Surface l nmintk 5Type 1 2 5 l nmaxt 4Type 1 C2 5 2 tmint 15 2 max 16 2 mint 14 2 maxt 13 The numeral in the first column 1 and 2 in this example represents the BC region s block number Each region in the block is then listed according to the type of computational index that is constant on it The number in the parentheses next to the computational index is the entity number of the boundary condition region in 2D it is the connector number in 3D it is the domain number Finally the text to the right of the entity number is the boundary condition type applied to that region Gridgen automatically determines the inter block connections and they are denoted by the text Type 1 in the Browser The data that follows the inter block connection text indicates the block number to which the region connects After selecting the regions BCs will be applied to you then choose a specific BC from a menu that is customized for the current ASW 17 2 2 Unstructured Grids Upon invoking the Set BCs command you select BC regions from the Browser Window For example the Browser text may look like The numeral in the first column is the block number which is followed by the string facN where N is the face number in the block The number in the parentheses next to the face number is the entity number of the boundary condition region in 2D it is the connector number in 3D it is the domain number Finally the
35. 125000 4 Zere t aaa 1 95000 A geese ESOO Zrjrjr e L JJe 77 246 1155000 i 150000 150000 B so 1 eee E 1 2 r rjeje jejee lil 287 a ad 1 yee a la a E ejejejes LL ejejejes i ii pm 1 10060 1 10000 EN 1 700000 MEE 1 05000 2830 1 00000 A a ala i 16 4 Mode The examine mode refers to whether the Examine command is being used in a very low level mode Local to examine the variation in a grid s diagnostic functions or whether it is being used in a very high level mode Global to assess the quality of the entire grid or large portions of it Local o o Globalo Mode Local Blackboard text corresponds to focus entity only Mode Global Blackboard text corresponds to all selected entities 16 5 Hiliter The hiliter consists of a small pink glyph in the Display window corresponding to a specific location on an entity You can move the hiliter by using the mouse with the right mouse button pressed Volume grid hili ters may also be moved using the VCR buttons and arrow hot keys The hiliter is not available for unstruc tured surface grids Information about the hilited point is listed in the Blackboard 16 10 Hiliter Connectors 16 5 1 Connectors on ho off Ah Okbrd pad E Pt m Oto min f 0 Oto max f 1 For connectors the hiliter is only the open circle glyph On Enables the hiliter for curve and surface entities Off Disables the hiliter for cur
36. 152 Bleed Area 3 153 Bleed Area 4 154 Bleed Area 5 155 However if the boundary condition you wish to apply is not available you may press the Create button and define your own boundary condition as shown below see Section 17 5 CUSTOM BC ATTRIBUTES Name BndCond 23 n CustomBCs Create c Modify m 23 i Delete d Del Alla Type Solid s O Permeable m Done ent Name Text The button labeled Name shows the default name for the new boundary condition If you press the button you may type in your own name which will then appear on the button ID Number Pressing the button labeled ID lets you type in the numeric code to be used for the new bound ary condition This numeric value is shown on the button Type This setting is used primarily for FIELDVIEW export FV UNS The two options available are described below Type Solid Enabling this toggle button indicates the boundary condition you are creating is a solid bound ary The boundary condition type is not used by all analysis software packages Type Permeable Enabling this toggle button indicates the boundary condition you are creating is a per meable boundary The boundary condition type is not used by all analysis software packages 17 4 Set VCs Structured Grids 17 2 1 Structured Grids Upon invoking the Set BCs command you select BC regions from the Browser window For example the Browser text may look like 1 6 Type 1 2 1
37. 2 Set BCs FDNS UNIC from Engineering Sciences Inc supports structured multi block grids only FLUENT v4 from Fluent Inc supports structured multi block grids only FLUENT from Fluent Inc supports hybrid grids GASP from AeroSoft Inc supports structured multi blocks grids only GUST from AeroSoft Inc supports hybrid grids INCA v2 from Amtec Engineering supports structured multi block grids only INCA v3 from Amtec Engineering supports hybrid grids NCC from NASA Glen Research Center supports hybrid grids NPARC versions 2 and 3 from the NPARC Alliance Reference 5 supports structured multi block grids only OVERFLOW from NASA Ames Research Center Reference 3 supports structured overlapping multi block grids only PHOENICS from Concentration Heat amp Momentum Limited supports structured multiblock grids only SCRYU from Software Cradle Ltd supports structured multi block grids only SCRYU Tetra from Software Cradle Ltd supports unstructured tetrahedral grids only Splitflow from Lockheed Martin Corp supports 3D unstructured Cartesian Hex grids STAR CD from Computational Dynamics supports hybrid grids TACOMA is an end user proprietary CFD solver for structured multi block grids TASCflow from AEA Technology Engineering Software supports structured multi block grids only TEAM from USAF Wright Laboratories Reference 8 Reference 14 supports structured multi block g
38. 3 There are two variations of the render density attributes one for grids and one for databases c o Grid Render Density Grid Render Density For domain and block face entities you may specify the display increment for i and j lines in the grid using this button You may specify a pair of values each between 0 and 9 for the i and j increment respectively When the grid is rendered every n i or j constant grid line will be drawn Setting the increment to zero will display only the boundary in other words the connectors t o Curv Render Density 2 26 Saving Screen Images Color Curv Render Density This command allows you to specify the number of points used to render the u and v constant curves respectively By default 25 points are used on both the u and v constant curves For linear curves and surfaces Gridgen always places render points at the corner of each interval on the surface regardless of the value set here For other entities Gridgen will adjust the number of render points so that u and v constant render lines cross at a common point Entering a value of 1 results in an optimal density of points 2 10 4 Color wireframe color 1 O41 OM 42 oB 3 oll 4 oi 5 oMl s O47 6 arg wireframe color solid shade color A total of seven colors are available for the display of entities the default database color and the six default grid colors one for each face of any potential 3D structured blo
39. 3 5 tetrahedral mesher memory limit 3 5 tolerances 3 6 triangle area maximum 3 4 minimum 3 4 Defaults menu 3 7 delete automatically created group entities for Version 8 compatibility 4 7 block 5 5 when changing analysis software 17 3 break point connector 5 4 control point during segment creation 7 10 control point during segment editing 14 21 database entity 5 4 domain 5 4 face during block creation 0 6 last 2 Point Connector 7 overwrite during Gridgen file import 4 5 dimension definition 7 disable block 75 7 connector 5 7 database entities 5 7 domain 5 7 display attributes for Examine 6 7 display editing 2 22 Display menu 2 9 display style 2 25 hidden line removal 2 24 off 2 23 shaded 2 24 shaded wireframe 2 24 solid 2 24 solid wireframe 2 24 wireframe 2 23 Display Style for Examine 6 8 Display window 2 7 background color 2 27 linewidth 2 27 distance between two pickable points 2 28 distribution definition 7 function default 5 5 Set As Values command 3 distribution function 7 copy 11 8 copy from network amp equal spacing 71 8 general 9 geometric progression S hyperbolic tangent 71 8 maximum deviation 9 maximum turning angle 9 monotonic rational quadratic spline amp MRQS 71 8 domain adding to block face 0 10 3 automatic grid initialization 9 3 9 7 background control function default 3 3 bad types 9 0 changing grid density 3 color codes 9
40. 5 5 domain 5 3 create block 70 1 import 4 15 structured 0 unstructured 0 3 linkage 70 6 reorient faces 10 6 break point connector 2 point 7 10 add segment 7 2 import 4 3 on database entities database placing connectors on 7 11 segment 3D Space Akima 7 3 3D Space Curve 7 3 3D Space Line 7 2 copy 7 7 DB cnstr Akima 7 3 DB cnstr Curve 7 3 DB cnstr Line 7 3 import 7 7 pole 7 8 control points 2 7 database fit curve 6 5 fit surface 6 12 linear sweep surface 6 11 note 6 4 plane 6 5 polyconic surface 6 9 ruled surface 6 7 surface 6 7 surface of revolution 6 0 database entity curve 6 2 akima 6 5 circle 6 5 conic 6 3 curve 6 3 intersect 5 5 line 6 5 note 6 4 plane 3 point 6 6 coefficient 6 7 constant 6 5 point normal 6 6 point average 6 2 intersect 5 5 surface 6 7 domain 9 7 import 4 3 structured 9 7 unstructured parametric 9 7 parametric fit 9 7 standard 9 7 Crinkle reference surface 6 5 CRUNCH asw 7 9 cursor 2 5 3D 2 16 centering 2 9 movement 2 6 during picking 2 8 panning 2 5 rotation 2 5 zooming 2 5 D data hierarchy block 4 6 connector 4 4 database 4 2 domain 4 6 database 6 7 associativity to grid 4 2 constraining domains to 72 77 create Akima curve 6 5 conic section 6 5 curve 6 2 extract curve from surface 6 4 fit curve 6 5 fit surface 6 12 line 6 3 linear sweep surface 6 11 note 6 4 offset curve 6 3 plane 6 5 point 6 7 polyconic surface 6
41. 69 of the commercial software product of the same name For detailed information on this format please consult Reference 16 For surface and volume grid files Gridgen recog nizes the following NASTRAN elements e CQUAD4 CTRIA3 e CTETRA CPENTA e CTETRA NASTRAN L type refers to the large format for real values in the NASTRAN file Large format uses 16 characters for real values whereas NASTRAN style uses only 8 characters UCD style refers to the FEA and CFD interface to Advanced Visual Systems AVS software For informa tion on this format please consult Reference 2 UCD style is available for domain and block export only VRML type refers to the Virtual Reality Modeling Language Version 1 0 For information on this format please consult Reference 41 VRML export is available in ASCII only for surface grids Gridgen recog nizes the following VRML keywords Coordinate3 ndexedFaceSet STL type refers to the Stereo Lithography file format described in Reference 42 STL export is available for triangular surface grids only Both ASCII and binary format STL files may be exported although the binary format is always little endian FV UNS style refers to the FIELDVIEW unstructured data file format by the visualization software of the same name and described in Reference 43 FV UNS export is available for volume grids only and includes tetrahedra hexahedra prisms and pyramids Both ASCII and binary format FV UNS files are availa
42. 7 project command closest point 14 15 cylindrical 4 74 linear 74 14 spherical 74 13 control point during Add by Picking 2 18 during elliptic PDE solver iteration 12 12 elliptic PDE solver attribute type 12 13 extrusion attribute 5 4 in elliptic PDE solver 2 5 unstructured solver attribute type 13 4 pyramid attributes 3 9 cell creation 73 8 pyramid aspect ratio 5 5 pyramid height maximum 3 5 minimum 3 5 Q Quick Keys 2 5 Quick Menu 2 6 enabling 2 27 R radio button 2 4 ReDimension ReDimension Grids 717 3 reference surfaces for Examine 76 14 references 9 7 render density 2 26 curve 2 27 grid 2 26 render mode 2 25 intervals 2 25 isolines 2 25 outline 2 25 triangles 2 26 Reorient Edge 9 8 report and paper references 79 7 ReSpecify LJ K 5 7 restart file backward compatibility 4 3 combining multiple restarts 4 3 restart file import 4 RGB file 2 27 rotate move rotation point to 3D cursor 2 9 pick rotation point 2 27 rotation point changing 2 28 rotational extrusion 8 2 attributes 8 4 S Save reference surface 76 14 scale scaled distribution function 3 screen capture 2 22 2 27 SCRYU asw 7 13 SCRY U Tetra asw 77 13 segment 3D Space Akima 7 3 Bezier 7 8 curve 7 3 line 7 2 add 7 2 branch 7 5 database constrained Akima 7 3 Bezier 7 8 curve 7 3 line 7 3 definition 2 7 1 edit 14 2 format of segment file 8 2 general 7 8 import database from segment file 4 7 pole 7 8 ratio
43. 9 ruled surface 6 7 surface 6 7 surface of revolution 6 0 creating domains on 9 9 creating entities 6 data hierarchy 4 2 definition display 2 20 gaps closing automatically 75 11 group 15 2 hierarchy intersection 5 5 layer manager 5 linkage 74 2 modify join 74 19 mirror 4 2 rotate 14 10 scale 14 8 split 14 16 stretch 74 9 translate 4 7 show enabled entities 2 20 STL feature extraction 15 17 Database diagnostic function 6 3 database entity copy 15 3 default name 75 7 delete 75 4 disable 5 7 enable 5 7 import composite 4 7 IGES 4 9 PATRAN 4 0 segment 4 7 wireframe 4 6 intersecting 75 15 name 5 name assigned on import 5 shell extracting curves 5 8 extracting surfaces 5 18 feature extraction 15 17 database hierarchy during modification 4 2 database parametrization default display 5 6 decay factor unstructured solver 5 7 default angular deviation maximum 3 4 average connector spacing 3 background control function 5 5 connector dimension 3 connector spacing beginning 3 3 ending 3 3 database parameter display 5 6 database parametrization display 5 6 decay factor 5 4 distribution function 3 5 domain initialization 5 4 foreground control function 3 5 join angle 3 5 maximum angular deviation 3 2 maximum chord height deviation 3 3 3 4 pyramid aspect ratio 3 5 pyramid height maximum 3 5 minimum 3 5 QuickSave file name 3 6 split angle 3 5 tetrahedral mesh size factor
44. Dist command is selected the resulting distribution function will be a General distribution indicating that it does not follow any of Gridgen s mathematical forms but was formed by copying from some other subcon nector Max Dev Max Ang This command allows you to enter values for the maximum deviation of the discrete connector from the segment shape the maximum turning angle allowed between adjacent grid points along the connector e a parameter designating whether or not the current beginning and ending spacing constraints should be maintained or released Note that unlike implementations of this feature in the Defaults menu Section 3 and during connector dimensioning Section 11 1 the connector dimension is NOT changed when this feature is applied as a dis tribution function This means that the deviation and turning angle limits you specify here will not be enforced exactly but the general trend in grid point clustering will be applied Furthermore if you choose to maintain the beginning and ending spacing constraints when applying this distribution function be aware that the level to which the limits will be enforced is seriously degraded General This type is not a distribution function that you can explicitly apply to a connector It is applied to connectors by Gridgen whenever the distribution of points along a connector is created by something other than one of the mathematical distribution functions This includes Co
45. Domains and Blocks RUN UNSTRUCTRD SOLVER Initialize t Tri Solver jRefine n Decimate d Smooth Only s Project Grid to DB ul Set Solver Attribs Ag Done Save ent Abort Don t Save esc Help Initialize Clear any existing interior grid points and create a new mesh by starting from the boundary points and applying the solver with the current attributes Tri Solver Refine Insert points into an existing mesh with the current attributes Tri Solver Decimate Remove points from an existing mesh with current attributes Tri Solver Smooth Only Apply smoothing to an existing mesh no point insertion Project Grid to DB Project the interior points of all selected grids with database constrained shapes using the current shape attributes Set Solver Attribs Set unstructured solver attributes such as grid parameters and shape function on the grids currently being run in the solver Done Save Exit the solver and save the current grids Abort Don t Save Exit the solver and revert the selected grids including the solver attributes back to the state that existed at the time the Done button was pressed The unstructured solver s Refine menu is slightly different for blocks as shown below Each time the unstructured solver is applied to blocks by pressing the Initialize button the grid generation procedure dis cards any current volume points and starts over from the boundary points and the current attributes
46. Function None in Global mode is similar to the Summarize command found in previous Gridgen versions which has been replaced by this feature 16 2 2 Usage Usage u Selecting Function Usage will highlight in the Display window the focus entity Local mode or all selected entities Global mode along with entities of other types that use or are used by the examined enti ties Tabular information about how the entity is used is listed in the Blackboard 16 2 16 2 3 Database DB di i on o MM off f Diagnostic Function Database For connectors and domains only selecting Function DB causes grid points that are on and or off the data base to be rendered in the Display window and listed in the Blackboard The toggle buttons on and off indi cate whether or not to render grids points that are on or off the database respectively Keep in mind that Gridgen considers a point to be off the database 1f the point does not have an explicit reference to a database entity and parametric coordinates A point flagged as off may actually be within the same point tolerance of the database The example below shows the database function displayed on a single quadrilateral domain that has been projected onto a trimmed surface in the database that is shaped like a mask Itis very easy to distinguish the points on the database green from those off the database red 16 2 4 Size 0094 64 5 OD 64 3 L Ld gt Ld Ld L L L L L
47. Gridgen s menu buttons act as a group of choices for the setting of a certain switch These buttons are called radio buttons since they function like the programmed station buttons on a radio In any group of radio buttons only one button may be active at any one time Radio buttons can be identified by the blue dia mond on the button The active option in a group of radio buttons is denoted by the filled blue diamond Pressing one radio button implicitly unpresses all other radio buttons in the same group In some instances pressing a radio button only sets the switches and another button must be pressed to acti vate the switch For example the FILE ATTRIBUTES menu contains three radio button groups that allow you to specify the style format and precision of a file during import A fourth button Done also appears on the menu and must be pressed before import proceeds with the switches set according to the radio button settings O Gridgen 1 PLOT3D 2 O PATRAN 3 NASTRAN 4 NASTRAN L 5 UCD 7 O VRML 8 ACAD A1 STL A2 LO Fv UNS s ASI OT binary 8 unfrmtd 9 single s gt double d Done ent 2 3 9 VCR Buttons When selecting items from the Browser Section 2 4 2 Gridgen displays in the Menu window a single row of six menu buttons for positioning the Browser s list of items These buttons are called VCR buttons since 2 4 Menu Buttons Quick Keys they function like the buttons on a vid
48. Gridgen file Q Exit Gridgen Invoke on line help 2 7 Graphical User Interface 2 3 8 Miscellaneous Prev Page L Next Page R Some menus have too many buttons to fit onto a single page In this case the menu will be split into two or more pages and buttons Next Page and Previous Page at the top of the menu may be used to step through all of the menu s pages d Dom s Fac b Some menus use abels to group similar commands and to provide additional information on command func tion Labels are identified by a thin black border in place of the beveled border around buttons Labels are not pickable Gridgen sometimes employs a user interface technique called mouse warping 1n which the cursor is automat ically positioned over a particular button usually the default command for the current menu Mouse warp ing may be disabled via the Warp command in the DISPLAY COMMANDS menu Section 2 9 2 4 Entity Selection Most of Gridgen s commands require you to select or pick an entity or entities to which the command will be applied For example a connector must be picked in order to distribute grid points on it and database entities must be picked in order to translate them There are two main mechanisms for picking the Display window and the Browser Depending on the command you may select entities from either the Display window the Browser or both When both mechanisms are available the choice is yours both yield equiva
49. Last 2 Pt Con This command allows you to delete the last 2 Point Connector that you created in case the wrong points were selected Erase Last Point del Erase Last Point This command allows you to delete the first point of a 2 Point Connector after the first point has been added but before the second point has been added 7 4 OnDB Entities The On DB Entities command allows you to rapidly create many two point connectors at one time The connectors created by this command are the same as 2 Point connectors in that they consist of a single seg ment with two control points The connectors to be created depend on the database entities picked 1 One connector is created on each curve entity 2 Four connectors are created on each surface entity one connector per boundary 3 One connector is created on each trimming curve of a trimmed surface entity The illustrations below show before top and after bottom pictures of an engine nacelle database and its connectors that were created using the On DB Entities command 7 11 Creating Connectors 7 12 8 Grid Extrusion Methods Domains and blocks may be created by extruding connectors and domains respectively along prescribed paths Although the extrusion methods are a means of creating domains and blocks Section 9 and Section 10 they are described in this section because the resulting grids depend strongly on the grid methods Three types of entities may be created by extrus
50. M Ld Lo neta LN A C MEM 15 7 15 6 A BIOCK tod chen de lost suos eh ees LS LLL A MEM LP A E 15 7 15 7 HeSpDecIIV ATA a COP 15 7 An 15 8 95 9 PeriodIiCIly ie Eta OL Mets oui ene talon ea LEM Re ad 15 8 19 10 C1 qo ER I 15 11 IS EE O E 15 11 A e a 15 12 15 10 3 Nodes and Connectors sss eene se nennen ets n nna 15 13 on as UIE AU ERNEUT REESE ou tans 15 15 iom SA NC c OE Eo O 15 15 19 106 Uppdal OMS T da oo S 15 15 15 10 7 Topological Filter Commands occccconnccnccnonocnncnononononononannononononanonos 15 15 IL TANTOS OO PER 15 15 19 12 Feature EXIFaC HORN suiit tpm duque obediant DA ded 15 17 16 Diagnostic FUNC LONS oooocoococcocccococonocacooonononncoonnoronnoronnononnnronnoso 16 1 16 1 FOCUS ENHI RE 16 1 16 2 DIaAgnostic FUNCION y corretti A n esa sid toda a es 16 2 10 21 eget LE 16 2 102 AN IIo O 16 2 16 2 9 Databas 6 uu EP Padi a itti it afud ede 16 3 RS A o a esses ao tps isd ee eno eae ease ee 16 3 15 29 e onto atu Merete e O 0 emer er meetin ear or er etme remy uon fett 16 4 1620 SZS tl eee ere ee ied nate ee an reer ce OT Rem ET cere ora 16 4 16 2 MODO Sois ona 16 5 16 20 ASPEC nal 16 5 16 2 9 OKEWNES O to ds 16 6 A A acces au ote i edust Kreis cupa EE 16 6 162 11 CUNO GO ANY 22 diestrus dae d Tela aclare ap rua edd 16 7 16 3 Display Attributes ioco ie br is 16 7 1o Sl TIS Oley Vlad oe nee 16 8 16 9 2 GOlOF B
51. Se mesa eee nee 17 8 1458 9 GEDO HIPO Wave viii ic o tele esa a mta d diede duse patietur 17 8 A T 17 8 FAO ees 17 9 NAO C o e 17 9 17 9 7 GOGONS SIFUGE tte oic et DR Deer ed Da Rama ors B Pc Qo e Da tr 17 9 EAS SA T E UE TTE 17 9 JP EB Si NK 17 9 jv o 17 9 A rn II ener eee 17 9 Sta CRUNCH Da cce ELLA UU e EL i i UE 17 9 IS TOS INSS A 17 10 17 9 E o A PA 17 10 Io lo FALCON da ao led oro A EDI 17 10 3146 2 FAN tutos lola See ated o door det arado id eto a nOs 17 10 io a BB nS oy ec ee ee ers ee 17 10 72 FEVENT VA achicha sare este ee Ae gains ae phate cleanses ete deta es 17 10 17 89 19 NN ieee tes EE 17 10 IWESELODeD CDM 17 10 jeu M B eee Ce RE A 17 11 Acto pom T ne em nT CE nee eee Ter 17 11 WT SIN AA A RI ate eS Ane eee E 17 11 Te digg Po o Po 17 12 AS AAA II E 17 12 17 95 26 0 VERLO Visitado dute a dr de dt e te led te 17 13 18 27 POI CS si ae co te se hgh eases ose ee cede eee 17 13 A AS ERE ENTIRE 17 13 17 95 29 SORT Tar dolio e DE 17 13 17 2330 SPINON ccrta A Ec DUE 17 13 18 2 1 0 TARO Dis a 17 14 172 32 AGO Aut dd eos M 17 14 14 8 95 A dU x ND IMMER S SUE EO e Me AE 17 14 aUa 17 14 A A O eRe Sea E SI 17 14 1 930 V SABERO sms a a e e EE EA 17 15 1 50 97 Y gt SAERON VO A pet T iude 17 15 TAS SO ANIN D PME A ee Oe 17 15 A A A o AEE OA EOE 18 1 IG T Introduction titio od A A dou ed 18 1 10 2 GNGOEM FI iioii AAA AA AA AA E OG 18 1 18 3 GRIDBLOCK F
52. The A to Prev O button will move a break point one control point toward the beginning of the connector The buttons are used by first position ing the cursor over the break point to be moved If the cursor is not positioned over a break point a notice is given and nothing changes If the control point to the right or left depending on the button selected is already a break point you are informed that the break point can not be shifted in the desired direction 11 3 3 2 Dimensioning Subconnectors When a connector has been split into multiple subconnectors you can control the number of grid points in each subconnector subject to the connector s total dimension Specifically the sum of the number of grid points in each subconnector should equal the connector s dimension minus the number of interior break points For example three subconnectors dimensioned 11 24 and 18 will have an overall connector dimen sion of 11 24 18 2 51 Here two points are subtracted for the two interior break points When a sub connector is split into two subconnectors by setting a break point on a control point the dimensions of the current subconnector are automatically divided between the two new subconnectors on the basis of the sub connectors arc lengths If the current subconnector contains only two grid points it will not be possible to select a break point on the subconnector interior since each subconnector needs at least two grid points Three command
53. a format for structured grid data and is described in Section 18 9 PLOT3D style refers to a format for structured grid data that was popularized by NASA s CFD visualization software of the same name Reference 38 This format 1s described in Section 18 4 This toggle is disabled for unstructured grids NASTRAN type refers to Version 69 of the commercial software product of the same name For detailed information on this format please consult Reference 16 For surface grid files Gridgen recognizes the fol lowing NASTRAN elements e CQUAD4 4 14 Import Grid Points Format e CTRIA3 NASTRAN L type refers to the large format for real values in the NASTRAN file Large format uses 16 characters for real values whereas NASTRAN style uses only 8 characters VRML type refers to the Virtual Reality Modeling Language Version 1 0 For information on this format please consult Reference 41 VRML import is available in ASCII only for surface grids Gridgen recog nizes the following VRML keywords e Coordinate3 e IndexedFaceSet STL type refers to the Stereo Lithography file format described in Reference 42 STL import and export is available for triangular surface grids only Both ASCII and binary format STL files may be imported and exported although the binary format is always little endian FV UNS style refers to the FIELDVIEW unstructured data file format by the visualization software of the same name and described in Reference 43 FV U
54. accomplished in two different ways 1 Parametric Triangulation or Parametric Fit Triangulation Section 13 2 Projection either via the Modify menu Section 14 4 or via the Run Solver menu Section 13 3 Proj Typ Lin Def This attribute tells Gridgen that the projection type is linear and the default projection orientation will be used The default projection orientation is computed by averaging the grid s normal vec tor at each grid point The projection vector direction is shown in the Display window as an arrow at each corner of the grid Proj Typ Lin Cur This attribute tells Gridgen that the projection type is linear and that points will be pro jected onto the database along a fixed vector perpendicular to the Display window screen z when the but ton is pressed Proj Typ ClosePt This attribute tells Gridgen that the projection type is closest point and a projection vector 1s not required Proj DBs Default The grids will be projected onto the default set of database entities The default data base entities are computed for each grid based on which entities are currently referenced by the grid points The entities to be projected onto are highlighted in the Display window Proj DBs Picked The grids will be projected onto database entities selected by you After this button is pressed you may select database entities from either the Browser or Display window The current set of pro jection entities is already picked when
55. analysis software handle What is the maximum number of grid points you can use What is the maximum number of grid blocks you can use 1 4 3 Plan the Grid What grid topologies will work best Which areas will require a finer grid to accurately resolve a boundary layer shock wave or other flowfield feature Which areas can be covered with a coarser grid Are there components of the geometry that will be changed for additional analyses Can they be isolated in the grid for later ease in editing 1 5 Outline of the Gridgen Process After you have planned your grid and familiarized yourself with Gridgen s terminology and command struc ture you are ready to begin generating your grid Gridgen is designed to guide you through the grid genera tion process in a specific order proceeding from grid curves the one dimensional grid elements through surface grids the two dimensional grid elements to volume grids the three dimensional grid elements This process allows Gridgen to automate many of the grid topology and dimension bookkeeping tasks you would have to keep track of yourself otherwise The basic steps you will follow are listed below Some of the steps are optional as noted Choose the analysis software you will use and whether the grid will be 2D or 3D Create or import the geometry model database optional Create the curves connectors that define the boundaries of surface grids Distribute grid points along the
56. axis system The rotation axes which are parallel to the body axes are drawn in red in the Display window at the rotation point and are fixed to your grid as the grid rotates the body axes rotate also The screen axes are not drawn in the Display window because as the name implies they are always aligned with the screen of your computer s monitor The x coordinate of the screen axis system screen x always points to the right screen y always points up and screen z always points out of the screen 2 1 2 Glide Toggle mM Glide Am The Glide toggle button in the DISPLAY COMMANDS menu determines how mouse movement controls image movement according to the following two states 1 Mouse movement imparts a rate of movement velocity to the image 2 Mouse movement displaces the image The default state of this toggle button is 1 mouse movement gives the image a velocity This implies that as long as the mouse button is pressed the image will continue to move even when the mouse is not moving In state 2 the image moves only when the mouse moves 2 7 3 Manipulation Device You may use either the mouse or the keypad keys in conjunction with the control key to manipulate the Dis play window image Note that the effect of the control key is to swap the roles of the mouse and keypad keys with respect to rotation and panning and zooming By default the mouse controls panning and zoom ing and the keypad keys control rotation With the cont
57. be constructed such that the intersection of the surface with each plane perpendicular to the spine will represent a conic curve defined by the rail and intersection curve points and the p value The component curves of a typical polyconic surface are illustrated below Polyconic Surface Rail Curve 1 Rail Curve 2 7 Slope Curve 3 Fit Tolerance 0 100E 02 value 0 750 Patches 27x 1 You may optionally select a fourth curve representing the spine of the surface or you may elect to have the spine lie along any of the three principal axes If no spine is selected the tangent intersection curve serves double duty as the spine The purpose of the spine is analogous to the axis required in the surface of revolu tion Section 6 5 3 it allows polyconics to be constructed along general curve paths Commands used during construction of a polyconic surface are Reselect Slope Curve del Reselect All Curves o Set Fit Tolerance 2 Adjust Conic Value al Spine on Principal Axis 5 Reselect Slope Curve This command allows you to replace the current tangent intersection curve with a different one Reselect All Curves This command allows you to restart the polyconic surface creation process Set Fit Tolerance This command allows you to set the tolerance with which the polyconic surface will match the rail curves By default the fit tolerance is set to 0 001 Section 3 7 1 Decreasing the fit tolerance improves the
58. boundary condition may be applied to a particular region For regions containing domains block deletion will cause each domain within the block to be tagged with that region s BC When 17 3 Analysis Software Interfaces a new block 1s created the new region containing that domain or domains will be assigned the tagged BC There is no method for manually setting an inter block connection inter block connections are set automati cally by Gridgen where adjacent blocks share a common domain 3D or connector 2D Boundary condi tions including inter block connections may be overwritten by simply applying another BC This allows for the specification of infinitely thin walls for example If the Browser text is blank where an inter block connection is expected check the type of connection relative orientation of block indices with what is sup ported by the analysis software Gridgen is programmed to eliminate connection types not supported by the current analysis software The list of available boundary conditions is dependent on the chosen solver Section 17 1 For example boundary conditions for the WIND solver are shown below Create Custom BC Undef i ned euo Reflection 5ymmetry 1 Freestream 3 Viscous wall 4 Arbitrary inflow 7 Outflow 8 Inviscid wall 9 Self closing 10 Singular axis 11 Mixed axis wall 12 Bleed Area 1 151 Pinwheel axis 16 Frozen 17 Chimera 18 Trailing edge 19 Discontinuous 20 Bleed Area 2
59. boundary conditions in GUST 17 8 22 INCA v2 INCA v2 export supports 2D and 3D structured grids only When you export data for INCA Version 2 you must first set several parameters specifying exactly how you would prefer the file to be formatted This menu is shown and described below solver compressible a incompressible b 3D o Format ASCII 3 unfrmtd 5 in compressible selects the compressibility of the flow for use with the SOLVERS ENABLED input in the INCA SETUP namelist and is used by some of the boundary conditions 3D 2D AXI the flow dimensionality is set by Gridgen s current setting from when the ASW was specified However if the blocks are 2D then you re given the option to choose between 2D and axi symmetric format how the grid file will be formatted either ASCII or Fortran unformatted Then the following INCA namelists are written RUN CONTROL INCA SETUP then for each block ZONE SETUP BC PATCH SETUP INTRZN PATCH SETUP if necessary UNIFORM FLOW initial conditions boundary condition specific namelists NS GENERAL CHEM SETUP NS ZONE The flowfield data and other parameters are initialized to zero Gridgen computes the index ranges for the patches by adding two boundary cells in each computational direction INCA s grid file is PLOT3D style Note that even though the boundary conditions are written assuming a two cell block overlap only the true grid without overlap is exported
60. button 15 3 Miscellaneous Delete d The Delete command allows you to remove entities from Gridgen Note that there is no undo command once an entity is deleted it is gone 15 4 1 Database Entities If any of the database entities picked for deletion have been used by connectors or domains the referenced connectors will be graphically highlighted in the Display window and the following text will appear in the Message window WARNING Ihe entities picked for deletion include some that are referenced by the hilited connectors Deleting the db entities will sever the linkage between the grid and db You must then choose from a button menu whether to proceed with the deletion and un link the grid from the database Delete Anyway or Abort and keep things the way they are Delete Anyway y Abor t esc 15 4 2 Connectors If any of the connectors picked for deletion are used in domains or blocks then those domains and blocks will be graphically highlighted in the Display window the number of domains and blocks to be deleted by deleting this connector will be tallied in the Blackboard and the following text will appear in the Message window DELETE CONNECTORS Deleting these connectors will cause all domains and blocks using them to be destroyed Select an option below You must then choose from a button menu whether to proceed with the connector deletion and the implicit domain and block deletion Delete Connectors or Abo
61. by this command 17 8 28 INCA v3 INCA v3 export supports 3D grids of both hexahedral and tetrahedral cells That means you may create a 17 11 Analysis Software Interfaces grid containing both structured and unstructured blocks for use in INCA v3 The volume grid from each of the blocks are agglomerated into one block for output INCA v3 export is supported on SGI platforms only under IRIX 6 5 17 8 24 NCC NCC export supports 2D and 3D grids of all cell types with the exception of pyramids When exporting BC data for NCC you must specify how you would prefer the BC file to be formatted This menu is shown below choose either the supersonic or subsonic attribute Subsonic 1 Supersonic Al 17 8 25 NPARC NPARC export supports 2D and 3D structured grids only When you export BC data for NPARC you must first set several parameters specifying exactly how you would prefer the BC file to be formatted This menu is shown and described below version O 2 ql 3 0 b bc style formatted format ASCII 3 unfrmtd 5 precision double 7 Mach number 1 200 m version 2 The BC data will be written for NPARC Version 2 which uses type 70 inter block connection and requires connecting blocks to overlap by one cell To meet this requirement Gridgen extrapolates each block by one cell in the J J K K L and L directions The indices in the BC file will reflect this extrapolation version 3 The BC data will be w
62. connector interpolates the control points break points are special control points that you designate at which a grid point will lie and spacing con straints can be specified They are drawn on the connector as large filled triangles The beginning and end ing of each connector will always be break points cursor is a large open circle drawn on the connector The cursor location and the grid point spacing at the cursor s location are displayed in the Blackboard Horizontal mouse movement with the right mouse button pressed will move the cursor along the connector subconnector is the region of a connector between two consecutive break points The subconnector in which the cursor lies is known as the current subconnector and is always drawn in yellow Menu buttons drawn in yellow are commands that apply only to the current subconnector Break points at the beginning and ending of the current subconnector are color coded in orange and blue respectively Break points lying on noncurrent subconnectors are drawn in red beginning and ending refer to the direction in which the connector was drawn Keep in mind that Gridgen does not restrict the manner in which connectors are drawn drawing a line from left to right is equivalent to drawing it from right to left Also the connector can be drawn without regard to its eventual orientation in a structured block s computational coordinate system However at some point you must be able to identify
63. creation If Parametric TFI or Parametric Fit TFI were used the new domain will be purple If Standard TFI was used the new domain will be green This color coding stays with the domain even if the domain s database relationship changes For instance if you project onto the database a domain that was created using Standard TFI it will still be green even though it is now on the database Similarly if you translate a domain that was created on the database using Para metric TFI it will still be displayed in purple even though it is no longer on the database The color coding only tells you how the domain was originally created You can determine the algebraic method last used on a domain using the Run Structured Solver com mand Section 12 1 the TFI method is listed in the Browser for each domain 9 3 Assembling Unstructured Domains An unstructured domain is created by selecting the connector s that make up its outer boundary and any inner boundaries Each boundary is called an edge in Gridgen s terminology Domain creation cannot begin until all connectors which lie on that domain s edges have been created Keep in mind each unstructured domain consists of at least one edge for the outer boundary and optional additional edges that define the boundaries of holes inside the outer boundary You can add connectors to an unstructured domain s outer boundary without regard for the orientation of the loop or its starting point as long as the conn
64. defines the shape of the object being gridded connectors curve grids domains surface grids blocks volume grids The data hierarchy s foundation is the database a geometry model of the object on and around which a grid is to be generated You typically obtain the database from a computer aided design CAD system and import it into Gridgen Gridgen also provides tools for creating database entities A database may consist of points curves surfaces and other topological data Keep in mind however Gridgen does not require a database the geometry of the grid entities you create may implicitly define the grid s shape Furthermore Gridgen does not require the database to represent a closed solid model The remaining three elements of Gridgen s hierarchy are the grid entities connectors curve grids domains Introduction surface grids and blocks volume grids Grid entities are ordered according to their computational dimen sion Note however all of Gridgen s grid entities may have a 3D shape in other words all three compo nents of the Cartesian coordinates x y z may vary Connectors the grid entity at the bottom of the hierarchy are curves on which grid points are distributed A connector what a CAD system would call a composite curve consists of one or more segments Segments are basic curve types which can be polylines polycurves conics and circles or curves obtained from a data base The middle grid ent
65. dimen From subcon keybrd Add In OMaxDe v LIMaxan g 11 1 1 Apply Dimension or Average Spacing You can explicitly dimension a connector by pressing the Apply dimen radio button The source of the total number of points is specified by the setting of the radio buttons labeled From You can implicitly dimension a connector by pressing the Apply avg As radio button The value of the average spacing is specified by the setting of the radio buttons labeled From This only sets the number of grid points Any existing spacing constraints will still be applied 11 1 2 From Keyboard or Subconnectors Pressing the From keybrd button allows you to type in either a number of grid points or a grid point spac 11 1 Grid Methods for Connectors ing depending on whether the Apply radio button is set to dimen or avg AS respectively If at least one other dimensioned connector exists in your grid you can press the From subcon radio button and dimension a connector by copying the dimension of one or more other subconnectors The selected sub connectors are referred to as the subconnector string If the Apply dimen radio button is set the sum of the dimensions of the subconnector string will be applied to the current connectors If the Apply avg As radio button is set the average spacing along the subconnec tor string will be applied to the current connectors The Blackboard window will display the dimension of each subconnector to be
66. exclusive non transferable license to use the Licensed Prod ucts in accordance with the terms and condi tions set forth herein As long as this License is in effect Licensee may transfer its use of the Licensed Products to a replacement computer system on a temporary or permanent basis provided that Licensee gives PWI written notice of such transfer 3 TERM and FEES The Term of the Right to Use License is annual or perpetual as set forth in the Purchase Order or Contract provided that the License has not been terminated as set forth in Section 10 All applicable fees are payable to PWI within thirty 30 days from Invoice Date Failure to pay such fees in a timely manner is a material breach of this License Licensee agrees to pay any legal or collection fees incurred by PWI in collecting any amounts that may be delin quent 4 COPIES and MODIFICATIONS Licensee may copy the Licensed Products in whole or in part in written or machine read able form for use in understanding the Licensed Software and for archive or backup purposes Licensee shall reproduce and include PWT s trade secret or copyright notices on and in any copies in any form Licensee shall not reverse assemble reverse compile or otherwise reverse engineer the Licensed Soft ware in whole or in part The license includes the right to reproduce the Gridgen Version 14 User Manual exclusively for the use of Licensee and its employees only All other repr
67. i kd 9 Last del MDomain Once 1 Merge Nodes n Conns c EraseDom CIPikd 9 Last del Nod Con 2 Auto a Merge Nodes An Conns Ac Pick k Update Ad Nod Con 2 amp uto a TopoFltr eA11 3 oFree 4 Pick k Update Ad NonMinfldt Free 5 TopoFltr e 411 3 oFree 4 Facerltr eAl1 6 OBndry y NonHnfldtFree 5 o Outsd d FaceFltr A11 s oBndrvv Save As Baffle Face b Outsd d AutoSave e Off o 0ff ol O Face _c oO Faces s Face c iMesh Both Sides h Abort esc Abort esc Pick Multiple Doms When this button is pressed you are able to select more than one domain to be added to the face using the Browser and Display window For unstructured blocks this makes it very easy to select all of the domains in a face Each domain selected in this mode will be successively added to the developing face using the first linkage found For structured blocks this method should only be used on faces that are not self connecting 1 e without multiple linkages Pick All Domains This command picks all domains and adds them to the face 10 4 Face Creation Commands Adding Faces to an Unstructured Block Pick Adjacent Doms This command adds to the current face all domains adjacent to the free yellow edges Using this command allows you to assemble the face in discrete layers Pick Struc Enabling this toggle button allows structured quadrilateral domains to be picked during face assembly By default this togg
68. image If you notice that portions of your grid image are being clipped as though an invisible plane is slicing through the image then use this command The rotation axes will be placed at the center of the 3D viewport after the new view limits are computed Wndw Linewid This command controls the thickness with which connectors and database entities are drawn default is 1 Values between 1 and 5 may be selected Wndw Rot Pnt By default the rotation point is at the center of the 3D viewport By pressing the Rot Pnt button the rotation point can be moved to any visible point in the Display window including grid points sim ply by picking it with the mouse The rotation point is reset whenever the original orientation is restored using the r hot key The rotation point may also be set at any time by holding the control key and then pick ing a point with the mouse Wndw FramBuf This command lets you change Gridgen s frame buffer configuration The availability of these configurations depends on your computer s graphics hardware which Gridgen determines at start up At start up Gridgen chooses what it considers to be the frame buffer configuration that will perform the best You may change the frame buffer configuration to one of these four options RECONFIGURE GRAPHICS 12 Bit Color Index Mode 1 RGB Mode w Overlay 2 8 Bit Color Index Mode RGB Mode 3 4 Graphics Prec Single s d 5 o Double Reset Colors
69. imported as database entities or domains The initial value for this default is 0 0 imported surface grids will not be split To change the default value press the Split Angle menu button and enter an angle in degrees Triangular surface grids will be split into closed regions on import if the dihedral angles between all the boundary triangles of a region and their neighboring regions are greater than the split angle If any of the angles are less than the split angle no action 1s taken The default split angle also is used as e the initial value for feature extraction in the Database menu the initial value for splitting connectors when creating On DB Entities domains 3 4 2 Join Angle The default join angle provides an initial angle for joining domains when joining unstructured domains in the Modify Domains menu creating a face for an unstructured block creating a face for extruding a prism block auto joining domains when creating by On DB Entities Two domains will be joined if at least interval has a turning angle less than the join angle 3 5 Setting Defaults 3 5 Database Parameterization You can choose to display database entity parametric coordinates varying from 1 to the number of intervals or normalized coordinates that vary from 0 to 1 To display coordinates corresponding to the intervals in the entity press the DB Coord IJ button To display normalized coordinate press DB Coord UV The initial value for this
70. include Gridgen restart files e Database files for example native CAD files IGES and STL Grid point files for example PLOT3D NASTRAN and VRML 1 0 e Glyph initialization and journal files Analysis software grid and BC files for many popular CFD and FEA solvers FIELDVIEW structured boundary surface files The INPUT OUTPUT COMMANDS menu is shown below INPUT OUTPUT COMMANDS Import 1 Export 2 Qui ckImp Import 3 Import 7 Expor t 8 Export Glyph Init File 0 Export Analysis BCs 5 Export Analysis Grid Export FY Bndry Surf Files5 Incorporate volume Grid 4 Block Ell Solver Glyph Al Done ent Cons C Doms DIBlks BIDB F Dflt T 1I o E AS W A Glyph Quit Q Save s Disp a Hel1pb Working with each of these file types is described in the following sections Additionally the format of many file types is described in Section 18 Many files for example grid point files database network files and some analysis grids allow you to choose from several attributes for importing and exporting the data These file attributes are set via a menu consisting of radio buttons for each attribute and the available options depend on the specific type of file being imported or exported 41 Import Gridgen File The Gridgen file is your grid model restart file and its default extension is gg It contains everything about the grid including nodes connectors domains blocks grid points analysis software s
71. ing the scissors cursor over the subgrid s pink outline and pressing the right mouse button Keep in mind that deleting a subgrid does not delete any grid points 12 3 3 Using SubGrids Subgrids are used with the structured grid solvers When the solver is run the Browser will list any subgrids as pickable entities in the Browser as shown below for domains 12 15 Grid Methods for Structured Domains and Blocks atndr stndrd lstndrd 2stndrd astndrd stndrd stndrd stndrd stndrd fitpar b fitpal b fitpar4 bz param b fitpar3 b stndrd b stndrd b stndrd b stndrd b h h h h h h h h h h h h h h h h h J Jl Jl Jl Jl Jl je Jl Jl je je Jl Jl Jl feat feat feat BJRJRJROJROJRJRONJROJNJNONOJNONONONOINI 200009 CO CO CO CO CO CO CO CO CO CO CO CO CO Cu As you can see from the illustration whenever a domain has subgrids each subgrid is listed in the Browser The subgrid number is shown to the right of the decimal point after the domain number The Browser appears differently for blocks as shown below The block name is listed first and any subgrids are listed in parenthesis next to the block name 12 16 13 Grid Methods for Unstructured Domains and Blocks Gridgen s unstructured grid methods are based on a Delaunay technique by which points are inserted into a triangular domain or tetrahedral block grid in order that the individual grid cells meet one or more criteria that yo
72. is time for file name selection Gridgen lists in the Browser all files within the current directory that match the default extension of the file type to be read or written The current directory name is displayed in the Message window List items correspond to either files or directories denoted by a trailing slash A list item is picked by moving the cursor over it at which time it will be highlighted indicating that it s pickable then pressing either the left or right mouse button If the picked item is a file name it will be queued and highlighted in white If the picked item is a directory it will become the current directory and a new list of file names will appear in the Browser Positioning of the file list in the Browser is controlled using VCR buttons Section 2 3 5 Other commands of interest during file name selection include Type In Name This command prompts you to type the file name including path if necessary Type In Dir This command prompts you to type in the name of the directory to make the current direc tory Go to Dir Unix only The root directory of the file system will become the current directory when this button is pressed Go to Dir lt drv gt Windows only The drive letters of the computer will be displayed in the Blackboard when this button is pressed Go to Dir Orig The directory from which Gridgen was started will become the current directory when this button is pressed
73. is written only in ASCII format Binary and either single or double precision composite database files written by older Gridgen versions may be imported 18 7 FIELDVIEW Unstructured File Tetrahedral volume grids may be imported Section 4 6 and structured unstructured hybrid grids may be exported Section 4 7 in the FIELDVIEW Unstructured File FV UNS format This neutral file is used by Intelligent Light s http www ilight com CFD post processing software of the same name Please contact Intelligent Light for further information on the format of this file 18 8 Generic Flow Solver BC File The generic flow solver s Section 17 8 1 boundary condition file is an ASCII file used to export boundary condition data for un supported analysis software The code fragment below describes this file s contents in detail to assist you in preparing a translator if necessary Note the generic flow solver boundary condition file is for structured grids only For unstructured grids the generic format grid and boundary condition is in FV UNS file format write flow_solver_id write number of blocks do number of blocks 18 3 File Formats write block imax block jmax and block kmax if 3D block name Cg fa M a a region is a boundary condition or interblock connection write number of regions on block do number of regions on block write source region imin source region Imax Source region jmin source region Jjmax and source regi
74. layer of grid points inward from the boundary You can choose from four methods for computing the spacing constraint As Calc Type In 1 Interpl 2 Cur Grd 3 Adj Grd4 Type In This command sets the spacing constraint equal to the value you enter via the keyboard Interpl The spacing constraint is computed by interpolating linearly from the perimeter of the boundary This gives a smooth variation of spacing that matches the spacing at the perimeter of the boundary The boundary s arc length is used as the basis for the interpolation This 1s the default method Cur Grd This command maintains the spacing currently in place in the grid Adj Grd The spacing constraint is copied from another grid selected for the elliptic solver sharing the selected boundary with the current grid If the adjacent grid cannot be determined either 1f none exists or if more than one exists the constraint is changed to Cur Grd This constraint provides spacing continuity across grid boundaries There are two methods for blending the spacing constraint portion of the control function from the boundary into the grid s interior 12 10 Elliptic PDE Methods Surface Shape As Blend Linear 1 Exponen e Decay k Linear The spacing constraint is blended linearly from the boundary into the interior Exponen An exponential function is used to rapidly decay the spacing constraint into the grid s interior This is the default blending function typ
75. listed in yellow text in the Blackboard In addition to the average point s location the Display window also shows spokes white lines emanating from the average point to all of the points used in its computation When the Done button is pressed the average point is saved along with the others as a data base entity Other commands involved in database point entity creation are 7 Keep Pts 1 4 Keep Avg 3 Keep Pts This toggle button toggles the save status for the points being added when toggled off they will not be saved You might do this when creating a point at the midpoint of two existing database locations Keep Avg This toggle button toggles the save status for the average point when toggled off the average will not be computed displayed or saved Note that if both toggle buttons Keep Pts and Keep Avg are toggled off then nothing will be saved when Done is pressed 6 3 Curve You can create eight types of database curves Line Curve Akima Curve Circular Arc Conic Section Off set Extract and Fit Only three of these curve types Offset Extract and Fit are unique to the database commands Creating the other curve types is similar to adding segments Section 7 2 during connector cre ation Curve Line d Curve e Akima h Conic a Circle b Offset o Extract Ax Fit f 6 2 Curve Line 6 3 1 Line Creation of Line database entities is similar to creation of Line connector segments Please refer
76. match between the surface and its defining curves but at the price of increasing the number of intervals in the surface Spine on Principal Axis This command allows you to choose either the x y or z body axes to use for a spine instead of selecting a curve entity By default the spine is the tangent intersection curve Adjust Conic p Value This command allows you to set the value of p in the range 0 lt p lt 1 The default p value is 0 5 The character of the polyconic changes with the p value as shown in the following table 6 9 Creating Database Entities Effect of p on conic section type aX conic section type hyperbola 6 5 3 Surface of Revolution A surface of revolution database entity is created by revolving a curve called the generatrix around a second curve called the axis A characteristic of the resulting surface of revolution is that at any plane perpendicular to the axis the intersection of the revolved surface and the plane is a circular arc One edge of the surface of revolution will lie on the generatrix two if the angle of revolution is 360 degrees You can also specify an angle of revolution in the range 360 to 360 degrees excluding 0 degrees Once the axis 1s selected the sur face is initialized using the default angle of 360 degrees A typical surface of revolution is depicted below Surface of Revolution Generatrix Curve Axis Curve 1 Fit Tolerance 0 100E 02 Angle of Revol 120 000 Patc
77. network may have either Gridgen or PLOT3D style 4 4 2 Format Format refers to the data format in the file format ASCII a 2 binary Ab O unfrmtd n ASCIl is a human readable format that is very portable between computers of different types However ASCII files will require significantly more disk storage than binary or Fortran unformatted files and will take longer to import and export binary is a compact format but suffers from a lack of portability between big endian and little endian computers unfrmtd refers to Fortran unformatted a format similar to binary in that it is very compact However binary and Fortran unformatted formats are not interchangeable Fortran unformatted format is available for importing and exporting Gridgen and PLOT3D style database network files importing FIELDVIEW unstructured data files and for exporting some types of analysis software data 4 4 3 Precision Precision refers to the word size 1n the data file single s double d single precision means that real floating point data will be written as 4 byte words double precision means that real floating point data will be written as 8 byte words 4 4 4 File Type File type refers to the brand of the file to be imported These files may be obtained from a variety of sources including user written programs and CAD systems Gridgen supports several file types since some file types do not provide for all
78. of the last segment If no other segments have been defined the imported segment can be translated and positioned in the usual manner The resulting segment will be of the Line type with a control point located at each data point in the file The input file format is described in Section 18 5 It is the same file type used to import a database curve Sec tion 4 4 Consecutive coincident control points are automatically deleted from this segment at the time of import 7 7 Creating Connectors dieu Miscellaneous Segments 7 2 5 1 Pole A pole segment 1s a segment of zero length Poles are not created directly Instead you create a Line seg ment Section 7 2 1 with two coincident control points Gridgen will warn you about the coincidence The pole connector is drawn in the Display window as a node surrounded by a large open circle 7 2 5 2 Bezier Curve Once a Line Curve or Akima Curve segment is created and saved it may be edited and converted to a more general mathematical form known as a Bezier Curve This provides explicit user control of control point locations and slopes When in the edit mode control points are adjusted in the usual manner but now the curve s slope at a control point can be manually adjusted by selecting either of the Edit menu buttons color coded so that blue refers to the slope preceding the control point and red refers to the slope following the control point Upon selection the cursor will move to
79. of the linear curve s control points The goal of the fit curve 1s to create a smooth representation of a faceted curve Often you are given a geometry definition that is sparsely defined Rather than use the sparse faceted curve you may create a fit curve which is more suitable for grid generation and some of the geometric calculations such as intersec tions 6 4 Plane Planes infinite planar surfaces may be added to the database for use in computing intersections of planes with curves and surfaces and for projection of grid entities Gridgen provides several different plane creation methods as shown below A Constant x Y Constant y Z Constant w Pt Normal 4n 3 Points 3 Coefs c Since a plane by definition is infinite Gridgen has adopted a finite representation for rendering in the Dis play window A plane entity in Gridgen is rendered as a small quadrilateral with a vector emanating from each corner pointing in the plane s normal direction 6 4 1 Constant Coordinate Plane Planes at constant x y and z locations may be created by pressing the Plane X Constant Y Constant and Z Constant buttons respectively The 3D cursor Section 2 8 is used to define the plane s location The cross is moved around the screen by moving the mouse with the right mouse button pressed The plane s position can be set using the standard control point creation buttons Section 2 8 2 Once the plane s location has been set the plane s image w
80. on what types of cells the new analysis software selection supports some domain and or block definitions may also be lost You first specify whether your grid is 2D or 3D by using the first row of radio buttons 2D al so bl 2D The grid will consist of computationally two dimensional blocks comprised of surface cells quadrilat erals and triangles only Structured 2D blocks will have dimensions I x J x 1 Note that to set BCs for a 2D grid or to specify the index orientations for a 2D grid you need to create a 2D block 3D The grid will consist of computationally three dimensional blocks comprised of volume cells hexahe dra pyramids prisms and tetrahedra Structured 3D blocks will have dimensions I x J x K 17 1 Analysis Software Interfaces Gridgen provides support for an extensive list of analysis software packages as shown in the following fig ure and list e generic INCA V3 oaae tf O9MC OCFDSHIP CIOU 2 ONPARC 0 oco aj ONSERO Oca 4 OQOMERLON O OCRE S OPHENIS coat 9 OSTAR D econo 0 OTAOMA OCRUNCH OTASCFlow 0 ooms 2 TEAM O OEXODUS II m OTETEX 0 0 0 0 j FALCON na OVSAERO sd OFDNS UNIC O WIND OFLUENT va OFLUENT 1 0 8 ETT 1 j INCA V2 generic is Gridgen s general purpose CFD style solver facsimile You may use it to export grid and bound ary condition data and then translate to your own for
81. periodic with the upper boundary of the grid We can accomplish this by entering the Connector menu pressing Periodic Trans selecting the lower connector and translating it into the upper position resulting in the image below 15 9 Miscellaneous we can change the distribution of points along the lower con gt We have now created the boundaries of the surface grids and established that the upper and lower boundaries are to be periodic With periodicity ensured nector and the distribution will automatically change on the upper connector as well see below The surface grids for the passages are shown below L LIT DI TT ECO A COT B LL RR 15 10 Merge Nodes 15 10 Merge Merge Nodes 4niConns c Nod Con 2 Auto At Pick k Update c These commands for removing coincident and overlapping connectors are available on the Connector menu and also from within domain and block face assembly 15 10 14 Nodes The Merge Nodes command allows you to select node pairs to be merged into a single x y z point This merging is not a topological merging as happens when using the Pick an Unlinked Con command during domain assembly Section 9 4 Nor does this command alter the node tolerance in the Defaults menu Section 3 7 1 Rather this command alters the physical location of one of the nodes of the selected pair to match the coordinates of the other node If one or both of the nodes are database constrai
82. range between 0 and 1 typically O 3 to be applied to the step size at Flat points adjacent to Corner points The Scndry step reduction is the coefficient to be applied to the step size at the grid point adjacent to a primary Flat point typically O 6 8 2 7 Boundary Conditions Boundary Conditions c You can apply boundary conditions to hyperbolic and normal extrusions by pressing the Boundary Condi tions button and then choosing from the menu shown below Splay 5 Step Suppression Ag Symmetry X 1 Y 2 F 3 Constant x s v amp E 7 Splay Pressing this button lets you type in the value of a coefficient in the range 0 1 that will cause the boundaries of the grid to move outward as the extrusion proceeds A value of 0 means no splay while a value of 1 means full splay The default value is 0 1 The two grids shown below compare no splay left with splay of 0 5 right Step Suppression This highly specialized boundary condition for normal extrusion scales the marching 8 11 Grid Extrusion Methods step size on the boundaries relative to the step size on the grid s interior The value you enter for the sup pression coefficient will be in the range 1 1 Positive values will increase the boundary step sizes rela tive to the interior step sizes Negative values will have the opposite effect The default value is 0 The two grids below demonstrate an application of step suppression The four oute
83. running Gridgen The database entities that you can create in Gridgen fall into one of five categories as listed below points curves e planes surfaces notes 6 2 Point Point entities can be added to the database using the Points command in the DB Creation menu Database points are most often used to Predefine all known locations that a curve should interpolate so they may be easily picked during curve 6 1 Creating Database Entities creation Section 6 3 2 Create a new point at the average location of other points such as the midpoint of a line The 3D cursor Section 2 8 1s used to identify locations at which point entities are to be created Each point added is shown in the Display window as a white filled circle You can create as many points as you need prior to pressing the Done button at which time each unique point is saved as a database entity Cursor Location 19 96835 y 9 966786 z 1 198263 Average Location x 12 39497 y 28 98827 z 1 198263 You may also choose to create a point that 1s the average of the 3D locations of the other points you are cre ating Once two points have been added the radio button Keep Avg becomes available no longer greyed out Toggling this button on will cause Gridgen to compute and display an additional point the 3D average of the other points The average point is rendered in the Display window as a yellow filled circle Its coor dinates are
84. satisfy the elliptic PDEs After each iteration the grid point solution is relaxed according to the following equation Phew 6 Fppgp 1 Pold in which r is the grid point vector and is the relaxation factor With a relaxation factor of O the grid will not move from iteration to iteration since the new value will be exactly equal to the old value Notice also that with 1 the new value of the grid point will be exactly that calculated from the PDE It is possible to use values of greater than one hence the term over relaxation The focus grid s relaxation factor is shown in the Blackboard with the label Relaxation Use Optimal Relaxation 2 Use Nominal Relax 0 7 3 Enter Relax via Keyboard 1 Use Optimal Relaxation This will calculate a unique optimal relaxation factor at each grid point based on an eigenvalue analysis of the finite difference stencil used to solve the PDE Reference 7 It works very well for most cases but is not always stable on grids with pronounced surface curvature because locally reaches values of 1 8 or more possibly shooting grid points off of the surface or causing convergence prob lems Use Nominal Relax 0 7 This button assigns an under relaxed value of 0 7 to all grid points This value almost always results in a stable iterative solution to the elliptic PDE and is best for database con strained grids 12 7 Grid Methods for Structured Domains and Blocks Enter Relax via Key
85. scale 74 8 stretch 14 10 angle constraint elliptic PDE solver 2 angular deviation maximum 3 4 default 3 2 append grids 4 3 ASCII mesh import 4 15 Aspect Ratio diagnostic function 6 5 associativity of grid and database 4 2 Auto Complete 9 7 Auto Next Edge 9 7 Auto Save 9 8 axis 3D cursor movement 2 6 Align LJ K command 75 8 body axes 2 14 computational 75 8 cylindrical projection 74 14 for Rotate command 74 11 image manipulation 2 4 plane 6 6 ReSpecify LJ K command 5 7 Rot Axes command 2 20 rotation point 2 9 screen axes 2 4 surface of revolution 6 0 XYZ Axes command 2 20 B background control function default 5 5 setting 12 8 type fixed grid 72 8 LaPlace 12 8 Thomas Middlecoff 72 8 backward compatibility of restart files 4 5 binary mesh import 4 15 Blackboard 2 3D cursor coordinates 2 6 block face creation 70 1 circular arc creation 7 6 copying connector dimension 7 2 database point creation 6 2 delete 75 4 domain creation 9 2 9 4 during database curve extraction 6 4 during database intersection 75 17 during elliptic PDE solver 72 6 during subdomain creation 72 14 12 15 during unstructured solver 3 2 face linkages 70 7 intersection 15 16 location of 2 2 rotate 74 11 setting elliptic PDE attributes 2 6 translation 4 7 14 9 14 10 block algebraic solver 2 changing grid density 3 copy 15 3 create 70 1 structured 0 unstructured 0 3 adding faces 70 3 linkage 70 6
86. sccssscncecccesscesenseecsesecssecssssesenesensass 13 9 19 7 9 Pyramid ASPECT RAO canada 13 9 13274 Pyramid DISDA Y onre ouk atem dus ciam rodeo cease Qul uted Ru atat te do ud 13 9 13 8 Grid Point Insertion on Boundaries sese 13 9 A ie a De town Su lacu cando od Dt c Lom a ahh Lect 13 9 13 9 2 DIOS tii LP od ie seated 13 9 14 Modifying Entities o ooooocooconocconocconoonoroccorocccnoonoronnoroos 14 1 ESI E 14 1 TAZAS 10 mets 14 2 14 2 1 D tabase LInkag6S ood pid e as 14 2 142 2 Gonnector EIHKagOS ios ccs ve eM nt ams E n Geel Co i ee 14 4 14 2 3 DOMAIN EINKAG CS aaa aiii 14 6 14 2 4 BIOCK EInKadeS osea dario dr toits da d nda E honda AA E padri Gu ad XU mra 14 6 14 3 TTansTOFIatiODS uo osicio oinnia Du Ges ace uc Deren ba x utat Du Go on 14 7 IAS MI I II EU UU TIT 14 7 A O dust Kr S LC Ua LIE 14 8 A M HORN MEME NUMEN 14 9 14 94 01819 inei oh eit hm D o o iia 14 10 p centro P Waneaneees 14 12 14 4 dioe T 14 12 A ceed a 14 13 TAA Cy WINING A saves iaa 14 14 MAATTI 14 14 VA AAs GIOSCSL POIN Errata abba dad aat 14 15 14 5 SI OOD t ER EH Mead oop ee da s EE CL EA M LIAE 14 15 14 6 HO OXIFIUOO o tee out inei etue o udo belt eiut da dra tiem 14 15 ELSE cabe bm EU M Um ED M RE 14 16 14 71 Database ENUOS asi ds 14 16 T r CONOCIO PP E TT 14 16 A a dc II AD h
87. some BCs are not set by Gridgen If namelist style is used for the BCs then Gridgen sets PRESS and TEMP equal to P and T respectively when required by the BC If formatted style is used for the BCs then Gridgen includes the strings PRESS and TEMP in the appropriate fields It is up to you to supply the correct values for PRESS and TEMP Also note that for NPARC a block interface or connection must be a block max face to a block min face Block connections not of this standard will be flagged as Type 3 non conformal BC s NPARC s grid file actually contains both grid and flowfield data Its format is described in Reference 5 17 8 26 OVERFLOW OVERFLOW export supports 3D structured grids only Gridgen writes only OVERFLOW s BCINP namel ist Please note that while Gridgen can create overlapping grids as required for OVERFLOW the hole cutting and other overlap calculations must be computed using some other software such as PEGSUS OVER FLOW s pre processor In fact the grid exported via OVERFLOW s Export Analysis Grid command is actually formatted for PEGSUS The PEGSUS grid file is Fortran unformatted and you are given a choice of single or double precision This grid file also contains the block names 17 8 27 PHOENICS PHOENICS grid format is ASCII PLOT3D but with each grid block written out to a separate file A boundary condition file is exported by Gridgen in the PHOENICS command language 17 8 88 SCRYU SCRYU ex
88. speci fying a control point adding a point at the current 3D cursor location picking an existing point numerically entering the coordinates of the point numerically entering the offset from the current point casting a ray from the current 3D cursor location onto the database and finding the closest point on the database to the current 3D cursor location 2 17 Graphical User Interface Add CPo lat padEnt by Picking pado via Keybrd pad A via Keybrd o by Linear Proj c at Clsest DB Pt 2 8 8 1 At Cross Select the Add CP O at Cross button to enter a control point at the current cross location The Pad Enter key performs the same command When a point is added a small open square is drawn at the point The Blackboard window displays the coordinates of the current cursor location This method of control point placement is best suited for control points that do not have to be positioned precisely 2 8 2 2 By Picking A second method of choosing a control point is by anchoring it to the position of an existing database point or anode To use this option position the cross over the node or database point to which the new control point is to be equated and hit the Pad 0 key or select the Add CP O by Picking button If Gridgen detects a point beneath the cross it checks for hits within a ten pixel cylinder around the cursor a control point will be added at that point otherwise the program will display a message indicati
89. spline 11 8 MRQS 71 8 edit segment 4 2 ending spacing 7 erase segment 4 20 hierarchy insert segment 4 20 least squares fit 4 25 line width 2 27 linkage 174 4 merging duplicates 5 2 modify join 14 19 mirror 4 2 rotate 14 10 scale 74 8 split 14 16 stretch 4 9 translate 4 7 number of 2 periodic 75 8 project 74 13 Quick Menu 2 7 redimensioning 77 1 reducing number of control points 4 23 segment 3D Space Akima 7 3 curve 7 3 line 7 2 branch 7 5 database constrained Akima 7 5 curve 7 3 line 7 3 insert 14 20 rational 7 4 circular arc 7 6 slide points 7 6 conic 7 4 segment file 4 7 setting average spacing setting number of grid points shape 7 smoothing shape 4 23 spacing constraint default beginning 3 3 ending 3 3 split using Merge Nod Con 5 3 subconnector 6 constraint slope Bezier curve 4 22 control point Add At Cross 2 6 Add By Closest Point Projection 2 18 Add By Linear Projection 2 8 Add by Picking 2 18 Add via Keyboard 2 18 Add via Offset 2 18 adding during distribution 77 11 convert to break point 0 database curve fitting 6 5 database surface fitting 6 2 definition 7 edit 14 21 Import segment type 7 7 pole segment 7 8 via 3D cursor 2 17 converting structured grids to unstruc tured 9 5 coordinates determining for a pickable point 2 28 copy block 5 3 break point spacing constraint 7 connector 5 3 connector dimension 2 database entity
90. system Obviously the Display and Button Menu windows are very important However the most important win dow for novice users to monitor is the Message window During command execution this window provides concise step by step instructions Gridgen s screen is repositionable and resizable The screen may cover your entire monitor or you can shrink it down to about one quarter of the monitor During screen resizing the tiled layout of the windows within Gridgen s screen is maintained automatically 2 1 Graphical User Interface Gridgen Gridgen 14 01 1 Blocks 362 Domains 3 884 Connectors 522 Nodes 0 DB ents CFD 3D AWAY MAIN MENU Database V4 Connectors Ipa Domains A Blocks Analysis S W Tutorials Defaults Glyph par Restart Gridgen esc y Quit Gridgen ent V Cons C Doms D Biks BJDB F mu Dflt T I O E AS W A GlyphY TA EN Quit Q Save S Disp a Help IYN T IN O 7h gt lt 0 0 22 The Mouse The mouse and mouse buttons are always used in conjunction with the cursor the small glyph usually an arrow pointing up and to the left that appears on the screen and is moved around the screen by moving the mouse Horizontal and vertical movements of the mouse result in horizontal and vertical movements of the cursor on the screen respectively In Gridgen s default configuration holding down one of the mouse keys while moving the mouse and while the cursor is in the Display window will have the f
91. text to the right of the entity number is the boundary condition type applied to that region Gridgen automatically determines the inter block connections and they are denoted by the text Type 1 in the Browser The data that follows the inter block connection text indicates the block number to which the region connects After selecting the regions BCs will be applied to you then choose a specific BC from a menu that is customized for the current ASW 17 3 Set VCs The Set VCs command allows you to apply a volume condition VC to a block A VC represents a flow solver condition assigned only to the interior cells of a block Each block may only have one applied VC For export VC s can be used to export blocks singly by setting each block s VC to No Volume Condition or they can be used to export merged blocks if all blocks are of the same VC except No Volume Condi tion The list of available volume conditions is dependent on the chosen solver Section 17 1 For example vol ume conditions for the Star CD solver are shown below 17 5 Analysis Software Interfaces STAR CD YCS Create Custom YC No volume Condition Fluid Cell o me Solid Cell 2 Baffle 3 Shell 4 Line 5 Point However if the volume condition you wish to apply is not available you may press the Create button and define your own volume condition as shown below see Section 17 6 CUSTOM VC ATTRIBUTES CustomYCs Create 6 Modify
92. the Defaults menu prior to shell import Refer to Section 15 12 for further details on Feature Extrac tion 44 4 6 IGES IGES files conform to the Initial Graphics Exchange Specification Version 5 1 Reference 15 Gridgen sup ports only a subset of entities contained in the full IGES standard Supported IGES entities include those shown in the following table IGES Entities Supported By Gridgen w CU 4 9 Importing and Exporting Files IGES Entities Supported By Gridgen trimmed surfaces only CE ETT singular subfigure instance The caveats of Gridgen s IGES file support are l A composite curve entity 1s treated as a group Points in composite curves are not added to the composite curve group Vectors are ignored in copious data entity form 3 Each subfigure instance entity becomes a group Subfigure members are duplicated LU d X o Colors specified in the IGES file are replaced by the closest Gridgen color closest hue using HSL color scheme 4 4 4 7 PATRAN Neutral Files The PATRAN Version 2 5 Neutral file contains any number of non rational cubic curves and non rational bicubic surfaces and is named for the software system that initially defined this file type The data in a PAT RAN Neutral file is described in Reference 13 Gridgen supports only PATRAN s packets 32 and 33 curve and patch data respectively All other packets in the PATRAN v2 5 Neutral file are ignored During PAT RAN file import G
93. the Licensed Products do not infringe any patent copyright or trade secret In the event any legal proceedings are brought against Licensee claiming an infringe ment of a patent copyright or trade secret based on Licensee s use of the Licensed Prod ucts PWI agrees to defend at PWI s own expense any such legal proceeding relating to such claim or claims and to hold Licensee harmless from any damage incurred or awarded as the result of settlement or judg ment against Licensee provided Licensee gives PWI prompt written notice within fifteen 15 days of any such claim or the institution of any such claims against Licensee and fur ther Licensee cooperates completely with PWI in providing all necessary authority information and reasonable assistance to enable PWI at PWI s option to settle or defend such claims 8 LIMITATION OF WARRANTY AND LIABILITY PWI warrants that the Licensed Products will perform substantially in accordance with all written specifications furnished to Licensee by PWI if properly used TO THE MAXIMUM EXTENT PERMITTED BY APPLICABLE LAW PWI DISCLAIMS ALL OTHER WAR RANTIES EITHER EXPRESS OR IMPLIED INCLUDING BUT NOT LIM ITED TO IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE WITH REGARD TO THE LICENSED PRODUCTS TO THE MAXIMUM EXTENT PERMIT TED BY APPLICABLE LAW IN NO EVENT SHALL PWI BE LIABLE TO LIC ENSEE OR ANY PARTY FOR ANY SPE CIAL INCIDENTAL INDIRECT OR
94. the curved connector on the right Extru sion with right and without left rotation are shown S NS Aie Sieg E T itis H MESES Hs a er ay i eee Ls TEE e eS si oe ts p e 8 2 6 Smoothing Parameters Several parameters are available for adding numerical smoothing to the solution of the PDEs during hyper bolic extrusion Solutions to systems of hyperbolic PDEs are notoriously unstable so smoothing will always be necessary The hyperbolic smoothing attributes are shown below Smoothing Explicit 1 Implicit 2 Kinsey Bar th3 Volume 4 The hyperbolic PDE attributes you can set are divided into two categories smoothing and spacing The smoothing terms are used to help prevent grid line crossing and to prevent numerical instabilities You can control both the explicit and implicit smoothing terms They are both terms of order one and the implicit smoothing value has to be at least twice the explicit smoothing value If you are having problems with grid lines crossing try increasing the smoothing Smoothing Explicit is used to specify the explicit smoothing coefficient for the transverse direction The default value is 0 1 Smoothing Implicit is used to specify the implicit smoothing coefficient for the transverse direction The default value is 0 5 Smoothing Kinsey Barth provides a means to control the smoothing in the marching direction Values greater than 1 help to prevent crossing of gr
95. the end of an existing connector See Section 7 2 for infor mation on adding segments to connectors 14 9 2 Insert Inserting a segment into a connector is very similar to adding a segment except that the inserted segment is positioned in front of any existing segment instead of at the connector s end When the Insert command is selected you will be prompted to select the existing segment in front of which the new segment will be located Operation then continues as if adding the segment When the segment is completed the start of the following segment is automatically moved to the end of the new segment to maintain continuity If the segment following the inserted segment is a database segment and hence is constrained to lie on a database entity the end point of the inserted segment is moved automatically to the beginning of the data base segment When inserting between two segments the first control point of the inserted segment is automatically set to the end of the preceding segment and does not need to be redefined The exceptions are the inserted data base segments which initialize the new segment s beginning point to the closest point on the entity to the previous segment and modify the last point of the previous segment so that continuity is maintained Also when inserting in front of the first segment you must set the first control point 14 9 3 Erase The Erase command is used to remove segments from a connector Position the c
96. tional clarification Spacing values at individual points on the boundary can be obtained by enabling the hiliter 16 2 11 Orthogonality orthogonality B For structured boundary condition regions domains the orthogonality of gridpoints adjacent to the region is rendered in the Display window and a tabular summary is listed in the Blackboard This function is intended to assist those building viscous structured grids since it in essence provides near wall orthogonality in a very accessible manner Since this function is considered a boundary diagnostic it is only available from the ANALYSIS S W COMMANDS menu The orthogonality function is a measure of the minimum angle between the line formed by a point on the structured boundary and the first point on the interior of the associated block and the surface of the boundary The maximum value or perfect orthogonality is 90 degrees The minimum value is 0 degrees Normals to the boundary are rendered for further directional clarification Orthogonality values at individual points on the boundary can be obtained by enabling the hiliter 16 3 Display Attributes The current Display Style for the diagnostic function is shown on the menu button next to the Display label DISPLAY o wire w Ohide d o solid h 4 solid wir e Spectrum s LIrev s Traffic Light t Display Solid Wire t o Minimum 1 4 Max imum 2 Type In pad Reset 0 pow o M Below 7 L1 In 8 I Above 9 MTets
97. to lie at a specific location since by definition a grid point will lie at every break point By placing a grid point via a break point at a slope discontinuity you would ensure that the dis crete grid point representation of the connector was true to the original shape To have the ability to specify a spacing constraint on a connector s interior rather than just at its ends 11 3 3 1 Setting Clearing and Editing Break Points Add Aat Jat O b all b Remove at O c All c Add CPo at a A connector is divided into subconnectors by identifying a control point as a break point This will divide 11 10 Distributing Grid Points on Connectors Break Points and Subconnectors the current subconnector into two subconnectors at the new break point To do this position the cursor O over the control point and select the Add A at L1 at O menu button If the cursor is not close enough to the control point Gridgen will give a warning Once picked the control point will have a filled triangle drawn on it meaning that the connector has been divided into two subconnectors The current subconnector will be indicated by a yellow color and information pertinent to the current subconnector will be displayed in the Blackboard window Moving the cursor using the mouse or menu button controls across the new break point will change the current subconnector Instead of adding one break point at one control point you can add a break point at
98. two highlighted nodes of the selected connector using the cursor and right mouse button This node will become the beginning point of the new segment If other segments have already been defined in the current connector the Copy segment will automatically be translated to the end of the previous segment If no previous segments have been defined the new copied segments can be trans lated using the picked node as the control point and by positioning the control point in the usual manner This segment type is the only type that can create more than a single segment at a time since the copied con nector may consist of several segments It is important to note that if the connector you choose to copy has any database constrained segments then that constraint will be lost in the copy The shape will be maintained but the underlying definition of control points will be altered 7 2 4 2 Import The Import segment type provides a means of using discrete geometry data from an external source to define a connector s shape Using the File Browser Section 2 5 first enter the name of the file containing the data and then select one of the two highlighted end points of the input data using the cursor and the right mouse button This end point will serve as the beginning of the new segment If other segments have already been defined in the current connector the input segment will automatically be translated so the cho sen node will be located at the end
99. typing in the desired maximum area This value is not explicitly set and is instead set to the area of an equilateral triangle with edge lengths equal to the largest boundary spacing This results in interior trian gles that are no larger than the largest triangles adjacent to the boundary Setting this attribute establishes a global maximum on the size of triangles rather than computing and using a different value in each domain 3 3 1 5 Maximum Angular Deviation The maximum dihedral angle allowed between two triangles sharing an edge may be specified by pressing the MaxAng button and typing in the value in degrees Initially this default is not enabled 3 3 1 6 Maximum Chord Height Deviation The maximum distance allowed between a domain s analytical shape the database on which it is defined and its discrete shape the triangular facets may be specified by pressing the MaxDev button and typing in the value Initially this default is not enabled This default only applies to domains that are database con strained 3 3 2 Blocks Unstructured grid attributes applied to blocks when they are initially created are set by the buttons labeled UnstrBlk in the Defaults menu 3 4 Domain Topology Controls Split Angle 3 3 2 1 Tetrahedral Mesher Memory Limit The maximum amount of memory to be used by the tetrahedral mesher in the Blocks Run Solver Unstructured command is set by pressing the UnstrBIk MaxMem button and entering a value in MBy
100. warning about missing data base references then the grid data will be loaded and the grid will appear to be unchanged However all references to the database will have been permanently lost Also any database constrained segments will have been converted to polylines through the grid points If you change your mind after choosing Read the File Anyway immediately exit Gridgen without saving the Gridgen file run Gridgen again and import the appropriate database files before importing the Gridgen file Abort Don t Bother This command aborts the import process and allows you to proceed with import ing the appropriate database files The importance of Gridgen s grid to database associativity is its ability to provide parametric grid regenera tion Two factors contribute to this capability 1 Gridgen associates grid elements to the database via the entity name and 2 the parametric coordinates of the database are stored in the Gridgen file with any entity that references the database What happens during Gridgen file import is as follows 1 Gridgen begins reading the grid elements from the Gridgen file 2 When the Gridgen file indicates that a grid element references a database entity for example a Line on DB segment defined on database entity wing upper it searches the database for an entity with the same name 3 When Gridgen finds the referenced database entity it evaluates the parametric coordinates u v stored i
101. you to copy the distribution of grid points from any sub connectors in the grid and apply it to the current subconnector After pressing the menu button position the cursor over the subconnector to copy from and press the right mouse button More than one subconnector can be selected as long as all picked subconnectors are pointwise continuous The selected subconnectors are rendered in the Display window as a highlighted string with an orange triangle at the beginning of the string and a blue triangle at the end of the string Each successive subconnector you pick may only be attached at the blue triangle To attach a new subconnector to the opposite end the string must first be reversed in direction using the Reverse the Direction menu button During selection of the subconnector string the last loaded subconnector can be erased with the Erase Last SubConn menu button All loaded subconnectors can be erased with the Restart String menu button When the desired string of subconnec tors to be copied is picked select the Done Picking Subconns menu button When copying the distri 11 8 Distributing Grid Points on Connectors Distribution Parameters bution function you are also given the choice of copying either the exact spacing constraints Copy A Values or the relative distribution of points Copy Scaled Dist Alternately the Abort Don t Copy Dist menu button will abort from the command retaining the previous distribution If the Copy Scaled
102. z are calculated from direct evaluation of the database entity The result is a grid that lies exactly on the data base entity If you apply Parametric TFI to grids that do not reference one and only one database entity you will be warned and the grid points will not be updated Parametric TFI is the first method that Gridgen tries to apply by default to create the initial surface grid for 12 3 Grid Methods for Structured Domains and Blocks domains Parametric TFI is not available for blocks 12 1 6 Parametric Fit TFI Param Fit TFI is similar to Parametric TFI in that it will produce grids that lie on the database shape As is the case for Parametric TFI the grid points will be on a single database surface entity However it is much more general than Parametric TFI because the boundary points do not have to lie on a single database entity Two less stringent conditions must be met before Parametric Fit TFI may be applied 1 Acertain percentage of the grid s boundary points must reference database entities of any kind 2 Allof the grid s boundary points must lie within the extent box of at least one database surface entity If the grid passes the two tests above then the grid s boundary points are projected using closest point onto each of the candidate according to 2 above database surfaces The projection that results in the smallest cumulative movement of the boundary points determines the database entity to use for Para
103. 0 3 Assembling an Unstructured Block Each face in a 3D unstructured block represents a closed surface on the boundary of the volume grid The boundaries of an unstructured block can be both structured and unstructured domains Wherever a structured quadrilateral domain 1s included in an unstructured face pyramid cells are used to transition from the struc tured portion of the face to the unstructured tetrahedral volume grid Only triangular domains can be added to a 2D unstructured block The first face of a 3D unstructured block is the closed outer boundary of the volume grid Additional faces if any are the closed boundaries of voids inside the volume Block assembly cannot be started until all domains on that block s faces have been created Section 9 3 Each 3D unstructured block requires at least one face Since a single domain cannot be created so that it closes on itself at least two domains must be added to each face Therefore you must have created at least two domains before a 3D block can be assem bled Since a 2D block only consists of one face at least one domain must be created prior to assembling the block After pressing the Create button begin assembling a face by pressing the Assemble Faces button and Add 1st Face button as described in the following section Repeat the process until all of the block s faces have been added 10 3 1 Adding Faces to an Unstructured Block An unstructured block face consists of tw
104. 16 The 3D Cursor Control Point Creation Xs and Ys 3D cursor is free to move in screen x and screen y X Only The 3D cursor moves in body x only Y Only The 3D cursor moves in body y only Z Only The 3D cursor moves in body z only Xs Only The 3D cursor moves in screen x only Ys Only The 3D cursor moves in screen y only Zs Only The 3D cursor moves in screen z only Normal to DB Surface The 3D cursor moves in the direction defined by the normal vector of the data base surface on which the previous control point was defined The keypad keys listed below may be used to restrict the 3D cursor s movement also Movement Restriction Hot Keys hot key 2D database coordinate restriction NN m 00000 If the current Gridgen command involves moving the cursor on a database entity for example creating a Line on DB segment then mouse movement translates into cursor movement in a slightly different way Horizontal and vertical mouse movement will still cause screen x and screen y movement of the cursor However the cursor will be further constrained to move along the database shape 2 8 2 Control Point Creation The 3D cursor s purpose is to allow you to create control points There are several places in Gridgen where this takes place for example segment creation and database point creation As the 3D cursor is moved across the screen you will be tasked with specifying control point locations There are six methods of
105. 30 days written notice to PWI PWI may terminate this License for any material breach by Licensee of the terms and conditions contained herein upon thirty 30 days written notice to Licensee Licensee will have thirty 30 days from the date of such notice to cure the breach and if the breach is cured to the sat isfaction of PWI this License will remain in full force and effect Upon termination Licensee shall promptly 1 discontinue use of the Licensed Products ii remove the Licensed Products from any software in Licensee s possession or control that incorporates or uses the Licensed Products in whole or in part iii erase or destroy any of the Licensed Products contained in the com puter memory or data storage apparatus under the control of Licensee Licensee s obligations under Section 6 shall survive any termination of this License 11 GENERAL TERMS The entire agreement between the parties is contained herein and in a valid Purchase Order or Contract which supersede all proposals oral or written and all other communications between the parties relating to this Agreement and it may be executed in any number of coun terparts each of which shall constitute an orig inal and all of which taken together shall constitute one and the same Agreement This Agreement is not assignable by Licensee with out prior written permission from PWI The section headings and subheadings herein are for convenience only and shall n
106. 4 constraining to a database 9 9 copy 15 3 create 9 Auto Complete 9 7 Auto Next Edge 9 7 Auto Save 9 8 Next Edge 9 6 On Database Entities 9 9 periodic 75 8 Previous Edge 9 6 Reorient Edge 9 8 structured 9 7 unstructured 9 4 example 9 4 from structured 9 8 multiple loop 9 4 parametric 9 7 parametric fit 9 7 standard 9 7 with holes 9 4 create during block creation 70 6 data hierarchy 74 6 default settings 5 4 decay factor 5 4 initialization 3 4 maximum angular deviation 3 4 maximum chord height deviation 3 4 maximum triangle area 5 4 minimum triangle area 5 4 delete 75 4 disable 75 7 display 2 20 duplicate 9 77 enable 5 7 enable disable 2 20 foreground control function default 5 5 hierarchy 1 2 linkage 4 6 linkages during modification 74 6 modify join 74 20 mirror 4 2 rotate 14 10 scale 14 8 split 14 17 stretch 4 9 translate 4 7 number of 2 overlapping 9 12 overlapping and adjacent 9 1 periodic 75 8 prohibited 9 72 project 74 13 Quick Menu 2 7 should be avoided 9 70 structured algebraic 9 3 algebraic grid method 2 database constrained 9 3 pole 9 10 transfinite interpolation 9 3 parametric 9 3 parametric fit 9 3 standard 9 4 topology default settings 3 5 join angle 3 5 split angle 3 5 DTNS asw 77 10 duplicate grid entities removing 75 11 E elliptic partial differential equations 72 4 elliptic PDE solver attributes 72 6 background control function 72 8 type fixed grid 72
107. 4 foreground control functions 2 9 Ortho TFI 2 3 Orthogonality diagnostic function 6 7 OVERFLOW asw 17 13 P paper and report references 79 7 Parametric Fit TFI 2 4 Parametric TFI 2 3 path based extrusion 8 3 attributes 6 4 PATRAN grid export to 4 17 import as database 4 70 periodic 5 8 Permanent reference surface 6 4 PHOENICS 7 5 picking 2 5 by page 2 11 By Text 2 11 from Browser 2 9 from Display window 2 8 get Ist 2 7 get last 2 71 in Box 2 11 on Box 2 Pick by Expression 2 71 Set to off 2 11 Set to on 2 Set to tog 2 Sort By 2 11 special controls 2 0 PLOT3D grid export to 4 17 import as grid 4 4 PNG file PostScript file 2 27 point anchor 4 6 14 10 break point 0 closest point projection 4 5 control point create 2 7 definition 7 edit 74 21 create offset curve through 6 3 created during intersection 5 5 database 3 point plane 6 6 create average 6 2 fit curve through 6 5 fit surface through 6 2 point normal plane 6 6 grid point algebraic methods 2 display of 2 23 effect of modifying an entity on 14 6 14 7 handle 14 10 14 11 node definition 7 number of database render points 2 27 origin for spherical projection 4 5 rotation point move to 3D cursor 2 9 pick 2 27 same grid point tolerance 3 7 same point node tolerance 3 7 slide point 7 6 slope point 4 22 Polar TFI 2 3 pole domains 9 70 Pole TFI 2 4 Previous Edge 9 8 Pro E prt asm import as database 4
108. 7 Name VolCond 3 n Delete 8 Del All 9 3 i Done ent Name Text The button labeled Name shows the default name for the new volume condition If you press the button you may type in your own name which will then appear on the button ID Number Pressing the button labeled ID lets you type in the numeric code to be used for the new vol ume condition This numeric value is shown on the button 17 3 1 Applying VCs Upon invoking the Set VCs command you select blocks from the Browser window For example the Browser text may look like The numeral in the first column 1 through 20 in this example represents the block number Each region in the block is then listed according to the name assigned to the block either by Gridgen or the user The text to the right of the colon 1s the volume condition type applied to that region After selecting the regions VC s will be applied to you then choose a specific VC from a menu that is customized for the current ASW For any newly created or imported block Gridgen will automatically assign the default VC of FLUID 17 4 Examine It is possible to obtain diagnostic information for block boundaries regarding wall adjacent cell spacing and orthogonality A detailed description of the Examine command and the functions specific to boundaries can be found in Section 16 17 6 Custom BCs Creating Editing amp Deletion Applying VCs 17 5 Custom BCs Creating Editing amp Deletion CustomBCs
109. 8 LaPlace 72 8 Thomas Middlecoff 72 8 boundary condition 2 3 fixed 12 13 floating 12 13 orthogonal 2 4 foreground control function 2 9 angle constraint 2 7 form 2 9 Hilgenstock White 2 0 Steger Sorenson 2 0 selecting boundaries for 2 9 setting 2 9 spacing constraint 72 10 relaxation factor 2 7 shape 72 11 database 2 2 fixed 2 12 free 72 12 background control function default 5 5 creating subgrids for 2 4 foreground control function default 5 5 preparing Glyph files for batch run 4 20 running 2 4 enable block 75 7 database entities 75 7 domain 5 7 enable disable in Display menu 2 20 entity display display style 2 23 render density 2 26 render mode 2 25 display of 2 22 selecting 2 8 selecting multiple 2 8 selection By Text 2 7 from Browser 2 9 from Display window 2 8 get Ist 2 7 get last 2 7 in Box 2 11 on Box 2 Pick by Expression 2 71 Set to off 2 11 Set to on 2 Set to tog 2 Sort By 2 11 special controls 2 0 analysis software grid 4 9 boundary condition file 4 9 FIELDVIEW boundary surface file 4 9 FVUNS grid 4 17 Glyph block smoothing batch files 4 20 Glyph rc file 4 19 NASTRAN grid 4 17 entity selection by page 2 11 Erase reference surfaces 6 6 Examine 6 PATRAN grid 4 17 PLOT3D grid 4 17 QuickSave file 3 6 block hiliter 6 Cells 76 16 connector hiliter 6 Crinkle 6 5 Diagnostic Function 6 2 Aspect Ratio 6 5 Database 6 3 Jaco
110. 8 Fixed Grid Fixed Grid background control functions are used to eliminate grid line slope discontinuities from the grid s interior while preserving the rest of the grid Its effects are very subtle The final grid will exhibit the same general features as the starting grid including regions of clustering and orthogonality but any slope discon tinuities will be smoothed This method should not be used unless the starting grid 1s of adequate quality except for the discontinuities 12 8 Elliptic PDE Methods Foreground Control Functions 12 2 5 Foreground Control Functions Foreground control functions are used to influence the distribution of grid points near the grid boundaries They are calculated by adjusting the control functions locally so the grid points one layer inward from the boundaries will satisfy a specified spacing and angle constraint with all other interior points blended smoothly Spacing constraint refers to the distance between a boundary grid point and the grid point one layer inward and angle refers to the angle that the grid line between these two points makes with the bound ary itself The current foreground control functions for each boundary of the focus grid are displayed in the table in the center of the Blackboard The left column lists how the spacing constraint is calculated the center column lists how the angle constraint is calculated and the right column describes the type of foreground control function With
111. Ak Linear The angle constraint is blended linearly from the boundary into the interior Exponen An exponential function is used to rapidly decay the angle constraint into the grid s interior This is the default blending function type Decay This command allows you to specify the number of grid points away from the boundary at which the angle constraint portion of the foreground control function will be equal to 10 of its boundary value The default value is 6 Smaller values are more stable but may dissipate the angle constraint too quickly Negative decay values are not allowed 12 2 6 Surface Shape Gridgen s elliptic PDE solver is a true surface solver in that grid points may be redistributed directly on a specified geometrical shape This command is used to specify how the shape is maintained during elliptic solution The following three techniques are available 12 11 Grid Methods for Structured Domains and Blocks Shape Free u Fixedf DB 4 Surface shape attributes are only available for domains 12 2 6 1 Free The shape is computed implicitly as a result of the elliptic PDE solution for the Cartesian coordinates x y z If the grid is constrained to the database and you run the elliptic solver with the free shape attribute the grid will no longer conform to the database This is the default shape attribute When this shape attribute is applied with LaPlace background control functions and no foreground co
112. Also note that since the unstructured solver for blocks is a strict Delaunay method the button for Smooth Only does not appear RUN UNSTRUCTRD SOLVER Initialize t Release Vol Grid LI Set Solver Attribs Ag Done Save ent Abort Don t Save esc Help Release Vol Grid This command is an explicit means of purging the unstructured volume grid from memory This will minimize Gridgen s memory usage and the size of the Gridgen 99 file at the cost of having to regenerate the volume mesh when it is needed The equivalent command for structured blocks is to apply the algebraic solver 13 2 Setting Attributes When the Set Solver Attribs command is invoked the Browser window will display the current attributes 13 2 Setting Attributes of the focus grid as shown below The various attributes may be set using the menu buttons Domain Num 1 1362 pts shape 1 pckd DBs 100 0 Closest Pnt Projection Relaxation Q 0 Min Edge Len Cbndary 2 Cactual 1 Max Edge Len Cbndar 12 3794E 000 1594E 000 8626E 000 Cactual 56309E 000 Max Surf Dev not applied Cactual unknown Max Ang Dev not applied Cactual unknown Bndry Decay 1 00000E 001 9 6 1 SET UNSTRUCTRD SOLVER ATTS Focus Next njPrev n Apply tojO Focus All s Surface Shape Params 1 Relaxation Parameter 2 Grid Control Params 3 Done Setting Attributes esc Help Focus Next Moves focus to the next grid in numerical order of
113. Backward Compaltibility oooooocooocococococonocononnonnnn oo 4 3 42 QUICK IMPO eie RED aei ia ooi odere es 4 3 4 3 Export Gridgen File itor o Pene Ee eue ede mede deve espe tte ass 4 3 4 4 Importing Database Files ooocoocccocccconnccccccoconoconnonornonannonnnnnonononannnnons 4 4 DAE o ie 4 6 pa A OL WN sepu A oa E IE LE 4 6 Ao al a A te EDI MINE MINUM SE Se RN 4 6 44 A FING TD esr T 4 6 4 4 5 Duplicate Name Detection ccsscccseccsssecseeceecsesensueccsecseeseuenseenentes 4 10 4 4 6 Automatic Entity Grouping on IMport cococcncnoccnccccncnoconononononoconnnarnnnos 4 11 4 4 7 Backward Compatibility esses 4 11 495 ExDOITt DalaDase Fil ox A E 4 12 4 6 Import GHG POTES ito iii decente tnodo 4 13 AO Eid ore 4 14 AGZ FOMA nene eaa ea reae 4 15 SA OA EN T 4 15 4 6 4 Importing Structured Grid Points ooccococcnccoconoccnnncononocononoconononannnnos 4 15 4 6 5 Importing Unstructured Grid Points oocccconnnnocncnonncncononannnnannonononanons 4 16 47 EXPO GHG POIDS oec ebat n dbi a eos tebe eats dea ae Meo its 4 16 Be Fe Evi E 4 17 Ai A icut uus e atu ie du E oer uad 4 17 4 o9 PESO ri dl Urat D DRE 4 18 4 7 4 Exporting Structured Grid Points cococccococonccoconcccnnonononocononononononannnnos 4 18 4 7 5 Exporting Unstructured Grid POINTS
114. Bell b Sens J Rst gt t Ap Q Aut lt r fAll r GetOri 19 26 us ed Jus e6 Putori 1p Jap es fea e5 r ILightSrc OO0bj o 4User_f Photo bmp j png n ps i Zoom In z Out z Done ent He1p Edit Dspla These three commands DB Dom Fac allow you to change the display of database entities domains and block faces respectively Section 2 10 En Disable These three commands DB Dom BIk allow you to enable and disable database entities domains and blocks respectively Section 15 6 Show DsbIdDB This toggle button controls whether or not disabled database entities will be rendered in the Display window Not displaying disabled entities reduces the visual clutter in the Display window By default this toggle is off disabled database entities will not be displayed Show EnbIdDB This toggle button allows you to easily turn off the display of all database entities without having to disable them By default this toggle is enabled When it is disabled enabled database entities are not drawn while in the DISPLAY COMMANDS menu and are drawn in a sparse mode elsewhere Show Con GPs This toggle button controls the display of grid points on connectors By default this tog gle is off When this toggle is on the grid points on all connectors will be rendered as small filled circles in the connector color Show Nods Cons Doms These three toggle buttons allow you to turn on and off the display of
115. Create c Modify m Delete d Del All a Create Pressing this button lets you create a new custom boundary condition as described in Section 17 2 Modify Allows a selected custom boundary condition to be changed to a new Name ID or Type Delete Removes selected custom boundary condition from the list of available boundary conditions for the current analysis software Any BC regions already specified with a deleted custom boundary condition return to the unspecified state Del All Removes all the custom boundary conditions from the list of available boundary conditions for the current analysis software Any BC regions already specified with a deleted custom boundary condition return to the unspecified state 17 6 Custom VCs Creating Editing amp Deletion Custom Cs Create 6 Modify 7 Delete 8 De1 All 9 Create Pressing this button lets you create a new custom volume condition as described in Section 17 3 Modify Allows a selected custom volume condition to be changed to a new Name or ID Delete Removes selected custom volume condition from the list of available volume conditions for the current analysis software Any VC regions already specified with a deleted custom volume condition return to the unspecified state Del All Removes all the custom volume conditions from the list of available volume conditions for the cur rent analysis software Any VC regions already specified with a deleted custom volume condition return
116. Gridgen File Backward Compatibility composite n a ASCII default single binary import only double default ASCII default binary After having determined the file s attributes Gridgen reads the file imports the entities and creates graphi cal objects that will appear in the Display window If for any reason reading the file produces an error bad attributes bad data in the file Gridgen will display a warning and then invoke the FILE ATTRIBUTES menu under the assumption that the attributes were determined improperly Use the menu to set the appro priate attributes and press Done to try to read the file again or press Abort if you think there is a problem with the file itself The Database Import command may also be invoked via the Database menu The FILE ATTRIBUTES menu is shown below L FILE ATTRIBUTES o network 1 Patran 2 composi te 3 segment al IGES 5 O NASTRAN NASTRAN L 7 STL 8 VRML 9 Pro Eng 4 CATIA V4 amp STEP 7 style otras io 1 pM a ob y b O al precision Osingle s double d ES Off b Done ent Abor t esc Help 4 5 Importing and Exporting Files 44 1 Style style jOGridgen g ePLoT3D 1 The style attribute pertains to the particular formatting of file types containing discrete data The style attribute is a subordinate to the type attribute For example database files of type
117. I Polar TFI method is best suited for grids intended to be shaped like a body of revolution Polar TFI requires you to either enter or pick via the Display window two non coincident points lying on the intended axis of revolution Gridgen then transforms the x y z grid point coordinates on the boundaries to polar coordi nates r amp z relative to the axis of revolution The TFI algorithm is applied to each of the polar coordi nates Finally the polar coordinates are transformed back to Cartesian coordinates Polar TFI is not available for blocks Polar TFI bottom is compared to Standard TFI top in the figure below E F 7 LAL EAT ETT D Ht Ti i Up i HH i pool SS ri 12 1 4 Ortho TFI Ortho TFI uses a generalized form of the TFI equations allowing the specification of first derivative values at the grid boundaries First derivatives are computed on the boundaries so grid lines intersect the bound aries orthogonally with spacing interpolated from the adjacent boundaries Ortho TFI is not available for blocks 12 1 5 Parametric TFI Parametric TFI can be used when all of the grid points on the boundaries of a grid are on the same database entity In this method the basic TFI algorithm is applied to the parametric database coordinates u v Once the parametric coordinates u v are computed at each grid point the physical coordinates x y
118. J L L L L L 5 L Ld De LJ LJ LJ LJ LJ Size Joi 1 o j 2 ok a o v 4 For grid entities only the cell size is rendered in the Display window and a tabular summary is listed in the Blackboard For structured domains the radio buttons I j and A indicate which cell size you would like to examine the i j direction lengths or the cell area respectively Only the cell area measure is available for unstructured domains Quadrilateral cell area is computed by taking the minimum of two areas computed by triangulating the cell along its two diagonals For structured blocks the radio buttons i j K and V indicate which cell size you would like to examine the i j k direction lengths or the cell volume respectively Only the cell volume measure is available for unstructured blocks Hexahedral cell volume is computed using the method of Davies and Salmond Refer ence 6 which uses pyramid decomposition The Size function is a point based measure Gridgen uses the current i j k coordinate differenced with the index 1 point in the computational direction chosen Furthermore this function will be calculated across entity boundaries as long as the adjacent entities are loaded into Examine as well Otherwise the stencil direction will be reversed as necessary at the entity boundary If a topological hiliter Section 16 5 is active the second index 1 point used in the calculation will be rendered with an open di
119. MENU button Defaults d indicates that the SET DEFAULT VALUES menu may be invoked by pressing the control and d keys simultaneously Gridgen has three special hot keys that correspond to commands that appear on most every menu These keys are named according to the color of the text that appears on the menu button and are described below Done ent The blue button corresponds to commands of the form Done or Continue The enter key is always the blue button s hot key Help The green button invokes Gridgen s on line help The question mark key is always the green button s hot key 2 3 Graphical User Interface labor t esc The red button corresponds to commands of the form Abort or Exit The escape key is always the red button s hot key 2 3 3 Toggle Buttons Menu SmalTxt 7 f On Left5 O QukMnu Aca M Warp w Some of Gridgen s menu buttons act as a toggle for the setting of a certain switch For example in the DIS PLAY COMMANDS menu there is a toggle button called Menu SmalTxt that determines whether to use a large or small font for menu button text Toggle buttons can be identified by the red square on the button If the red square is empty the setting denoted by the button text is inactive If the red square contains a red check mark the setting is active Pressing the toggle button changes the state of the setting 2 3 4 Radio Buttons Bokgr_ CF LaP1 1 Ttan 2 OFixd3 Some of
120. Mt Pyramids Shrink 1 0 i Histoaram m 10 j Done ent The manner in which the diagnostic function is rendered for example colored grid lines versus solid fill and the values of the colors used for the rendering are controlled by the DISPLAY menu The default dis play style is Solid Wire which draws the diagnostic measure by filling in each cell with a color and outlin ing each cell in the background color Each diagnostic measure saves its last display attributes and subsequent rendering of that diagnostic function will be initially rendered using the saved settings 16 7 Diagnostic Functions 16 3 1 Display Style Display Style wire w o hide d solid h solid vir e The radio buttons wire hide solid and solid wir under the label Display Style indicate whether the diagnostic function is to be rendered in the Display window by colored grid lines left colored grid lines with hidden lines removed 2nd from left solid shading of filled grid cells 2nd from right or combined solid shading with wireframe right M Sh teeth TAN NA PRSE UN SENS 53 ati oS i Y Y O AA t des M 5 t E C xx se eS i e CS j E a8 N F E 1 B a M Dita Rit AO LT TE HT well t un Aum ul NN MM ENS a M Hy sU n XN d QUINA L1 a T M 16 3 2 Color Bar Type Color Bar Type Spectrum s rev s Traffic Light t Th
121. NS import is available for tetrahedral grids only Both ASCII and binary format FV UNS files are available although no wall information is available in the binary format 4 6 2 Format Format refers to the data format in the file format ASCII a 2 binary Ab Sunfrmtd n ASCII is a human readable format that is very portable between computers of different types However ASCII files will require significantly more disk storage than binary or Fortran unformatted files and will take longer to import and export binary is a compact format but suffers from a lack of portability between big endian and little endian computers unfrmtd refers to Fortran unformatted a format similar to binary in that it is very compact However binary and Fortran unformatted formats are not interchangeable Fortran unformatted format 1s available for importing Gridgen and PLOT3D style structured surface and volume grids FV UNS data files and for exporting some types of analysis software data 4 6 3 Precision Precision refers to the word size 1n the data file single s double d single precision means that real floating point data will be written as 4 byte words double precision means that real floating point data will be written as 8 byte words 4 6 4 Importing Structured Grid Points The Grid Pts Import command allows you to import the following structured grid types 4 15 Importing and Exporting Files St
122. Numerical Grid Generation ed by Thompson J North Holland NY 1982 pp 137 170 Soni B K Two and Three Dimensional Grid Generation for Internal Flow Applications of Computa tional Fluid Dynamics AIAA paper no 85 1526 Sorenson R L The 3DGRAPE Book Theory Users Manual Examples NASA TM 102224 July 1989 Steinbrenner J P Chawner J R and Matus R J Evolution of Gridgen s Data Hierarchy to Unstruc tured Grids from 6th International Conference on Numerical Grid Generation in Computational Field Simulations ed by Cross M et al publ May 1998 by NSF Research Center for CFS Mississippi pp 833 842 Steinbrenner J P and Chawner J R Gridgen s Synergistic Implementation of CAD and Grid Geome try Modeling from Numerical Grid Generation in Computational Field Simulations ed by Soni B K et al publ by Engineering Research Center for CFS Mississippi 1996 pp 363 372 Steinbrenner J P and Chawner J R Automatic Structured Grid Generation Using Gridgen Some Restrictions Apply NASA CP 3291 Surface Modeling Grid Generation and Related Issues in CFD Solutions NASA Lewis Research Center Cleveland OH May 1995 Steinbrenner J P and Chawner J R Incorporation of a Hierarchical Grid Component Structure into GRIDGEN AIAA paper no 93 0429 AIAA 31st Aerospace Sciences Mtg Reno NV Jan 1993 Steinbrenner J P and Chawner J R Recent Enhancements to the GRIDGEN Str
123. SAERO asw 17 15 W WIND asw 17 15 window Blackboard 2 Browser 2 7 picking items from 2 9 Button Menu 2 Display 2 7 Message 2 Status 2 Text Input 2 7 Version 2 7 Z zoom box 2 15 undo 2 16 using orthonormal view 2 21
124. Split Join Of course the commands for working with the grid points also follow this parallelism Dimension for assigning a number of grid points to a connector Distribute for clustering grid points along a connector and the Solvers for the domain and block grids The object of this command parallelism is obvious once you know how to copy and translate connectors for example you will also know how to copy and translate database entities domains and blocks 1 4 Planning Your Grid Before you start generating a grid with Gridgen or by any other means you should first consider many Introduction issues related to the analysis For example if your grid is to be used for a CFD analysis you can save a lot of time and avoid costly false starts and rework by considering all of these items before you begin generating your grid 1 4 1 Define the Modeling Goals What specific results are required from the analysis Are you just looking for general flow patterns or more detailed information about pressure heat transfer and separation locations in the flow field What degree of accuracy is required Are you looking for trends or absolutes How much time do you have to complete the analysis Do you have the time both labor hours and com puter to analyze the complete system or can you obtain meaningful results by analyzing only the component of interest 1 4 2 Identify Your Grid s Constraints What types of grid topologies can your
125. Swansea UK 1988 pp 137 146 Klopfer GH and Molvik G A Conservative Multizonal Interface Algorithm for the 3D Navier Stokes Equations AIAA Paper 91 1601 CP June 1991 Matus R J Steinbrenner J P and Chawner J R Preprocessing Complex Geometries for Computa tional Analysis presented at the ASME Energy Sources and Technology Conference 01 03 Feb 1999 PDA Engineering Inc PATRAN Plus User Manual Vols I and II Release 2 5 Publication Number 2191025 1990 Raj P Sikora J S and Olling C R Three dimensional Euler Navier Stokes Aerodynamic Method TEAM Vols I III AFWAL TR 87 3074 United States Air Force Wright Research and Development Center June 1989 Reed K The Initial Graphics Exchange Specification IGES NISTIR 4412 National Institute of Standards and Technology September 1991 Reymond Michael and Miller Mark MSC NASTRAN Quick Reference Guide Version 69 The Mac Neal Schwendler Corp 1996 19 1 References 17 18 19 20 21 22 225 24 25 26 PA 28 29 30 31 32 35 19 2 Rizzi A and Eriksson L E Transfinite Mesh Generation and Damped Euler Equation Algorithm for Transonic Flow Around Wing Body Configurations AIAA paper no 81 0999 1981 Shoof Larry A and Yarberry Victor R EXODUS II A Finite Element Data Model Sandia Report SAND92 2137 September 1994 Smith R E Algebraic Grid Generation
126. Tetrahedral Iterations The Tetra Iterations attribute allows you to run the tetrahedral solver when a single run produces a bad mesh and additional iterations can be performed to improve the quality of the grid in inadequate regions The number of iterations always starts from an initialization for example iterations 2 followed by an appli cation of iterations 4 will result in a total of 6 runs of the tetrahedral solver Default 21 maximum 10 19 6 3 Tetrahedral Size Factor The Tetra Size Factor attribute controls the relative size of the tets on the volume interior Enter a factor between 1 and 0 0 small 1 large Default 0 5 13 7 Pyramid Mesh Attributes Pyramid cells are created by Gridgen adjacent to any quadrilateral cell on the faces of an unstructured block Obviously they result from the use of structured domains during unstructured block face creation Section 10 4 The pyramid generation process is as follows 1 The area of the quadrilateral cell is computed via triangular decomposition 2 The normal vector to the quadrilateral cell is computed by averaging the cross products at the four cor ners 3 The centroid of the quadrilateral cell is computed by averaging the location of the four corner points 4 The nominal pyramid height is computed as the square root of the quadrilateral area 5 The true pyramid height is obtained by multiplying the nominal pyramid height by the user specified aspect ratio
127. This radio button lets only connectors on the boundary of the developing face be candi dates for merging with their neighbors FaceFltr Outsd This radio button filters lets only connectors outside the current face boundary be candi dates for merging Save As Baffle Face This command is only available for unstructured block faces For structured grids baffles must be integrated into the block face topology For structured and unstructured grids baffles should be assigned as walls within the Set BCs command Once the free edges have been eliminated from an unstructured face or when a structured face has a rectan gular computational mapping the following command appears Save the Face ent off 0 Face 8 o Faces Save the Face Save the current domain s as one face of the block When a face is saved its outline is rendered in white and its grid points are rendered in blue in the Display window AutoSave Off This radio button is the default setting which requires manual saves of all faces AutoSave Face This radio button instructs Gridgen to automatically save each selected domain as a face AutoSave Faces This radio button instructs Gridgen to save all possible faces and baffles in conjunction with the All command This command is available for unstructured grids only Mesh Both Sides h 10 5 Creating Blocks Mesh Both Sides For nested faces enable this toggle to have Gridgen created tetrahedral mesh thr
128. VIEW Unstructured format The unstructured generic file supports hexahedral and tetrahedral volu metric elements only See Section 18 7 for more information If your grid contains any unstructured blocks the unstructured format is automatically chosen as the generic format If all blocks contain structured grids you are given the option to export the grid as either structured or unstructured and choose the format as shown below GENERIC SOLVER ATTRIBUTES structured 1 o unstructured 2 Format eascii al o binary 4 o unfrmtcd 5 17 8 2 ADPAC ADPAC supports structured multi block grids only Gridgen exports two files for ADPAC the boundary data boundata file and the grid mesh file Any physical values such as pressure and temperature required by the boundary data file are set to zero It is up to you to edit this file and supply the correct values prior to running ADPAC ADPAC s grid file is a Fortran unformatted double precision PLOT3D multi grid file Only 3D grids supported 17 8 8 CFDSHIP lowa CFDSHIP Iowa supports 2D and 3D multi block structured grids 17 8 4 CFD CFD supports all cell types that can be created in Gridgen Both 2D and 3D grids are supported Multiple data files are written in big endian binary regardless of platform 17 8 Export Analysis Data Grid and BCs CFX 4 17 8 5 CFX 4 CFX 4 supports structured 2D and 3D grids Gridgen creates an input file for CFX 4 c
129. a S et al Pineridge Press Ltd Swansea UK 1988 pp 539 548 Steinbrenner J P Karman S L Jr and Chawner J R Generation of Multiple Block Grids for Arbi trary 3D Geometries from AGARDograph No 309 Three Dimension Grid Generaion for Complex Configurations Recent Progress ed by Yoshihara H Mar 1988 pp 40 55 34 35 36 34 38 39 40 41 42 43 44 Thomas P D and Middlecoff J F Direct Control of the Grid Point Distribution in Meshes Generated by Elliptic Equations ATAA Journal Vol 18 pp 652 656 1979 Thompson J F Thames F C and Mastin C W Boundary Fitted Curvilinear Coordinate Systems for Solution of Partial Differential Equations on Fields Containing Any Number of Arbitrary Two Dimen sional Bodies NASA CR 2729 July 1977 Vinokur M On One Dimensional Stretching Functions for Finite Difference Calculations NASA CR 3313 1980 von Lavante E Elliptic Generation of Two Dimensional Grids For Internal Flow Calculations TEES Technical Report No 12415 82 01 March 1982 Walatka P P and Buning P G PLOT3D User s Manual NASA TM 101067 1989 White J A Elliptic Grid Generation With Orthogonality and Spacing Control On An Arbitrary Num ber of Boundaries AIAA paper no 90 1568 June 1990 Winslow A Equipotential Zoning of Two Dimensional Meshes Journal of Computational Physics Vol 149 pp 153 172 1966 http www vrml org
130. a Gridgen composite file The composite file includes entity names 15 1 2 Blocks Each block must have a unique name of no more than 15 characters Gridgen automatically assigns a name to each block when it is created The default block name consists of combinations of the uppercase alpha betic characters For example the first 26 blocks created will be named A B Z You can assign a more descriptive name to a block using the ReName command in the Block Modify menu Gridgen checks for duplicate block names and if necessary you will be prompted to enter another name It is strongly recommended you not assign block names that contain the block number for example block19 Because Gridgen s blocks change numerical order quite frequently due to grid editing the name will very quickly become different from the block number In other words the block with name block19 may actually be block number 2 15 2 Group The Group command allows you to select a set of a particular entity type and apply a name to that set to use as a handle for other regular operations 15 2 1 Database Entities To group a set of database entities follow this procedure starting from the DATABASE COMMANDS menu 1 Press the Group button Select the entities to be included in the group Press the Done button ee S Enter the group name via the keyboard Group 4 Ungroup AB The Group database command allows you to assemble one or more entities into a logical c
131. a structured block left red and a prism block yellow right The center block is unstructured therefore no computational surface is available 16 14 Reference Surfaces Blocks Crinkle Gridgen finds the cells in the volume mesh that are intersected by a x y or z physical hiliter For every touched tetrahedral cell that has only three of its four faces cut by the plane the fourth un cut face becomes part of the crinkle surface The selection of the uncut face is also biased based on which half of the volume grids extent box the hiliter is in The resulting reference surface is not flat Rather it has the appear ance of a crinkled sheet of aluminum foil hence the name An example of a crinkle surface is shown below for a structured unstructured and prism block left to right Flat Gridgen calculates a flat surface through a volume grid at the location of a x y or z physical hiliter Gridgen creates the reference surface from the actual intersection of the hiliter with every cell in the volume mesh The resulting surface is planar as shown in the example below 16 15 Diagnostic Functions Cells Gridgen calculates a complete cell surface through a volume grid at the location of a x y or z phys ical hiliter The reference surface is composed of every cell touched by the hiliter Not only is the reference surface not planar it has thickness as shown below Erase Cur To erase only one of several reference sur
132. ace added to the block The block image in the Display window is color coded to indicate the index orientations according to the following table 10 7 Creating Blocks Computational Axis Colors coordinate color orange The Display window also shows the direction of increasing computational coordinate along each block edge using color coded arrows The block s dimensions number of grid points are listed in the Blackboard using the same color coding The orientation of the computational axis system may be changed at any time using the ReSpecify n G button Section 15 7 A structured block s initial volume grid is automatically created using Standard TFI Section 12 1 A unique name is assigned automatically to each block when it is created The default block name consists of combinations of the uppercase alphabetic characters For example the first 26 blocks created will be named A B Z You can assign a more descriptive name to a block using the Name command Section 13 1 10 8 11 Grid Methods for Connectors 11 1 ReDimension The ReDimension command is used to assign a number of grid points to one or more connectors The ini tial dimension for new connectors is zero undimensioned You may override this value by using the Defaults command Section 3 Connectors are the only entity to which you can assign a number of grid points The dimensions of domains and blocks are defined implicitly by the connectors
133. ackboard indicates the current cross position and translation offset When the handle is repositioned the entity is translated along the vector defined from the initial to final handle locations The Enter Transl Offset command allows you to type in the amount of translation in each of the x y and z directions Other commands used during translation include 14 7 Modifying Entities Repick Handle Point n Set Handle by Picking padd via Keybrd pad Axyz via Keybrdo Acp via Keybrd o by Linear Proj at Clsest DB Pt Enter Transl Offset e Original Location 1 Movement Restrictions m Sensit Decr lt Resetl Incr gt Move to Screen Center c Rotation Pt To Cross t Done Translate ent Abort Dont Translate esc Repick Handle Point Lets you pick a new handle point if you picked the wrong one the first time Set Handle The buttons following this label are the standard mechanisms for selecting the final location of the handle Original Location Move the handle back to its position prior to movement The entity is not copied prior to translating Use the Copy command first if that is what you want In fact after copying the entities the Copy command will automatically invoke the Modify menu for the copies The translation is not saved until the Done Replace button is pressed 14 3 2 Scale The Scale command is used to alter one or more entities by scaling The scaling factors may be different for each of th
134. adius of the inscribed sphere Prism aspect ratio is the ratio of the average height of the prism and the average length of the base s trian gle edges The aspect ratio of a prism can be less than 1 16 5 Diagnostic Functions Pyramid aspect ratio 1s the ratio of the height of the pyramid and the average length of the base s quadrilat eral edges The aspect ratio of a pyramid can be less thanl 16 2 9 Skewness Omina vw 4 max a w Qangle i volume k For grid entities the skewness is rendered in the Display window and a tabular summary is listed in the Blackboard The min a skewness function is represented by the cell s included minimum angle in degrees for all types of grid The max a skewness function is represented by the cell s included maximum angle in degrees for all types of grid The angle skewness function is represented as the maximum ratio of the cell s included angle to the angle of an equilateral element The angle skewness applies to all cell types and is available for domains and blocks The angle skewness varies between 0 good and 1 bad It is recommended this skewness mea sure be kept below 0 8 for a good grid values below 0 9 are acceptable depending on the solver The angle skewness is computed as follows max Qmax Qe 180 Qe Qe Qmin Qe where Qmax largest angle in cell in degrees Qmin smallest angle in cell in degrees Qe angle for equilateral element 1 e 60 for tri
135. ae AM M 14 17 A AA 14 18 TAB 0 ROI 14 19 14 8 1 Database Entities settee astute rw dod a 14 19 Wee COC CLO RE TEE 14 19 148 2 DOMAINS Usadas 14 20 DE A BIB KS eeu eae A LEE MEO AE UE 14 20 14 9 Connector Segment Modification essere 14 20 A RENT RSEN RM RM PEE EP 14 20 a RT NET TU EMT 14 20 t49 S ASI nT Ae A eee ee 14 20 A Elo RR oO ERU E TENTER ECRIRE RCE eR 14 21 14 10 Connector Least Squares Fit esses eese nns 14 23 15 Miscellaneous sse nnn n nennen 15 1 EA PP na 15 1 A Database OT 15 1 215 12 Bo II 15 2 15 2 GFOUD neu ota peut ORA AP eatin alain he cup ecu e cece ease eto 15 2 152 1 Database Nile natalidad 15 2 15 2 2 Connectors Domains and Blocks eese 15 2 195 3 CODY c E 15 3 153 11 Database ENIIES uoa ttr buste ti ded Ua tet De muda attri data 15 3 15 3 2 Connectors Domains and Blocks seen 15 3 IS T DSIOlB c he EE MM AE A UE M 15 3 1541 Database Ens ia o coUe Aoc ud 15 4 15 2 Ille CLOS oec oret oir ies II LIA E 15 4 o4 DOMAN ET A ii 15 4 19524 2 BIOO a E A DS I IM NICA ML EMO MASSIL 15 5 A eT a uon UE A LAE CDM MILIA DEO E PEE 15 5 15 6 Enable Disable it tmo sie used ac et coe eto need nd Dus Vu D dod ae ALIE 15 7 156 1 Database Entities uada di dao o ene da aces iii 15 7 1545 2 GORNCCIONS oie orbes Dauid catulus eiu ett pul lia Dei 15 7 A A UEM MIN
136. aintain its left or right handedness After selecting mirror you must choose a mirror symmetry plane You can either pick an existing database plane entity from the Display window or use one of the buttons below to select a x y or z constant plane through the origin A 0 0 Y 0 1 Z 0 2 14 4 Project The Project command is used to modify a grid s shape by moving its grid points onto the database Each database entity onto which grid points may be projected is highlighted in salmon when this command is invoked The candidate database entities for projection can be changed via the En Disable command in the Database menu Only enabled surface entities can be projected onto Turning off the entities that the grid points should not be projected onto has two effects First it prevents the projection algorithm from placing the grid points on the wrong surface Second it reduces the number of surfaces the projection algorithm has to go through and therefore the process will run a little faster It also reduces the visual clutter Prior to projecting you must select whether or not grid points from the entity s boundaries will also be pro jected The menu below is an example for projecting domains 14 12 Project Spherical Int Pts k Cons Too 1 Int Pts Only the interior points of the domain or connector are projected If for example your domain s connectors are already database constrained e g Line on DB segment types you sho
137. along a fixed vector perpendicular to the Display window screen z when the button is pressed Proj Typ ClosePt This attribute tells Gridgen that the projection type is closest point and a projection vec tor is not required Proj DBs Default The grids will be projected onto the default set of database entities The default data base entities are computed for each grid based on which entities are currently referenced by the grid points The entities to be projected onto are highlighted in the Display window Proj DBs Picked The grids will be projected onto database entities selected by you After this button is pressed you can select database entities from either the Browser or Display window The current set of pro jection entities is already picked when the Browser is first invoked Show Proj DBs This toggle button controls whether or not the database entities being projected onto will be highlighted in the Display window Turning off this toggle will un clutter the display Show Proj Vector This toggle button controls whether or not the projection vector with which grid points are projected onto the database entities is rendered in the Display window Turning off this toggle will un clutter the display Align View w Proj Vector This command changes the orientation of the Display window image so that the focus grid s projection vector is parallel to screen z 12 2 7 Boundary Conditions By default boundary grid points are
138. along the range of possible split 14 18 Join Database Entities locations by pressing the left arrow and right arrow keys to decrease and increase respectively the split location The grid index to be split can be changed to other coordinate families by pressing the I J or K buttons When the proper split line is identified by the highlighter press the Done Split At Surface but ton to perform the actual splitting A necessary side effect of splitting a block 1s that the four domains on the block s boundaries that are opposite the split direction will also be split The figures below show a simple structured block before during and after splitting from left to right respectively Nn Wi Ti b UM OH TA pem Wn gee a HN Hi 7 mE mrt ae einig I ru voy or AE Wee Y y 1 i LA d pm E m V M jJ d y A A E ii b mul P LL Ld LZ E jd BH E AW A uy n wis mr iy y wy UO 7 mah n Y Other commands of interest during block splitting are shown below SPLITTING A BLOCK o n ile E k IVILYIVIALALS Type In amp plane 2 Done Split at Surface ent Abort Dont Split esc The VCR menu buttons may be used to move the highlighter and the Type In I plane button may be used to type in the index of the grid location to which the highlighter should be moved Only structured blocks
139. ameter is used primarily as a safeguard so combinations of the other parameters will not allow the grid to be refined to infinitesimal sizes 13 5 2 Maximum Triangle Edge The Triangle Max Edge attribute allows you to set largest triangle edge that will be allowed in the grid If a cell s edge is greater than the specified maximum edge a point will be inserted into the cell This attribute is used to compute triangle areas where each triangle 1s assumed to an equilateral triangle that has a spacing equal to that of the maximum edge size on each of its three sides 13 5 3 Maximum Surface Deviation A point will be inserted into a cell if the estimated maximum distance between the cell s centroid and the underlying database surface exceeds the specified maximum surface deviation By default the maximum surface deviation is not applied When specifying the maximum surface deviation entering a value of O dis ables this attribute The maximum surface deviation parameter is not available for blocks and is only applied to domain grids that are constrained to database surfaces In the figure below two surface grids have been generated on a database surface with a highly curved shape In the grid on the left no surface deviation value has been specified In the grid on the right a surface devi ation was used to ensure that highly curved regions of the grid are resolved E onn Ek ta iat a 13 5 4 Maximum Angular Deviation A point will
140. amine Ax M Show Examine Data Ae Focus n n Done 5ave ent Abort Don t Save esc Initialize via TFI Apply the last used algebraic method to each picked grid Section 12 1 Run Begin execution of the elliptic solver and continue indefinitely until you select the Pause menu but ton Run 1 Iter Run 1 iteration of the elliptic solver and return the solver to the paused state Run N Iters You type in the number of iterations to run the solver Execution begins immediately after the number is entered and will continue through the input number of iterations unless you select the Pause but ton Pause Stops the solver not shown on above menu Project Grid to DB Will project any grids with database constrained shapes to the database using the cur rent shape attributes This command is not available for blocks Set Solver Attribs Set solver attributes such as control functions on the grids currently being run in the solver Examine Go to the Examine menu to inspect grid quality and select the grid quality function to be dis played Show Examine Data Display grid quality while elliptic solver is paused using the functions available in the Examine menu Focus Next Examine the next grid entity in the list of grids being run in the elliptic solver Only applies if Mode Local has been selected in the Examine menu Focus Prev Examine the previous grid entity in the list of grids being run in the ellipti
141. amond adjacent to the hiliter intersection Since this function is directional along computational coordinates adjacent entities must be computationally aligned Section 15 8 in order for reference surfaces to exhibit a continuous variation in the function across entity boundaries Non aligned entities will display a discontinuity across their common boundary Block 16 3 Diagnostic Functions 2D or 3D adjacency is determined by block connections using a common boundary If a connection between two blocks is overridden with a baffle type boundary condition no adjacent entity information will be available at that boundary 16 2 5 Jacobian Jacobian i pos O pos skew O zero M neg skew d neg For structured blocks and prism blocks the Jacobian is computed for each cell The Jacobian computation for hexahedra consists of computing the triple product at each of the cell s corners using only other grid points from that cell and then computing the average of the corner Jacobians For prisms the triple product is pre multiplied by a coefficient of 0 5 The toggle buttons for pos pos skew zero neg skew neg indi cate whether or not to render positive positive skew zero negative skew and negative Jacobian cells in the Display window respectively The cell Jacobians are classified according to the table below Cell Jacobian Classifications Jacobian menu average value of signs of corner classification button corne
142. amp n G command is used to specify the orientation of a structured block s computational coordinate axes Recall that connector domain and block creation proceed without regard for the block s eventual computational directions This is the only command in Gridgen in which the computational axis system is important This command is useful for ensuring that the block s axis orientation is consistent with the requirements of the your analysis software package Specifying the computational axis system in no way affects the grid analysis software boundary conditions or block construction details and may be applied as many times as necessary ReSpecify n is located in Modify Blocks menu When it is invoked all connectors on the twelve edges of the block are highlighted in pink and are grouped according to the three computational directions in the block Position the cursor over an edge and all edges in the same group of like indexed block edges in other words the four block edges with the same varying index will be highlighted After you press the right 15 7 Miscellaneous mouse button to select an edge you will select from the button menu whether the connector group is positive or negative n or G directed as shown below amp direction 1 amp direction 2 n direction 3 direction 4 direction 5 direction The arrows on the connectors in the Display window indicate the direction of increasing computa
143. andidates for merging If the two connectors have the same dimension Gridgen compares corresponding grid points on the two connectors If the maximum distance between grid points is less than the tolerance you entered the connector pair becomes a candidate for merging If the two connec tors have different dimensions Gridgen compares a small sampling of the grid points on one connector to the shape of the other connector and vice versa If the maximum distance computed between the two connectors is less than the tolerance you entered the connector pair becomes a candidate for merging After all the com parisons are complete Gridgen lists in the Browser all candidate connector pairs 4 B5 A 0 500000 7 A 0 500000 Each Browser item consists of three bits of information The two integer numbers separated by dashes are the two connector numbers The real number on the right is the actual maximum distance between the two connectors For example the second line shown above indicates that connectors 4 and 5 are separated at most by a distance of 0 5 Pointing at the Browser entry using the mouse highlights the two connectors in the Display window To merge connectors select the pairs to be merged from Browser and press Done In the Browser illustration above line 3 contains an exclamation point This means that the two connec tors do not have the same dimension However they will still be merged if you select them Connectors 15 12 Merge
144. ane Geometries Journal of Aircraft Vol 27 No 10 October 1990 pp 873 877 Advanced Visual Systems Inc Unstructured Cell Data AVS User s Guide pp 2 39 Release 4 May 1992 Part Number 320 0011 02 Rev B Buning Pieter G et al OVERFLOW User s Manual Version 1 6ak NASA Ames Research Center Sep 1992 Chan W M and Steger J L A Generalized Scheme for Three Dimensional Hyperbolic Grid Genera tion AIAA paper no 91 1588 CP 199 Cooper G K and Sirbaugh J R PARC Code Theory and Usage AEDC TR 89 15 United States Air Force Arnold Engineering and Development Center 1989 Davies D E Salmond Deborah J Calculation of the Volume of a General Hexahedron for Flow Pre dictions ATAA Journal Vol 23 No 6 June 1985 pp 954 956 Ehrlich Louis W An Ad Hoc SOR Method Journal of Computational Physics Vol 44 pp 31 45 1981 Goble B D Raj P Kinnard T A Three dimensional Euler Navier Stokes Aerodynamic Method TEAM Upgrade Version 713 User s Manual United States Air Force Wright Laboratory November 1993 Gordon W J Blending Function Methods of Bivariate and Multivariate Interpolation SIAM Journal of Numerical Analysis Vol 8 No 158 1971 Hilgenstock A A Fast Method For The Elliptic Generation of Three Dimensional Grids With Full Boundary Control Numerical Grid Generation in Computational Fluid Mechanics 88 ed by Sen gupta S et al Pineridge Press Ltd
145. angle 90 for quad etc The volume skewness function is represented as a ratio of the cell s volume to the optimum cell volume and only applies to triangles and tetrahedral The volume skewness varies between 0 good and 1 bad It is recommended this skewness measure be kept below 0 8 for a good grid values below 0 9 are acceptable depending on the solver The volume skewness is computed as follows Optimal Cell Size Actual Cell Size Optimal Cell Size where the Optimal Cell Size is the area for 2D or volume for 3D of an equilateral cell with the same circumradius as the actual cell The angle and volume functions are based on Fluent s equiangle and equivolume grid quality criteria 16 2 10 Spacing spac ing AT For structured boundary condition regions domains the spacing of gridpoints adjacent to the region is ren dered in the Display window and a tabular summary 1s listed in the Blackboard This function is intended to assist those building viscous structured grids since it in essence provides near wall spacing in a very acces sible manner Since this function is considered a boundary diagnostic it is only available from the ANALY 16 6 Display Attributes Orthogonality SIS S W COMMANDS menu The spacing function is a measure of the distance from each point on the structured boundary to the adja cent point on the interior of the associated block Normals to the boundary are rendered for further direc
146. angle defined by the final and initial handle locations relative to the axis Other commands of interest used during rotation include 14 11 Modifying Entities Repick Handle Point n Set Handle by Picking pad via Keybrd pad Axyz via Keybrdo Acp via Keybrd o by Linear Proj at Clsest DB Pt Enter Rotation Angle e Original Location 1 Movement Restrictions m Sensit Decr lt Reset Incr gt Hove to Screen Center c Rotation Ft To Cross t Done Rotate ent Abort Dont Rotate esc Enter Rotation Angle Enter the numerical value of the rotation in degrees following a right handed con vention around the axis where the axis is oriented from the first to second axis points The valid range for rotation angles is 180 lt lt 180 The default value for the rotation angle is determined by the current loca tion of the handle Once the rotation angle is input the entities are rotated and the rotation process is com plete The entity is not copied prior to rotating Use the Copy command first if that is what you want In fact after copying the entities the Copy command will invoke the Modify menu for the copies The rotation is not saved until the Done Replace button is pressed 14 3 5 Mirror The Mirror command is a special version of the scale command to reflect database and grid entities about a plane For structured grid block entities it also respecifies the mirrored block s computational coordinates to m
147. aphical User Interface 2 1 The Gridgen Screen Gridgen s screen is divided into several non overlapping tiled windows each of which serves a specific function as illustrated in the figure below and described in the following list From top to bottom the windows on the left side of the screen are The Version window displays the program s name and its version number We refer to the number to the left of the decimal point as the major version number The number to the right of the first decimal point is the minor version number The total number of blocks domains connectors nodes database entities and the current analysis soft ware are displayed in the Status window The Message window is the guidance and prompting window Messages appear here to provide brief step by step instructions and to prompt you when input is required from the keyboard The Text Input window is where text or numerical data is displayed as you type during input Section 2 6 Various context sensitive diagnostic information is displayed in the Blackboard window This same win dow also goes by the name Browser window when it is used for picking Section 2 4 items for example file names blocks database entities etc The command menu is displayed in the Button Menu window Most of your interaction with Gridgen will be through this window The main graphics window is called the Display window and is used to display the database entities and the grid
148. ar Duende he E ette om oa Oed vs Lese Dane ade 16 8 16 9 9 G0l0F Bar Valles o iris aetate tarii se Soho eue h esie o nooo 16 9 16 94 Show GellS aran bie Dou t ute SE v bo pee tear Loud bed oe 16 9 16 3 S ISO Maat ae 16 10 OMS 0 0 eam ne ta ee tea REO RR ae ea eR MES M LP p te OPE SENI 16 10 IN LII i 16 10 RA de oiu etal Mele dt sud tuno tees died utah dts 16 11 16 5 2 DOMAINS esos euet ada epa is lidad 16 11 A A E E T A E T 16 11 10 6 Helerence Surfaces oc E eoo deti E E E AOE 16 14 17 Analysis Software Interfaces ooooocococonocononnccanocorecoronoonono 17 1 17 1 Select Analysis Software oooococccococococonocoocononononononononoronnncononanononnnos 17 1 E BO S uo ovi ess sess eee 17 3 172 ES dE UI sie Kom TM 17 5 172 2 Unstructured GOS metodi vet uta Eom ACER an 17 5 TZS SC VCS m eee 17 5 TAa AAD DIVING VOS iore sorta ted ebur ed A 17 6 IZA EXAMINE 17 6 17 5 Custom BCs Creating Editing Deletion suussss 17 7 17 6 Custom VCs Creating Editing amp Deletion ooooccoococooomocomoo 17 7 T7 7 Mirror BIOCKS for EXDOTN onorare E EE RE 17 7 17 8 Export Analysis Data Grid and BCS oococccoconccococonoconoconconononononono 17 7 P5 ozl dgelletlG usto tete uio dedacthtiuutmetu i Fustisu dung cm Uie duudtaen dct AT 17 8 CA A
149. are listed in the Blackboard Focus Next n Prev An Focus All s Focus Next Move focus to the next selected grid in numerical order Focus Prev Move focus to the previous selected grid in numerical order Apply to Focus Attributes you select will be applied only to the focus grid Apply to All Attributes you select will be applied to all grids regardless of which grid is the focus grid 8 2 2 Surface Shape Surface Shape Params 5 Domains created by extrusion either can obtain their shape purely from the mathematics of the extrusion or can be constrained to the database Surface shape attributes are not available when creating blocks by extru sion The surface shape attributes are described below Shape Free u DB d Proj Typ Lin Def 1 Lin Cur 2 ClosePt 9 Proj DBs Default 3 Picked 4 I Show Proj DBs 7 MM Show Proj Vector 8 Align View w Proj Vector amp Shape Free The shape of the surface grids will result solely from the mathematics of the extrusion method Shape DB The surface grids will be constrained to the database while they are being extruded Proj Typ Lin Def This attribute tells Gridgen the projection type is linear and the default projection orien tation will be used The default projection orientation is computed by averaging the grid s normal vector at each grid point The projection vector direction is shown in the Display window as an arrow at each corner of the grid Pr
150. ary conditions When exporting the grid for WIND you must select the grid units from a menu for inclusion into the cgd file Please note that selecting units for WIND does not scale your grid It simply indicates to WIND what the units are of the grid that you have already made WIND export in Gridgen now uses ADF Library Version A02011 Asa result executables based on older ADF libraries are no longer supported WIND export is not supported under HP UX WIND ATTRIBUTES length units meters centimeters millimeters feet 4 inches 5 17 15 Analysis Software Interfaces 17 16 18 File Formats 18 1 Introduction Several of the files that may be imported and exported by Gridgen are described in this section Please note the distinction between binary and Fortran unformatted files Fortran unformatted files contain extra data at the beginning and end of each record whereas the binary file contains only the data Furthermore please note that binary and Fortran unformatted files are not portable among all of Gridgen s supported hardware platforms due to an issue called endian ness whether the bits in word are stored from highest to lowest or lowest to highest The Gridgen file however is portable among all supported hardware platforms because it contains the endian ness setting with which it was written so that it can be reversed if necessary by the receiving system Native byte formats f
151. as no effect whatsoever on the grid or the values of the diagnostic functions It simply provides an interesting visual effect that helps you distinguish a cell from its neighbors Triangular grid cells colored by aspect ratio and rendered with wireframe style are shown below with shrink factors of 1 0 0 8 and 0 5 respectively Entering a value of zero 0 0 causes the cells to rendered by only a dot at their centroids These dots have a fixed size regardless of model zoom level and therefore this shrink factor value may aid in locating extremely small cells in the Display window P X AS as as SCA k URN S INIA DAN Ao AND S AT P ON Y AV UA KA PA Sey er d gt X IS SMS wid RE Y RE MIS ASESOR OS zw du ERIR STA ETa V END db AC 4 BAVA aa LE gat QoS SSP dp dA qd L SWRA SMS URN S Ap UIN ec a 16 9 Diagnostic Functions 16 3 5 Histogram vf Histogram m Num Levels 10 j Enabling this toggle button adds a histogram to the color bar in the Display window with horizontal bars representing the number of cells with diagnostic function values in the color bar range that is graphically cut by the bar Num Levels By default histograms are drawn with 10 horizontal bars levels You may enter a new number of levels bars with which the histogram is to be drawn Histograms with 10 left and 20 right levels are shown below Aspect Ratio Aspect Ratio 2 00006 2 00060 1105000 1 JE L jejejeje 21
152. atabase entity groups during intersec tion 75 16 IGES composite curves 4 0 in browser via sorting 2 11 of commands via labels 2 8 of radio buttons 2 4 Un Group database command 5 2 GUST asw 7 11 H handle rotate 74 11 stretch 14 10 help menu button for 2 3 Quick Menu 2 7 using on line help 2 27 hierarchy Hiliter block Examine 76 17 connector Examine 76 11 domain Examine 16 11 Examine 76 10 Histogram for Examine 6 0 Histogram Levels 6 0 hot keys 2 3 hyperbolic extrusion S 2 attributes 6 4 I IGES database import 4 9 entities supported by Gridgen 4 9 image capture 2 22 image manipulation axis systems 2 4 demote 2 22 devices 2 4 glide toggle 2 4 hot keys for 2 5 light source 2 22 panning 2 4 Quick Menu keys for 2 6 recomputing view limits 2 27 restoring views 2 22 rotating 2 4 saving views 2 22 screen capture 2 22 sparse mode image manipulation of large models 2 22 view transformation 2 27 zoom box 2 5 zooming 2 4 import ACIS SAT file as database 4 7 ASCII 4 15 binary 4 5 CATIA v4 as database 4 7 composite database file 4 7 curves 4 13 Fortran unformatted 4 5 FVUNS as grid 4 5 Gridgen restart file 4 7 grids from other sources 4 13 IGES database 4 9 NASTRAN as grid 4 4 PATRAN as database 4 10 PLOT3D as grid 4 14 Pro E prt asm file as database 4 7 Quick Import Gridgen file 4 5 Quick Key for Input Output menu 2 5 STEP as database 4 7 STL as database 4 8 STL as grid 4 5 su
153. ave all of the information regarding a database This includes not only the geometric information but also entity names and graphical display states Unless the entities are lin ear the composite file is the only mechanism for saving any entities created or modified in Gridgen Linear 4 12 Import Grid Points Backward Compatibility curves may be exported to segment files and bilinear surfaces may be exported to network files Note that trying to quit Gridgen without saving a modified database will generate a warning in the Message window stating that the current database contains information which has not been saved This provides a good opportunity to press Abort Don t Quit so you can save your database file 4 6 Import Grid Points The Grid Pts Import command in the INPUT OUTPUT menu is used to read a file containing only grid points and from the grid points build the appropriate Gridgen elements connectors domains or blocks Once the grid points have been imported the entire range of Gridgen commands may be applied to the grid You are urged strongly to closely inspect the grid after import to ensure that creation of connectors domains and blocks was completed properly Upon completing your work with this grid you may either 1 Save the modified grid in a Gridgen file Section 4 3 2 Export the modified grid as a grid point file Section 4 7 Typical uses for importing grid points include applying Gridgen s grid methods to
154. be inserted into a cell if the estimated maximum angle between the cell s centroid and the vertex surface normals lying on the database exceeds the specified maximum angular deviation angle When spec ifying the maximum angular deviation entering a value of 0 disables this attribute The maximum angular deviation parameter is not available for blocks and is only applied to domain grids that are constrained to database surfaces 13 6 Tetrahedral Mesh Attributes Boundary Decay Factor In the figure below two surface grids have been generated on a database surface with a highly curved shape In the grid on the left no angular deviation value has been specified In the grid on the right an angular deviation was used to ensure that highly curved regions of the grid are resolved 13 5 5 Boundary Decay Factor The boundary decay factor qualitatively controls how far into the grid s interior the boundary cell size effects the interior cell size A decay factor of 0 turns off this attribute interior cell size is not affected by boundary cell size A decay factor of 1 applies full boundary influence on the grid s interior Therefore valid values for the boundary decay factor fall in the range 0 1 The figure below illustrates a domain grid with boundary spacings on the circular arc that are smaller than those on the vertical line The grid on the left has the boundary decay factor turned off 0 while the grid on the right has the boundary deca
155. begins the extrusion process which will continue until you press the Pause but ton Run 1 Extrudes one step Run N Extrudes N steps where N is a number you type in Back Reverses the extrusion process backing up and removing extruded cells stopping either when you press Pause or all of the extruded cells are removed Back 1 Back up one step Back N Back up N steps where N is a number you type in Restart Remove all extruded cells Set Attributes Set a variety of attributes that will control the extrusion Set Stop Criteria Set grid quality parameters which when exceeded will pause the extrusion 8 3 Grid Extrusion Methods Done Stop the extrusion process save all extruded grids and exit the Extrude menu Abort Stop the extrusion process remove all extruded grids and exit the Extrude menu 8 2 Extrusion Attributes You can change attributes at any time in the marching solution For example one set of attributes can be applied for the first 20 marching steps and another set for the next 40 The various attribute categories some of which are only available for certain extrusion types are described in the following subsections 8 2 1 Focus The Focus and Apply to buttons are available when you are extruding either From Cons or From Doms and you select more than one connector or domain for your initial grid respectively The focus grid is the one highlighted in the Display window and whose attributes
156. bian 16 4 None 6 2 orthogonality 76 7 Size 16 3 Size Ratio 16 4 skewness 16 6 Smooth 6 5 Spacing 16 6 Usage 16 2 Display Color Bar Type 6 amp Color Bar Values 6 9 Display Style 76 8 Histogram 6 0 Show Cells 6 9 Display Attributes 6 7 domain hiliter 6 Erase 16 16 extend 6 2 Flat 16 15 Focus 6 Hiliter 6 0 Mode 6 0 Permanent 6 4 Save 16 14 examine block face 0 6 Exodus II asw 7 0 export analysis software data 4 9 17 7 Quick Menu 2 7 selecting file name for 2 2 STL grid 4 17 VRML grid 4 17 extend Examine toggle 6 2 extracting curve from surface 6 4 extracting curves from shell database enti ties 75 78 extracting surfaces from shell database en tities 15 18 extrusion see grid extrusion F Falcon asw 7 10 FANS asw 77 10 FDNS UNIC asw 77 10 feature extraction 75 17 FIELDVIEW boundary surface file export 4 19 file style attribute 4 15 4 17 file analysis bcs export 4 19 analysis data export 4 19 analysis grid export 4 19 attributes format 4 6 4 15 4 17 ASCII 4 6 4 15 4 18 binary 4 6 4 15 4 18 unformatted 4 6 4 15 4 18 precision 4 6 4 15 4 18 style 4 14 FVUNS 4 15 4 17 Gridgen 4 4 4 17 NASTRAN 4 14 4 17 PATRAN 4 17 PLOT3D 4 14 4 17 STL 4 6 4 15 4 17 VRML 4 6 4 15 4 17 type composite 4 7 IGES 4 9 network 4 6 PATRAN 4 10 segment 4 7 database import 4 4 export image file display command for 2 22 Glyph export rc file 4 19 G
157. ble although no wall information is available in the binary format XPATCH style refers to the XPATCH unstructured data file format Gridgen currently supports XPATCH export of unstructured domains 4 7 2 Format Format refers to the data format in the file format ASCII a binary Ab o unfrmtd n 4 17 Importing and Exporting Files ASCIl is a human readable format that is very portable between computers of different types However ASCII files will require significantly more disk storage than binary or Fortran unformatted files and will take longer to import and export binary is a compact format but suffers from a lack of portability between big endian and little endian computers unfrmtd refers to Fortran unformatted a format similar to binary in that it is very compact However binary and Fortran unformatted formats are not interchangeable Fortran unformatted format is available exporting Gridgen and PLOT3D style structured surface and volume grids and for exporting some types of analysis software data 4 7 3 Precision Precision refers to the word size 1n the data file single s double d single precision means that real floating point data will be written as 4 byte words double precision means that real floating point data will be written as 8 byte words 4 7 4 Exporting Structured Grid Points The Grid Pts Export command allows you to export the following structured grid types
158. board You can type in a value for with this option Input values must be in the range 0 lt lt 2 0 12 2 4 Background Control Functions Control functions control the distribution of grid points during iterative solution of the elliptic PDE These control functions are calculated and updated automatically between elliptic PDE iterations and are formed as a blended combination of two independent function sets known as background and foreground control func tions Background control functions are used to influence the distribution of grid points on the interior of the grid Three different background control functions described below are available in Gridgen The current back ground control function applied to the focus grid is displayed in the Blackboard window with the label BG CODE Um LaPlace 1 Thomas Mi ddlecoff 2 Fixed Grid 3 12 2 4 1 LaPlace LaPlace background control functions provide a very smooth distribution of grid points in the grid interior but provide no degree of orthogonality or clustering 12 2 4 2 Thomas Middlecoff Thomas Middlecoff Reference 34 background control functions will cluster grid points on the grid s inte rior based on how the grid points are clustered on the boundaries This method is very reliable and stable for a wide range of applications and is therefore Gridgen s default background control function Thomas Mid dlecoff right is compared to LaPlace left below 12 2 4
159. braic or Unstructured initialization methods are applied to the connectors around each database surface to create the initial domain grid Structured domains will only be created by this command for instances where four connectors can be used around the database surface s perimeter and the default connector dimensioning has resulted in equal num bers of grid points on opposite edges The connectors are still created even in cases where structured domains cannot be created n DB Entities 3 M AUTO Join e Set Angle b vf Auto Merge o Set Toler 1 MCon Split i Set Angle il Options you can set before On DB Entity domain creation are Auto Join Set Angle is used to merge multiple domains into a single domain This is useful if you have many small database surfaces and do not need their edge topology maintained in the final grid If Auto Join is checked on you can enter a join angle by pressing the Set Angle button Two domains will be joined if the bending angle between every pair of adjacent triangles along their common edge is less than the specified angle Auto Merge Set Toler is used to automatically merge and split connectors to try to form a water tight geometry as domains are created If Auto Merge is checked on you can enter a merge tolerance by pressing Creating Domains the Set Toler button Gridgen applies the Merge Nodes Merge Conns and Merge Nod Con com mands Section 15 10 based on this tolerance Con Split Set Angle
160. but may be part of a perfectly legal grid Therefore Gridgen does not automatically save overlap ping and adjacent domains In the example below the square domain ABHG already exists and the rectangular domain ACFD has just been created Gridgen has identified the two as overlapping and adjacent since they share connectors AB and AD and node A You must then choose one of the two menu buttons shown below 9 11 Creating Domains Save This Domain Anyway y Abort Dont Save It esc Save This Domain Anyway The new domain ACFD will be saved anyway despite the warning There are rarely instances when you will choose this option Abort Don t Save It Do not save domain ACFD You will be returned to the beginning of domain cre ation There are three ways you could create domains for the above topology without getting overlapping and adja cent warnings 1 Create two domains ABHG and BCFE 2 Create two domains ACFD and DEHG 3 Create three domains ABED BCFE and DEHG 9 8 4 Overlapping Sometimes Gridgen cannot detect domain overlap as illustrated below Here the smaller domain lies entirely within the boundaries of the larger domain but since there are no shared connectors in the two domains no overlap is detected In general it is impossible for Gridgen to detect this type of overlap since the domain is defined solely by its connectors and not by the surface on which the domain is intended to lie Therefore you should
161. c solver Only 12 5 Grid Methods for Structured Domains and Blocks applies 1f Mode Local has been selected in the Examine menu Done Save Exit the solver and save the current grids Abort Don t Save Exit the solver and revert the selected grids including the solver attributes back to the state that existed at the time the Done button was pressed Elliptic Solver RUN Iteration Total Residual 9003E 01 Max Residual 4047E 01 100 04 of Grid Points are DB Constrained While the elliptic solver is running the current iteration number the total residual and the maximum resid ual are displayed in the Blackboard window The total residual is the root mean square RMS of the grid point movement per iteration summed over all points in the selected grids The maximum residual refers to the largest single RMS term The grid point where it occurs is highlighted in the Display window using the same small glyph red diamond shown in the Blackboard The percentage of the grid points that are cur rently constrained to lie on database entities 1s also displayed 12 2 2 Setting Attributes When the Set Solver Attribs command is selected the Blackboard will display the current attributes of the focus grid as shown on the left below The various attributes can be set using the menu shown on the right Domain Num 1 8x 17 SET STRUCTURED SOLVER ATTS TFI standard Shape Free Relaxation Optimal BG ConFun Thom
162. chematic of the domain in the 9 2 Assembling Structured Domains Blackboard follows the same color scheme and also prints the number of grid points on the edge After pressing the Next Edge button the three connectors that comprise the right hand side edge 2 of the domain are picked proceeding from bottom to top As shown below edge 2 s connectors are highlighted in red The Blackboard changes to indicate you arenow Defining the Second Edge Note that the node at the end of the first edge will be a corner of the I x J surface grid on the domain 21 Defining the Second Edge Pressing the Next Edge button completes the assembly of the domain Since Auto Complete is on and there is only one connector adjoining edge 2 at its end Gridgen automatically starts edge 3 and adds the con nector Gridgen knows how many grid points are required on edge 3 same as edge 1 It automatically applies the Next Edge command when enough connectors are added to edge 3 so its dimension matches that of edge 1 Following the same logic Gridgen completes edge 4 and hence the domain Gridgen saves the domain automatically generates its interior grid points and prepares for assembly of the next domain as shown below HELE T mu LEUTE 0 Defining the First Edge The domain s surface grid is automatically initialized using an algebraic method called transfinite interpola tion TFI Section 12 1 Gridgen chooses the specific TFI method to apply from
163. ck These buttons allow you to specify the colors used to render the picked entities The All button is used on database and domain entities to assign an alternating color from a six color sequence to those entities queued for display modification an 2 11 Saving Screen Images The Display window image may be saved to either a Silicon Graphic s RGB screen dump on sgi systems only a Windows BMP on Windows systems only a Portable Network Graphics image or a PostScript line drawing via the Photo buttons in the DISPLAY COMMANDS menu Section 2 9 Note that the image will consist of the contents of the Display window only Gridgen s other windows such as the Menu Button window and Blackboard are not included PostScript files from Gridgen contain vector images and not raster images like the other formats Therefore they are best for line drawings Several options are available for customizing the image as described below Color e Color on White c Grey Shades on White d Black on White b Color An image of the Display window as you see it is created Color on White Same as Color except that the background is converted temporarily to white Gray Shades on White The colors of the current Display window image will be converted to a gray scale and the background color will be converted to white Black on White With this option the background will be changed to white and all other colors will be converted to black After s
164. connectors Pick closed loops of connectors to define surface grids domains Apply a grid method to improve the distribution of surface grid points optional Pick closed shells of domains to define volume grids blocks Apply a grid method to improve the distribution of volume grid points optional pe wes ES ue Gu o Se d Set analysis software boundary conditions optional 10 Export analysis software data files Gridgen s History Plan the Grid 11 Save the Gridgen file While the detailed operations performed in each of these steps will vary for each grid you build you will always follow these basic steps in this general order We also recommend you create some of your domains surface grids as soon as you have enough connectors created This will allow you to see immediately whether or not the distribution of grid points you applied to your connectors results in a good domain surface grid By doing this you will be able to identify and correct potential problems at the earliest possible stage in the grid generation process resulting in a better final grid 1 6 Gridgen s History Gridgen has been a product of Pointwise Inc since 1994 The software was initiated and has been continu ally developed by Pointwise s founders since 1984 Portions of Gridgen Versions 12 and 13 were developed under the sponsorship of the United States Air Force Research Laboratory Prior to 1994 Gridgen was developed by Pointwise s founde
165. ctions you can add to the dimension by enabling either or both of the MaxDev and MaxAng toggle buttons These buttons allow you to enter the maximum distance allowed between the connector shape and the discrete shape defined by the grid points and the maximum turning angle between successive grid points respectively In the illustra tion below the curve on the left has been dimensioned by copying the dimension of the 3 line connector string on the right with points added to limit the maximum turning angle between successive grid points to 5 degrees N 11 2 ReDimension Grids The ReDimension Grids command is available in the Connector Domain and Block menus This com mand can be used to redimension a grid system containing multiple blocks and or domains and to assign dimensions quickly to previously undimensioned connectors The ReDimension Grids command is the only way to assign new dimensions to connectors belonging to structured domains since the connector ReDimension command in the Modify menu Section 11 1 is grayed out when modifying a connector used by a structured domain Redimensioning proceeds by selecting connectors assigning new dimensions to them and for structured grids letting Gridgen propagate the new dimension to other related connectors automatically For a struc tured grid when you position the cursor over a connector the connector and all connectors in the entire grid that must have the same dimension the connector
166. ctors are colored red if they are i directed and orange if they are j directed The indices i and j in this discussion corre spond only to a local set of coordinates used to set up the face these local coordinates have no relationship to the final n and G computational coordinates of the block The Blackboard also shows the dimensions of the face and each node shown as a filled circle 10 1 Creating Blocks If the entire face consists of a single domain then nothing more is required and the face can be loaded into the block by pressing the Save the Face button In the case of a multi domain face such as the example above other domains need to be added to the face Select each additional domain to be added to the face using the procedure described above with one excep tion each domain added to the face must be adjacent to domains already in the face The Blackboard and Display windows are updated to reflect the new face structure Notice that only the connectors on the perim eter are rendered in red or orange these are the only possible regions to which another domain may be adja cent If the selected domain does not connect to the existing face structure you are warned and can select another domain It is not possible to save the face until it is a rectangular shape in computational space as displayed in the Blackboard window below 10 2 Assembling an Unstructured Block Adding Faces to an Unstructured Block 1
167. ctured SubGrids For structured surface and volume grids you can define a subset of the grid known as a subgrid for the appli cation of the grid methods You may consider a subgrid to be a template that isolates a subregion of the overall grid that allows you to precisely control where the grid methods are to be applied In fact only the structured grid solver commands can utilize subgrids You would use a subgrid to apply a grid method only to the portion of a grid that needed improvement rather than the entire grid There are three aspects to work ing with subgrids adding them deleting them and using them 12 3 1 Adding a SubGrid The SubGrids Add command is used to specify a subset of a structured domain s or block s grid points called a subgrid for later use with the algebraic Section 12 1 and elliptic PDE Section 12 2 grid meth ods Subgrids are used only in conjunction with the algebraic and elliptic grid methods The subgrid lets you apply grid methods to the precise regions where control is necessary without having to alter the grid s topology by splitting domains and or blocks Each subgrid must have at least three grid points in each computational direction SubGrids can overlap or abut one another or they may be separate The set of all subgrids on a given grid need not encompass all of the grid s grid points 12 3 1 1 Adding a SubGrid to a Domain When the SubGrids Add button is pressed for creating a subgrid the highlighte
168. d into a computational rectangle This includes sur faces that connect to themselves and surfaces with poles The straight line connector in the cylindrical domain shown below represents two edges of the domain This is called self connecting and should be avoided because it introduces ambiguities when the domain is used in a block Splitting this domain into two 180 degree half cylinder domains by adding another straight line connector to the front would be a better approach 9 10 Bad Domain Types Duplicates Bad A single self connecting domain Better Tuo domains It is best if domains are not partially singular For example the domain shown below should be split into two domains a pole and a triangle ARSEENSRETIZTSI 9 8 2 Duplicates Sometimes you inadvertently will create the same domain twice Gridgen automatically compares each new domain with all other domains in the system If the new domain already exists in the grid you are notified and the new domain is not saved This comparison takes into account the different ways in which a domain can be constructed 9 8 3 Overlapping and Adjacent When a domain is created Gridgen checks whether it overlaps and is adjacent to any other domain Overlap means that the new domain is not identical to any other domain but is adjacent to another domain on at least part of two edges and one corner node Overlapping domains usually signal an inconsistency in the grid system
169. d while you edit them It is important that you understand linkages and their implications when you are modifying the database or grid because you will be given the opportunity to unlink an entity from its neighbors Linkage effects for each member of Gridgen s data hierarchy are described in the following sections The grid shown below will serve as the example used throughout the descriptions There are two square database entities shown in pink one cannot be seen because it s below the block on the right The grid contains one structured block shown on the right with the dark blue connectors one structured domain on the database entity in the lower left and five free connectors light green Y i oj i Y l PH TEE ERA Eo fag zz A LX ae aS NA P 14 2 1 Database Linkages Database entities are topologically independent of other database entities Because of this you do not need to consider linkages to other database entities when modifying the database One minor exception to this rule is the Group entity Section 15 2 any modifications to the Group will affect all the members of the group The database is topologically linked to connectors and domains Connectors their control points and grid points become linked to a database entity by l creating them using a adatabase constrained segment type Section 7 2 2 b the two point connector Section 7 3 c On DB Ents Section 7 4
170. dd other control points to the seg ment s definition These control points do not alter the shape of the circular arc or conic section but simply slide along the shape For this reason they are referred to as slide points They provide a control point location that may be used for setting a break point during grid point distribution Section 11 3 3 and to pro vide a packable location on the arc 7 6 Add Segment Other Segments Original Location o Store Pt at o via Kbrd il Remove del Insert pad5 Edit Prev n p4 Next n p Pick o s Original Location return the slide point to the location it had before it was moved Store Pt at o via Kbrd type in the relative angle from the first control point at which the slide point is to be added Remove n delete the slide point Insert o add a slide point to the segment Edit Prev o move the 3D cursor to the control point before the current point Edit Next o move the 3D cursor to the control point after the current point Edit Pick n select the control point to edit 7 2 4 Other Segments 7 2 4 1 Copy A Connector The Copy segment type allows previously defined connectors to be copied and translated to a new location This segment type is often useful for constructing domain or block edges opposite those already created After selecting this command position the cursor over the connector to be copied and press the right mouse button Next pick one of the
171. default all nodes and connectors are pickable Free When this button is enabled only connectors used by a single domain are pickable NonMnfld Free When this button is enabled all connectors that meet the above Free criteria as well as connectors used by one or more domains are considered 15 11 Intersect The Intersect command allows you to create new point and curve database entities by intersecting existing entities The following table lists the entity combinations that can be intersected along with the results of the intersection operation 15 15 Miscellaneous Intersection Results curve points and new knots added to each curve plane points and new knots added to the curve surface points and new knots added to the curve surface plane curves surface surface curves The only manner in which curve entities are changed during intersection is that a new knot control point is added to the curve s definition The new knot does not alter the curve s shape but it does provide a pickable location for subsequent operations Curves are not split by intersecting Curve curve intersections are computed relative to a plane Gridgen uses the plane perpendicular to the line of sight parallel to the plane of the screen The implication is that Gridgen computes both true and apparent curve curve intersections A true intersection is one in which the curves truly intersect in 3D space In this instance Gridgen creates one n
172. default is normalized coordinates 3 6 QuickSave File Name The QuickSave file name is the name used for the Gridgen file exported by the QuickSave quick key Sec tion 2 3 6 The initial value for this defaultis quicksave gg To change the default value simply press the QuickSave Filename button and use the file Browser to choose a new file name 3 7 Tolerances Tolerances are an important feature in Gridgen They are used to control how grid entities are logically con nected across gaps in the database and the way many database creation and intersection operations perform Tolerances are set in a submenu of the DEFAULTS MENU To set tolerances press Tolerances 3 7 1 Node Tolerance The node tolerance is the real value within which Gridgen considers two nodes Section 7 to be the same The initial value for this default is 0 0001 To change the value of the default press the Node button and type the new value in the Text Input window When you enter a new node tolerance the entire grid system is updated to reflect the new value Any for merly distinct nodes falling within the new tolerance will be combined The importance of the node tolerance is it affects whether or not Gridgen s grid topology logic will consider two connectors to be end to end adjacent and therefore whether a domain can be built using them The node tolerance is also used by the Merge command Section 15 10 3 7 2 Connector Tolerance The connector tolerance
173. der such that the inner loop direction is opposite of the outer loop You may have to use the Reorient Edge command to do this Defining the Second Edge Finally press the Save Domain button and the domain grid will be triangulated automatically in the region between the outer and inner boundaries 9 6 Special Domain Assembly Commands Gir aan ec Pg a GEN a T TA EA RA ADO ro AAA A grad mE E t Ej Es cen EE EE ERA E na Se EU a KSEE DA E E e E ra DOOR Fi mu ma e ny Puy A Defining the Outer Edge CRUS a a SEE GS ex E e aa ry A E EJ a A RARE EA ARE EA 3 A EC PEA is a EY ja i A E m Ai m me eer um Fi i The domain s interior grid is automatically initialized using a triangulation method when the domain is cre ated Gridgen chooses how to apply the triangulation method from the following list 1 Parametric Triangulation Gridgen will apply the triangulation method in the parameter space of a database surface if the domain s connectors have been defined in terms of one and only one database entity The connector s may have been created directly on the entity for example DB cnstr Line seg ment type or may have been projected onto the database Parametric Triangulation ensures the grid will conform to the database shape 2 Parametric Fit Triangulation If Gridgen cannot apply Parametric Triangulatio
174. deviation maximum 3 4 default 3 3 CNSFV asw 7 9 Cobalt asw 7 9 Color Bar Type for Examine 6 8 Color Bar Values for Examine 76 9 combine separate restart files 4 5 COMO asw 17 9 composite database file import 4 7 computational coordinates 0 7 align with chosen block 75 8 respecifying 5 7 conic rho value 6 9 connector adding break points 0 adding subconnectors 71 10 approximating shape 4 23 beginning spacing 11 7 break point 6 changing spacing and distribution 3 color coding 7 control point edit 74 21 copy 15 3 create 2 point connectors 7 0 add segment 7 2 miscellaneous commands 7 9 on database entities 7 71 periodic 75 8 segment 3D Space Akima 7 5 3D Space Curve 7 5 3D Space Line 7 2 copy 7 7 DB cnstr Akima 7 3 DB cnstr Curve 7 3 DB cnstr Line 7 3 import 7 7 pole 7 8 creating 7 data hierarchy 74 4 definition 2 7 1 delete 75 4 dimension chordal deviation 3 default 3 maximum angular deviation 3 2 maximum chord height deviation 3 3 maximum turning angle 71 3 disable 75 7 display grid points 2 20 display status 2 20 distribution break point 0 Set As Values command 3 spacing constraint 6 spacing continuity 7 spline type 71 9 unconstraining 7 distribution function 71 7 copy 11 8 copy from network 77 6 equal spacing 71 8 general 9 geometric progression 71 8 hyperbolic tangent 71 8 maximum deviation 9 maximum turning angle 9 monotonic rational quadratic
175. dgen file is large and normally takes a long time to import 2 There is no chance of ambiguity between the database if any and the Gridgen file in other words the Gridgen file was created on the database file that has been imported 3 There are no unsatisfied database references in the Gridgen file 4 3 Export Gridgen File The Gridgen file is your grid model restart file It contains everything about the grid including nodes con nectors domains blocks grid points analysis software specifications display attributes and database entity name associativities You will save a Gridgen file for each grid The Gridgen file does not contain the data base entities Upon selecting the Gridgen Export button from within the INPUT OUTPUT COMMANDS menu you will be placed in the file Browser to determine the name for the file If the file to be exported already exists it may be overwritten by selecting the file name from the Browser assuming that write privileges exist for the selected file You are encouraged to export Gridgen files often so recovery from errors may be made by 4 3 Importing and Exporting Files starting from the last saved restart file 44 Importing Database Files The Database Import command in the INPUT OUTPUT COMMANDS menu allows you to read data base entities from a file into Gridgen for use in defining the shape of the object being meshed The Import command immediately invokes the Browser from which you may c
176. dges of the surface A third curve called the shoulder curve determines the depth of curvature of the surface Revolution makes an axi symmetric surface by rotating a generatrix curve around an axis Linear Sweep builds a surface by sweeping a generatrix curve along a specified linear rail curve Fit creates a slope continuous cubic polynomial surface through a bilinear surface Coons constructs best possible surface from a group of user selected curves 6 5 1 Ruled Surface A ruled surface is constructed by selecting two curves called rails that define the surface s opposite bound 6 7 Creating Database Entities aries When the second rail is picked the ruled surface is created and immediately displayed on the screen For ruled surfaces all constant parameter curves between the rails are straight lines Ruled Surface Rail Curve 1 Rail Curve 2 Fit Tolerance Patches 99x Commands used during construction of a ruled surface are Erase 2nd Rail Curve del Erase Both Rail Curves o Reverse the Direction s Set Fit Tolerance 2 Erase 1st Rail Curve After the first rail has been selected but before the second rail has been selected this command allows you to pick another first rail curve Erase 2nd Rail Curve After the second rail has been selected and before the ruled surface is saved this command allows you to pick a different second rail curve Erase Both Rail Curves This command allows you t
177. domain extrusion only March Set Pressing this button uses the current graphical orientation of the Display window image and the setting of the Plane Vector radio button to set the marching direction Available for domain extrusion only March Flip Reverses the current marching direction by 180 degrees Translation and rotation extrusions use special attributes to control the direction of the extrusion as described below Total Tranlation Dist 1 Total Rotation Angle 1 Set Translation Yetr 2 Set Rotation Axis 2 Total Translation Dist Pressing this button lets you type in the total distance to be extruded for a trans lational extrusion Set Translation Vctr Pressing this button lets you choose the vector along which the translational extru sion will proceed The translation vector menu is described below Enter Vector via Keybd 1 Use X Axis 3l Use Y Axis 4 Use Z AXIS 5 Enter Vector via Keybd Pressing this button lets you type in the 3D components of the translation vec tor It does not have to be a unit vector Use X Axis Pressing this button uses the body x axis as the translation vector Use Y Axis Pressing this button uses the body y axis as the translation vector Use Z Axis Pressing this button uses the body z axis as the translation vector 8 7 Grid Extrusion Methods Total Rotation Angle Pressing this button lets you type in the total rotation angle to be extruded for a rotational extrusion There ar
178. ds will become available For example if no domains have been created the MAIN MENU button for the BLOCK COMMANDS menu Blocks will be grayed out because domains are nec essary for block creation As soon as you create a domain the menu button for the Blocks command will become available and its text will be black in color To select a button from the menu and thereby activate the command described by the button text position the cursor over the button using the mouse thereby highlighting the menu button s display Then press and release the right mouse or left mouse button to activate the command described by the button In the remainder of this manual this process of selecting a menu button will be referred to by the phrase pressing the X button where X is the command name Notice that the menu button is not selected until the mouse button is released so the cursor may be moved to a different menu button or even off the menu after the mouse button is pressed 2 3 2 Hot Keys Database T Almost every command can be selected by pressing a specific keyboard key called a hot key A command s hot key is shown right justified on its menu button after the command name For example the MAIN MENU button Database f indicates that the DATABASE COMMAND menu may be invoked by press ing the f key A caret preceding a hot key means that the control key must be pressed at the same time as the hot key to invoke the command For example the MAIN
179. e Decay This command allows you to specify the number of grid points away from the boundary at which the spacing constraint portion of the foreground control function will be equal to 10 of its boundary value The default value is 6 Smaller values are more stable but may dissipate the spacing constraint too quickly Negative decay values are not allowed 12 2 5 4 Angle Constraints The angle constraint refers to the angle that transverse grid lines make with the boundary You can choose from four methods for computing the angle constraint a Cale lor thgn1 5 Interpl Cur Grd 7 Adj Grd8 Orthgnl This command sets the angle constraint to 90 degrees This is the default method Interpl The angle constraint is computed by interpolating linearly from the perimeter of the boundary onto the interior A simple linear basis is used for the interpolation Cur Grd This command maintains the angle currently in place in the grid Adj Grd The angle constraint is copied from another grid selected for the elliptic solver sharing the selected boundary with the current grid If the adjacent grid cannot be determined either 1f none exists or 1f more than one exists the constraint is changed to Cur Grd This constraint provides angle continuity across grid boundaries There are two methods for blending the angle constraint portion of the control function from the boundary into the grid s interior a Blend Linear Al Expnen e Decay
180. e button is pressed 14 3 4 Hotate The Rotate command is used to alter an entity by rotating it about a specified axis One or more entities may be rotated at a time In the figure below the domain is rotated 30 degrees about an axis perpendicular to 14 10 Transformations Rotate the page emanating from the lower left corner After the entities are selected you define the axis about which to rotate You can do this by either specifying the two end points of the axis or by choosing to use one of the three principal axes Repick Axis _l Point n Enter Axis_1 via Keybrdpad Enter Axis_2 via Keybrdpad Use A principal Axis 1 Use A directed Axis 1 Use Y principal Axis 2 Use Y directed Axis 2 Use Z principal Axis 3 Use Z directed Axis 3 Abort Dont Rotate esc Abort Dont Rotate esc You can control the rotation by pressing the Enter Rotation Angle button and then typing in the rotation angle in degrees Repick Axis_2 Point n Enter Handle via Keybrdpad Enter Rotation Angle a Abort Dont Rotate esc You may also control the rotation by picking a point called the handle Candidate handles are any pickable points on the entity or a point you type in You then move the cross on the screen using the mouse with the right mouse button pressed During rotation the Display window shows the entities current rotated posi tion The Blackboard indicates the current cross position and the rotation angle The entity is rotated by the
181. e Set A Values command you may choose to sort the break points by the numerical value of the spacing constraint so that all like constrained connec tors are grouped together Also you may choose to sort the Browser list by database entity type when using the Database Delete command Pick by Expression Pressing this menu button allows you to type in a Glyph expression to select enti ties For instance if you have defined a Glyph variable MyDomains that is a list of domains you want to select you can push this button and then type MyDomains or pick MyDomains from the list of variables in the Browser DB Pick Mask This button sends you to the DB PICK MASK menu see Section 2 4 3 which allows you to filter which database entities can be selected from the Browser Done All picked entities will be processed by the command Abort No entities are selected and control is passed back to the command that invoked the Browser 2 11 Graphical User Interface 2 5 Selecting File Names To select a file name from the Browser follow this procedure 1 Position the cursor over the file name text in the Browser The text will be highlighted in salmon 2 Press and release either the left or right mouse button The text will be highlighted in white 3 Press the Open button Gridgen s Input Output commands require you to select the name of the file from to which data will be read or written This 1s done through the Browser window When it
182. e all subconnectors from the string and start over Done Apply the cumulative dimension of the subconnector string to the current connector Abort End the subconnector selection process without changing the dimension of the current connector If the connector being dimensioned consists of a single subconnector which will be the case if the connector is being dimensioned for the first time you will have the opportunity to copy the distribution Section 11 3 of grid points from the selected string of subconnectors to the current connector 11 2 ReDimension Grids Aaditional Effects Copy A Values d Copy Scaled Dist 5 Done Dont Copy Dist esc Copy Values If the string consists of a single subconnector then this command allows you to copy the distribution parameters distribution function spacing constraints etc from the subconnector to the current connector Copy Scaled Dist Create a general distribution function Section 11 3 2 2 on the current connector that has the same features as the distribution of grid points along the selected string but scale the distribution from the selected string to the current connector based on the relative arc length of the string and connector Done Don t Copy Dist Do not copy any distribution parameters from the string to the current connec tor just copy the dimension 11 1 3 Additional Effects In addition to dimensioning the connector by the means described in the previous subse
183. e button automatically executes the Next Edge command after each connector is picked The implication 1s that at least two adjacent edges of the domain consist of a single con nector If you pick those two first Gridgen can determine when the third and fourth edges are complete by comparing the number of grid points on edges one and two Auto Complete When this toggle is enabled default Gridgen will attempt to automatically complete the assembly of structured domains after you define the first two edges In instances where two distinct domains can be created by the automatic completion process Gridgen does nothing Rather you proceed with the 9 7 Creating Domains connector selection process for the third and fourth edges After each connector is picked Gridgen again attempts to automatically complete the domain Another command is available for automating the assembly of unstructured domains Auto Save al Auto Save This command causes the Save Domain command to be executed automatically when the domain s first edge outer boundary closes on itself The implication is that the domain has no inner bound aries Several other commands are available during domain assembly Next Edge n Reorient Edge e Erase Last Connector del Restart Domain 0 Merge Nodes n Conns c Nod Con 2 Auto t Pick k Update d TopoFltr A11 3 OFree 4 NonMnf ld F ree 5 Next Edge Saves the picked connectors as the current edge a
184. e color bar type indicates the palette from which the colors used to render the diagnostic function are cho sen The two palette types are indicated by the radio buttons Spectrum and Traffic Light labeled Color Bar Type The Spectrum color bar below left gives a rainbow effect with colors varying from blue to red The Traffic Light color bar below 2nd from right gives a good bad effect with in range above range and below range cells rendered in green red and yellow respectively The radio buttons rev for each color bar type allow you to reverse the order of colors in the color bar For example the Spectrum color bar uses by default blue for the low values and red for the high values If the rev button is toggled on red will be used for the low values and blue for the high values below 2nd from left The reversed version of the traffic light color bar is shown on the right below mas 2S t Ratio mas Apot Ratio mas Apot Ratio mas Apot Ratio 16 8 Display Attributes Color Bar Values 16 3 3 Color Bar Values Color Bar Values Minimum 1 4 Max i mum 2 Type In pad Reset Nn e The buttons following this label allow you to change the range of diagnostic function values represented by the color bar By default when a diagnostic function 1s first rendered the color bar values are computed to cover the entire range of the current diagnostic function s values so that all cells are in range Those mini
185. e ea Moeatsed aos sepia la ds 5 8 6 Creating Database Entities oooooococonoconocanocaroconronoronooo 6 1 EIU ti dla 6 1 62 POINT ii A nda 6 1 GCF CUI EEO EESE ls 6 2 ol 6 3 0 2 QUIN 6 3 D 0 9 AIM A UV Etc 6 3 6 94 GONIC urs ele pisito tii 6 3 FEO A A I ED DE MU Ru 6 3 6 5D OBSPbo ae ee uM UD MEM MM III CIE 6 3 SR e o estote dus get eae unde Esiste O Roos cd uaa PVP d UTE uo Mood eines 6 4 A AA etta LL HM E MU MEE M AM TIE 6 5 04 PIANC sos ETE TEE 6 5 6 4 1 Constant Coordinate Plane cccccccsssecccseeccseeecaeeeecseeessaesesseesssneessaees 6 5 04 2 PolnmEINOFTIAl PIfio lp 6 6 Bio OPONT AN Oea siii 6 6 0 44 COMA Om 6 7 BG SUT ACC ic TIEREN ET TER 6 7 Col RUSA SUM ACO NE 6 7 6 5 2 Polycohle SU THO nu tet thesia aoe s uta tabe tos EM UR ERU Lau ee UL E CR co henateh ts 6 9 6 0 0 OUMaCe Ol ROYO iii 6 10 6 5 4 Einear SW CCD IA dadas 6 11 e e O O 6 12 A aha essai de eed es 6 12 60 6 INOUE arcsec 6 14 7 Creating COMMECHOSS sse eene tnnt 7 1 ES QU T di is 7 1 Ti POO Segment opem adan E E 7 2 15 2 NOW Space SegdmelllS A 7 2 7 2 2 Database Constrained Segments cccccseeccsneeeeeeeeseeeeesseeessaeeeseaeeeeeas 7 3 732 9 HaltonaloegiTielis d o otn e a eile audi ousted ttes dereud 7 4 1 24 Other Segments aea rd iaa 7 7 7 2 5 Miscellaneou
186. e entities first disable them Section 15 6 and then disable the Dis abld DB toggle Section 2 9 in the DISPLAY COMMANDS menu Wireframe The entity will be rendered as a wireframe see below 2 23 Graphical User Interface Solid The entity is rendered as an opaque surface of a single color without light source shading see below Shaded The entity is rendered as a single color opaque surface with lightening and darkening based pri marily on the angle between the surface normal and the light source see below Solid Wireframe Solid and Wireframe display styles are superimposed If the solid shade color and the wireframe color are the same the wireframe will be drawn in the background color for improved visibility see below Shaded Wireframe Shaded and Wireframe display styles are superimposed If the solid shade color and the wireframe color are the same the wireframe will be drawn in the screen background color for improved visibility see below Hidden Lines Removed The entity surface is rendered as a wireframe model with all hidden wireframe lines removed from display see below 2 24 Display Editing Render Mode 2 10 2 Hender Mode Render mode is for use with database entities only and lets you specify how many curves are used to render a database surface render mode Outline n Intrvls 1 Isolines c Triangles t Outline For database entities outline mode i
187. e first several chapters of this User Manual are meant to be used as a reference You will consult them to get detailed information about particular commands you are trying to use 1 1 Grid Types Gridgen may be used to generate multi block grids A multi block grid 1s created by dividing the overall region to be gridded into one or more sub regions called blocks Gridgen may be used to generate both 2D and 3D blocks A 2D block consists entirely of surface cells while a 3D block contains entirely volumetric cells All blocks in the same grid must either be 2D or 3D you can not combine blocks of differing dimensionality in the same grid The grid in each block may either be structured unstructured or hybrid A structured grid consists entirely of hexahedral cells that have been arranged in an ordered IxJxK array An unstructured grid consists of tet rahedral pyramid and prism cells having no implicit order If all blocks contain structured grids then the overall grid is called structured When all blocks contain unstructured grids then the overall grid is called unstructured If the overall grid consists of both structured and unstructured blocks the overall grid is called hybrid a special type of unstructured grid 1 2 Data Hierarchy Data hierarchy refers to the four types of data called entities you will work with during the construction of your grid Gridgen organizes the entities into four types database geometry data that
188. e re applied 2 For unstructured domains and blocks a The grid is re initialized according to the saved attributes 14 2 3 Domain Linkages The same issues that affect connector linkages during modification affect domains In fact all of the link ages to other grid components are through the connectors that belong to the domain The only difference is the effect on the grid points interior to the domain Transformations are applied to each individual grid point to obtain its new location Stretching and scaling transformations will result in grid point distributions that cannot be replicated by any of the grid methods In addition modifying a domain that is on a database can cause the interior grid points to lose their link with the database If you later apply a grid method or perform an operation like ReDimension Grids that causes them to be applied automatically the grid could change drastically This can usually be repaired quickly but it is something to be aware of when modifying domains 14 2 4 Block Linkages As is the case for domains blocks are linked to other blocks by domains that they share interblock connec tions Blocks are linked to the domains that are used on their faces Blocks are linked to connectors that are used on their edges The same issues that effect connector and domain linkages therefore also effect blocks 14 6 Transformations Translate The only difference is the effect on the grid po
189. e three coordinate directions The example below shows the results of copying and then scal ing a domain relative to its lower left corner After the entities are selected you must pick a point called the anchor as shown in the menu below The anchor is a point that will remain fixed during scaling You can pick the anchor from the Display window using the right mouse button or you may press the Enter Anchor via Keybrd button and type in the 3D coordinates of the anchor point Enter Anchor via Keybrdpad Abort Dont Scale esc Once the anchor has been selected two mechanisms may be used to control the scaling as described below 14 8 Transformations Stretch Repick Anchor Point n Enter Handle via Keybrdpad Enter Scaling Factors e Abort Dont Scale esc The scaling can be controlled using the 3D cursor After selecting the anchor you may also pick a point called the handle from the Display window The handle 1s a point controlling the scaling The handle can be any pickable point or a point for which you type in the coordinates after pressing the Enter Handle via Keybrd button Scaling control is accomplished by moving the 3D cursor on the screen using the mouse with the right mouse button pressed During scaling the Display window shows the entities current trans lated position The Blackboard indicates the current cross position and scaling factors The scale factors then multiply the difference between the original point loca
190. e two means of setting the rotation angle as described below Enter via Keybd 1 Pick endpoints 2 Done Setting Angle ent Enter via Keybd Pressing this button lets you type in the total rotation angle in degrees in the range 0 360 Pick endpoints Pressing this button lets you pick from the Display window two points The angle of rotation from one point to the next around the current rotation axis determines the total angle of rotation Done Setting Angle Pressing this button saves the current rotation angle Set Rotation Axis Pressing this button lets you choose the axis around which the rotational extrusion will proceed The rotation axis menu is described below Axis Ft 1 lvia Keybd 1 via Picking 2 Axis Ft 2 lvia Keybd 3l via Picking 4 Axyz Keybd 5 Use X Axis Use Y Axis T Use Z Axis 8 Done Setting Axis ent Axis Pt 1 via Keybrd Pressing this button lets you type in the 3D coordinates of the first axis point Axis Pt 1 via Picking Pressing this button lets you pick the first axis point from the Display window Axis Pt 2 via Keybd Pressing this button lets you type in the 3D coordinates of the second axis point Axis Pt 2 via Picking Pressing this button lets you pick the second axis point from the Display window Axis Pt 2 Axyz Keybd Pressing this button lets you position the second axis point by typing in a 3D offset from the first axis point Use X Axis Pressing this button uses the body x axis as t
191. e user has the option of reselecting the boundary curves Reselect Coons Surfaces This option is available only with the Auto option when more than one sur face can be created out of the chosen set of curves This option returns the user to the Browser list of poten tial Coons surfaces Set Point Tolerance The point tolerance is used to check the selected database curves The point toler ance checks curve intersections coincident curves and curve endpoint matching to determine if curves need to be split deleted or joined as a vertex respectively 6 6 Note Notes single line character strings limited to forty characters may be added to the database Notes are use ful for providing a descriptive title creation instructions or brief reminders The 3D cursor is used to posi tion the note s text Pressing the Done button saves the note and keeps Gridgen in note creation mode The Abort button may be used to exit from note creation mode Curves Points Other commands used during note creation are Enter the Note e Enter the Note This command allows you to enter up to 40 characters of text 6 14 7 Creating Connectors 7 1 Overview Connectors are Gridgen s lowest level one dimensional grid element They are curves on which grid points will be distributed The complete definition of a connector includes three attributes shape as defined by one or more segments dimension the number of grid points on a connec
192. ect individual or sets of layers to operate on using commands in the Layer operations section of the panel see Section 5 5 4 There is a great deal of information conveyed sim ply by what is shown in the list and by the colors used The list is broken into three columns Tarer ento orent TA all disabled 1 hub e 2 x nacelle 3 4 5 6 5 a 10 11 12 13 14 The first column labeled Layer contains the layer number starting at layer O zero and ending at layer 1023 Also in the first column one layer number is preceded by an asterisk This as well as the green highlight of that layer indicates it is the current working layer This is the layer into which any newly cre ated database entities will be placed The second column labeled Ents contains a plus and or minus symbol indicating the layer contains either enabled plus and or disabled minus database entities Absence of either symbol indicates the layer is currently empty The third column labeled Description contains an alpha numeric description of that particular layer Cre ative and consistent descriptions can facilitate and enhance your use of the list filtering capability described in the next section see Section 5 5 3 Text color used in the layer Browser indicates the status of the layers Red text indicates that layer is cur rently on or its entities are currently rendered subject to whether or not they are enabled see S
193. ection 15 6 Black text indicates that layer is currently off its entities are not currently rendered regardless of whether or not they are enabled Double clicking of any individual layer will toggle its status between on and off Layers highlighted in royal blue are currently selected for use of the Layer operations discussed in see Sec tion 5 5 4 Not all operations will be available according to whether one or multiple layers are currently selected Simply move the cursor over a layer entry in the list and press the left mouse button to select it You can also press and hold the left mouse button while moving the cursor up or down the list to select mul tiple layers in sequence Standard conventions can be used for more elaborate picking operations For instance you can select a sin gle layer move down in the list using the right hand scroll bar and then use Shift pick left mouse to select a contiguous list of layers Use Ctrl pick left mouse to select multiple non contiguous layers 5 5 3 List Filters The layer Browser does not always have to list all 1024 layers The list shown in the Browser is subject to the filtering options in the following section of the panel Keep in mind the current working layer shown with an asterisk in the Layer column and highlighted in green will always be shown in the Browser list regardless of any filtering applied The three filters are arranged in order of precedence Show Empty Description a
194. ectors are selected end to end However all inner boundary loops must proceed in the direction opposite to that of the outer boundary Before beginning to create a domain you must choose 1 the node from which the domain s perimeter will begin and end 2 the direction in which the connector loop will be selected Defining the Outer Edge After selecting Cell Type unstructured and pressing the Assemble Edges button the Blackboard prints the message Defining the Outer Edge The outer boundary is always the first edge in an unstructured domain 9 4 Assembling Unstructured Domains Defining the Outer Edge Define the edge by selecting the connector or connectors starting from the chosen corner node and proceed ing in the desired direction The example above starts the domain from the lower left node and proceeds in a counter clockwise direction The node to which connectors can be added to the domain s perimeter has an open circle drawn around it After at least two connectors have been selected the node at the beginning of the domain s perimeter has a filled circle drawn over it When a connector is added to the edge the screen is updated Continue the connector selection until all connectors on the perimeter of the domain have been added If you select an un dimensioned connector while creating a domain you will be prompted to enter a dimension via the keyboard When the domain s perimeter is closed press the Save Domain bu
195. ed entities will display a discontinuity across their common boundary Block 2D or 3D adjacency is determined by block connections using a common boundary If a connection between two blocks is overridden with a baffle type boundary condition no adjacent entity information will be available at that boundary 16 2 7 Smoothness Snooth oi ei 5 ok ag For structured grid entities the normalized turning angle from one side of a gridpoint to the opposite is ren dered in the Display window and a tabular summary is listed in the Blackboard The radio buttons i j and k indicate the direction in which the turning angle measure is to be computed the i j or k computational direction respectively The Smooth function is a point based measure Gridgen computes the angle turned while traversing three adjacent coordinates index 1 the current 1 j k and index 1 in the computational direction chosen A value of 1 indicates there is no turn or the three points are colinear A value of 0 5 indicates a 90 degree turn And a value of 0 indicates a 180 degree turn or the grid 1s folded onto itself Furthermore this function will be calculated across entity boundaries as long as the adjacent entities are loaded into Examine as well Other wise the value at boundaries will be set to 1 If a topological hiliter Section 16 5 is active the index 1 and index 1 points used in the calculation will be rendered with open diamonds on either side of the hilite
196. een successive user defined control points in three dimensional x y z space At least two control points are required to create 3D Space seg ments The Line Curve and Akima segment types differ in how the polynomial is computed The 3D Space Line segment above top is a piece wise linear curve a polyline 7 2 Add Segment Database Constrained Segments The 3D Space Curve segment above center is a cubic polynomial in x y z space between successive control points resulting in a curve with continuous slope at interior control points The cubic polynomial is constructed so the slope at a given control point is parallel to the chord between the two adjacent control points Catmull Rom spline At the Curve segment s end points control points from adjacent segments are used to compute the slopes If no adjacent segment exists the curve slope will be tangent to the end control point and adjacent control point The 3D Space Akima segment above bottom is a cubic polynomial between successive control points resulting in a curve with continuous slope at interior control points The cubic polynomial is constructed using a stencil of five adjacent control points to account for possible linear slopes Akima segments gener ally have fewer wiggles than Curve segments and should probably be used when a smooth curve with min imal overshoot is needed 7 2 2 Database Constrained Segments The database constrained segments are simple pol
197. efaults d Modify Other Edges m Reset to Defaults Change all foreground control function attributes on the boundaries to their default values Modify Other Edges Return to the boundary selection menu 12 2 5 2 Form Form oft o on o Hilgensh Sorensn s Off Foreground controls are turned off on the selected boundaries On Foreground controls with the specified attributes including form are applied to the selected boundaries This is the default for all non singular boundaries 12 9 Grid Methods for Structured Domains and Blocks Sorensn Apply the Steger Sorenson Reference 21 foreground control function formulation to the selected boundaries The resulting grid 1s smooth clustered and orthogonal at the boundaries However the constraints are only maintained in an approximate sense especially in concave regions Hilgens Apply the von Lavante Hilgenstock White Reference 10 Reference 37 Reference 39 fore ground control function formulation to the selected boundaries This method yields virtually exact enforce ment of the constraints but the grid may lack some of the smoothness provided by Steger Sorenson This method is the default von Lavante Hilgenstock White left is compared to Steger Sorenson right below m d TAE I NT 12 2 5 3 Spacing Constraints The spacing constraint refers to the distance between the boundary edge for domains and face for blocks grid points and the first
198. electing one of the options you are placed in the File Browser Section 2 5 to select the name of the image file to be exported After the picture file is created the program will return to the DISPLAY COM MANDS menu 2 12 OnLine Help To read the on line help text description of commands on the current menu follow this procedure 1 Either press the key or the Help button 2 27 Graphical User Interface 2 Readthe text that appears in the HTML browser that Gridgen starts The Gridgen Help Library provides immediate context sensitive on line assistance with all of the soft ware s features The Help command is invoked at any point in Gridgen by pressing the Help button or the key When it is enabled the Help text will appear in an HTML browser such as Netscape Communicator that is invoked by Gridgen The help text is the Gridgen User Manual formatted in HTML The on line help is formatted using cascading style sheets Therefore your browser must be CSS compatible Netscape Gridgen User Manual I File Edit View Go Communicator Help y ES E Ab lt lt Y 4 2 y 4 4 A d Back Forward Reload Home Search Netscape Print Security Stop SE E 3 13 On Line Help To read the on line help text description of commands on the current menu follow this procedure 1 Either press the key or the Help button 2 Read the text that appears in the HTML browser that Gridgen invokes The Gridgen Help Library provides immed
199. element They are surface grids Two types of domains are supported in Gridgen structured and unstructured A structured domain consists of an IxJ array of quadrilateral cells and 1s defined by the four edges on its perimeter An unstructured domain consists of triangular cells and is defined by one perimeter edge and possibly several interior edges enclosing holes in the domain Examples of structured and unstructured domains are shown below on the left and right respectively L PJ Ls a CD ET L3 ep a z S Xen FR FAO ri DP e Es F a Ez E rta m m Di o VD AA A AS This chapter describes three methods for creating domains Assemble Edges The process of assembling edges involves selecting the connectors on a domain s perimeter Triangulate Struct Doms This command creates an unstructured domain by converting an existing structured domain On DB Entities This highly automated command creates a domain on every database surface that you pick and then trims the connectors between adjacent domains so they fit together topologically Domain creation by extruding connectors is covered in Section 8 The chapter concludes with a discussion of special domain types 9 2 Assembling Structured Domains The four edges of a structured domain represent the curves on which the domain s i and j indices are at their minimum and maximum values Each edge consists of one or more connectors Domain creation can
200. ent generatrix and select another Erase Rail Curve After the generatrix and rail have both been selected you can use this command to erase the current rail and select another Erase Both Curves After the generatrix and rail have both been selected you can use this command to erase both the current rail and generatrix and start over Reverse the Direction This command allows you to reverse the sweep direction by implicitly reversing the parametrization of the rail The figure below shows the results of reversing the sweep direction of the sweep surface shown above 6 5 5 Fit A fit surface is used to create a slope continuous cubic polynomial surface through a bi linear surface The fit surface will interpolate each of the bi linear surface s control points The goal of the fit surface 1s to cre ate a smooth representation of a faceted surface Often you are given a geometry definition that is sparsely defined Rather than use the sparse faceted surface you may create a fit surface which 1s more suitable for grid generation and for some of the geometric database calculations such as intersections 6 5 6 Coons The Coons surface creation tool constructs a NURB surface based on a set of curves that form a closed perimeter Coons surfaces can often be very useful in filling the holes and gaps sometimes found in database models The Coons command requires the input of a set of four or less curves which can be existing data base curves su
201. entities 1 disabled entities are rendered in a minimal sense reducing visual clutter in the Display window 2 disabled entities are not loaded into the pick list which can substantially improve the graphical response during picking especially for large grids En Disable t Upon invoking the En Disable command the Browser lists each entity according to its enable disable sta tus The browser text will be white if the entity is enabled The browser text will be salmon if the entity is disabled Picking an entity will immediately toggle its enable disable status and the Display window image will change accordingly The En Disable command is also available via the Display menu 15 6 1 Database Entities Disabled database entities are not rendered by default When a disabled database entity is enabled its previ ous display attributes are recalled and the entity is rendered as before 15 6 2 Connectors Connectors cannot be disabled 15 6 3 Domains Only domains that are not used in blocks may be disabled To disable a domain used in a block you must disable the entire block The display of a disabled domain s grid points 1s turned off and the domain s con nectors are rendered in a half tone color 15 6 4 Blocks A disabled block s connectors are rendered in a half tone color and the grid point display of each of its con stituent domains is turned off 15 7 ReSpecify y and ReSpecify 8 n AX The ReSpecify
202. eo cassette recorder for example fast forward rewind VCR buttons are easily identified because they use symbols instead of text Scroll Y Y IV JA t e The button with an arrow pointing downward to a horizontal line is the End of List button When it is pressed the list is positioned so that the last item is at the bottom Its hot key is gt e The button with two downward pointing vees is the Page Down button When it is pressed the list is moved downward by one page Its hot key is 44 The button with one downward pointing vee is the Scroll Down button When it is pressed the list is moved downward by one line Its hot key is J The button with one upward pointing vee is the Scroll Up button When it is pressed the list is moved upward by one line Its hot key is f e The button with two upward pointing vees is the Page Up button When it is pressed the list is moved upward by one page Its hot key 1s f The button with an arrow pointing upward to a horizontal line 1s the Beginning of List button When it is pressed the list is positioned so that the first item is at the top Its hot key is 2 3 6 Quick Keys To jump to a command menu using the Quick Keys follow this procedure 1 Position the cursor over the Quick Key 2 Press and release either the left or right mouse button Cons C Doms D B1ks B DB F Dflft T 1 o E AS W A G1yphY Quit Q Save s Disp a Help Quick K
203. eps 1D smooth ing is used and all subsequent marching steps use 2D smoothing 8 10 Extrusion Attributes Boundary Conditions Turning Angle Corner Flat Stp Reduction Pr imry Sendry The Turning Angle and Stp Reduction parameters prism extrusion only allow you to identify regions along the extrusion front that should be considered to be corners and flats Identification of these regions is necessary because special actions will be taken in these regions Specifically the Turning Angle parameters identify the regions and the Stp Reduction parameters specify the special actions to be taken Turning Angle Corner Flat The turning angles entered here are used to identify concave regions in which special actions are to be taken The Corner angle is the angle between adjacent grid cells the rela tive turning angle between the two cells normal vectors above which the edge is marked as a corner For example if the included angle in the corner is 30 degrees the Corner angle would be entered as 150 The Flat angle is the angle between adjacent grid cells below which the edge is marked as a flat region For example if the included angle between the two cells is 160 degrees the Flat angle would be entered as 20 Stp Reduction Primry Scndry These two parameters control the reductions in marching step size to be applied at and near Flat points that are adjacent to Corner points The Primry step reduction is a coefficient in the
204. er symbol indicates the layer is currently empty The last column contains the layer description if one has been applied using the layer manager panel see Section 5 5 4 Selection of a layer from this list instantly assigns the entities to that layer If the selected layer s status is currently off the newly reassigned entities will no longer be rendered in the Display window 5 4 3 The Layer Move Combine Commands The only other manner in which database entities can be assigned to a new layer is using the Layer Move or Layer Combine commands in the Layer Manager panel Please refer to Section 5 5 4 below for more information 5 5 The Layer Manager Panel The Layer Manager panel is used to control the status of layers 9 9 1 Opening the Layer Manager Panel There are two ways to open the Layer Manager panel use the Layer Manager command in the MAIN MENU shown below or use the associated key board hot key Shift m see Section 2 3 2 Note that this hot key can also be used to pop the Layer Manager panel to the top of your desktop windows even when the panel has already been opened 5 3 Layer Manager An example of the full panel is shown below It is divided into four logical sections the layer Browser list the Filter tools the various Layer operations and the Saved Layer Sets tools hub isolated nacelle isolated 5 4 The Layer Manager Panel Layer Browser 9 9 2 Layer Browser The layer Browser list is used to sel
205. every control point by pressing the Add A at O All button Break points and therefore subconnectors can be deleted by positioning the cursor over the break point and selecting the Remove A at O menu button This will turn the break point into a control point and will com bine the subconnectors on each side of the break point into a single subconnector To delete all of the break points and get only one subconnector you should press the Remove A All button When a break point is needed where no control point exists the Add CP L1 At O menu button may be used This will add a control point to the connector at the current cursor position This new control point can then be picked to be a break point as described in the previous paragraph The Add CP L1 At O menu button is the only command available under the Distribution commands menu that will alter the segment definition though not the shape of the connector Any control point added using this technique can only be deleted using the Edit command in the Connector Modify menu The Add CP O At O command should not be used indiscriminately For example if the cursor is on the branch segment between two database constrained segments a control point may not be added and you will be warned A to Next o i amp to Prev o i Two additional buttons are available for quick editing of the subconnector setup The A to Next O is used to move a break point one control point toward the end of the connector
206. ew point entity and adds a knot to each curve An apparent intersection is one in which the curves intersect only in the plane onto which they are projected for intersec tion For example consider intersecting the line 0 0 0 1 0 0 with the line 0 5 0 5 1 0 5 0 5 1 These lines do not truly intersect the first is defined in the z 0 plane and the second in the z 1 plane However they do apparently intersect when projected into the z 0 plane In this instance Gridgen creates two new points one at the apparent intersection on each curve and adds a knot to each curve Database point entities are not candidates for intersection Nor are plane plane intersections allowed Con nectors domains and blocks cannot be intersected The intersection process is controlled by selecting two groups of entities called Group A and Group B You do not have to create group entities and use them for computing intersections the term group in this dis cussion refers to the two collections of entities that you pick for intersecting Group A may consist of a sin gle curve or surface as can Group B Every entity in Group A will be intersected with every entity in Group B Each new entity resulting from the intersections will be drawn in the Display window in yellow as it is computed The Blackboard window will display a horizontal bar that indicates the percent of the entity pair ings for which intersections have been attempted ReRun s Cont inue c
207. ex regions and increases the local step size in concave regions Stretching Factor Set 4 Stretching Factor normal extrusion only Pressing the Set button allows you to enter the coefficient of a scale factor that reduces the local marching step size in convex regions and increases the local marching step size in concave regions The default stretching factor value is 5 and it must be specified in the range 1 10 The two grids shown below compare the effects during a normal extrusion of the minimum allowed stretching factor 1 0 left and the optimal stretching factor 5 0 right 8 6 Extrusion Attributes Marching Direction A NU lt S SS Ar RS SE 8 2 5 Marching Direction For hyperbolic and normal extrusion the following attributes control the marching direction Note that many of these attributes are available for domain extrusion However for block extrusion the marching direction 1s uniquely defined except for reversal by the normal of the initial surface grid Plane o Vector Set e Flip d March Plane When enabled this radio button indicates that the marching trajectory is to be parallel to the screen xy plane in other words in the plane of the Display window Available for domain extrusion only March Vector When enabled this radio button indicates that the marching direction is parallel to the screen z vector in other words perpendicular to the Display window Available for
208. eyboard This button allows you to type in any value for the relaxation parameter in the range 0 lt lt 0 5 The figure below illustrates the difference between an un smoothed 0 grid on the left and a fully smoothed grid 0 5 on the right AX AA e SS PS N EN B XN SOLAS ISS LO INDY L AX SN 5 D AN OY SJ SCC DEVE y p 7 BA YS ake YN NIN NA A is Y AV nh N A FN eae JUR KA IN 13 5 Triangular Mesh Attributes The unstructured solver s grid control parameters allow you to establish the criteria by which the solver decides whether a point needs to be inserted into the grid As long a cell is larger than the minimum cell size a point will be inserted into it if any of the other grid control parameter values are exceeded 13 5 Grid Methods for Unstructured Domains and Blocks Triangle Min Edge 1 Max Edge 2 Max Surf Dev 4 Max Ang Dev 5 Boundary Decay 13 5 1 Minimum Triangle Edge The Triangle Min Edge attribute allows you to specify a lower limit on triangle edges If a cell s edge is smaller than the specified minimum edge a point will not be inserted into the cell This attribute is used to compute triangle areas where each triangle 1s assumed to an equilateral triangle that has a spacing equal to that of the minimum edge size on each of its three sides The minimum edge par
209. eys are available when the QukMnu toggle in the DISPLAY COMMANDS menu Section 2 9 is turned off They are used to e jump from your current location in Gridgen s menu structure into another menu to export a Gridgen file to exit Gridgen When they are available the Quick Keys appear as three rows of four buttons each at the bottom of the menu The Quick Keys hot keys are all uppercase The Quick Keys are e Cons CONNECTOR COMMANDS menu e Doms DOMAIN COMMANDS menu e Blks BLOCK COMMANDS menu e DB DATABASE COMMANDS menu e Dflt SET DEFAULT VALUES menu I O INPUT OUTPUT COMMANDS menu AS W ANALYSIS SOFTWARE COMMANDS menu 2 5 Graphical User Interface e Glyph GLYPH COMMANDS menu Quit exit Gridgen e Save QuickSave writes a Gridgen file to the file name set in the SET DEFAULT VALUES menu Disp DISPLAY COMMANDS menu Help start Gridgen s help system 2 3 7 Quick Menu To use a Quick menu command follow this procedure 1 Make sure the Quick menu is enabled by the QukMnu toggle Section 2 3 7 button in the DISPLAY COMMANDS menu 2 Position the cursor over the desired Quick menu button 3 Identify the command you wish to use by the descriptive text that appears when the cursor is over the button 4 Press and release either the left or right mouse button 9 6 s s ss os p u r z z Z plrlodo tete LL E The Quick menu is available when the QukMnu toggle in the Displa
210. f Group B Group B entities are colored pink Set Tolerance Intersections are computed within a tolerance the computed intersections will vary from the theoretical intersections by no more than the tolerance By default intersections that result in a curve use the surface fit tolerance Section 3 7 1 Intersections that result in a point use the same point tolerance Section 3 7 1 Pressing the Set Tolerance button allows you to enter your own tolerance value for the intersection calculations Abort When the intersection process is paused pressing the Abort button will exit the intersection com mand and delete any intersection curves it had computed Done When the intersection process is paused pressing the Done button will exit the intersection com mand and save any intersection curves it had computed INTERSECT Paused tolerance default Group A 10 entities Group B 10 entities 2 X num intersections 1 intersecting 3 11 The above illustration shows many of the graphical features of the intersection procedure The Group A and Group B entity numbers currently being intersected are listed in the Blackboard and their images in the Dis play window are highlighted with a thicker line width relative to other members of the group New intersec tions immediately appear in the Display window yellow in color as does a numerical tally of the number of intersections in the Blackboard The percent complete bar the hor
211. f the Display window image so that the focus grid s projection vector is parallel to screen z 8 2 3 Aspect Ratio Aspect Ratio Factor Ad The Aspect Ratio Factor adjusts the local marching step size based on the size of the local cell At each step the smallest cell will receive the initial physical step size All other cells will receive a larger step size based on their size compared to the smallest cell and the value of the aspect ratio factor The default aspect ratio factor value is O no change to the step size and it must be specified in the range 0 1 The two grids shown below compare the effects during normal extrusion of the minimum aspect ratio factor 0 0 on left and the maximum aspect ratio factor 1 0 on the right Py Fre dn 8 2 4 otep Size s Init 5 Hin Max 7 Growth Rate 4 Geometrical Set 8 o Subcon b As Init This command lets you set the size of the first marching step By default this value is obtained from the Defaults menu Section 3 1 5 If the Defaults value is not set the default first marching step size is DOM M 8 5 Grid Extrusion Methods As Min This command lets you specify a lower limit for the marching step size By default this attribute is not enabled As Max This command lets you specify an upper limit for the marching step size By default this attribute is not enabled Growth Rate Geometric Enabling this radio button means that the march
212. f their common node is also shared by one or more other connectors This is due to the fact that joining implicitly deletes nodes 14 8 3 Domains Domain joining proceeds in the same manner as block face creation Section 10 5 in that many domains can be joined to create a new domain Structured domains must be joined in a manner that results in a computa tionally rectangular region whereas no such restrictions are place on joining unstructured domains It is not possible to join domains that span multiple blocks regardless of how they fit together This is because the collection of joined domains is replaced by a single domain that would not fit into either block If you attempt to join domains in this manner a warning message is displayed All connectors on the interior of the joined domain previously on the perimeters of the constituent domains are deleted For structured domains each constituent domain becomes a subdomain in the joined domain 14 8 4 Blocks Only blocks that share an entire common face may be joined Unstructured blocks may not be joined Once a block has been picked for joining you simply pick the block to which it will be joined 14 9 Connector Segment Modification Segment Add n Insert n Edit e Erase e The commands Add Insert Erase and Edit allow you to modify the component segments of a connector and are described in the following subsections 14 9 1 Add The Add command is used to add a segment to
213. faces currently displayed you would position the hiliter over that surface and press this button Erase All Pressing this button erases all of the reference surfaces 16 16 17 Analysis Software Interfaces A powerful feature of Gridgen is its ability to customize the grid for a particular analysis software package When you choose one of the supported analysis codes Gridgen will use the analysis software s nomenclature enforce the analysis software s grid topology requirements allow you to apply the analysis software s boundary and volume conditions export boundary condition volume condition and grid data in files that may be used directly in the analy sis software The following sections discuss each of these capabilities in more detail following the order of the ANALY SIS S W COMMANDS menu as shown below ANALYSIS S W COMMANDS Select Analysis S W Set BCs Set YCs Examine CustomBCs Create c Delete d CustomVCs Create Delete 8 Mirror Blks for Export b Export Analysis Data 2 Export FY Bndry Surf File 5 Done ent dE 17 1 Select Analysis Software Selecting your analysis software ASW will usually be your first step in creating a grid By choosing your ASW first you ensure that Gridgen will create a grid that meets your ASW s requirements You can change analysis software including 2D and 3D at any time but all boundary condition information you have set will be lost Depending
214. filter The value entered after pressing this button is the coefficient in the range 0 1 for the smoothing A value of 0 means smoothing is fully enabled while a value of 1 means that smoothing has no effect The default value is O 7 Grid Count The marching direction is smoothed by adding a component to the local trajectory of each grid line This additional component is obtained by smoothing the grid at the current step computing the relative movement of each grid point and adding that movement to the normal vector in the marching direc tion The value entered after pressing this button 1s the number of iterations of the smoothing algorithm The default value is 0 Grid Angle The component added to the marching direction from the grid smoothing sweep will be lim ited to the angle in degrees entered after this button is pressed This angle must be in the range 0 90 The default value 1s 20 Edges 1D 2D and Cnt prism extrusion only In 1D mode the smoothing of normals step size and grid points behaves as follows points extruded from nodes are not smoothed points extruded from connectors are smoothed using only other points on the same connector points extruded from a domain s interior are smoothed using all neighboring points In 2D mode the smoothing is performed without regard for where the extrusion originated The optional parameter Cnt is used to transition from 1D to 2D smoothing For the first Cnt marching st
215. from the boundary point information only Section 12 1 Surface Shape Params These attributes define how the shape of the selected surface grids is computed These settings are not available for blocks Relaxation Parameter This attribute controls the convergence rate of the iterative solution of the PDE Background Cont Funcs The background control function influences the distribution of grid points on the interior of the grid Foreground Cont Funcs The foreground control function influences the distribution of grid points near the boundaries of the grid Solver Bound Conds Movement of the grid points on the grid boundaries during elliptic refinement is controlled with this attribute Two other commands come into play when you are setting attributes The following two buttons appear within each of the specific attribute menus Set Other Attributes esc Done Setting Attributes ent Set Other Attributes Pressing this button will invoke the main solver attributes menu so that you may select a new attribute type to set Done Setting Attributes Pressing this button will invoke the solver and enter pause mode You may then press the Run button to continue running the solver with the new attributes 12 2 3 Relaxation Parameter Gridgen calculates the elliptic PDE solution on a grid using a successive over relaxation SOR numerical algorithm This is an iterative method to converge upon the grid point locations that
216. g highlighted may be moved using the menu s VCR buttons the left arrow and right arrow key or by entering the plane index using the Type In E plane button The highlighter is moved around the constant index plane by moving the mouse with the right mouse button pressed When the open circle at the intersection of the highlighter lines is positioned over one of the corners of the desired subgrid press Add Corner at O button Then move the highlighter to the grid point at the opposite corner of the subgrid During this process the subgrid s outline is rendered in the Display window in pink The Black board shows the subgrid s dimensions Save the subgrid by pressing the Save button The saved subgrid is rendered in the Display window with a pink outline and Gridgen remains in subgrid mode awaiting the defi nition of the next subgrid SubGrid creation is completed by pressing the Done button Block box Ls total dims 7161 E max 31 max max LON Creating SubGrid AA er Cursor at amp 23 15 4 re este tentative dims EM B e 23C 1 ts I ADDING A SUBGRID Restart Move O via Keybrd pad o n ile E k wiyi viAalal a Type In amp plane 2 Save ent 12 3 2 Deleting SubGrids The SubGrids Del command is used to remove subgrids from a structured domain or block Upon invoking this command the grid s subgrids are rendered with pink outlines A subgrid is selected for deletion by mov
217. gment is used to create a general conic section spanning an arc of no more than 180 degrees Since conics are essentially quadratic polynomials they are restricted to lie within a plane how ever the plane need not be at any particular orientation The Conic Section segment is defined by three con trol points as shown below The first control point P defines the beginning of the segment and the second control point P defines the ending of the segment The third control point defines the tangent intersection point P The initial location of P is midway on a line connecting P and P called P As P is moved via the cursor the conic section segment is drawn as both a curve and two tangent slope lines The segment passes through Py P and P where the shoulder point P is the point on the conic that intersects the line 7 4 Add Segment Rational Segments between P and Pp y Pi Instead of the third point in the conic definition being the shoulder point P you may choose to position the tangent intersection point P using the menu buttons shown below Store Picked Inters Pt i Store Inters Pt via Kbd i Store Picked Inters Pt Position P at a picked point Store Inters Pt via Kbd Enter the location of P via the keyboard In addition to positioning point P you can also adjust the p value of the conic p will approach 0 as the shoulder point P approaches Pn and p will approach 1 as the shoulder point P approaches P
218. grid for use with your analysis software package Tutorials import one of Gridgen s tutorial grids Defaults commands for setting various Gridgen switches Glyph commands for creating modifying and replaying script and journal files Restart Gridgen is used to quickly delete all or a portion of the current project You can choose to delete the grid and or database You can also reset tolerances the selected analysis software and Default menu items back to their original default settings Quit Gridgen exit Gridgen Input Output e Database f Connectors c Analysis S W a Tutorials 5 Defaults Ad Glyph Restart Gridgen esc Quit Gridgen ent Cons El DB F Dflt T 1I o E AS W A GlyphY Quit a DispAa Help Planning Your Grid Display Commands commands for changing Gridgen s appearance and the display of your grid and database Help invoke Gridgen s on line help One feature that makes Gridgen easy to learn and use 1s the parallelism of the menu structures for the four data hierarchy entities database connectors domains blocks These menus all contain similar commands for each entity type Create make a new entity Copy duplicate an existing entity Delete remove an entity Modify change an existing entity Examine obtain detailed information about an entity Furthermore the Modify menu commands listed below operate similarly for each entity type Translate Scale Stretch Mirror Rotate
219. grids created in another application and applying Gridgen s analysis software commands Section 17 to post process a grid from another application for one of Gridgen s supported analysis software packages Gridgen creates connectors from grid point data by fitting the equivalent of a Line segment through each grid point on an edge Therefore even though an edge may be a straight line or a circular arc in the grid file Gridgen will create a connector that is a Line segment containing as many control points as grid points MM Multi Loop Domains m During unstructured surface domain grid import you may use the Multi Loop Domains toggle button shown above to determine whether triangular surface meshes with multiple loops internal holes will be imported into Gridgen intact By default this button is enabled If it is disabled Gridgen will automatically split the surface grid into more than one domain each domain with a single outer loop Split Ang Off b Connections between blocks imported from grid point files are only detected by Gridgen if the connection is full face to full face The implication is that some instances of grid point import may result in Gridgen cre ating connectors and or domains that overlap a situation that is not recommended You may apply the split ting commands to designate where partial face connections are Upon completion of the splitting Gridgen automatically culls duplicate connectors and domains and
220. group will be highlighted When the new dimension is 11 3 Grid Methods for Connectors typed in it will be applied not only to the picked connector but to all other highlighted connectors System Redimensioning 34 Total Connectors 34 Initial Dimensions 0 Auto Set Dimensions 0 User Input Dimensions System is Dimensionally alance REDIMENSIOM GRIDS Reset to Balanced Sys a Done Apply New Dims ent Abort Use Orig Dims esc When the Blackboard shows the System is Dimensionally Balanced message you may Reset to Balanced Sys Undo your most recent redimensioning changes and return the system to its last balanced state which Gridgen saves as the process proceeds Done Apply New Dims Gridgen will perform the following steps automatically Apply the new dimensions to each redimensioned connector in the entire grid Distribute the new number of grid points using the existing distribution function and spacing constraints nitialize surface grids of each touched domain using each domain s last applied transfinite interpolation grid method nitialize volume grids of each touched block using each block s last applied transfinite interpolation grid method Abort Use Orig Dims Terminate the re dimensioning process without making any changes Any surface or volume structured grids touched by the redimensioning process previously run in one of the grid solvers or projected onto the database wil
221. guration Controlled Design and AP214 Automotive Design file formats Note The STEP file reader is an optional product Gridgen currently supports the Native CAD import on the platforms shown in the table below Native CAD Import Platform STEP CATIA Y 4 7 Importing and Exporting Files Native CAD Import Sun Solaris 4 4 4 5 Shells Gridgen can import unstructured surface grid files triangular faceted data such as STL VRML and NAS TRAN and use them as database entities The term shell represents the faceted equivalent of a continuous B Spline surface in Gridgen s database A shell is a set of point to point contiguous triangles All polygons in a unstructured grid file will be triangulated before use as a shell in Gridgen Files that have a quadrilateral surface grid are converted to triangles during shell import and are represented as shell database entities in Gridgen The following file type attributes are supported for shell import in Gridgen NASTRAN 6 QNASTRAN L 7 STL 8 VRHL 9 NASTRAN type refers to Version 69 of the commercial software product of the same name For detailed information on this format please consult Reference 16 For surface grid files Gridgen recognizes the fol lowing NASTRAN elements e CQUADA e CTRIA3 NASTRAN L type refers to the large format for real values in the NASTRAN file Large format uses 16 characters for real values whereas NASTRAN style uses
222. he 3D cursor Gridgen then examines each of the two points and checks whether or not they reference the same database entity If they do not Gridgen creates a 3D space line segment between the two points If both control points are on the same database entity Gridgen creates a database constrained line between the two points The image on the left below shows a 2 Point Connector during creation after the first point upper left has been saved and the dashed line connects it to the cursor location before the Store at Picked Pnt button has been pressed After the second point is picked from the same database entity the connector shape is snapped to the database curve as shown on the right below and the next 2 Point Connector is started with the cursor at the second point of the previous connector When Gridgen snaps the 2 Point Connector to the database it follows this hierarchy 1 Gridgen determines the shortest distance on the database entity between the two points and creates a database constrained line segment 7 10 On DB Entities Miscellaneous Commands 2 Ifthe shortest distance is already defined by an existing connector Gridgen tries to find a second path between the two points 3 Ifthe shortest path and the alternate path are both already defined by connectors Gridgen creates a 3D space line segment between the two points Other controls are available during creation of 2 Point Connectors Erase Last 2 Pt Con e Erase
223. he Database Connector Domain and Block menus Using these tools you can change the shape of any entity that you create in Gridgen or import from an external source The modification tools work the same way no matter what type of entity you are dealing with however some modification commands do not apply to all entity types The modification commands and the entities they work on are listed in the following table Modify Commands And The Entities On Which They Act command database connector Se unstr Nido domain un block translate B RRARARARARAEA wee fe Cm 0 p ILL e LEER a Lr CA CA CA ATALS TD NG o SI SNS S SAS AT S SS S H D E ES S ES omm qo c or AAA ome o qr App j smooth fT o o o 5 N E BEL Lo oL ome qo A 1 l o IC O A a O a a AE PY SN S Before discussing each modification command the manner in which Gridgen maintains the relationship called the linkage between database entities connectors domains and blocks during modification will be 14 1 Modifying Entities described 14 2 Linkages Gridgen maintains relationships between database entities and grid entities and between the different grid entities themselves These relationships called inkages allow Gridgen to keep connectors and domains attached to the database entities on which they were created or projected and allow Gridgen to keep adjacent grid entities attache
224. he new edit point Edit e Bezier segments only Control is passed from the current control point to the left or right side slope point of the control point depending on the color selected Mouse movement will then control the selected slope point in the usual manner DB Ent Next database segments only This command will move the current edit point to the next entity in the list of toggled entities Under some circumstances this may cause the addition and or deletion of control points surrounding the edit point but only when such a modification is necessary to maintain a viable defini tion on a surface DB Ent Prev database segments only This command will move the current edit point to the previous entity in the list of toggled entities Under some circumstances this may cause the addition and or deletion of control points surrounding the edit point but only when such a modification is necessary to maintain a viable definition on a surface DB Ent Pick database segments only This command will move the current edit point to the entity picked graphically by you Under some instances the picked entity will cause control points surrounding the edit point to be added and or deleted in order to maintain a viable definition on a surface Return to Control Point Bezier segments only Control is passed from the control point s slope point back to the control point itself Cnvrt to Line not for Circles or Conics The current segment
225. he rotation axis Note that this 1s the true body x axis and doesn t necessarily correspond to the location of the body axes as drawn in the Display window Use Y Axis Pressing this button uses the body y axis as the rotation axis Note that this 1s the true body y axis and doesn t necessarily correspond to the location of the body axes as drawn in the Display window Use Z Axis Pressing this button uses the body z axis as the rotation axis Note that this is the true body z axis and doesn t necessarily correspond to the location of the body axes as drawn in the Display window Done Setting Axis Pressing this button saves the current rotation axis A path based extrusion uses the following attributes to establish the marching direction Pick Path Cons 1 M Path Rotations 2 Pick Path Cons Pressing this button lets you pick from the Display window the subconnector string that will define the path the extrusion is to follow The marching step size is also obtained from the subconnector string 8 8 Extrusion Attributes Smoothing Parameters Path Rotations If this toggle button is enabled the extruded grid will rotate relative to the tangent vector of the subconnector string defining the path Otherwise the grid will remain parallel to the initial grid The example below shows the effect of enabling path rotations for a path based extrusion The initial grid 1s the horizontal connector at the bottom of each domain The path is
226. here are no hot keys for orientations 3 6 These six orientations will be saved in your Gridgen file PutOri Buttons 1 through 6 in this row allow you to recall Put the six orientations of the Display win dow image saved by the Get Ori command Note that there are no hot keys for orientations 3 6 LightSrc The Obj and User radio buttons set the type of light source used when rendering shaded surfaces User fixes the light source at your location in other words light rays are cast in the screen z direction This means that surfaces will appear lighter in color where the surface normal is parallel to screen z and darker in color where the local normal is nearly perpendicular to screen z On the other hand Obj fixes the position of the light source with the object so that as the 1mage is rotated the relative shading depends on the light source and the viewpoint Photo The rgb png bmp and ps buttons in this row are used to save the Display window image in a file Section 2 11 either Silicon Graphics RGB IRIX only Portable Network Graphics Window Bitmap Windows only or PostScript formats Zoom The In and Out buttons in this row are used to invoke the zoom in and zoom out boxes respec tively Section 2 7 5 The Undo button restores the image s orientation prior to the last zoom box 2 10 Display Editing To change the display of grid or database entities follow this procedure 1 Press the Display Commands button 2 Choo
227. hes dx 2 There are several interesting features regarding the axis in Gridgen s surface of revolution which are illus trated in the figure below Surface of Revolution Generatrix Curve 2 Axis Curve 1 Fit Tolerance 0 100E 02 Angle of Revol 180 000 Patches 109x 2 The axis of revolution does not have to be a line but can be any curve This allows the creation of very general surfaces of revolution including pipes with substantial bends If the generatrix was created as an offset curve Section 6 3 6 from the axis then you can create a constant radius pipe Surface Linear Sweep Surface f the axis extends beyond the ends of the generatrix the surface of revolution will be defined only up to the end of the generatrix e If the axis is shorter than the generatrix the axis will be extended based on its end point slopes to the end of the generatrix Commands used during construction of a surface of revolution are Reselect Axis Curve del Reselect Both Curves 0 RejSet Fit Tolerance 2 Re5et the Angle a Reselect Generatrix After the generatrix has been selected but before the axis has been selected this command allows you to erase the current generatrix and select another one Reselect Axis Curve After the generatrix and axis have both been selected this command allows you to erase the current axis and select another one Reselect Both Curves After the generatrix and axis have both been selected thi
228. hoose the file name By default Gridgen lists in the Browser all files with extensions corresponding to database file types Gridgen determines the file type Section 4 4 4 based on the selected file name s extension If the extension cannot be determined it is assumed to be IGES Gridgen can import geometry data for use as a database via the formats in the table below Database File Extensions network net gore varada Gridgen com posite IGES igs iges Shell SEL wrl Mas Pm mo STEP AP203 AP214 For network files Gridgen can automatically detect whether the file s format is ASCII or binary However it cannot determine the file s data precision For composite files Gridgen cannot determine the format or precision automatically Whenever you set attributes using the FILE ATTRIBUTES menu the attributes are saved for use during any future imports during the current Gridgen session For example if you import a Gridgen style binary single precision network file once by setting the file attributes using the menu then the next time you import a network file Gridgen will recall the previous attributes and read the file directly The file attribute options used for the various Gridgen database file types are shown in the table below 4 4 network File Attribute Options Per Database File Type PLOT3D default ASCII default Fortran unformatted double default binary Gridgen Importing Database Files
229. hrough you may use this command to type in the offset distance 6 3 7 Extract An extract curve is a curve entity created by copying a constant u or v parameter line from an existing data base surface Shown below is an example of the Blackboard and Display window as the constant parameter curve at the hiliter location pink line on surface is being defined for extraction O interval xX Commands used in Extract curve creation include Extract Constant eu 1 ov 2 Jump To U mina U maxb V minc Y max c Move Ovia Keybrd pad Extract Hiliter ent Extract Constant U Convert the hiliter to show lines of constant u parametric coordinate Extract Constant V Convert the hiliter to show lines of constant v parametric coordinate Jump To U min Move the hiliter to the surface s minimum u coordinate line Jump To U max Move the hiliter to the surface s maximum u coordinate line Jump To V min Move the hiliter to the surface s minimum v coordinate line Jump To V max Move the hiliter to the surface s maximum v coordinate line 6 4 Plane Fit Move O via Keybrd Type in the u or v coordinate at which to place the hiliter Extract Hiliter Create a new database curve entity by extracting the curve at the hiliter location 6 3 8 Fit A fit curve is used to create a slope continuous cubic polynomial curve dark curve above through a fac eted linear curve light curve above The fit curve will interpolate each
230. iate context sensitive on line assistance with all of the software s features The Help command is invoked at any point in Gridgen by pressing the Help button or the key When it is enabled the Help text will appear in an HTML browser such as Netscape Communicator that is invoked by Gridgen The help text is the Gridgen User Manual formatted in HTML The on line help is formatted using cascading style sheets Therefore your browser must be CSS compatible Iles If BP m 3 s 3 s Em 2 2 ES D 2 a B es 5 e E h IR R ig Poe ua X http Zinside pointwise com jrc ri 3man fm help grdext htm 2 13 Miscellaneous Pressing the control key in conjunction with the right mouse button lets you pick a new rotation point The coordinates of the new rotation point are displayed in the Message window Pressing the shift key in conjunction with the right mouse button lets you query a picked point so that its coordinates are displayed in the Message window Furthermore the distance between the current point and the previously picked point will also be displayed The space hot key causes a redraw of the Display window Gridgen attempts to trap fatal errors before they cause a code failure You will receive a warning in the Mes sage window that an error occurred You should then save your work to a file exit Gridgen then restart Gridgen with your last saved file and continue 2 28 3 Setting Defaults The Defaults Main menu c
231. id lines in the marching direction The default value is 0 but you should set this smoothing factor to at least 3 if your initial grid contains any severe concavities Smoothing Volume This coefficient in the range 0 1 determines how rapidly grid point clustering along the initial grid will be relaxed as the grid is extruded A value of 0 will retain clustering on the initial grid all the way out to the outer boundary see left figure below The default value of 0 5 will rapidly relax the clustering see right figure below 8 9 Grid Extrusion Methods Count Count 2 Count 3 Angle 3 Edges 1D 2D Normal Count The vectors in the marching direction are smoothed locally using a LaPlace filter The value entered after pressing this button is the number of iterations for this filter The default value is 5 Normal Relax The vectors in the marching direction are smoothed locally using a LaPlace filter The value entered after pressing this button 1s the coefficient in the range 0 1 for the smoothing A value of 0 means smoothing is fully enabled while a value of 1 means that smoothing has no effect The default value is 0 5 otep Count The marching step size is smoothed locally using a LaPlace filter The value entered after pressing this button is the number of iterations for this filter The default value is 3 Step Relax The marching step size is smoothed locally using a LaPlace
232. idgen will examine the grid and automatically determine which of the three coordinate components x y or z should be held constant 8 2 8 Stop Criteria Set Stop Criteria c The category of attributes accessed by pressing the Set Stop Criteria button allow you to specify grid quality constraints if exceeded will cause Gridgen to pause the extrusion process so that you can take cor rective action For example you may choose to limit the total height of the extrusion Or you may have Gridgen calculate the Jacobian of hexahedra after each marching step and pause if any skewed cells are found In this later case pausing gives you the opportunity to back up the extrusion change some attributes and continue extruding In the figure below the extrusion has been stopped because the aspect ratio of the highlighted cell exceeds the specified upper limit of 7 You have three choices on how to proceed 8 12 Extrusion Attributes Copy Attributes SELECT OPTION Cont inue PAUSE save step PAUSE delete step Help Continue Pressing this button continues the extrusion process without regard to the highlighted cells Pause Save Step Pressing this button pauses the extrusion as it is and invokes the main extrusion menu so that you may change extrusion attributes to obtain a grid that meets your criteria or to relax your stop cri teria Pause Delete Step Pressing this button deletes the last marching step pa
233. ighlighted 2 Press and hold either the left or right mouse button 3 Move the cursor in the Browser to sweep over several items and release the mouse button The text will be highlighted in white 4 Repeat the selection process until all desired entities are queued and then press the Done button Picking multiple items from the Browser is facilitated by the fact that the list automatically scrolls up or down when the mouse button is held down and the cursor is moved above or below the Browser respec tively 2 9 Graphical User Interface 2 4 3 Pick Masks Enitity filtering is currently available only for database entities throught the DB Pick Mask command DB Pick Mask can be found in the SET DEFAULT VALUES menu and within the Browser list for data base commands where the selection of entities 1s required With this command users can filter the list of entities in the Browser so that only certain database entities types can be selected by the picking functions Database entities available for filtering are displayed in the DB PICK MASK menu seen below on the left These entities may be toggled to On or Off individually or in groups All entities toggled Off will appear darkly shaded in the Browser window list and users will not be able to select them The figure below on the right shows an example of the Browser window list with only B spline surfaces toggled to On DB PICK MASK Surfaces On s Ooff s parametric surface
234. iles x Ee dE pac eoe d oO te bent o redu 18 1 18 4 Database Network File 0 cccccecececcccececncnceccecececececueneeaeaeseseeesnsesneeaes 18 2 10 5 Segen E Hes sacs is dE 18 2 18 6 Composite Database File esses esee eren 18 3 18 7 FIELDVIEW Unstructured File ooooooococccccocococococonoccnonononcnnnnos 18 3 18 8 Generic Flow Solver BC File csse nnne nnn 18 3 18 9 Surface Grid File oue D e tet tds es 18 5 18 10 Volume Grid File oooooooococcccocccococoncococononcononononnononcnnonnnnnnnnnnnnnnnnnos 18 5 19 References 1 7 sees nsns asas nass asas assassins ss nsns 19 1 o ONU ERE he eee red cece ee eh cess 20 1 10 1 Introduction Gridgen is a software system for the generation of three dimensional 3D grids and meshes You may build a grid around any type of object using Gridgen it is not limited to any particular geometry The grids you create in Gridgen can be used with any type of analysis software including computational fluid dynamics CFD and finite element analysis FEA In fact Gridgen has built in filters for many analysis codes as well as popular neutral formats The following sections describe in detail the use of each Gridgen command If you are a new user and are interested in learning about how to run Gridgen we recommend that you begin by reading and running the Tutorials in the Tutorial Workbook Th
235. ill 6 5 Creating Database Entities appear on the screen Even though the plane can be defined at any location of the 3D cursor the plane icon will be rendered along the appropriate body axis During creation of the plane Gridgen draws a line between the cross location and the center of the plane icon Save the plane by pressing the Done button Location 3 680021 9 280132 19 40000 680021 Plane 6 4 2 Point Normal Plane A plane can be created by specifying two points a point P that lies on the plane and a second point P The vector P P is the plane s normal vector The 3D cursor is used to define both points using the standard control point creation methods Section 2 8 2 The first point the point on the plane is drawn as an open circle after it is added After the second point s location is added the plane icon is drawn at the first point s location with a line connecting P and P Save the plane by pressing the Done button Location 4 473934 11 43009 7 433350 uui uii 6 4 3 3 Point Plane A plane may be created by defining three points P4 P5 and P3 that lie on the plane The plane icon will be located at the average location of the three points The 3D cursor is used to define all three points using the standard control point creation commands Section 2 8 2 Each point is drawn as an open circle after it is added The triangle P P5 P5 P4 is drawn during construction up until the third point
236. in both the spacing and angle constraint columns the left entry tells how the constraint is computed and the right entry tells how the constraint is blended into the grid s interior 12 2 5 1 Selecting Boundaries When you are setting foreground control function attributes with the Apply to All toggle button enabled the attributes are applied to all boundaries of all grids selected for the solver However if the Apply to Focus toggle button is enabled you must designate the boundaries to which you intend to set the attributes This is done using either of the two menus below depending on whether you are running the solver on domains and setting attributes on edges left or blocks and setting attributes on faces right Edges i M3 Faces 1 M 3 E 5 E E 4 B om 4E 5 All a None o Set s All a None o Set s The buttons with the squares indicate the grid boundaries 4 edges for domains and 6 faces for blocks They are color coded to match the Blackboard listing and the highlights in the Display window These buttons act like toggle buttons when pressed they change state from enabled filled square to disabled empty square The state of these buttons is maintained even after you exit the solver All Enable all boundaries None Disable all boundaries Set Proceed with attribute selection for the enabled boundaries The foreground control function attributes menu has two other commands related to the boundaries Reset to D
237. inar vein Eee Etat baii 12 15 12 353 SING SUD GIGS odis ota 12 15 13 Grid Methods for Unstructured Domains and Blocks 13 1 13 7 RUNNING the SOLVel ai oe iuo o o AE Ee Eb adstat eas 13 1 13 2 Selling ALITIDUTCS ooo EET M SRI EORR REOR ae wads 13 2 13 3 Surface Shape Attributes o ooooocccoconcccoconococononoconononononcononononononos 13 4 A Eo NN 13 4 O A O o A 13 4 13 4 Relaxation Parameter Attribute essere 13 5 13 5 Triangular Mesh Attributes o ooooocccooncococncoconoccnocooncononcnonnonannonannonoos 13 5 13 5 1 Minimum Triangle EdE nii rare a 13 6 13 5 2 Maximum Triangle Edd m tenete a de 13 6 13 5 3 Maximum Surface Deviation occcoccccoccncconcconnnconncconnononnnoncnonnnnononoos 13 6 13 5 4 Maximum Angular Deviation neresti enra i a a 13 6 13 5 5 BOUNGALY Decay Facto sancion dora oap tius Een ipod 13 7 13 6 Tetrahedral Mesh Attributes sess nenne 13 7 13 6 1 Tetrahedral Solver Memory LiMit coooccccocncccocnncccnnnononncnononononononos 13 8 13 6 2 Tetrahedral Iterations sese 13 8 13 6 3 Tetrah dralSIZe FaclO s measea io a pe asas EU ap ise 13 8 13 7 Pyramid Mesh Attributes ooooccocccocccocccooconocnonononanonanonnnnonononancnnnnonos 13 8 13 71 Minimum Pyramid Helg nitses cius ete poa oar ud a RR Ebo ut ed aoo 13 9 13 7 2 Maximum Pyramid Height
238. indow image so that the rotation axes are at the Display window center The zoom depth and rotation of the image are not changed u un zoom Move the Display window image so that the zoom factor is set to one relative to the current view limits The panning and rotation of the image are not changed r un rotate Move the Display window image so that the body and screen axes systems are aligned The panning and zooming of the image are not changed Z Open the zoom in box AZ Open the zoom out box Z Pop to the orientation prior to the last issued zoom in or zoom out command p Restore put orientation 1 P Restore put orientation 2 P3 Restore put orientation 3 p4 Restore put orientation 4 ps5 Restore put orientation 5 pg Restore put orientation 6 comma Decrease mouse sensitivity period Increase mouse sensitivity gt Reset mouse sensitivity dash Decrease keypad sensitivity Increase keypad sensitivity Reset keypad sensitivity r Restore original orientation Simultaneously un pans un zooms and un rotates the image and resets the rotation point a Go to DISPLAY COMMANDS menu C Go to CONNECTOR COMMANDS menu D Go to DOMAIN COMMANDS menu B Go to BLOCK COMMANDS menu F Goto DATABASE COMMANDS menu E Go to INPUT OUTPUT COMMANDS menu A Go to ANALYSIS SOFTWARE COMMANDS menu Y Go to GLYPH COMMANDS menu S Export a QuickSave
239. inds the node at the lower end of the vertical connector and the circular arc connector MERGE MODE COM PAIRS Pick the node connector pairs to merge After selecting the node connector pair from the Browser or Display window and pressing Done Gridgen splits the arc at the location closest to the node and merges the node with the new node resulting in the three connectors shown below 15 14 Intersect Automatic 15 10 4 Automatic If you select Merge Auto you can specify a merge tolerance Gridgen will then apply the merge connec tors and merge connectors and nodes commands with that tolerance to try to create a watertight geometry 15 10 5 Pick If you select Merge Pick you can pick two connectors from the Display Window and Gridgen will merge them together After you pick the second connector Gridgen will highlight both connectors one in pink and one in orange You will be given the option to merge the connectors or abort the merge operation 15 10 6 Update Doms This command updates the triangulation of domains after merging connector Only used on unstructured domains 15 10 7 Topological Filter Commands You may filter the list of mergeable connectors by enabling the menu buttons on the TopoFltr menu prior to pressing one of the Merge command buttons By default TopoFltr will consider all connectors as can didates for merging TopoFltr All 3 Free 4 NonMinfld Free 5 All When this button is enabled
240. ing step size will grow from its initial value following a geometric progression law Section 11 3 2 2 Geometric is the default setting for growth rate Pressing the Set button lets you type in the value of the geometric growth rate Growth Rate Subcon Enabling this radio button means the marching step size will grow based on a sub connector string that you select after pressing the Set button When Subcon has been selected the value for As Init is ignored Growth Rate Set If geometric growth rate is enabled pressing this button lets you type in the factor by which the marching step size will be multiplied to obtain the marching step size for the next step The default value is 1 01 which means that the step size will grow by 1 each step If subconnector growth rate is enabled pressing this button lets you select the subconnector string from which the step sizes will be obtained The figure below demonstrates the difference between the Geometric and SubCons growth rates for a hyperbolic extrusion The grid on the left used a geometric growth rate of 1 1 The grid on the right obtained its growth rate from the curved connector in the lower right HITS Translational and rotational extrusions also allow you to use equal grid point spacing by enabling the Equal radio button shown below Spacing Equal a Normal extrusions also provide an additional control on the step size that reduces the local step size in con v
241. ints along new connectors The initial value for this default is the hyperbolic tangent function To change the default value simply press either the Con Dist Tanh hyperbolic tangent or Con Dist MRQS mono tonic quadratic rational spline buttons 3 2 Elliptic PDE Solver Control Functions 3 2 1 Background Control Function The background control function Section 12 2 4 default will be set on all new structured domains and structured blocks The initial value for this default is Thomas Middlecoff To change the default value sim ply press either the Bckgr CF Lapl LaPlace Bckgr CF T amp M Thomas Middlecoff or Bckgr CF Fixd fixed grid buttons 3 2 2 Foreground Control Function The foreground control function Section 12 2 5 default will be applied to all boundaries of new structured domains and structured blocks The initial value for this default is Hilgenstock White To change the default value simply press either the Forgr CF Srns von Lavante Steger Sorenson or Forgr CF Hign Hilgenstock White buttons If you do not want any foreground applied to newly created domains and blocks press Forgr CF None 3 3 Setting Defaults 3 3 Unstructured Grid Attributes 3 3 1 Domains Unstructured grid attributes applied to domains when they are created are set by the buttons labeled Unstr Dom in the Defaults menu 3 3 1 1 Interior Grid Points Toggle Whether or not grid points are inserted into unstructured domains at the time the
242. ints interior to the block Transformations are applied to each individual grid point to obtain its new location Stretching and scaling transformations may result in grid point distributions that cannot be replicated by any of the grid methods 14 3 Transformations The Translate Scale Stretch Rotate and Mirror commands are categorized as transformation com mands They may be applied to all entity types and are described in the following subsections Translate tiRotate Ag Scale s Stretch s Mirror AmiProject j 14 3 1 Translate The Translate command lets you alter one or more entities by moving them to a new position in Cartesian space In the figure below the domain on the left has been copied and translated to the right You can control the translation via two mechanisms described below Enter Handle via Keybrdpad Enter Transl Offset e Abort Dont Translate esc The translation can be controlled using the 3D cursor Immediately upon entering translation mode you may pick a point called the handle from the Display window The handle is a point controlling the translation The handle can be any pickable point or a point for which you type in the coordinates after pressing the Enter Handle via Keybrd button Translation control is accomplished by moving the 3D cursor on the screen using the mouse with the right mouse button pressed During translation the Display window shows the entities current translated position The Bl
243. ion 1 Structured domains extruded from connectors 2 Structured blocks extruded from structured domains 3 Prism blocks extruded from unstructured domains Five different extrusion methods may be applied 1 Hyperbolic a partial differential equation PDE based method for extruding structured domains and blocks The hyperbolic PDE extrusion method is the most mathematically elegant of Gridgen s extru sion methods and produces grids of very high quality that are smooth clustered and orthogonal 2 Normal an algebraic method mimicking the properties of the hyperbolic PDE method but which is also applicable to the extrusion of prism blocks from unstructured domains 3 Rotation an algebraic method for rotating grids about a user specified axis 4 Translation an algebraic method for linearly extruding grids 5 Path an algebraic method for extruding grids along an arbitrary 3D path defined by connectors 8 1 Running the Extrusion To create a domain or block by extrusion you press the Create button in the DOMAIN COMMANDS or BLOCK COMMANDS menu respectively From the CREATE DOMAIN or CREATE BLOCK menu you then press one of the two buttons labeled Extrude as shown below for domains left and blocks right Extrude From Cons 9 Extrude From Doms 9 From An Edge 0 From A Face ol The first decision you must make is the manner in which the extrusion is to take place 1 For domains a From Cons A separate ext
244. is added Then the plane icon is rendered at the average location and spokes are drawn from the average location to each of the three points The plane entity is saved by pressing the Done button 6 6 Surface Coefficient Plane Cursor Location 7 923078 2 575467 3 970420 7 i uH uuceHu wg u ugg aa a x y Zz z X y z Sec x y zZ i X y z 6 4 4 Coefficient Plane A plane may be created by entering the coefficients of the plane equation A 3c By EC ow sg ee The button Store A B C via Keyboard allows you to enter the three coefficients defining the normal vec tor A second button Store D via Keyboard allows you to define the location of the plane The plane icon is rendered once the values for A B and C are entered The plane entity is saved by pressing the Done button Store A B C via Keyboard a Store D via Keyboard d Done Save Plane ent 6 5 Surface Gridgen has tools for creating several different types of surfaces Except for the Fit surface each tool uses database curves or existing surface boundary curves to construct database surfaces Descriptions for each of the surface creation tools can be found in the following sections Surface Ruled ul Polyconic 1 Revolution q Linear Sweepn F i t T Coons Ac MaAuto i Ruled fills in linearly between two curves that define opposite edges of the surface Polyconic builds a fillet between two rail curves that define opposite e
245. is the real value used by Gridgen to determine whether two connectors Section 7 with equal non zero dimensions are the same This determination is made by computing the distances between grid points on the two connectors If the maximum distance between corresponding grid points on the two connectors is less than the connector tolerance the two connectors are considered the same One is deleted and replaced with the other The initial value for this default is 0 0001 To change the value of the default press the Connctr button and type the new value in the Text Input window When you enter a new connector tolerance the entire grid system is updated to reflect the new value Any formerly distinct connectors that fall within the new tolerance will be combined Note the connector tolerance may be significantly larger than the grid point spacing along the connector allowing for instances of connectors with tight grid point spacing on opposite sides of a large gap in the data base 3 7 3 Grid Point Tolerance The grid point tolerance is the real value used by Gridgen to determine whether two grid points are the same The initial value for this default is 1077 To change the value of the default press the Grid Point button and type the new value in the Text Input window The grid point tolerance is used to identify singularities poles in the grid in order to avoid divide by zero conditions during the computation of various grid control parameters
246. is used to split connectors at break lines in the geometry If Con Split is checked on you can enter a break angle by pressing the Set Angle button Connectors created after this will be split at locations where the angle between any three adjacent points along the connector is greater than the speci fied angle 9 7 Pole Domains A pole domain is a structured surface grid collapsed to a line Pole domains are necessary for certain struc tured grid topologies requiring singularities For example if a block was to be constructed for a prism one of the block s faces would correspond to the peak vertex of the prism and the entire surface grid is collapsed to a line 15 Defining the Fourth Edge Need 15 more grid points A pole domain is created in Gridgen from three connectors two pole connectors Section 7 2 5 1 and another curve The two poles will be situated at either end of the third curve Domain creation for the pole proceeds in exactly the same manner as any other domain except the curve is picked twice in other words the domain s edges will be pole 1 curve pole 2 curve Gridgen automatically detects that a domain is a pole and applies a grid method other than TFI to ensure a mathematical singularity 9 8 Bad Domain Types 9 8 1 Allowable But Should Be Avoided In general domains can be created to represent any surface For structured domains that requirement is extended further to require that domains must be mappe
247. itly either a region of the Display window that will be expanded to fill the entire Display window zoom in or a region of the Display window into which the entire Display will be com pressed zoom out The zoom in and zoom out boxes may be activated using the z and z hot keys respectively There are also Zoom In and Zoom Out buttons on the DISPLAY COMMANDS menu Section 2 9 In either case you specify the extents of the zoom box first by positioning the upper left corner marked with a small open square to the desired screen location and then by pressing and holding down the mouse and stretching the lower right corner of the box marked with a small open square to the other location When the mouse is released the zoom box is complete When zooming in the zoom box is labeled Zoom In and the effect is to redraw the screen so that everything inside the zoom box fills the entire Display window When zooming out the zoom box is labeled Zoom Out and the effect is to redraw the screen so that everything in the Display window fills the zoom box at the zoom box s location 2 15 Graphical User Interface Zoom In z Out az Undo z Zooming can be aborted by pressing the Esc key The zoom box works best when the viewing transforma tion is orthonormal use the v hot key to toggle between orthonormal and perspective viewing transforma tions The Zoom Undo button activated with the Z hot key allows you to return the image to its position im
248. ity is the domain a surface grid An initial domain grid is generated automatically using a default method when the domain is first created A variety of grid methods can then be applied to improve the grid s quality Volume grids called blocks are at the top of the data hierarchy As with domains the initial block grid is cre ated automatically and a variety of grid methods may then be applied to improve the grid s quality This data hierarchy provides the framework by which modifications to any entity are propagated throughout the rest of the hierarchy For example modification of a connector s shape will update all domains and blocks that use it The term forward editing refers to grid changes propagated up the hierarchy while backward editing refers to downward propagating changes Gridgen s data hierarchy and forward and backward editing allow you to change one entity of your grid and have Gridgen make the entire grid system consistent with your change 1 3 Command Hierarchy and Menu Structure The commands you will execute while running Gridgen are arranged in nested menus Gridgen s main menu is described below Input Output commands for reading and writing data files Database commands for manipulating the geometry model Connectors commands for manipulating curve grids Domains commands for manipulating surface grids Blocks commands for manipulating volume grids Analysis S W commands for preparing your
249. ive feature is that it can pass a smooth curve through relatively coarse data its drawback 1s that it can produce false inflection points The only instance where this type of spline might be beneficial is when a large number of grid points are to be distributed on a smooth shape represented by a relatively coarse collec tion of straight line segments as might be obtained by an Import segment type Even then the cubic spline shape should be inspected carefully Exponential Spline This spline type has features of both the linear and cubic spline It should be used when a cubic spline is needed but cannot be used because of unwanted wiggles in the grid point representa tion The exponential spline will eliminate those wiggles i Arclength X The spline variable can be changed with the Spline Var menu button By default grid points are distrib uted based on arc length along the connector Hence a spacing constraint of 0 4 will make the distance between adjacent grid points at the end be 0 4 However you may want to distribute grid points on the basis of only one of the coordinate components such as x y or z instead of arc length If the spline variable is changed to x for example a spacing constraint of 0 4 will result in a grid point distribution such that the dif ference in x values of grid points at the break point will be 0 4 The arc length spacing at the break point will in general not be equal to the Ax value In orde
250. izontal bar yellow in color indicates the progress of the intersection procedure based on the total number of combinations of Group A and B entities Grid entities connectors domains and blocks may not be intersected 15 12 Feature Extraction The Feature Ext command is used to subdivide and extract curves from database shell entities to make them easier to use Many shell entities only contain shape information They do not have any internal topol ogy to attach grid to specific locations Using feature extraction you can create curves at natural breaks in the geometry and subdivide shells into smaller pieces along these feature lines The feature extraction process is controlled by entering a split angle Database shell entities are composed of triangular facets If the angle between two adjacent facets if greater than the entered split angle the edge they share 1s identified as a feature and Gridgen will consider it a candidate for curve extraction and surface 15 17 Miscellaneous splitting You can control whether curves are extracted surfaces are split or both Controls available for feature extraction are ReRun 5 Set Split Ang 2 Extract MSurfaces 3 Mf Curves 4 Done ent Run ReRun The Run command starts the feature extraction process and is available only after a shell has been selected The ReRun command allows you to restart the feature extraction process by deleting any current extracted curves and spli
251. l be selected 0 Domain Um 0 Defining the First Edge As shown above after pressing the Assemble Edges button the Blackboard displays a computational schematic a square of an empty domain of dimensions 0 x 0 The Blackboard window also displays the message Defining the First Edge The first edge is simply that the first of the four edges being added to the domain The edge number has nothing to do with the eventual computational axes Defining the First Edge You define the first edge by selecting the connector or connectors on edge starting from the chosen corner node and proceeding in the desired direction The example above starts the domain from the lower left node and proceeds in a counter clockwise direction The node to which connectors may be added to the domain s perimeter has an open circle drawn around it After at least two connectors have been selected or after Next Edge has been pressed the node at the begin ning of the domain s perimeter has a filled circle drawn over it When a connector is added to the edge the screen is updated If you select an un dimensioned connector while creating a domain you will be prompted to enter a dimension via the keyboard The Display window shows that connector displayed in either yellow edges 1 and 3 or red edges 2 and 4 The pairing of edges is meant to reinforce the idea that opposite edges of a structured domain must have the same number of grid points The s
252. l have to be rerun or reprojected Other than propagating dimensional changes from one full connector to another full connector Gridgen will not make decisions for you Because of this redimensioning one connector may unbalance the dimensions of other domains in a structured grid requiring you to redimension a second connector before the entire grid is once again dimensionally balanced Inside Gridgen after a connector s new dimension is typed it 1s assigned to all members of the connector group and each domain s dimensions are checked If a particular domain becomes unbalanced by virtue of the new dimension Gridgen attempts to correct the imbalance by redimensioning connectors on its own and the process is repeated for the next domain All domains are checked again until repeated application of the domain balancer does not change the connector dimensions At this point a summary of the current system dimensional status is provided in the Blackboard Window any unbalanced domains are highlighted in the Display window and all connectors are assigned one of three color coded classes according to the following table 11 4 Distributing Grid Points on Connectors Additional Effects ReDimension Grids Colors color connector dimension status yellow original user set Note that the Blackboard keeps a tally of the number of connectors of each class and the number of unbal anced domains as shown below System Redimensioning 16 Total Con
253. le You may choose to save the Gridgen file without the volume grids and save a separate volume grid file for use with your analysis software Incorporating the volume grid into the Gridgen file will substantially increase the size of the Gridgen file and the memory required to run Gridgen Gridgen uses two criteria to determine which blocks of the current system the blocks in the volume grid file correspond to 1 the block dimensions IxJxK must match and 2 the distance from the corners of the volume grid to the corners of the block must be less than the node tolerance 4 14 Block Ell Solver Glyph To prepare the files necessary to run Gridgen on one or more structured blocks the following procedure starting from the INPUT OUTPUT menu 1 Press the Block Ell Solver Glyph button 2 Select from the button menu whether you will be working from Gridgen or volume grid files and set the number of iterations to be run for structured grids 3 Select the block or blocks to be run in Gridgen 4 Select the grid file name from the Browser 5 Set the file attributes using the radio button menu volume grid files only 6 Select the Glyph file name from the Browser The default extension for the file name is g1 f The BIk Ell Solver Glyph command is a mechanism for writing a Glyph script to use the elliptical PDE solver on structured blocks The first step is to select the blocks to be run Usually this selection is made after viewi
254. le is enabled This button is available when assembling unstructured blocks only Pick Unstr Enabling this toggle button allows unstructured triangular domains to be picked during face assembly By default this toggle is enabled This button is available when assembling unstructured blocks only Pick NonMnfld Cnnct Enables non manifold connections to be picked during face asembly Non mani fold domain connections are defined as three or more domains sharing the same edge By default this toggle is enabled This button 1s available only for unstructured grids Pick Join Angle z Any This command lets you specify a maximum join angle between adjacent domains After you enter an angle Gridgen checks any new domains you try to add to the developing face to make sure the dihedral angle between each cell on their boundaries and the adjoining cells already in the face are less than the specified angle If any of them are greater the domain will not be added to the face EraseDom Pikd This command lets you pick using the normal picking mechanisms the domains to remove from the current face As long as it is toggled on picking domains removes them from the face EraseDom Last This command removes from the current face the last domain you picked The Merge and TopoFltr commands are described in Section 15 10 FaceFlitr All This radio button lets all connectors be candidates for merging when using the Merge com mands FaceFltr Bndry
255. lected you must pick a point called the anchor The anchor is a point that will remain fixed during stretching Enter Anchor via Keybrdpad Abort Dont Stretch esc Next you pick a point called the handle The handle is a point controlling the stretching Anchors and han dles can be any pickable point or points for which you type in coordinates Repick Anchor Point n Enter Handle via Keybrdpad Abort Dont Stretch esc Stretching is controlled using the 3D cursor Stretching control is accomplished by moving the 3D cursor on the screen using the mouse with the right mouse button pressed During stretching the Display window shows the entities current translated position The Blackboard indicates the current cross position and scal ing factors The scale factors then multiply the difference between the original point locations and the anchor point to find the new point locations Repick Handle Point n Set Handle by Picking pado via Keybrd pad Axyz via Keybrdo Acp via Keybrd o by Linear Proj at Clsest DB Pt Original Location 1 Movement Restrictions m Sensit Decr lt Reset Incr gt Move to Screen Center c Rotation Pt To Cross t Done Stretch ent Abort Dont Stretch esc The entity is not copied prior to stretching Use the Copy command first if that is what you want In fact after copying the entities the Copy command will invoke the Modify menu for the copies The stretching is not saved until the Done Replac
256. lent results Note that when both picking mechanisms are available pointing to and highlighting an entity s graphical image in the Dis play window also highlights its text listing 1n the Browser and vice versa The cursor looks like a hand with a pointing index finger during selecting When picking database entities an additional filter may be applied to limit the type of selectable entities see Section 2 4 3 When a command allows multiple entities to be picked keep in mind that the picked entities are added to and held in a queue until the Done button is pressed at which time the command begins operating on the entities Before the Done button is pressed items can be removed from the queue A command that is lim ited to working on a single item begins operating as soon as you pick the entity 2 4 1 selecting From The Display Window 2 4 1 1 Selecting Entities One At A Time Entities may be picked one at a time by pointing at the entity and pressing and releasing either the left or right mouse button depending on the setting of the LeftPk toggle button in the DISPLAY COMMANDS menu Section 2 9 When the cursor is positioned over an entity the entity is highlighted in salmon mean ing that it is pickable After the right mouse button is pressed the entity is highlighted in white meaning it has been picked For historical reasons this document often refers to entity selection with the phrase pick with the right mouse button keep in mi
257. line geom geometric progression e gnrl general The final field lists the current value of the spacing constraint in terms of arc length along the connector If the spacing constraint is surrounded by angle brackets lt and gt the break point is actually unconstrained and the current spacing is being listed If the spacing constraint is surrounded by parentheses the subcon nector has a spline variable Section 11 3 2 3 other than arc length Constraints without angle brackets are ones specified by you Once you have selected the spacing constraint locations break points you wish to set you are prompted to enter the new constraint value Valid entries are 3 convert the distribution function of all of the subconnectors referenced by the picked spacing con straints to MRQS monotonic rational quadratic spline 2 convert the distribution function of all of the subconnectors referenced by the picked spacing con straints to TANH hyperbolic tangent O unconstrain all selected constraints gt 0 enter a new spacing constraint The average spacing constraint of all of the picked spacing constraints is listed in the message window When a new constraint value is entered three things happen Gridgen redistributes grid points on connectors subject to the new constraints Domain grid points are updated to reflect the new connector grid point positions Block grid points are updated to reflect the new domain g
258. liptic methods can be constrained to a database so that grid quality is improved and the desired shape is maintained 12 2 1 Running the Solver The Elliptic Slvr Run menu button is used to apply an elliptic partial differential equation PDE method Reference 40 Reference 35 to one or more grids The elliptic solver iteratively solves a set of PDEs to improve the quality of the grid In the following discussion the term refine refers to improving the grid s quality not improving its resolution through the addition of grid points The first step in running the elliptic solver is to select from either the Browser or Display window the grids to be run During selection of the grids a terse description of the current elliptic PDE attributes described in the next section will be displayed for each grid in the Browser 12 4 Elliptic PDE Methods Running the Solver f2123 f2123 f2123 f2123 f2123 f2123 f2123 f2123 f2123 f2123 f2123 f2123 For example in the sample shown above grid number 2 has Thomas amp Middlecoff background control functions b T amp M and with foreground control functions turned on for boundaries 1 2 3 and 4 1234 When you have selected any number of grids the elliptic solver is invoked and immediately enters the paused state with the menu shown below RUN STRUCTURED SOLVER Initialize via TFI t Elliptic Slvr Run 8 Run 1 Iter Run N Iters n Set Solver Attr ibs Ag Ex
259. llowable But Should Be Avoided esee 9 10 9 02 DUDIG AICS isestrasrenalnta der ete racio dolus Dada aacku oup lib 9 11 9 8 3 Overlapping and Adjacent selle esses esee 9 11 Je OMC Ir c 9 12 8 90 Pronibile desatar A 9 12 10 Creating BLOGS vans sio is 10 1 IA A ER a et LU A A A a 10 1 10 2 Assembling a Structured Block sse 10 1 10 2 1 Adding Faces to a Structured Block oooccconccccccnnccononocononcconnnonao 10 1 10 3 Assembling an Unstructured Block ooooocooocccoccccocccnocncnnccconcnonarnonannos 10 3 10 3 1 Adding Faces to an Unstructured Block s usus 10 3 10 4 Assembling a Hybrid Unstructured Block ooooooocccooncoocoooo0 10 4 10 5 Face Creation COImmanhas bo ee at 10 4 10 56 LINKAQCS t Dt dass cados 10 6 10 7 Structured Block Topologies and Orientations 10 7 11 Grid Methods for CONNEectorS oooococonoconoconoccconnocanonococonnnoonoso 11 1 11 1 HeDImensiOln E eie wed a seed 11 1 11 1 1 Apply Dimension or Average Spacing cccccoocccconoccnccnoconcnnncccconorononnncnnos 11 1 11 1 2 From Keyboard or SUDCONNECHONS cccsececeseeeeeeeeeaeeeeeeseesaeeeenanees 11 1 MaS Addillohal ENEC S suu oap Seed eee arate a een eee ceed 11 3 11 2 ReDimension Grids 2000 iba 11 3 11 3 Distributing Grid Points on Connec
260. lume condition export is supported for FLUENT Blocks with common VC s are automatically merged in the AS W file with the VC used as the zone name To have separate blocks written out with assigned VC set a different VC to each block to avoid automatic merge Alternatively setting block VC s to No Volume Condition will cause the blocks to be exported separately under their block names Wherever Gridgen detects a pole line singularity in a structured grid it will convert the cell from a hex quad to a wedge triangle when exporting it for FLUENT Whenever Gridgen detects a completely singu lar face point singularity in a structured grid it will convert hexes to pyramids 17 8 20 GASP GASP export supports 2D and 3D structured grids only Three files are written by Gridgen GASP s grd 17 10 Export Analysis Data Grid and BCs GUST inp and sIn files Two dimensional grids are assumed to lie in the x y plane Since GASP expects 2D grids to be one cell thick Gridgen extrudes the grid by 1 0 units in the z direction GASP export is not supported under MS Windows or Linux 17 8 21 GUST GUST supports 3D unstructured grids comprised of both hexahedral and tetrahedral cells That means you may use a grid comprised of both structured and unstructured blocks in GUST The volume grids from each of the blocks are agglomerated into a single block for output Gridgen s Set BCs command is used to assign GUST groups for later application of
261. lved using special terms accounting for surface curvature This method does not keep the point exactly on the DB entity but will be fairly close particularly if grid point movement is minimal PDE solution is followed by projection of the grid point onto the database ensuring that it conforms exactly to the desired shape Though two different equation sets are used to move grid points the equations are equivalent through a transformation of coordinate variables Therefore there is no improvement in grid quality of one method over the other The parametric method is considerably faster to apply but can be used only in special cir cumstances Several attributes can be set to control how Gridgen manages database shape control as shown in the figure below and described in the following sections 12 12 Elliptic PDE Methods Boundary Conditions Proj Typ Lin Def 1 Lin Cur 2 ClosePt 9 Proj DBs Default 3 Picked 4 MM Show Proj DBs 7 Mt Show Proj Vector 8 Align View w Proj Vector 6 Proj Typ Lin Def This attribute tells Gridgen that the projection type is linear and the default projection orientation will be used The default projection orientation is computed by averaging the grid s normal vec tor at each edge grid point The projection vector direction is shown in the Display window as an arrow at each corner of the grid Proj Typ Lin Cur This attribute tells Gridgen that the projection type is linear The projection is
262. lyph batch block smoothing export 4 20 Gridgen quick import 4 3 Input Output menu Quick Key for 2 5 QuickSave Quick Key for 2 6 setting name 3 6 QuickSave file Quick Menu 2 7 selecting name for 2 2 Flat reference surface 6 5 FLUENT v4 asw 7 0 FLUENT v5 asw 17 10 foreground control function angle constraint 2 default 5 5 form 2 9 Hilgenstock White 2 0 Steger Sorenson 2 0 selecting boundaries for 2 9 setting 2 9 spacing constraint 72 10 Fortran unformatted mesh import 4 5 frame buffer 2 2 FVUNS grid export to 4 17 import as grid 4 5 G gaps closing automatically 75 11 GASP asw 17 10 generatrix linear sweep surface 6 11 offset curve 6 5 surface of revolution 6 0 generic asw 7 8 Global Mode for Examine 6 0 Glyph export files for batch block smoothing 4 20 rc file 4 19 grid associativity to database 4 2 types 7 1 grid extrusion S attributes 6 4 aspect ratio 8 5 boundary conditions S marching direction S 7 smoothing parameters 8 9 step size 8 5 surface shape 8 4 automatic cell quality checking 8 2 hyperbolic Hyp 8 2 normal Nrml 8 2 path based Path 8 3 rotational Rot 8 2 stop criteria 8 12 translational Tran 8 3 grid point changing number of grid spacing global change 71 13 Gridgen history 5 Version 6 5 Version 7 1 5 Version 8 5 Version 9 1 5 group automatically created during database file import 4 11 connector groups in ReDimension Grids command 3 d
263. main will not be saved if the number of extrusion steps differ 14 15 Modifying Entities Changes to the total number of extrusion steps for domains or blocks will cause those domains or blocks to be automatically unlinked from the grid when they are saved see Section 14 2 No change to the total num ber of extrusion steps will cause a prompt to appear for the user to decide whether to maintain linkage or not Certain conditions will make selected domains or blocks ineligible for re extrusion A domain or block split since its original extrusion A domain or block extruded along a connector path Multiple domains or blocks whose extrusion types are not identical e Multiple domains or blocks of different grid type i e structured unstructured Multiple domains or blocks having an unmatched number of extrusion steps 14 7 Split The Split command is used to divide a database or grid entity into two separate entities 14 7 1 Database Entities Database curve and surface entities can be split at any parametric u or v location Trimmed surfaces may not be split The hiliter may be moved along the entity by moving the mouse with the right mouse button pressed When the desired split location has been hilited the entity is split by pressing the Split at Hiliter button SPLIT Split At Constant eu i ov 2 Move via Keybrd pad Split at Hiliter ent Abor t esc Other commands of interest during database entit
264. mat using the descriptions in Section 18 10 This is the default ASW ADPAC is an end user proprietary CFD solver for structured multi block grids CFDSHIP IOWA is a structured grid CFD code from the Iowa Institute of Hydraulic Research at the Uni versity of Iowa CFD from Metacomp Technologies uses a unified grid treatment for all grid and cell topologies includ ing patched nonaligned and overset grids CFX 4 from AEA Technology supports structured multi block grids only CFX 5 from AEA Technology supports structured unstructured and hybrid grids CGNS Struct is the CFD General Notation System CGNS standard for transferring structured grid infor mation CGNS Unstr is the CFD General Notation System CGNS standard for transferring unstructured grid information CNSFV from NASA Ames Research Center Reference 11 supports structured multi block grids only Cobalt from the United States Air Force Research Laboratory supports unstructured grids only COMO is an end user proprietary CFD solver that supports hybrids grids CRUNCH from CRAFT Tech supports unstructured hybrid grids only DTNS from NSWC Carderock Division supports structured multi block grids only EXODUS ll is a finite element data model from Sandia National Laboratories Reference 18 FALCON is an end user proprietary CFD solver for structured multi block grids FANS from NSWC Carderock Division supports structured multi block grids only 17
265. may be split 14 8 Join The Join command is used to assemble individual entities into a larger entity If the Join menu button is not available exit to the Main menu for the entity type select Modify pick one of the entities to be joined and select the Join menu button 14 8 1 Database Entities When database entities are joined you simply select the two entities to be joined They must both either be curves or surfaces In order for surfaces to be joined they must share an entire edge including knots and control points In order for curves to be joined they must share an end point The polynomial degree parametrization and rationality of the entities must also be identical If the entities cannot be joined you are warned If the joining is successful a new entity consisting of the two joined entities is created The original entities remain intact 14 8 2 Connectors When joining connectors Gridgen highlights in the Display window those connectors that are candidates for joining to the current connector You simply pick the connector to join using the mouse After each join operation Gridgen stays in joining mode so you may join several connectors at one time Gridgen remains in joining mode until you press the Abort button or until there are no more candidate connectors left for join ing 14 19 Modifying Entities It is not possible to join connectors that span multiple domains It is also not possible to join two connectors i
266. me diately prior to the last zoom in or zoom out You can think of it as an additional saved orientation 2 8 The 3D Cursor Many Gridgen commands require you to select or define points in 3D space For example a curve is drawn by placing several control points through which the curve will pass Whenever control points need to be defined the 3D cursor appears as a small white cross in the Display window It will be referred to as the cross in the discussion to follow and also in the help messages that appear in the Message window Do not confuse the white cross 3D cursor with the upper left pointing arrow mouse cursor The location of the cross is controlled with the mouse and the right mouse button Position the arrow cursor anywhere in the Display window and hold down the right mouse button The red arrow cursor will disap pear and mouse movement will control the cross s movement The 3D coordinates of the cross will be dis played in the Blackboard 2 8 1 3D Cursor Movement Horizontal mouse movement is translated into horizontal screen x 3D cursor movement and vertical mouse movement is translated into vertical screen y 3D cursor movement Furthermore the 3D cursor is situated in a plane of constant screen z called the drawing plane The drawing plane s depth screen z coor dinate is set implicitly by Gridgen as you place control points Because control of the 3D cursor actually takes place in the screen coordinate system b
267. metric TFI The grid s boundary points are projected onto the entity and the resulting u v coordinates are used to drive Parametric TFI Note that the projection of boundary points is only a temporary operation the original coor dinates of the boundary points are restored Parametric Fit TFI is the second method after Parametric TFI that Gridgen tries to apply by default to create the initial surface grid for domains For Parametric Fit TFI to be applied automatically to a new domain a third condition must be satisfied 3 The total distance projected from the grid s boundary points to the candidate surface must be less than a tolerance Parametric Fit TFI 1s not available for blocks 12 1 7 Pole You cannot explicitly apply Pole TFI However no matter what TFI method you choose if Gridgen deter mines the domain is a pole a surface collapsed to a line it uses a special method for creating the interior domain grid points Specifically the grid is made by copying the edge points onto all other grid lines in the domain This approach prevents round off error that sometimes results from applying a TFI method to a sin gularity Domains constructed in this manner will be tagged with the label pole in the Blackboard win dow 12 2 Elliptic PDE Methods Gridgen s elliptic PDE methods let you improve the smoothness of structured domains and blocks while at the same time controlling orthogonality and clustering For domains the el
268. mplicitly sets the number of render curves Section 2 10 3 in both the u and v directions to 2 and renders the entity s boundaries Also the corner of each interval on the surface 1s rendered with a small filled square to aid in identification for picking see below Intrvis For database entities Interval mode implicitly sets the number of u and v render curves so that the outline of each of the entity s intervals is rendered Interval mode is not available for trimmed surface enti ties see below Isolines For database entities this mode allows you to specify explicitly the number of u and v render curves The illustration below shows an 11 x 11 isoline rendering Isolines may be applied to trimmed surfaces as well as normal database surface entities 2 25 Graphical User Interface triangles For trimmed surface database entities only the graphical object is a triangulated surface You specify the approximate number of triangular facets to use along the entity s longest coordinate extent The figures below show a contrived trimmed NURB surface rendered with 15 triangles the default above and 51 triangles below Entering a value of 1 creates an optimal arrangement of triangles Fn T ame as y y 4 K A 4 A S Fa Fa Fa Fa ra ra ra ra Fa Wh WSO ANAS Fai Pe Pd Pd Fak Fa WANA AN ALTAS ANA AIN O de RADA LIN Fa EJ J Fa Fa Fa Render Density 2 10
269. mum and maximum color bar values are then saved and re used each time that function 1s examined You may change either the minimum or maximum color bar value depending on which of the Minimum or Maximum radio buttons is selected by entering the value via the keyboard Type In by re computing it according to the current function value range for the currently examined entities Reset or by decreasing or increasing by 10 percent of the current color bar range using the arrow buttons 16 3 4 Show Cells M Below 7 I3 In 8 M Above 9 M Tets Mt Pyramids 1 0 i The Below In and Above buttons labeled Show Cells Range allow you to specify which cells are to be rendered in the Display window according to the cell s diagnostic function value below range in range or above range with respect to the color bar values respectively For connectors and domains the default condition is to show all cells For blocks the default condition is to show everything except for in range cells otherwise every cell in the volume grid would be displayed The toggle buttons Tets and Pyramids let you set whether or not tetrahedral and pyramid cells respec tively will be shown in the Display window when examining hybrid unstructured blocks Pressing the button labeled Shrink lets you enter a real number between 0 and 1 inclusive that determines how much the grid cells being rendered in the Display window are shrunk about their centroids The shrink factor h
270. n it tries to apply Parametric Fit Triangulation In order to apply Parametric Fit Triangulation a certain percentage of the domain s connectors must have been defined in terms of any database entity the connector s grid points must lie within the bounding box of a single database surface entity and the distance from the connec tors to the database must be less than a tolerance If these conditions are met the domain s connector s grid points are projected onto the database entity and the parametric coordinates obtained from the pro jection are used to apply Parametric Triangulation This will ensure that the grid will conform to the database shape 3 Standard Triangulation If neither of the two methods above can be applied Gridgen applies Standard Triangulation A Standard Triangulation grid will not adhere to the database You must modify the domain via projection Section 14 4 if you want the grid to lie on the database As with structured domains Gridgen color codes the newly created domains to show how they were created purple for database constrained and green for free You can determine the method last used on a domain using the Run Unstructured Solver command Section 13 1 the method is listed in the Browser for each domain 9 4 Special Domain Assembly Commands The two commands shown below help automate the assembly of structured domains Auto Mext Edge a Auto Complete c Auto Next Edge Enabling this toggl
271. n 15 2 of the User Manual 5 3 Scripting and the Layer Manager Glyph commands which take actions in any manner related to database entities ignore layer status of the database entities Layer information is only addressed by layer specific Glyph commands See Section 5 of the Glyph Reference Manual for more information regarding Glyph commands for the layer manager 5 4 Layer Assignment Assignment of database entities to layers takes place in three different functional areas of Gridgen as described in the following subsections 5 4 1 Database File Import For IGES and native CAD database file import using Database Import in the INPUT OUTPUT COM MANDS menu see Section 4 4 all level information in the file is transferred to Gridgen s layers This capability allows users to preserve the layering assignments made in their original CAD models It is always recommended users save imported database information to a new composite database file All layer assign ments and layer status are preserved in the composite file Database models imported from files containing no layer or level information or imported from file types for which Gridgen does not support layer data have all entities assigned to layer O zero 5 4 2 The Assign Layer Command The Assign Layer command in the DATABASE COMMANDS menu is used to manually reassign the layers to which entities belong The command is shown in the menu example below 5 1 Layer Manager
272. n the Gridgen file in terms of the database entity resulting in Cartesian coordinates x y z If the referenced database entity is not found a warning indicating that there are missing database entities appears in the Message window The name of the file containing the missing database entities is printed to the shell window 4 Gridgen repeats this process for every node connector domain block and grid point in the file Therefore if you have imported the same database file as you used when you created the Gridgen file every thing will appear the same as it was before However if you have substituted a new wing upper surface for the previous one you will notice that the grid now conforms to the new wing upper 4 2 Quick Import Overwrite vs Append 4 1 2 Overwrite vs Append If at least one connector exists in Gridgen prior to your invocation of the Gridgen Import command you must choose how to treat the existing grid SELECT OPTIONS Overwrite Current Grid y Append to Current Grid m Overwrite Current Grid All current Gridgen grid information will be deleted and the grid system in the file will be imported You must confirm your selection of this option via an additional button menu since deleting the current grid cannot be undone Append To Current Grid The contents of the Gridgen file will be added to the current grid system This capability allows several users to work simultaneously on portion
273. n upon network or PATRAN Neutral file import must be deleted using the UnGroup command in the DATABASE COMMANDS menu prior to GRIDBLOCK Version 8 file import Only the connector shapes from GRIDBLOCK Version 6 default extension b1k files will be imported Furthermore there is no adherence of connectors to the database and all of Version 6 s ellipse segments are converted to circular arc segments the shape may change 18 1 File Formats If the grid has been generated using a database then the database file must be imported before the Gridgen file 18 4 Database Network File A database network file default extension net consists of one or more bilinear surfaces wireframes to be used as part of the geometry model database Gridgen can import Section 4 4 and export Section 4 5 database network files in binary Fortran unformatted and ASCII formats and in Gridgen or PLOT3D style Gridgen reads from a Gridgen style network file until the end of file is encountered Each network in the file must consist of at least 2x2 points a single quadrilateral The formats described below are also those used for importing Section 4 6 and exporting Section 4 7 structured surface grids A code fragment for exporting a network file in Gridgen style is shown below o MENS nmax is number of networks Cae eas ni n number of points in the i direction for the nth network a NC nj n number of points in the j direction for the nth network
274. nal 7 4 circular arc 7 6 slide points 7 6 conic 7 4 segment file 4 7 using 3D cursor with 2 17 Set BCs 7 3 17 5 Set As Values 3 Show Cells for Examine 6 9 Show EnbldDB 2 20 Size diagnostic function 6 3 Size Ratio diagnostic function 6 4 Skewness diagnostic function 6 6 Smooth diagnostic function 6 5 spacing average default 3 beginning default 3 3 ending default 5 5 spacing constraint 6 beginning spacing 7 elliptic PDE solver 72 9 12 10 ending spacing 7 unconstrained 7 Spacing diagnostic function 6 6 spine polyconic surface 6 9 split block 14 18 connector 14 16 connector into subconnectors 77 10 creates General segment 7 8 database 14 16 database entity 74 16 domain 14 17 split angle 5 5 Standard TFI 2 2 STAR CD asw 7 14 Status window 2 7 Steger Sorenson 2 0 STEP import as database 4 7 Stereo Lithography STL grid export to 4 17 import as database 4 8 import as grid 4 5 structured grid 2 algebraic methods 2 creating subgrids for 2 4 Linear TFI 72 2 Ortho TFI 2 3 Parametric Fit TFI 2 4 Parametric TFI 72 3 Polar TFI 2 3 standard TFI 2 2 elliptic methods 2 4 attributes 72 6 background control function 12 8 type fixed grid 72 8 LaPlace 72 8 Thomas Middlecoff 12 8 boundary condition 72 13 fixed 2 13 floating 12 153 orthogonal 2 4 foreground control 12 9 angle constraint 2 form 2 9 Hilgenstock White 12 10 Steger Sorenson 12 10 selecting boundaries f
275. namelists are written by Gridgen CNSFV s grid file is a PLOT3D multi grid Fortran unformatted dataset Only 3D grids supported 17 8 10 Cobalt Gridgen exports structured and unstructured volume grids to Cobalt s grid file The volume grid from all of the blocks are agglomerated into one zone for output to the grid file Cobalt s boundary condition file con tains place holders for all of the assigned boundary condition patches However you must modify the boundary condition file prior to use in Cobalt Note that while you may set periodic BCs on certain grid regions patches Gridgen makes no effort to ensure the grid faces are indeed physically periodic Both 2D and 3D grids supported 17 8 11 COMO COMO is a proprietary file format based on the PATRAN Neutral File Gridgen exports all cell types for both 2D and 3D grids 17 8 12 CRUNCH Crunch export supports only 3D grids of all cell types That means you may create a grid containing both structured and unstructured blocks Gridgen exports a generic BC and a double precision FV UNS file 17 9 Analysis Software Interfaces 17 8 13 DTNS Only the formatted boundary condition and inter block connection data is written by Gridgen A Fortran unformatted DTNS specific grid file is created for each block Only 3D structured grids sup ported 17 8 14 Exodus Il All cell types are supported for 2D and 3D grids 17 8 15 FALCON FALCON is a proprietary format 17 8 16 FANS Onl
276. nd Range 5 5 Layer Manager List Filterz Show Description f M Empt Y Range o 1 023 Show Empty is a toggle command which is on by default This instructs the Layer Manager to list all of the layers including those containing no entities Toggling off this option will remove all empty layers from the Browser list as shown in the following example all disabled 1 hub nacelle El Description is a text entry field where a text string can be entered with wildcards to be matched against each layer s description With each new character added to the string the list is updated instantly Non matches are removed from the Browser list Range is a text entry field where multiple numeric ranges or individual layer numbers can be entered sep arated by commas with no spaces You must hit Enter on your keyboard for the new range s to be acti vated Valid examples would include 5 10 25 30 e 10 100 200 1023 e 0 10 5 5 4 Layer Operations These operations act on the layer or layers selected in the layer Browser Some require a single layer to be selected some multiple and others one or more Layer Isalate Description Set Current Move Status All on All ort on Off Tess Isolate only available when a single layer is selected This command sets the selected layer to the current working layer and turns off all other layers Description available when one or more laye
277. nd begins creation of the next edge Since an edge in an unstructured domain has to form a closed loop Gridgen will not let you save the edge in an unstructured domain until the beginning and end are at the same node Previous Edge Returns control to the previous edge structured domains only Reorient Edge Changes the direction of an edge unstructured domains only This is used to ensure the inner loops of an unstructured domain are oriented in the opposite direction from the outer loop Erase Last Connector Removes the last connector you added Restart Domain Remove all connectors from all edges of the domain and start over Save Domain Save the domain as defined by the selected edges You must use this command for unstructured domains if you have not enabled Auto Save Abort Same as Restart Domain except the domain Create command is exited The Merge and TopoF ltr commands are described in Section 15 10 9 5 Convert Structured to Unstructured Domains To convert structured domains to unstructured domains use one of the buttons below the Triangulate Struct Doms label after pressing Create Triangulate Struct Doms Initialize Best Fit 5 Alianed 4 The Initialize command will create new unstructured domains by taking each selected structured domain s connectors forming a new domain and applying the unstructured solver in the same manner as if the domain had been created as unstructured originally The original s
278. nd that either the left or right mouse button may be used In some instances several pickable entities will lie beneath the cursor In these cases Gridgen highlights in salmon one of them for which one see Section 2 4 4 If this is not the entity you want to select you can step through all pickable entities beneath the cursor one at a time by pressing the x or x keys on the key board with the cursor held in the same location The x key steps through the list of entities beneath the cur sor in ascending numerical order while the x key moves in descending numerical order When the desired 2 8 Entity Selection Selecting From The Browser entity is highlighted in salmon it can be picked using the mouse 2 4 1 2 Selecting Several Entities At Once To select several entities at one time from the Display window follow this procedure 1 Press either the Pick in box or Pick on box buttons These buttons allow you to draw a box in the Display window called the pick box Position the upper left corner of the box using the mouse Press and hold either the left or right mouse see LeftPk in Section 2 9 button and move the mouse to posi tion the lower right corner so that the box encloses the desired entities Release the mouse button 2 Ifthe in box is being used every entity that is fully enclosed by the pick box is picked If using the on box every entity either enclosed or touched by the pick box is picked Repeat the selection process un
279. nector Gridgen first checks to see whether there are any other connectors that share the same break point with the current connector If there are all adjacent connectors are highlighted and you can pick one from which to copy the spacing constraint Positioning the cursor over a highlighted connector will cause the connector to be redrawn with its grid points turned on Also information will be displayed about the highlighted connec tor in the Blackboard including its spacing constraint at the adjacency In this manner you can browse through all highlighted connectors until the desired spacing is found O Entering a value of zero removes the spacing constraint from unconstrains the break point If both of a subconnector s break points are unconstrained the grid points will be equally spaced along the connector If one of a subconnector s two break points is unconstrained the distribution function switches to a one sided form If neither break point is un constrained the distribution function uses a two sided form gt 0 A positive value will constrain the distance between the break point and the first grid point from the break point to be the typed in value The maximum allowable spacing constraint is 40 of the total distance between the two subconnector end points An input value above the limit will result in a request for a more reasonable number Three menu buttons allow you to assign spacing constraints Begin 4 i Endins amp
280. nectors 0 Auto Set Dimensions 1 User Input Dimensions 2 Inconsistent Domains Note that the inconsistently dimensioned domains are highlighted It is up to you to select and redimension another connector to help Gridgen propagate your changes throughout the system 11 3 Distributing Grid Points on Connectors The Redistribute command allows you to change the distribution of grid points along a connector This command is not available for undimensioned connectors Distribution of grid points involves two basic tasks the distribution of points within each subconnector the division of the connector into subconnectors optional 11 5 Grid Methods for Connectors 11 3 1 Definitions Connector Segments 1 Connector Dimensions 15 subConnector 1 info Dimensions 11 spline Linear on 5 Distribution TANH beg AS input 0 00000E 00 S actual 0 36848 input 00000ET00 AO Cursor E y z grid points refer to discrete locations along a connector s shape that will become the grid points on the boundaries of surface and volume grids The number of grid points assigned to the connector is the connec tor s dimension set via the ReDimension command Section 11 1 During grid point distribution Grid gen draws the grid points small filled circles on the connector shape control points are used to define the shape of the connector during connector creation Section 7 2 and are rendered using small open squares The
281. ned a branch seg ment is added After pressing the Merge Nodes button you must enter the distance within which two existing nodes must lie in order to be candidates for merging After you enter this value Gridgen lists in the Browser all node pairs that lie within this tolerance 4 7 A 0 800000 5 7 A 0 500000 Each Browser item consists of three bits of information The two integer numbers separated by dashes are the two node numbers The symbol between the two node numbers indicates whether the nodes are database constrained as follows Neither node 1s database constrained Both nodes are database constrained gt Only the first node is database constrained lt Only the second node is database constrained The real number on the right is the actual distance between the two nodes For example the second line shown above indicates that nodes 4 and 7 are separated by a distance of 0 5 Pointing at the Browser entry using the mouse highlights the two nodes in the Display window To merge nodes select the pairs to be merged from the Browser and press Done Consider the example shown below There are two connectors each consisting of a single straight line seg ment The labeled nodes are A x 0 B x 1 C x 1 1 and D x22 Therefore the gap between B and C is 0 1 Perhaps this gap exists because connectors AB and CD were created on sloppy database entities with a gap We wish to merge nodes B and C using the Merge N
282. ng image manipulation Sparse mode turns off the display of domain grid points and draws database entities as outlines The Demote value in the range between 0 and 10 represents the approxi mate time in seconds between your release of the image manipulation device letting go of the mouse but ton and the redraw of the Display window A large value of drawing lag prevents the image from being redrawn unnecessarily between successive manipulations If you set Demote to 10 the Display window image will only be redrawn in full mode when you press the space bar Mous Bell This toggle button changes the status of the bell between an audible tone and a flash of the Version window in the upper left corner of the screen The bell rings whenever a button is pressed it is off visual bell by default Mous Sens J Rst 1 These buttons allow you to decrease reset and increase respectively the sensitiv ity of the mouse with regard to image manipulation Kybd Sens J Rst 1 These buttons allow you to decrease reset and increase respectively the sensitiv ity of the keyboard with regard to image manipulation Hset The buttons in this row allow you to un pan un zoom and un rotate the Display window image Sec tion 2 3 7 The All button will un pan un zoom and un rotate the Display window image at once GetOri Buttons 1 through 6 in this row allow you to save Get up to six orientations of the Display win dow image Note that t
283. ng that no point was picked so no control point was added Picking searches for hits from in order nodes control points database enti ties and domain points When you are creating a database constrained segment and add a point by picking Gridgen first tries to pick from the current database entity If Gridgen does not find any points on the current database entity it will try to pick other points returning the first hit found If it finds a pickable point that is not on the current data base entity then Gridgen will inform you project the picked point onto the current entity and add it to the segment Wherever possible you should add points by picking because this will ensure that components of your grid match end to end 2 8 2 3 Via Keyboard A third method of choosing a control point is selected with the Add CP O via Keyboard button or by hit ting the Pad Period key A prompt appears in the Message window and the program waits for the numeri cal input to be typed in the input window You will be expected to input x y z coordinates if the current segment is not database constrained and parametric u v coordinates if the segment is surface con strained Default values are the current cursor location so entering nothing is the same as using the Add CP O at Cross button It is not necessary to type all components of a coordinate unless it is to be different from the default For example to change only the z coordinate say
284. ng the volume grid using the Examine command in the BLOCK COMMANDS menu Section 16 You choose whether Gridgen will import and export grid data from a Gridgen file or a volume grid file You may also have Gridgen work from your primary Gridgen gg file Should you choose to work from the Gridgen file be advised that your new volume grids from Gridgen will become a permanent part of the Grid gen file thereby increasing its size and the time to import and export On the other hand for small and mod erately sized grids this is a good way to maintain a single file for your entire grid If you choose to use volume grid files with Gridgen you will have to provide for the management of separate Gridgen and vol ume grid files If you ever wish to merge the structured volume grid and Gridgen files you will have to use the Incorporate Volume Grid command Section 4 13 However the relatively small size of the Grid gen file improves Gridgen s interactive performance We recommend that you work with volume grid files if you are generating a large grid The Glyph file contains the Glyph commands necessary for running Gridgen including most importantly 4 20 Block Ell Solver Glyph Exporting Unstructured Grid Points how to apply the grid methods See Section of the Glyph Reference Manual for a detailed discussion of the contents of the Glyph input file Please be advised that the Glyph files produced by this command for running Gridgen may have
285. nnector Usually it has many more control points than the segment types which can make it cumbersome to edit Gridgen will not warn that you are moving a connector off the database so exercise extra caution when modifying connectors that are on databases Connectors are linked to other connectors at their nodes It is possible to break this linkage during modifica tion Referring to the example grid suppose that the two vertical connectors on the left were scaled Section 14 3 2 Since these connectors are linked to other connectors you must choose from the following menu 14 4 Linkages Connector Linkages Unlink Connectors y Maintain Linkages esc If you choose Unlink Connectors only the selected connectors will be modified in this case by scal ing As you can see in the figure below only the two vertical connectors were changed and new nodes were created at their end points The three horizontal free connectors did not move On the other hand by choosing Maintain Linkages vou force Gridgen to update all connectors that are linked by their nodes to the modified connectors resulting in the grid shown below A connector is linked to a domain if it is used on the domain s edges A connector is linked to a block if it is linked to one of the domains that define the block Fortunately it is impossible to unlink a connector from a domain or block even by pressing the Unlink Connectors button This prevents error
286. nodes connectors and domains respectively By default each of these three toggles is on By turning off the Nods and Cons toggles you can make a very nice picture of just the grid However Nods and Cons only affect the display while in the DISPLAY COMMANDS menu On the other hand Doms remains in effect throughout the entire code allowing you to easily toggle between a nice rendering for visualization of surface grids and a sparse rendering for ease in image manipulation Show Rot Axs This toggle button controls the display of the rotation axes in the Display window By default this toggle is on The rotation axes are drawn in red with their origin at the center of the grid image they are not necessarily rendered at the 0 0 0 point of the body axis system Show XYZ Axs This toggle button controls the display of the xyz axes in the Display window By default this toggle is off The xyz axes are drawn in blue and centered at the 0 0 0 point of the body axis sys tem Menu SmalTxt This toggle button controls the point size of the text used in Gridgen s menus The nor mal text is approximately 14 point The small text available by toggling this switch on is approximately 8 point By default this toggle is off 2 20 Display Commands Menu Miscellaneous Controls Menu On Left This toggle button allows you to choose the side of the screen on which Gridgen draws the Version Status Text Input Blackboard and Menu windows By defaul
287. not moved by the elliptic solver There are instances however when moving the boundary points subject to the PDE solution may be advantageous Gridgen s three types of boundary conditions are described below Note that these boundary conditions are not related in any way whatsoever to the analysis software boundary conditions Section 17 2 Before selecting the boundary condition you must first select the boundaries to which it applies as described in Section 2 4 Fixed 1 Floating 2 Orthogonal 3 Fixed Boundary points are not affected by the elliptic PDE solution This is the default boundary condi tion Floating Boundary points will float as though they were interior grid points Floating boundary condi tions are only applicable if Gridgen is able to find a unique neighbor to the boundary among the grids selected for the elliptic solver If a unique neighbor cannot be found for a particular grid point then the boundary condition is converted to fixed for that grid point Although the grid points on floating boundaries 12 13 Grid Methods for Structured Domains and Blocks are computed as though they are interior grid points the control functions are computed in each grid individ ually This may result in control function discontinuities across the boundary leading to unexpected results Orthogonal Boundary points will move along the boundary shape in order to maintain orthogonality with the interior points 12 3 Stru
288. note that for a single curve to be selected with Coons it must be self connecting Each of these cases is illustrated sequentially below starting with the four curves case on the left Auto This toggle allows the user to select up to fifty curves that will automatically be processed for the user The Coons command will then be applied to create as many surfaces as possible from those curves These potential surfaces will be listed for the user in the Browser list so that desired surfaces can be selected and saved The Coons Auto option is limited to creating only 100 potential surfaces If the desired surface 1s not created the user should start over with a different curve set Once the Coons surface is created to the user s satisfaction one of the following two menus will be pre sented The menu on the left represents the Coons surface creation menu with the Auto toggle off while the menu on the right is seen when the Auto toggle is on 6 13 Creating Database Entities CREATE COONS SURFS CREATE AUTOCOONS SURF Reselect Boundary Curves 0 set Point Tolerance 2 Set Point Tolerance 2 Reselect Coons Surfaces 3 Done Save Coons Surf ent Done Save Coons Surfacesent Abort Dont Save Surf esc Abort Don t Save Surfacessc Commands that can be used during Coons surface creation are Reselect Boundary Curves If a Coons surface could not be created on the selected curves or if the wrong curves were chosen by mistake th
289. ns use a glyph that outlines the cell If a diagnostic function has been selected the topological hiliter will be directly rendered by color variation for that func tion For a prism block the topological hiliter displays planes of triangular surface grids in the extrusion direction For both structured unstructured and hybrid volume grids the physical hiliter allows you to position a con stant cartesian coordinate plane x y or z at which a cut will be made through the volume grid There are no hiliter isolines or circular point or cell glyphs rendered on a physical hiliter Also no diagnostic function data is rendered directly on a physical hiliter but instead is rendered on the various cuts that can be made at the hiliter location Topological left and physical right hiliters are shown below for a structured grid The topological hiliter cuts through the grid at 254 while the physical hiliter cuts the grid at x 45 0 16 11 Diagnostic Functions Commands that allow you to manipulate the hiliter for blocks are described below Hiliter O off e LIextend Topo o ilon jle k Phy ox i ov i oz ak S vlvi lAl T _Okbrd pad Rot Pt m Oto min f 0 Oto max f 1 Off Pressing this radio button turns off the hiliter extend Toggling on this button causes a topological hiliter to be extended beyond the Local block into all appropriate blocks currently picked for Examine E N Pressing these but
290. nt of setup However it should be applied with care since it sometimes is not readily apparent beforehand what the closest database location is and bad grids sometimes result The results of normally projecting our sample grid onto the database are shown below EN mh an L A EN 14 5 Smooth The Smooth command found in the Database Modify menu smooths database curves through fitting A smoothing tolerance 1s available so that the maximum deviation of the smoothed curve from the original can be prescribed by the user 14 6 Re extrude The Re Extrude command available in the Domain and Block Modify menus provides a way to re extrude previously extruded prism and hexahedral domains and blocks This command may be applied to single or multiple domains or blocks Note that re extrude is only available when all domains or blocks selected for modification have been previously extruded Re Extrude 1 Pressing the Re Extrude button places domains or blocks eligible for re extrusion in the state that they existed in before being saved as domains or blocks The full extrusion menu is available to extrude the domains or blocks forwards backwards or completely over Section 8 1 The beginning extrusion attributes are inherited from the original domain or block If a domain selected for re extrusion belongs to a block the re extruded domain has to contain the same number of extrusion steps as the original domain The resulting re extruded do
291. nto the database are shown below 14 4 3 Linear Fick Pnt of Rotation t In the Linear projection grid points are projected along parallel rays The ray cast direction is along the Dis play window s line of sight Gridgen s screen z coordinate direction After pressing the Linear button and before pressing the Done Project button manipulate the image on the screen until you are visually satis fied that rays cast through the grid points and along the line of sight vector will intersect the database in the desired manner The Pick Pnt of Rotation button may be used to change the image s rotation point in order to more easily obtain the desired projection direction Linear projections are general purpose and can be used in most cases with easily predicted results It is rec ommended that you use an orthonormal viewing transformation when orienting the image prior to projec tion The results of linearly projecting our sample grid onto the database are shown below 14 14 Smooth Closest Point 14 4 4 Closest Point Closest point projection is orientation independent Grid points are simply moved to the closest point on the database This procedure is also known as Normal projection because the rays cast through each grid point will intersect the database orthogonally at the closest point After choosing the Closest Pt button press the Done Project button This projection method is the easiest to apply since it requires the least amou
292. ntrol functions the resulting surface shape will be of minimum area similar to a soap film across a general boundary 12 2 6 Fixed The grid will maintain the shape it had when the Fixed button was pressed The solution of the elliptic PDEs is performed in a parametric space corresponding to the grid s original u v coordinates If the grid is constrained to the database this method will not destroy the grid database relationship This method 1s generally used when the existing grid points lie on the intended shape but are not distributed in the desired manner and no database is available 12 2 6 8 DB This method is used to have the grid conform to one or more database entities For best results the starting grid should already lie on the database entities This can be accomplished in two different ways Parametric TFI Section 12 1 5 or Parametric Fit TFI Section 12 1 6 2 Projection either via the Modify menu Section 14 4 or via the Run Structured Solver menu Section 12 2 Assuming the grid points have been initially constrained to the database Gridgen attempts to make grid points conform to the database using either of two methods Gridgen chooses automatically on a point by point basis 1 Ifa grid point is surrounded by grid points that all lie on the same database entity the grid generation equations are solved in the parametric u v coordinates of the database entity 2 Otherwise the elliptic PDEs are so
293. nts on adjacent entities It is up to you to ensure the shape of the branch segment does not deviate unacceptably from the shape of the database In the illustration above a connector is being drawn across two database entities a horizontal line and a circular arc Two control points have already been added on the line The last 1s at the junction of the line and circle The cursor has already been moved to the circle entity and the branch segment is being dis played as a dashed line The deviation of the branch segment s linear shape from the intended circular arc shape is readily apparent Minimize this deviation by keeping the branch segment as short as possible However you should not use coincident control points putting the first control point on the circular arc at the line arc junction since this will cause a lot of editing and grid point distribution problems later The database entity on which the segment is being created may be selected using the following commands As you move from entity to entity the 3D cursor is positioned at the closest point on the database entity to the last saved control point in the segment DB ent Next n Prev b Pick n Next Move to the next database entity in increasing numerical order Prev Move to the previous database entity in decreasing numerical order Pick Graphically select the database entity on which to create the segment 7 2 9 Rational Segments 7 2 3 1 Conic The Conic Section se
294. o one more than the total number of intervals traversed on the network by the connector Mono Rat Quad Spin The Monotonic Rational Quadratic Spline MRQS function Reference 1 can be applied to several subconnectors simultaneously The MRQS function will force a grid point to be fixed to a break point and automatically provide spacing continuity and spacing variation continuity across the break point Gridgen links two MRQS subconnectors if their spline variables and spline types are the same and if the spacing constraints across their common break point are equal Geometric Progression This is a one sided distribution function It is available only if a spacing con straint is specified at one end of the subconnector If no spacing constraints are specified the grid points will be distributed uniformly Geometric progression works by distributing the grid points from the constrained end so the ratio of spacing between adjacent grid points is constant Therefore if tight clustering is specified at one end the distance between successive points will increase monotonically towards the other end of the subconnector A warning will be issued if both ends of the subconnector are constrained and the subconnec tor will be converted to a hyperbolic tangent distribution Therefore you must unconstrain at least one of a subconnector s break points before you can apply the geometric distribution function Copy From SubConnects This option allows
295. o or more domains After the Add 1st Face button is pressed select the first domain to be added to the face by positioning the cursor over one of the domain s edges until it highlights and pressing the right mouse button The pickable part of the domain is the row of cells adja cent to its boundary If the wrong domain highlights try moving the cursor to lie only over the desired domain or use the x hot key to cycle through the available choices until the one you want is highlighted The picked domain is highlighted in the Display window and the cumulative count of domains in the face is listed in the Blackboard Free edges those on the perimeter of the face are drawn in yellow Since each face of a 3D unstructured block must be a closed surface the appearance of yellow connectors indicates that the face 1s not yet complete In the illustration below only 3 two on the symmetry plane and one on the valve stem of the 6 domains in the block s face have been added note the yellow connectors around the perimeter 3 domains in uns face a A AA A AA Eire ot ote ACE T AL RAE TI Pret utc a Each additional domain to be added to the face is selected using the procedure described above Each domain added to the face must be adjacent to the domains already in the face The Blackboard and Display windows are updated to reflect the new face structure If the selected domain does not connect to the existing face
296. o start over by picking another set of rail curves Reverse the Direction This command allows you to untwist the surface by implicitly reparameterizing the second rail curve A twisted ruled surface such as the one shown below will result when the two rails are parametrized in opposite directions the ruled surface 1s created by linearly interpolating between similar parameter values on the rails Ruled Surface Rail Curve 1 1 Rail Curve 2 3 Fit Tolerance 0 100E 02 Patches 99x 1 Set Fit Tolerance The tolerance with which the ruled surface matches the rails may be changed using this command Decreasing the fit tolerance will result in a ruled surface with a larger number of intervals The default fit tolerance is 0 001 Section 3 7 1 6 8 Surface Polyconic Surface 6 5 2 Polyconic Surface A polyconic surface is the surface equivalent of a conic curve Section 7 2 3 with control points replaced by control curves Whereas a conic curve is defined by two end points a tangent intersection point and a p value a polyconic surface is defined by two rail curves a tangent intersection curve and a p value Polycon ics are very useful for creating fillets Construction of polyconics begins with graphical selection of the two rail curves The third curve selected is the tangent intersection curve By default the tangent intersection curve serves double duty as the poly conic s spine The resulting polyconic surface will
297. odes command Enter the node merging tolerance Every node pair closer to each other than the tolerance is a candidate merger pair In the example shown below we know that the distance between B and C is 0 1 so we enter a tolerance of 0 2 to be sure the test identifies node pair B C as a candidate 15 11 Miscellaneous Enter a tolerance within which node pair merger candidates will be listed l2node t 2 con es ol default 0 200000 In the figure below Gridgen shows in the Browser the node pair within the tolerance and the actual distance between the nodes You can then select from the Browser or Display window the pair to merge MERGE NODES Pick the node pairts to merge After picking node pair B C and pressing Done Gridgen merges the two nodes together In the example shown below node C has been relocated to node B x21 Now the two connectors match end to end and can be used to create a domain 15 10 2 Connectors The Merge Conns command allows you to select pairs of dimensioned connectors to be merged together into a single connector This merging 1s not topological one of the connectors is replaced with the other Merging connectors is good for removing coincident connectors from your grid This command does not alter the connector tolerance in the Defaults menu Section 3 7 2 After pressing the Merge Conns button you must enter the distance within which two existing connectors must lie in order to be c
298. oduction and distribution is strictly prohibited RIGHT TO USE LICENSE 5 OWNERSHIP All Licensed Products and the information they contain any updates and all copies of them are PWI s or PWI s licensors property and title to them remains in PWI or such licen sors All applicable rights in patents copy rights or trade secrets in the Licensed Products are and will remain in PWI and PWI s licen sors No title to or ownership of the Licensed Software or the information they contain is transferred to Licensee Licensee agrees that any terms and conditions imposed by PWI s licensor and communicated by PWI to Lic ensee by PWI shall apply to the Licensed Products 6 CONFIDENTIALITY a Licensee will take all reasonable precau tions to maintain the confidentiality of the Licensed Products and agrees to take all rea sonable and necessary steps to protect the pat ents trademarks copyrights trade secrets and any other forms of intellectual or industrial property of PWI in the Licensed Products b Licensee will not provide the Licensed Products to any person other than employees of Licensee without PWI s prior written con sent except during the period any such person is on Licensee s premises with Licensee s per mission for purposes specifically related to Licensee s use of the Licensed Products 7 COPYRIGHT AND PATENT INDEM NITY PWI assures Licensee that to the best of PWI s knowledge
299. ody shape could be substituted for the original by simply importing a new database file with the same entity names but different shapes and importing the old Gridgen file Since Gridgen thinks the data base and grid match since all of the entity names are the same all components are regenerated in terms of the new database shape Here is the strategy Gridgen uses to set the default entity names For IGES files 1 Use the name entity if specified 2 Usethe subfigure name for subfigure instance entities 3 Use the entity label and subscript directory entry fields If the label field is blank then use a string of the form entity type for example conic for a conic section If the subscript field is blank then use a string of the form sequence number for example 2 for the second entity in the file For all other database file types 1 Use a string that is a concatenation of base name of file entity type and sequence number in file For example the second entity in a network file called wing net would be wing psurface 2 2 If the default name is already taken use a string of the form Entity where is the entity number If the Name command is used to assign names to database entities then one of two approaches must be taken when re running Gridgen 15 1 Miscellaneous 1 Import the entities as before and repeat the naming process prior to importing the Gridgen file 2 Save the database in
300. of radio buttons provides options for the display of the focus connector s grid points e ee This radio button displays the connector s grid points as small filled yellow and white circles depending on whether or not the grid point is in the current subconnector respectively This is the default setting e e This radio button displays the connector s grid points as slightly larger filled pink circles and con nects the grid points with a dashed pink line This display option is useful for visualizing the faceting effect of the grid point distribution on the connector shape Off This radio button turns off the display of grid points The second row of radio buttons provides two options for the display of the focus connector s control points O L1 O This radio button displays the connector s control points as small open white squares This is the default setting Off This radio button turns off the display of the focus connectors control points Individual control points are temporarily displayed when the connector hiliter moves near them 11 4 Setas Values Rather than use the Redistribute command in the Connector Modify menu for each connector in your grid one connector at a time you can use the Set As Vals command to specify spacing constraints for many break points at once This command also allows you to change the distribution function of these connectors And like the ReDimension Grids command the changes are propaga
301. of the surface to calculate grid points on the interior Only Parametric TFI and Parametric Fit see below constrain grid points to the database shape All other methods calculate x y and z solely from the distribution and location of points on the boundaries The resulting grid shape depends on the particular TFI method used The TFI methods are described in the following sections Standard TFI 1 Linear TFI 2 Polar TFI 3 Ortho TFI 4 Parametric TFI 5 Param Fit TFI 12 1 1 Standard TFI Standard TFI applies blending functions based on the relative spacing of the grid points on the boundaries Reference 20 The TFI algorithm is applied independently to the x y z coordinates of a grid Because the blending functions are arc length based the resultant grids usually have satisfactory clustering Standard TFI is the third method after Parametric and Parametric Fit TFI that Gridgen tries to apply by default to create the initial surface grid for domains Standard TFI is the default method for new blocks 12 1 2 Linear TFI Linear TFI applies the TFI algorithm to the x y z coordinates of the grid but the blending functions are no longer related to the distribution of grid points on the boundaries This method is rarely better than Standard TFI but is provided for comparison and historical purposes Standard TFI left is compared to Linear TFI right below 12 2 Algebraic Methods Polar TFI 12 1 3 Polar TF
302. oint Once the point is defined you can press the Repick Source Point button to change to a different point Select the Proj In or Proj Out radio button depending on the relative position of the grid and database and whether you prefer to move the points inward or outward Spherical projections are useful for projecting grid points onto blunt geometries such as the nose of a missile The results of spherically projecting our sample grid onto the database are shown below 14 13 Modifying Entities 14 4 2 Cylindrical Repick Axis _l Point n Enter Axis_2 via Keybrdpad Use A directed Axis 1 Use Y directed Axis 2 Use Z directed Axis 3 o Proj In ij Proj Out o Cylindrical projection 1s named for 1ts analogy with a cylindrical coordinate system This method projects grid points along rays relative to a user defined axis of projection The rays emanate orthogonally from the axis and pass through each grid point After pressing the Cylindrical button define the projection axis by defining two points on the axis or selecting one of the menu buttons corresponding to the principal axes Select the Proj In and Proj Out radio button depending on the relative position of the grid and database and whether you prefer to move the points inward or outward Cylindrical projections are useful for projecting grid points onto ducted geometries such as the inside of an aircraft engine intake duct The results of cylindrically projecting our sample grid o
303. oj Typ Lin Cur This attribute tells Gridgen the projection type is linear and that points will be projected onto the database along a fixed vector perpendicular to the Display window screen z when the button is pressed 8 4 Extrusion Attributes Aspect Hatio Proj Typ ClosePt This attribute tells Gridgen the projection type is closest point and a projection vector is not required Proj DBs Default The grids will be projected onto the default set of database entities The default data base entities are computed for each grid based on which entities are currently referenced by the grid points The entities to be projected onto are highlighted in the Display window Proj DBs Picked The grids will be projected onto database entities selected by you After this button is pressed you may select database entities from either the Browser or Display window The current set of pro jection entities is already picked when the Browser is first invoked Show Proj DBs This toggle button controls whether or not the database entities being projected onto will be highlighted in the Display window Turning off this toggle will un clutter the display Show Proj Vector This toggle button controls whether or not the projection vector with which grid points are projected onto the database entities is rendered in the Display window Turning off this toggle will un clutter the display Align View w Proj Vector This command changes the orientation o
304. ollection Group entities are useful for enabling and disabling a large number of entities for grid point projection for modify ing many entities at once or for changing the display of many entities Two points should be made regarding database groups in conjunction with the layer manager First data base groups are a picking mechanism only and as such do not belong to a layer Second if any child of a group is disabled or 1s in a layer that 1s off the group itself will be unavailable for picking or selection For more information about the layer manager see Section 3 of the User Manual 15 2 2 Connectors Domains and Blocks To group a set of connectors domains or blocks entities follow the procedure below 1 Press the Define button 2 Type in the group name via keyboard 3 Select the entities to be included in the group 4 Press the Done button 15 2 Copy Database Entities Group Define i Undef 2 The grid entity Group command allows you to assemble one or more entities into a logical collection Grid entity groups are useful for modifying many entities at once for changing the display of many entities and for many other regular operations A group always available for picking may contain entities existing in database layers Section 5 which are not currently visible A group of a particular entity type is available for all operations that can be used on that entity type and groups are homogeneous The Grou
305. ollowing effects left mouse The image in the Display window will be panned across the screen e middle mouse The image in the Display window will be zoomed on the screen e right mouse The 3D cursor will be moved The right mouse button is also used to pick items including both menu buttons and graphical objects in the Display window The left mouse button may also be used to pick menu buttons but not graphical objects If you prefer to use the left mouse button for picking all the time us the LeftPk option in the DISPLAY COMMANDS menu Gridgen s cursors are context sensitive and will change depending on whether the menu is being probed the image is being rotated panned or zoomed or whether an error condition has been detected The cursor may also be restricted to move only in directions that you choose Section 2 8 1 Menu Buttons Commands A23 Menu Buttons 2 3 1 Commands To select a command via its menu button follow this procedure 1 Position the cursor over the menu button The button will be highlighted 2 Press and release either the left or right mouse button Input Output e The Menu window displays menu buttons with text corresponding to the commands that you may execute The text on each menu button 1s left justified and either black in color or grayed out The grayed out text represents commands that are not available to you in the current state of the grid As the grid evolves the grayed out comman
306. ommand allows you to specify your preferences for a variety of grid attributes Except for the four tolerances these defaults are not saved in the Gridgen file We recommend you utilize a Glyph rc file Section 1 in the Glyph Reference Manual in order to have a consistent set of defaults each time you run Gridgen When you enter the Defaults menu the current default settings are displayed in the Blackboard window 3 1 Connector Defaults 3 1 1 Dimensions The connector dimension default is the number of grid points that will be applied automatically to new con nectors The dimension and average spacing defaults Section 3 1 1 and Section 3 1 2 are mutually exclu sive The initial value of this default is 0 new connectors will be un dimensioned To change the value of the default press the Con Dim dimen button and type the new value in the Text Input window Setting a default dimension is especially useful when used in conjunction with the On DB Entities and 2 Point Connector connector creation commands Section 7 4 and Section 7 3 respectively because it allows a large number of connectors to be created and dimensioned at one time The same holds true for the On DB Entities domain creation command Section 9 6 3 1 2 Average Spacing The connector average spacing default is the grid point spacing that will be applied automatically to new connectors The average spacing and connector dimension defaults Section 3 1 2 and Section 3 1 1 are m
307. on kmin source region kmax if 3D bc number if region is a connection bc number 0 then Ed iuis TE ia For an aunterblock connection there are three E E EEEE E E EE pairs of indices that must be matched three on oar ae Be S rhe bs Bite the source face and three on the target face 35d os ens oe ee sate St The index that s constant on both the source and SPR o RE Se eae Ben Si target faces is easy to determine simply by cola rau fes comparing the min and max indices and finding the EAEE a ee UEUNES pair in which min and max are the same o M Lm On each of the source and target faces Gridgen Dias a E Bose rt dudes writes one of the two remaining min max index DES ME E combinations as negative numbers The negative Cod y qe ar ea oves min max pair on each face correspond Once you hone io exis Sa ee en e determine the corresponding negative indices Nets ae ea oed eint iss dela just convert them to positive numbers E Ne aD uie ts s RR That leaves one pair of indices that align PER PO oak lee Keep in mind that the max index may actually Ciao adi capte de be less than the min index You can either use ob puo a ee ba Sas a negative increment to step through the index Cod dons e dep af ede or you can swap the min and max indices on BOTH QUO EA Stace t Rte te dt Source and the matching target indices write target region imin target region imax target region jmin target region jmax and target region kmin target region kmax if 3D ta
308. only 8 characters STL type refers to the Stereo Lithography file format described in Reference 42 STL import and export is available for triangular surface grids only Both ASCII and binary format STL files may be imported and exported although the binary format is always little endian VRML type refers to the Virtual Reality Modeling Language Version 1 0 For information on this format please consult Reference 41 VRML import and export is available in ASCII only for surface grids Grid gen recognizes the following VRML keywords e Coordinate3 e IndexedFaceSet VRML s Translate Scale Rotate and Transform keywords are ignored Although both triangular and quad rilateral surface grids may be exported to a VRML file all polygonal cells are triangulated when a VRML file 1s imported All mesh data between VRML separators will be converted to at least one Gridgen shell Split Ang Off b During shell import Gridgen allows you to manually set the Split Ang tolerance shown above used to find 4 8 Importing Database Files File Type geometric features for example slope discontinuities in the shells By default the split angle is set to off and is disabled but enabled during shell import only Split Ang This allows shells to be divided into smaller shells along edges of the model that meet a turning angle criterion any triangular surface with a turning angle less than this is split angle This angle can also be set in
309. ontaining the global data patch data glue data and grid points Gridgen does not support CFX 4 s volumetric conditions The following CFX 4 physical types may be used in the creation of custom bc s SYMMET INLET OUT LET PRESS and WALL If a custom bc is created that begins with a physical type keyword then the phys ical type for that bc will be set to the keyword type If no keyword is found at the beginning of a custom bc name the default physical type USER2D will be assigned For example if a customer creates a bc called OUTLET CHANNEL the bc patch will written out as OUTLET CHANNEL of physical type OUTLET Two dimensional grids are assumed to lie in the x y plane The grid is extruded by 1 0 units in the z direc tion to create a 3D grid of one cell thickness 17 8 6 CFX 5 Gridgen exports fully hybrid grids containing hexahedra tetrahedra prisms and pyramids User defined VC s are allowed Gridgen includes VC names in CFX 5 export 17 8 7 CGNS Struct This ASW selection supports 2D and 3D structured only User defined VC s are allowed Gridgen includes VC names in CGNS Struct export 17 8 8 CGNS Unstr All cell types are supported for 2D and 3D grids User defined VC s are allowed Gridgen includes VC names in CGNS Unstr export 17 8 9 CNSFV Although CNSFV permits only a single boundary condition per block face Gridgen does not restrict the grid construction in this manner Only the ZONAL and BOUNDCND
310. or 12 9 setting 72 9 spacing constraint 72 10 relaxation factor 2 7 shape 72 11 database 2 2 fixed 2 12 free 12 12 creating subgrids for 72 14 running 2 4 transfinite interpolation 2 2 structured grids domains create 9 7 subconnector copy dimension from 2 copying distribution from amp definition 71 6 dimensioning summarize Status window 2 function T TACOMA asw 17 14 TASCflow asw 17 14 TEAM asw 17 14 technical references 9 tetrahedra attributes 5 7 tetrahedral mesh size factor 5 5 tetrahedral mesher memory limit 5 5 TETREX asw 7 14 Text Input window 2 three dimensional 3D grids 7 toggle button 2 4 tolerance 5 6 connector 3 6 grid point 3 6 model size 3 7 node 3 6 TopoF ltr 5 5 transfinite interpolation 2 transformations 4 7 translational extrusion 5 attributes 8 4 triangle area maximum 3 4 minimum 3 4 two dimensional 2D grids 7 U unstructured grids attributes shape 3 4 block create 70 3 boundary point insertion 3 9 convert from structured 9 8 domains create 9 4 solver 73 1 unstructured solver 5 attributes 3 2 boundary decay factor 3 7 maximum angular deviation 73 6 maximum surface deviation 3 6 maximum triangle size 73 6 minimum triangle size 73 6 shape 13 4 smoothing 3 5 projection 3 4 Usage diagnostic function 6 2 V VCR button 2 4 Version window 2 VRML grid export to 4 7 import as database 4 8 import as grid 4 5 V
311. or Gridgen s supported hardware platforms are as follows 1 SGI HP SUN and IBM have the Big Endian byte format 2 PC Windows and LINUX and DEC have the Little Endian byte format 18 2 Gridgen File The Gridgen file default extension gg contains all of the data used by Gridgen to create and maintain the grid including connectors domains blocks analysis software boundary conditions display options grid attributes and database references entity names and parametric coordinates The Gridgen file does not contain the databases even those created in Gridgen If you create database entities in Gridgen for exam ple using the Copy command in the DATABASE COMMANDS menu you must save them in a database file A detailed description of the Gridgen file is omitted due to its complexity The Gridgen file is written in binary format If the grid has been generated using a database then the database file must be imported before the Gridgen file 18 3 GRIDBLOCK Files Gridgen can only import GRIDBLOCK files from GRIDGEN Versions 8 and 6 using the Gridgen Import command in the INPUT OUTPUT COMMANDS menu Section 4 1 3 However these file types are sub ject to the following restrictions GRIDBLOCK Version 8 files default extension b1k are fully compatible However due to the manner in which older versions of GRIDGEN maintained adherence of the grid to the database the database entity groups that are automatically created by Gridge
312. ore note that the default values for a multiple word text input can be used by taking advantage of the delimiters For example if the default value for a point being entered is 2 4 6 and you wish simply to change z to 8 you could enter 8 at the text prompt Text input can also be a Glyph expression When you enter text input mode the Browser will display the Glyph variables you have already defined You can pick variables from the browser to use in expressions or type them directly in the Text Input window You can turn off the display of variables using the Hide Vari ables button Please note that if variables are defined they will appear in the Browser window when in text 2 13 Graphical User Interface input mode regardless of what menu the text input prompt occurs 2 7 Image Manipulation Manipulation of the Display window image is controlled by three factors the axis system in which you want to manipulate the image either the body or screen axes the state of the Glide button in the DISPLAY COMMANDS menu and the device you use to affect the manipulation either the mouse or keypad keys 2 7 1 Axis Systems Gridgen works with two axis systems the body axes and the screen axes The body axis system is the three dimensional coordinate system in which your database and grid are defined The body axis system may be visualized by enabling the display of the XYZ Axes which are drawn in blue and located at the origin of the body
313. ore than 180 degrees by selecting three con trol points on the circle The first control point P specifies the beginning of the arc and the second control point P specifies the end of the arc When P is defined a third control point Py is initially drawn halfway between P and P and the current center of the circle as defined by the three control points is drawn with a center of gravity symbol and 1s listed in the Blackboard The menu changes to the Edit Circular Arc menu and P can be moved using the mouse to modify the shape of the circular arc The circular arc is drawn so it passes through points P4 P5 and P Pz can be positioned anywhere on the circular arc Gridgen will restrict the cursor movement so the circular arc will subtend no more than 180 degrees Arcs spanning more than a semicircle must be created by more than one segment P1 P3 P2 center Instead of the third point in the circle definition being P4 you may choose to position the center point directly Store Picked Center Pt i Store Center via Kbrd Aj Store Pt at amp via Kbrd i Store Picked Center Pt Pick a point at which the circular arc s center will be located Store Center via Kbrd Type in the point at which the circular arc s center will be located Store Pt at o via Kbrd Type in the angle relative to P4 at which P5 will be located 7 2 3 3 Slide Points Although only three points are used to define rational segments you can a
314. ormation is shown below Y N SN Hiliter Blocks 16 13 Diagnostic Functions blocks 1 Z 1 points 8582 of 8582 dimension maximum 8582 A average minimum 8582 A A 56 000000 16 6 Reference Surfaces A reference surface is the result of cutting a volume grid with the hiliter Reference surfaces are always ren dered to reflect the current diagnostic function drawn with the current display attributes You may create multiple reference surfaces In local mode the physical hiliter only cuts the focus block when creating a ref erence surface In global mode the physical hiliter cuts all blocks when creating a reference surface Commands for controlling reference surfaces are described below and illustrated for a 3 block grid consist ing of a structured block a hybrid unstructured block contains both tetrahedra and pyramids and a prism block Ref Surf M Permanent Crinkle c Flat l Cells 5 Erase Cur d Erase All d Permanent This toggle button sets the state of the reference surfaces that you create When the perma nent state is toggled on each new reference surface you create persists until you exit the Examine com mand Otherwise if the permanent state is toggled off each new reference surface replaces the previous one Save This command saves the current structured block topological hiliter location as a reference surface The illustration below shows Saved reference surfaces through
315. ot affect the interpretation or construction of this Agree ment PWI shall not be liable for any failure or delay in performance due in whole or in part to any cause beyond PWI s control This Agreement and all transactions under it shall be governed by the laws of the State of Texas All claims arising under or related to this Right to Use License Purchase Order or Contract shall be settled finally and exclu sively by arbitration in accordance with the Commercial Arbitration Rules of the Ameri can Arbitration Association AAA Arbitra tion shall take place in Dallas Texas and be administered by the AA A s Dallas Texas office ies mw 3 get the i Volume 1 Gridgen User Manual Version 15 TABLE OF CONTENTS 1 Introduction carro 1 1 LIOGO TYPES oee E E E E E EE E EE 1 1 1 2 Data Hierarchy ccccccccccsecccncccseensuecsuecsueeaunessuessuensuensaessaeensuessuessessaunsanssags 1 1 1 3 Command Hierarchy and Menu Structure cooooccccocncccoccnoccnnncnonononos 1 2 1 4 Planning Your Grid ooocooocncocccccocncconccncncnonnnnncnononnnnnononnnnonannonanonnrnnnannnnos 1 3 1 4 1 Define the Modeling Goals serere 1 4 1 4 2 Identify Your Grid s Constraints esee essere 1 4 1 4 3 Plan the Grl l oocccconnconccconcccoccccconococnnconnononnnnonnonnnnnonnononnnonnnonanonnnnenaninnons 1 4 1 5 Outline of the Gridgen Process
316. ough out the entire volume Otherwise Gridgen will mesh between the nested faces By default this 1s disabled This command is available for unstructured blocks only Abort esc Abort Clear the current collection of domains from the face pause the face creation process and invoke the following menu Add 2nd Face a Create Domain c Remove a Face d Reorient Faces Ax ReName n Done Save Blocks ent Abort Dont Save Blocks esc Add nth Face Continue the block creation process by creating the nth face where n is one more than the number of faces currently in the block Create Domain This command is used to create a domain during face creation in case it is discovered a domain necessary for a block has not yet been created Remove a Face Delete one face in its entirety from the block You select the face to be removed from the Display window This does not delete the face s domains but only the topological face entity Examine Faces You may step through a graphical display of each face currently in the block using this command This command is available for structured blocks only Reorient Faces Since any face has two possible normal directions you may have to flip the face orienta tion automatically chosen by Gridgen to ensure that each face s normal vector points into the volume grid When you invoke this command the face s normal vectors are drawn as shown below Selecting a face causes the normals to be flipped to the opposi
317. p Undef command allows you to remove entities from the Group This command does not delete the entities from themselves 15 3 Copy To copy an entity follow this procedure 1 Press the Copy button 2 Select the entity or entities to copy 3 Press the Done button 4 Perform any entity transformations e g translation etc 5 Press the Done button Copy c The Copy command allows you to duplicate entities Note that after selecting and copying the entities Grid gen immediately puts you into the Modify menu Section 14 so that you can translate scale or otherwise change the copies 15 3 1 Database Entities When copying database entities it is not necessary to modify the copy since two or more identical entities can occupy the same physical space The string copy is appended to the original entity name If several copies are made of the same entity the string copyN is appended to the name where N indicates the nth copy 15 3 2 Connectors Domains and Blocks Copies of connectors domains and blocks must be modified so they are not coincident with their originals This is because Gridgen culls duplicate grid entities after the copy operation 1s complete Block copies are re named according to the default block naming scheme Section 10 15 4 Delete To delete an entity or entities follow this procedure 1 Press the Delete button 2 Select the entity or entities to delete 3 Press the Done
318. pe while keeping the same set of control points You can convert between Line Curve Akima Bezier Smooth Control Points Apply a LaPlace filter to all of the connector s control points in order to smooth its shape Movement Restrictions This command invokes a menu that allows you to restrict the motion of the 3D cursor to aid in drawing the segment Sensit These commands allow you to adjust the sensitivity of the 3D cursor to mouse movement Move to Screen Center Move the 3D cursor to the center of the Display window For a database con strained 3D cursor if the location of the screen center is outside the current database entity s boundaries the 3D cursor is moved to the location on the entity that 1s closest to the screen center Move Rotation Pt To Move the rotation point the graphical origin of the body axes to the current location of the 3D cursor Done Save Segment Save the current segment definition and add it to the connector definition Con trol is passed out of segment creation insertion Abort Don t Save Segment Exit segment creation mode without saving the developed segment 7 3 2Point Connectors The 2 Point Connector is a means of very quickly creating many connectors The resulting connectors will consist of only one segment each They will be either 3D Space Line or DB Constrained Line segments As the name implies a 2 Point Connector consists of only two control points You define them using t
319. pecifications display attributes database entity name associativity and database filename associativity You will save a Gridgen file for each grid it will serve as the restart file or state file for continuing the grid generation process over several sessions The Gridgen file does not contain the database entities created in Gridgen or database entities imported from 4 1 Importing and Exporting Files another file If you create delete or modify database entities a separate database file must be exported Section 4 5 If your grid and therefore the contents of the Gridgen file was built using a database you must import the database file s before you import the Gridgen file Section 4 1 1 4 1 1 Gridgen File Database Associativity If any grid elements in the Gridgen file are defined in terms of a database entity e g Line on DB segments projection the database file must be imported before the Gridgen file is imported If the Gridgen file is imported before the database file a warning message will be posted to the Message Window WARNING N nodes N connectors and N domains in the input file contain references to database entities not in memory Affected connectors and domains will be PERMANENTLY modified You will also be presented with the following button menu CONF IRMA Read the File Anyway Y Abort Dont Bother esc Read the File Anyway If you choose to import the Gridgen file despite the
320. picked when the cursor is positioned over it and the cumulative dimension and average As to be applied to the current connectors The subconnector string the subconnectors must be selected in an end to end order is highlighted in the Display window with an orange triangle at the beginning of the string and a blue triangle at the end of the string As each subconnector is picked it must attach to the blue triangle In the illustration below the three straight line connectors on the right have been selected as a subconnector string to dimension the curve on the left Note that the Blackboard displays the current connector the dimension of the subconnector string and the average As computed from the subconnector string total string length divided by total string number of points Connector Num 1 ilipts Subcon String Dims 31 94A Avg As 2 4730 Several commands are available to assist you in picking the subconnector string Erase Last SubConn del Reverse the Direction h Restart String 0 Erase Last SubConn Remove the last subconnector from the string Reverse the Direction Change the direction of the subconnector string reversing the order of the blue and orange triangles New subconnectors may only be added to the blue end of the string If you choose to copy any of the string s distribution parameters to the current connector the colored ends of the string and the current connector must correspond Restart String Remov
321. port supports 2D and 3D grids containing hexahedral quadrilateral prism and triangle elements Boundary condition regions are written to the S file in REGN format 178 29 SCRYU Tetra Tetrahedral elements only are supported and written to a NASTRAN formatted file No boundary condition information is exported 17 8 30 Splitflow Splitflow export supports only 2D grids with unstructured triangulated domains 2D blocks must be created out of all unstructured domains sub parts for Splitflow export Within the Splitflow export file sub part names and material IDs are listed as the block names and numbers respectively Volume condition export using both the VC name and number is supported for Splitflow The volume con dition SOLID is used as the default 17 13 Analysis Software Interfaces 17 8 31 STAR CD STAR CD export supports 2D and 3D grids of all cell types Two dimensional grids are assumed to lie in the x y plane Gridgen writes three files for Star CD s units 14 15 23 and 24 The name of the files that Gridgen exports is obtained from the base name of the file that you select via the Browser or keyboard with the numerals 14 15 23 and 24 appended respectively The files have no extension Volume condition export is supported for STAR CD Blocks with common VC s are automatically merged in the AS W file with the VC used as the zone name To have separate blocks written out with assigned VC
322. pported by Gridgen It is provided as a means of consolidating all entities within a single database file It is the only mechanism for saving database enti ties created in Gridgen A composite file is also useful if the entities were imported from several different files Gridgen is able to import composite database files written by all previous Gridgen versions 4 4 4 4 Native CAD Import CAD data geometry models in their native formats such as CATIA Pro E and STEP can be imported directly into Gridgen thus providing a more streamlined mesh generation process by eliminating the need for the translation of CAD data into a IGES neutral file format Note The Native CAD reader is an optional feature of Gridgen and is licensed separately Please contact Pointwise Inc for further details on the licensing of this feature The following file type attributes are supported for Native CAD file import Pro Eng Ag O CATIA Ya 8 STEP 7 CATIA V4 type refers to the native file format of CATIA Version 4 from Dassault Systems Gridgen will only read versions 4 1 x and 4 2 x Note The CATIA Version 4 native file reader is an optional product Pro E type refers to the native assembly and part file formats of Pro ENGINEER design software from Parametric Technology Corporation Gridgen will read versions up to Pro E 20001 Note The Pro ENGI NEER native assembly file reader 1s an optional product STEP type refers to the STEP AP203 Confi
323. pulation ooooooonccocccnocncnccnnonononononnonononcnnonnnnnnonannnnnnnnnnnnanenanonnns 2 14 ZAR Pel SC IMS EN T 2 14 ate G 9 a TOO E 2 14 221 9 MANIPULATION DEVICE ueni ibus deoa eJ Pastel ao laser e a Jav eday ad 2 14 2 7 4 Manipulation Hot KeyS ri 2 15 PESO ZOOM A diptins viwdenelitiavius dais bce taiacen Das 2 15 2 0 he 3D CUI SOR oii sss ase ates a tcl uae ee Ga estate ete nds 2 16 2 6 10 Gursor MOVEMOCNt 2 o LEID o M seed 2 16 2 0 2 GONTO Polit Chea NOI sats soci eee EL orar oia te su Iob brat ova eae ete Ron Darse E 2 17 2 8 3 Miscellaneous GohlrolS 3 iaa 2 19 2 9 Display Commands Menu sessi eene nnn 2 19 2 10 DISDIay EUIIHO uito ctt em ii t RE Gad Ns E dte 2 22 2X TOR DIS OIA S VIE ERE ERE E EM 2 23 2410 2 Render Mode tata iii nr ena 2 25 2 10 3 Fender Denis ii 2 26 2 10d O NT r 2 27 2 11 Saving Screen Images sessi esee rne 2 27 2 12 ONLINE Help too Luna Cube 2 27 2 13 MISCellalieOUS ci E vaio ME Adi tl 2 28 3 oetung Detalla ree 3 1 J T Gonhector Defaults ii DR risp teases eee ae dut 3 1 Sl DIMENSION TN UD T TU DEO Senn ee eer nana 3 1 9 ke AVerade Spach esnan gend tde due etes DR uet Be opeves meu dude rta 3 1 3 1 3 Maximum Angular Deviation ooccconccoccococccncccnononononnnnoncnoncononononnnnnronnonos 3 2 3 1 4 Maximum Chord Height Deviation cooocccocccccnnccocncconncconncoccnonanonnnnnos 3 3 3 susr eaeugm iiie
324. py from SubConnects distribution function Ortho BC in the elliptic PDE solver Grid point import Projecting a connector onto the database Copying a connector off the database 11 3 2 3 Spline Gridgen uses the distribution function and the spacing constraints to establish an array of grid point coordi nates in terms of the splining variable It then couples the grid point spline variable array with the connector shape to create Cartesian coordinates x y z using a spline function Spline Type t Spline var v Three spline types are available in Gridgen and are selected with the Spline Type menu button Linear Fit 1 Cubic Spline 2 Exponential Spline 3 Linear Fit This is Gridgen s default spline type The connector definition is treated as a series of con nected line segments and grid points are placed on these segments Since Gridgen uses the same dense col lection of points used to render the connectors as the basis for the spline routines the result of using a linear spline fit will be grid points that almost always appear to stay on the connector definition Cubic Spline This spline type will fit a cubic polynomial through successive discrete data points that define the connector shape Cubic splines have the benefit of having slope continuity at both sides of a con trol point instead of mere point continuity as exhibited in the linear spline The cubic spline s most attrac 11 9 Grid Methods for Connectors t
325. r Jacobians Jacobians misce poss sve meii negative negative mixed signs skew 16 2 6 Size Ratio Size Rat O i joj 2 ok 8 For structured grid entities the ratio of adjacent cell sizes is rendered in the Display window and a tabular summary is listed in the Blackboard The radio buttons i j and k indicate the direction in which the cell size ratios are to be computed the i j or k computational direction respectively The Size Ratio function is a point based measure Gridgen computes the ratio between the distance from the current 1 j k coordinate to the index 1 point and the distance from the current i j k to the index 1 point in the computational direction chosen The larger of the two distances is always divided into the smaller so all values range between 0 and 1 Furthermore this function will be calculated across entity boundaries as long as the adjacent entities are loaded into Examine as well Otherwise the value at boundaries will be set to 1 If a topological hiliter Section 16 5 is active the index 1 and index 1 points used in the calculation will be rendered with open diamonds on either side of the hiliter intersection 16 4 Diagnostic Function Smoothness Since this function is directional along computational coordinates adjacent entities must be computationally aligned Section 15 8 in order for reference surfaces to exhibit a continuous variation in the function across entity boundaries Non align
326. r appears on the domain s grid The Blackboard shows the number of the subgrid being added and the index location of the high lighter The highlighter is moved around the domain by moving the mouse with the right mouse button pressed When the open circle at the intersection of the highlighter lines is positioned over one of the cor ners of the desired subgrid press Add Corner at O button Then move the highlighter to the grid point at the opposite corner of the subgrid During this process the subgrid is rendered in the Display window with a yellow wireframe The Blackboard shows the subgrid s dimensions Save the subgrid by pressing the Save button The saved subgrid is rendered in the Display window with a pink outline and white grid lines and Gridgen remains in subgrid mode awaiting the definition of the next subgrid SubGrid creation is completed by pressing the Done button Domain 1 Number of SubGrids Number of Connectors Dimensions 27 x 2 Creating E Cursor at ADDING A SUBGRID aun ii Restart HEEEEEL TATE TITULOS RISE FU eee ee Move O via Keybrd pad For tn es ent ECC 12 14 Structured SubGrids Deleting SubGrids 12 3 1 2 Adding a SubGrid to a Block When the SubGrids Add button is pressed for creating a subgrid the highlighter appears in the block s grid The Blackboard shows the number of the subgrid being added and the index location of the highlighter The constant index plane bein
327. r grids in each case were extruded normally into the interior of the circle The interior grid represents an H grid that was created by assembling edges The grid on the left has step suppression turned off while the grid on the right has the step suppres sion coefficient set to 0 5 so that the boundaries in this case the connectors heading from the circles to the interior would grow slower than the interior points The result is that the middle region has more of a square shape resulting in a better quality H grid in the middle RA RA RAI a du a RR 7 gt BE Se os ay te Sa PERS be fy A n TH BU de c s a EU i A Mum A s 5 e SE Coe A M SS A Sos 1 o x SS eS d A SB i a Symmetry X The grid will be kept symmetric in the x direction Symmetry Y The grid will be kept symmetric in the y direction Symmetry Z The grid will be kept symmetric in the z direction oymmetry Auto Gridgen will examine the grid and automatically determine the direction in which the grid will be symmetric Constant X The x coordinate of grid points on the boundary will be held constant during the extrusion Constant Y The y coordinate of grid points on the boundary will be held constant during the extrusion Constant Z The z coordinate of grid points on the boundary will be held constant during the extrusion Constant Auto Gr
328. r inter section Since this function is directional along computational coordinates adjacent entities must be computationally aligned Section 15 8 in order for reference surfaces to exhibit a continuous variation in the function across entity boundaries Non aligned entities will display a discontinuity across their common boundary Block 2D or 3D adjacency is determined by block connections using a common boundary If a connection between two blocks is overridden with a baffle type boundary condition no adjacent entity information will be available at that boundary 16 2 8 Aspect Ratio aspect ratio a For grid entities the cell aspect ratio 1s rendered in the Display window and a tabular summary is listed in the Blackboard Quadrilateral cell aspect ratio is computed from the ratio of the average length and average width The aspect ratio is always greater than or equal to 1 with a value of 1 representing a square Hexahedral cell aspect ratio is computed from the ratio of the maximum of the length width and height and the minimum of the length width and height The aspect ratio is always greater than or equal to 1 with a value of 1 representing a cube Triangular cell aspect ratio is computed as the ratio of the radius of the cell s circumscribing circle to 2 times the radius of the inscribed circle Tetrahedral cell aspect ratio is computed as the ratio of the radius of the cell s circumscribing sphere to 3 times the r
329. r to use a spline variable other than arc length the subconnector must be monotonic either increasing or decreasing in the spline variable If the subconnector is not monotonic Gridgen prints a warning and the spline variable is set to arc length Furthermore if the connector shape is later modified so that the subcon nector is no longer monotonic in the selected spline variable the spline variable will be reset automatically to arc length A spacing constraint prescribed on a non arc length splined subconnector is stored in terms of the arc length spacing that would provide the specified spacing constraint in the splining variable In this way if the spac ing on the end of a subconnector is copied from the adjacent subconnector the spacing will be continuous in terms of arc length at the common break point even if the splining variable is not arc length on either side of the break point This will also keep the spacing identical at the ends of a subconnector if the splining vari able 1s changed from its original value 11 3 3 Break Points and Subconnectors To gain further control of grid point distribution on a connector it can be split into two or more subconnec tors By splitting the connector into subconnectors at user specified break points you can apply distribution functions and spacing constraints to each individual subconnector There are two main reasons you would need to add a break point to a connector To force a grid point
330. reached The segment file must be ASCII A code fragment for writing a segment file is shown below o M nmax is the number of segments Eu aa ni n is the number of points on segment n On eae imax is the number of points integer nmax integer ni nmax real x imax y imax z imax do n 1 nmax write 1 ni n do i 1 ni n Welee tls ALA VUL n ZL end do end do 18 6 Composite Database File Gridgen s composite database file is provided as a means of consolidating all database entities and database display information in a single file Since not all entities are supported by each of the file types for example conic arcs may only be imported via an IGES file the composite file provides a means of exporting Section 4 5 an entire geometry model that may have originated in several file formats in a single convenient file The composite file is also a convenient mechanism for storing database entities that are created or modified by Gridgen for example use of the Copy and Translate commands in the DATABASE COMMANDS menu Finally the composite file also stores the database display data which entities are enabled how they are displayed and in what color and entity names and groups created in Gridgen The bottom line is the composite database file should be used whenever any changes have been made to the database after import A detailed description of the composite file is omitted due to its complexity The composite file
331. reated automatically by Gridgen when importing from Network and PATRAN Neutral files that contain more than one entity 4 4 7 Backward Compatibility 1 If you are starting Gridgen using a GRIDBLOCK file b1k extension from GRIDGEN Version 8 and If that GRIDBLOCK file requires a database and If that database is imported from more than one Network or PATRAN Neutral file and If any database file contains more than one entity then You MUST import the database files first and p sd d e d You MUST import the database files in the same order as you did when you created the GRIDBLOCK file and 7 You MUST delete the group entities that Gridgen automatically creates during import Gridgen associates grid entities with the database by saving the u v coordinates and database entity name of any grid point that adheres to the database GRIDGEN Version 8 associated grid entities with the database by the u v coordinates and the entity number Therefore to ensure that Gridgen establishes the correct grid to database associativity when importing GRIDBLOCK Version 8 files it 1s imperative that the entity numbering be consistent The database entity numbering will be made inconsistent because of the group entities that Gridgen creates automatically when importing a Network or PATRAN Neutral file that contains more than one entity Consider a GRIDBLOCK file containing a grid that was generated on a database consisting of four entities 4 11
332. rent edit point and the control point preceding that point in the segment definition and will make the new point the edit point It will only be available when the current control point is not the first one in the segment On Conic Section and 3 Pt Circle segments this command creates a slide control point positioned initially between the two control points and is displayed by a small solid circle Slide control points are moved along the segment via mouse control to any position between the two surrounding control points within 1 of the points themselves but will not modify the Cartesian shape of the segment The shapes of the conic sections are controlled only by the true control points not by slide points Slide points are primarily used to define points along the seg 14 21 Modifying Entities ment that will be used as break points in the distribution of grid points on the connector Edit New Segment Pressing this button while editing one segment of a multi segmented connector will allow you to pick another segment to edit Edit Prev O This menu button will move the edit point to the control point immediately preceding the cur rent edit point in the current segment definition Edit Next L1 This menu button will move the edit point to the control point immediately following the cur rent edit point in the current segment definition Edit Pick O This command will allow you to pick a control point on the current segment to be t
333. reorient faces 10 6 data hierarchy 4 6 default settings 3 4 maximum pyramid height 3 5 minimum pyramid height 3 5 pyramid aspect ratio 3 5 tetrahedral mesh size factor 3 5 tetrahedral mesher memory limit 3 5 delete 75 5 disable 75 7 display 2 20 elliptic PDE solver background control function default 3 3 foreground control function default 3 3 enable 5 7 hierarchy 1 2 linkage 74 6 maintaining linkages 4 6 modify join 14 20 mirror 4 2 rotate 74 10 scale 14 8 split 14 18 stretch 74 9 translate 74 7 name 5 2 number of 2 preparing to run batch elliptic smoothing 4 20 Quick Menu 2 7 sort 5 5 structured 2D 10 1 computational coordinates 70 7 restrictions 70 7 BMP file 2 27 boundary connectors on database boundaries via on DB Entities command 7 2 rendering domain boundary 2 26 boundary conditions custom Create 7 7 Delete 17 7 Delete All 77 7 Modify 17 7 Examine 17 6 export 4 19 for elliptic PDE solver 2 3 setting 17 3 17 5 structured grids 17 5 17 6 unstructured grids 77 5 branch segment 7 3 break point create 71 11 definition 71 6 delete 11 11 setting spacing constraint 7 setting spacing constraint at 71 7 uses for 11 10 Browser window 2 Button Menu 2 C capturing screen images 2 27 CATIA v4 import as database 4 7 Cells reference surface 6 6 CFD asw 7 8 CFDSHIP Iowa asw 177 8 CFX 4 asw 17 9 CFX 5 asw 17 9 CGNS structured asw 77 9 CGNS unstructured asw 7 9 chord height
334. rev Moves the hiliter 1f enabled and the Blackboard text 1f in Local mode to the previous selected entity in numerical order If focusing on the first selected entity focus will be moved to the last selected entity 16 1 Diagnostic Functions 16 2 Diagnostic Function The term diagnostic function refers to the particular type of information to be calculated and displayed for the selected entities The current diagnostic function is printed on the button next to the label Function Prev Page Mext Page R None c OUsage ul gt DE Lu o off f 2 Size joi 1 0 2 Funct ion None f Ok 8 Smooth Oi safoj 15 Ok A aspect ratio a min o w max 0 Aw Qangle i volume The default diagnostic function is None which simply provides entity dimension information in the Black board Pressing the button next to the Function label allows you to select the diagnostic function to visual ize in the Display window for the selected entities Each Gridgen entity type connector domain block saves the last diagnostic function examined and subsequent invocations of the Examine command will begin with that diagnostic function Note that all diagnostic functions are not available for every Gridgen entity or mesh type 16 2 1 None None e The focus entity Local mode or all selected entities Global mode will be hilited in the Display window and size information will be listed in the Blackboard
335. rface boundaries or a combination of both If the chosen curves form a closed loop a single Coons surface is created from the loop and the user is prompted to save the surface 6 12 Surface Coons Surface Ruled ul Polyconic 1 Revolution al Linear Sweepn F i t AF Coons Ac MaAuto i To create a Coons surface a user will generally have to process potential boundary curves via the join inter sect and or split commands first These curves must be processed so that they form one continous loop The figure below on the left illustrates a example set of curves that need to be processed To make these curves form a continuous loop they must be intersected where they cross each other then split at the intersection points The user can then select Coons and use the four curves which form a closed perimeter The figure below on the right shows a network representation of the Coons surface that would be created The type of Coons surface constructed will depend on the number of curves selected If a user selects four curves a surface similar to the one illustrated above on the right will be created For three curves the sur face will be created with a singularity at the corner with the smallest interior angle For two curves the sur face will be created with two singularities For a case in which only one curve is selected the curve will be split in half and a two singularity surface is created from the resulting curves It is important to
336. rface grids from other sources 4 5 VRML as database 4 8 VRML as grid 4 5 INCA v2 asw 17 11 INCA v3 asw 17 11 Incorporate Volume Grid command 4 20 intersect 5 5 J Jacobian diagnostic function 6 4 join block 4 20 connector 4 9 database 4 9 domain 4 20 join angle 5 5 L layer manager 5 layers 5 7 Linear TFI 2 2 linkage 4 2 block 4 6 connector 4 4 database 4 2 domain 4 6 Local Mode for Examine 6 0 M menu split 2 8 menu button grayed out 2 5 Next Page 2 8 Prev Page 2 8 Quick Key 2 5 Quick Menu 2 6 radio 2 4 selecting 2 3 small text 2 20 toggle 2 4 VCR 2 4 merge connectors 5 7 15 12 nodes 5 nodes and connectors 5 3 topological filter 15 15 Message window 2 mirror 4 2 for export only 17 7 model size 5 7 modify 4 database hierarchy 4 2 linkage 4 2 mirror 4 2 rotate 14 10 scale 14 8 stretch 74 9 transformations 4 7 translate 4 7 mouse 2 2 bell 2 22 glide 2 4 left button picking 2 22 sensitivity decrease 2 9 increase 2 9 reset 2 9 warp disabling 2 27 warping 2 8 N NASTRAN grid export to 4 7 import as grid 4 14 NCC asw 17 12 Next Edge 9 8 node definition 7 display status 2 20 merging duplicates 75 77 tolerance 3 6 None diagnostic function 6 2 normal algebraic extrusion 5 2 attributes 6 4 NPARC asw 7 2 O On Database Entities 9 9 Ortho TFI 2 3 orthogonal closest point projection 4 5 elliptic PDE boundary condition 2
337. rget block number endif end do number of regions on block end do number of blocks The boundary condition codes used by the generic flow solver are described in the table below 18 4 Surface Grid File Generic ASW Boundary Conditions oo om connection CO NN s eme b eme 10 generic 3 18 9 Surface Grid File Surface grid files are used to import and export grid data Surface grid files are identical in content to data base network files Section 18 4 18 10 Volume Grid File The volume grid file is used to import Section 4 6 and export Section 4 7 volume grid data The volume grid file may be written in Gridgen or PLOT3D style binary Fortran unformatted or ASCII format single or double precision A Fortran code fragment for a Gridgen style volume grid file follows number of grid points in block integer ni nmax nj nmax nk nmax grid point coordinates real x imax Jmax kmax y imax Jmax kmax z imax jmax kmax write 1 nblocks do mb e 1 nblocks write 1 ni mb n3 mb nk mb weite l C Oc i J k 1 1 ni mb j91 nj mb k l nkimb yl Jk 1 L m1 m6 3 1 03 M5 k L nk mb y ALAS TAL nimbo o Lyi mb k L nx mb end do 18 5 File Formats 18 6 19 References 10 11 12 13 14 I5 16 Abolhassani J Sadrehaghighi I Smith R E and Tiwari S N Application of Lagrangian Blending Functions for Grid Generation Around Airpl
338. rid point positions Note that structured domains and blocks that have been run in one of the solvers Section 12 will be regrid ded in a manner that takes into account the grid s current qualities In other words TFI is only applied to those grids that have only been TFPd Elliptically smoothed grids will be modified in a manner that takes into account the smoothness clustering and orthogonality the grid currently has This is true even for struc tured domains constrained to the database This regridding technique works well for small perturbations of the connector s spacing constraints Large perturbations may yield unacceptable results in which case the grid methods should be reapplied manually There is no regridding technique for unstructured grids Unstructured domains are regridded using the last applied unstructured solver attributes Unstructured blocks must be regridded manually 11 14 12 Grid Methods for Structured Domains and Blocks There are two types of grid methods that you can apply to structured surface domain and volume block grids algebraic and elliptic PDE Algebraic methods in Gridgen are based on transfinite interpolation TFI Domain and block grids are ini tialized using TFI Gridgen automatically chooses the specific TFI method for you in order to make the best possible grid You may re apply TFI to any grid at any time to start over with a new grid TFI methods have the advantage that they can be comp
339. ridgen attempts to append adjacent curves and surfaces into larger curves and surfaces respectively 4 4 5 Duplicate Name Detection During database file import Gridgen automatically checks to ensure that each database entity has a unique name Section 15 1 Each database entity must have a unique name in order for Gridgen to correctly asso ciate your grid with your database If Gridgen detects duplicate database entity names during file import the following menu appears 4 10 Importing Database Files Automatic Entity Grouping on Import DUPLICATE ENTITY NAMES Allow Duplicates 1 Skip Duplicates 2 Rename Duplicates 3 Abor t esc Help Allow Duplicates Pressing this button means that you choose to override Gridgen s requirement for unique entity names We strongly recommend that you do NOT choose this option Skip Duplicates Pressing this buttons means that only the database entities with unique names will be imported from the file and the other entities the ones whose names match entity names already in Gridgen will be skipped Rename Duplicates Pressing this button tells Gridgen to import all entities from the file but rename the duplicates by appending 1 2 etc to the name Abort Pressing this button terminates the import process so that you can diagnose why duplicate names were detected 4 4 6 Automatic Entity Grouping on Import A group entity containing all entities in a file will be c
340. ridgen s logic Creating Domains 10 Creating Blocks 10 1 Overview Blocks are Gridgen s highest level grid element They are volume grids in 3D and surface grids in 2D A structured block consists entirely of hexahedral cells arranged in an TxJxK array An unstructured block consists of either all tetrahedral cells or a combination of tetrahedra and pyramids the latter is often referred to as a hybrid unstructured block A prism block consists entirely of prismatic cells that are generated by extruding an unstructured triangular cell domain This chapter describes the procedure for assembling structured and unstructured blocks by selecting the domains on each of the block s faces Creating structured blocks and prism blocks by extrusion is covered in Section 8 10 2 Assembling a Structured Block The faces of a structured block are the surfaces on which the block s n and G computational coordinates are at their minimum and maximum values It is assembled from structured domains A block cannot be assembled until all domains on that block s faces have been created Section 9 Each structured 3D block requires six faces even if a face or a portion of that face is collapsed to a line a line singularity or pole Sec tion 9 7 Therefore you must have created at least six domains before a 3D block can be assembled Because a 2D block has only one face at least one domain must have been created in order to assemble a 2D block On the o
341. rids only TETREX from Tetra Research Corp supports hybrid grids VSAERO from Analytical Methods Inc supports surface grids only VSAEROhybrid from Analytical Methods Inc supports unstructured and structured surface grids only WIND from the NPARC Alliance supports structured multi block grids only After choosing the ASW its dimension and pressing the Done button you must confirm your selections since any boundary conditions that have already been set will be cleared when the analysis software is changed Furthermore all 3D blocks will be deleted when a 2D analysis software package is selected Like wise if structured blocks exist in the model and an ASW that supports only unstructured elements is chosen the structured topology will be deleted as necessary Please note Gridgen s support for any particular analysis software package is not an endorsement of that package Furthermore selection of a suitable analysis package is the sole responsibility of the user You are strongly advised to consult the documentation for each analysis software package prior to using it with Grid gen 17 2 Set BCs The Set BCs command allows you to specify that a particular boundary condition BC is to be applied to one or more block boundaries It is important to note that BCs can only be applied to blocks In 2D the BC regions the block boundaries are connectors In 3D the BC regions the block boundaries are domains Note that only one
342. ritten for NPARC Version 3 which uses the Type 77 inter block connec tion and does not require connecting blocks to overlap bc style namelist Input nbcseg is set to 0 so that NPARC s boundary conditions will be written using the BOUNDS namelist bc style formatted Input nbcseg is set so that NPARC s boundary conditions are written in a formatted tabular list format ASCII NPARC s restart file will have ASCII format format binary NPARC s restart file will have binary format format unformatted NPARC s restart file will have Fortran unformatted format precision single NPARC s restart file will have single precision 4 byte real words precision double NPARC s restart file will have double precision 8 byte real words Mach number This command allows you to enter the Mach number that will be used to compute the ini tial flowfield in the restart file The flowfield is computed using the technique described in the NPARC 17 12 Export Analysis Data Grid and BCs OVERFLOW User s Guide Reference 5 Gridgen s formatting of the NPARC BC file includes A 2 line comment string An INPUTS namelist containing NBLOCKS An empty TURBIN namelist For each block A one line comment containing the block name A BLOCK namelist containing JMAX KMAX and LMAX if 3D blocks NBCSEG and NPSEG Either the BOUNDS namelists or formatted BC data INVISC and LAMIN namelist inputs Note that the PRESS and TEMP inputs required by
343. rol key pressed the mouse controls rotation and the keypad keys control panning and zooming Image Manipulation Devices device component component default with control key left mouse screen x and screen x and screen y panning screen y rotation middle mouse screen z zooming screen z rotation Image Manipulation Manipulation Hot Keys Image Manipulation Devices derce component component default with control key screen z zooming Note that during image panning the cursor is changed to four arrows during zooming the cursor is changed to a magnifying glass and during rotation it changes to two circular arrows as shown below ja o 2 4 Manipulation Hot Keys Several hot keys are available to assist you with image manipulation Pad Pad These two hot keys when pressed in conjunction with other keypad image manipulation keys will reverse the direction of the rotation or panning Page Up This so called turbo key increases the speed of image manipulation by three times when pressed in conjunction with an image manipulation device Page Down When pressed in conjunction with an image rotation key the image is rotated by 90 degrees Alt When pressed in conjunction with an image manipulation key the image moves in single step incre ments 2 7 5 Zoom Box Gridgen s zoom box provides an alternate method for enlarging or shrinking the Display window image It allows you to specify explic
344. rs are selected This command opens a dialog panel shown below where you can type in a new alpha numeric description When multiple layers are selected the same 5 6 The Layer Manager Panel Saved Layer Sets description will be applied to all Description nacetiel Cancel Ok Set Current only available when a single layer is selected This command sets the selected layer to the current working layer All newly created database entities will automatically be assigned to the current working layer Move available when one or more layers are selected This command opens a dialog panel shown below where you can type in a target layer number and choose whether or not the moved layer s will take with them their description and or their on off status Info The entities in the selected layers willbe moved as a group to a new location in the layer list beginning with the target layer The move may optionally include the layer description and status Target Layer F Move the source layer description Move the source layer status Cancel OK Combine available when two or more layers are selected This command opens a dialog panel shown below where you can type in a target layer into which all entities from those layers selected will be com bined Info The entities in the selected layers will be combined into the target layer Target Layer fi d Cancel OK Status commands simply change the on off s
345. rs under contract to various U S Government agencies GRIDGEN Version 9 s development was sponsored by NASA Ames Research Center during the period between October 1992 and April 1994 Additional sponsorship was provided by NASA Lewis Research Center the U S Naval Surface Warfare Center Carderock Division and the U S Army Research Laboratory GRIDGEN Version 8 s development was sponsored by NASA Langley Research Center during the period between July 1991 and December 1992 Additional sponsorship was provided by the Naval Surface Warfare Center Carderock Division GRIDGEN Version 7 was a developmental version that was incorporated into Version GRIDGEN Version 6 s development was sponsored by the Aeromechanics Group Wright Research and Development Center Wright Patterson AFB during the period between October 1987 and September 1990 GRIDGEN originated in mid 1984 and was developed through September 1987 as an Independent Research and Development IR amp D project at General Dynamics Fort Worth Division 1 7 Document Conventions Buttons on Gridgen s menus will appear in a bold Helvetica font for example Translate Labels for menu buttons will appear in a Helvetica font for example Solvers Hot keys keyboard keys invoking a menu button command when pressed appear in a bold italic font for example the x hot key Data you type and messages that Gridgen prints appear in a Courier font for example 1 2 3 Introduction 2 Gr
346. rse the Offset see below It allows you to offset the generatrix in either of two directions Connector Segments 1 Connector Dimensions 0 Generatrix Curve 1 Cursor Location 8048289 x y 0 3647588E 01 z 5 232549 Offset Distance D 2 350120 You can specify the offset distance directly or you can specify a point that the curve should pass through If you use the latter method of specifying the offset you should be aware it is possible to choose a point through which the offset curve cannot pass In that case Gridgen will produce an offset curve that is the same 3D distance from the generatrix as the specified point yet does not pass through the point Other commands involved in offset curve creation are 6 3 Creating Database Entities ReDefine Generatrix del Set Fit Tolerance 2 Reverse the Offset 5 Enter Offset Distance o ReDefine Generatrix This command lets you re start the offset curve creation process if you pick the wrong generatrix Set Fit Tolerance This command lets you enter a precision tolerance for the offset curve This deter mines how closely the offset curve will match the specified offset distance The default fit tolerance is 0 001 as described in Section 3 7 1 Reverse the Offset This command switches the offset curve to the opposite side of the generatrix from its current position Enter Offset Distance Rather than use the 3D cursor to define a point for the offset curve to pass t
347. rt and keep things the way they are Delete Connectors y Abort Dont Delete esc 15 4 3 Domains If any of the domains picked for deletion are used in blocks then those blocks will be graphically highlighted in the Display window the number of blocks to be deleted by deleting this domain will be tallied in the Blackboard and the following text will appear in the Message window DELETE DOMAINS Deleting these domains 15 4 Sort Blocks will cause all blocks using them to be destroyed Select an option below You must then choose from a button menu whether to proceed with the domain deletion and the implicit deletion Delete Domains or Abort and keep things the way they are Delete Domains y Abort Dont Delete esc You are also given the option to delete either just the domain representation Delete Domains Only or the domain representations and the domains connectors Delete Connectors Also Should you choose to delete connectors then only the connectors unique to the deleted domains will be deleted Delete Connectors Also y Delete Domains Only m 15 4 4 Blocks When deleting blocks you are given the option to delete either just the block representation Delete Blocks Only or the block representations and the blocks domains Delete Domains Also Should you choose to delete domains then only the domains unique to the deleted blocks will be deleted Delete Domains Also y Delete Blocks Only m You are also given the op
348. ructured Grid Point Import foie ov ov o mom Y mm NN ems x AC Z Z K Z Z 5 lt ii Te zZ Z Z Z XPATCH ze Z 4 6 5 Importing Unstructured Grid Points The Grid Pts Import command allows you to import the following unstructured grid types Unstructured Grid Point Import CC mom x N mmm x wem Y 0 N VRML 1 0 FV UNS XPATCH lt 2 2 Z Z e y rr 4 7 Export Grid Points The Grid Pts Export command in the INPUT OUTPUT menu is used to write a file containing only the grid points from curve surface both domains and block faces and volume grids selected by you The default extension for the file name is grd This command is most often used to transfer grid data from Gridgen to another application 4 16 Export Grid Points Style 4 7 1 Style The following style attributes can be exported in Gridgen Gridgen style refers to a format for structured grid data and is described in Section 18 9 PLOT3D style refers to a format for structured grid data that was popularized by NASA s CFD visualization software of the same name Reference 38 This format is described in Section 18 4 This toggle is disabled for unstructured grids PATRAN style refers to Version 2 5 of the commercial software product of the same name For information on this format please consult Reference 13 PATRAN style is available for domain and block grid point export only NASTRAN type refers to Version
349. rusion is performed on each individual connector that you select When selected connectors share a node a floating boundary condition is automatically applied so the extruded grids blend together smoothly Otherwise a unique domain is formed by extrusion from each connector b From An Edge All selected connectors are joined into a single edge from which the extrusion takes place forming a single new domain 2 For blocks a From Doms A separate extrusion is performed on each individual domain that you select When 8 1 Grid Extrusion Methods selected domains share a connector a floating boundary condition is automatically applied so the extruded grids blend together smoothly b From A Face All selected domains are joined into a single face from which the extrusion takes place forming a single new block In the example below the results of extruding three connectors left using From an Edge center and From Cons right are compared Notice that extruding From an Edge results in a single domain whereas extruding From Cons results in three domains one for each of the original connectors Whenever possible we recommend you extrude From An Edge or From A Face The grid quality and stability of the extrusion algorithms are both improved when floating boundary conditions such as you would get automatically when using From Cons or From Doms and selecting multiple adjacent connec tors or domains respectively are avoided
350. s Segments ccssccccsseecneeecseecseeeecesesessaneesseesesaeessaneessas 7 8 7 26 Miscellaneous COMMAMO Siria ores erate albino er oot tat bsec di Pena P 7 9 43 2 POINT CODDecloESs iuo A AA ti 7 10 74 On DB ENTES ula qe ecce et laudare 7 11 8 Grid Extrusion Methods oro petat dos 8 1 6 1 RUNNING INC EXIFUSIOD Sd 8 1 0 2 EXIFUSION ATIFIDUTEOS 000 aa ea a ii 8 4 A o non O H 8 4 8 2 2 DUMaCO Sla De secre sd oca 8 4 02 9 ASPECTO ia 8 5 A A es ences ig 8 5 6 2 0 Marchi DIFCCUON P es 8 7 9 2 0 oSmoothihg Fatatietel uere id dde 8 9 o 2 7 Boundary CondlllolS unxe cedar pris tol se 8 11 9 2 9 S O eet uat dotada eid deco ae Ren eee Mt io ee E ME 8 12 9 2 COPY ANTIDUIGSu uiscera o ono dene Ic Hsu C AUD doi ten LE Cus 8 13 62240 JRESCL ATU DUNS siet br be ER bk ERE Erba a 8 14 9 Creating DOME Sri 9 1 9 1 OvervieW 0002 cccccccccceccccccecsccececcaceneccuceneatenetensdententatansnennedtacenseunstatensetensueananses 9 1 9 2 Assembling Structured Domains sessi nnns 9 1 9 3 Assembling Unstructured Domains oooocooncccocccononccocnonoconnnononncnnonononannnnons 9 4 9 4 Special Domain Assembly Commands sese 9 7 9 5 Convert Structured to Unstructured Domains sesuuss 9 8 9 6 On Database Entities sss essen nnn nna 9 9 9 7 PO DOMAINS s e ERE Ud NM M M III i Ed 9 10 9 8 Bad DOMAIN TVDes o stia bis 9 10 9 8 1 A
351. s allow you to change a subconnector s dimension Change No of Grid Pts m Push gt h q Pull CA q Change No of Grid Pts This command allows you to type in a new dimension Push e gt A This command reduces the current subconnector s dimension by one and adds one to the 11 11 Grid Methods for Connectors dimension of the following subconnector Pull e A This command increases the current subconnector s dimension by one by taking one grid point from the following subconnector In order to keep the number of grid points on the connector constant when re dimensioning a subconnector Gridgen confines its dimension changes to the current subconnector and the subconnector immediately fol lowing it Notice that this limits the range of new dimensions for the current subconnector to the range 2 to n4 n5 2 where n is the number of points in the current subconnector and n is the number of points in the following subconnector Notice also that it is not possible to change the number of grid points in a con nector s last subconnector The dimension of the last subconnector can only be modified implicitly by changing the dimensions of any or all of the subconnectors preceding it 11 3 4 Miscellaneous Controls Focus Next njPrev n Focus All s When more than one connector has been selected for the ReDistribute command the Focus Next and Focus Prev commands move focus to the next and previous selected connector
352. s always output as TGRAD n FIXED f I node e The additional line of input for the MFR Mach Number Pressure Ratio and Speed Ratio Inlet boundary conditions are always output as MFR n MACH n PRATIO n and QRATIO n respectively e The additional line of input for the EXHAUST boundary condition is always output as NPR n TRA TIO n NX a NX n Na n EXTIMACH An e If your grid is 2D two SYMMETRY X2 boundary conditions will be added on the Kmin and Kmax block faces TEAM s grid file is ASCII double precision and its format is described in Reference 8 You must create 2D grids for TEAM in the x z plane When the grid is exported it is automatically extruded in the y direction by 1 0 unit to create a 1 cell thick block 17 8 85 TETREX TETREX export supports both 2D and 3D grids of all cell types 17 14 Export Analysis Data Grid and BCs VSAERO 17 8 80 VSAERO Since VSAERO is a panel method only 2D structured blocks are supported and boundary conditions need not be applied A complete VSAERO file is written but all non grid data are set to zero 17 8 37 VSAEROhybrid VSAEROhybrid export supports 2D structured and unstructured blocks Blocks must be either structured or unstructured Hybrid blocks are not supported 17 8 88 WIND WIND export supports 2D and 3D structured grids Gridgen exports the cgd Common Grid Data file used by WIND which contains the grid and bound
353. s command allows you to erase both the current axis and current generatrix and start over Re Set Fit Tolerance The tolerance with which the surface matches the generatrix is changed using this command The default fit tolerance is 0 001 Section 3 7 1 Decreasing the fit tolerance will result in a sur face with a larger number of intervals Re Set the Angle This command allows you to set the angle of revolution in the range 360 to 360 degrees The default is 360 degrees Setting the angle to O will result in a surface that will not be saved 6 5 4 Linear Sweep Surface A linear sweep surface also called an extruded surface or a tabulated cylinder can be created in Gridgen First select the curve to be extruded called the generatrix Then select a line that defines the sweep direc tion called the rail The rail must be a line in other words not a curve circle etc but it does not have to share an end point with the generatrix The resulting surface starts at the generatrix s location and sweeps in the direction of and for the length of the rail Linear Sweep Surface Generatrix Curve 2 Rail Curve Patches ox Commands used during construction of a linear sweep surface are 6 11 Creating Database Entities Erase Rail Curve del Erase Both Curves 0 Reverse the Direction 5 Erase Generatrix After the generatrix has been selected but before the rail has been selected you can use this command to erase the curr
354. s in numerical order The Apply to Focus and All radio buttons establish whether the grid point distribution attributes you select should be applied to the focus connector only or all selected connectors The cursor may be moved along the connector by moving the mouse to the left and right with the right mouse button pressed Other controls are available for moving the cursor Sensi t Decr Reset Incr gt Decr Reset and Incr allow you to decrease reset and increase the sensitivity of the cursor movement with respect to mouse movement respectively Move O via Keyboard k U centity 5 Y Centity 5 pz Move O via Keyboard Pressing this button allows you to move the cursor to a specific x y or z value on the connector You can also choose to move to a specific u or v value if the connector shape is con strained to a database entity Choose the coordinate via the menu and type in the specific value If there are several locations on the connector that have the value of the coordinate that you specify Gridgen will move the cursor to the value that is closest to the original cursor location Oto Nexte elOto Preve Ac O to Next Pressing this button moves the cursor to the next grid point on the connector O to Prev Pressing this button moves the cursor to the previous grid point on the connector 11 12 Set As Values Miscellaneous Controls e o oe wj ooftf h ALES x o OFF y The first row
355. s of interest during connector splitting allow you greater control over the split location Split at Picked O Pressing this button will split the connector at the control point beneath the cursor s current location Move O via Keyboard You may type in the x y or z or u and v for database constrained connectors coordinate to which the cursor should be moved In the case of a multi valued connector the cursor 1s moved to the typed in location closest to the cursor s original location O to GP e via Keybd You may type in the index of the connector grid point to which the cursor should be moved O to Next Grid Pt e Move the cursor along the connector to the next grid point in the direction from the connector s beginning to ending O to Prev Grid Pt e Move the cursor along the connector to the previous grid point in the direction from the connector s ending to beginning 14 7 3 Domains When the Split command is invoked for a structured domain the highlighter appears on the domain Unstructured domains may not be split The highlighter location is the split location The highlighter can be moved along the range of possible split locations by moving the mouse with the right mouse button pressed 14 17 Modifying Entities The highlighter can be changed to other coordinate families by pressing the Lines or J Lines buttons When the proper split line is identified by the highlighter press the Split At Hiliter button to perform
356. s of the same grid and later assemble them into one grid system When two grid systems are merged using this command Gridgen culls all duplicate connectors and domains it encounters allowing the two grids to connect to each other 4 1 3 Gridgen File Backward Compatibility Gridgen can import Gridgen restart files from all previous Gridgen releases Note that in Gridgen Versions 6 and 8 these files were known as GRIDBLOCK files and have a b1k extension by default Gridgen Version 8 files are fully supported subject to the database associativity rules described in Section 4 1 1 Only a portion of the data in a Gridgen Version 6 b1k file is imported by Gridgen Specifically only the connector shapes will be loaded Any Ellipse Segments in the Version 6 file will be automatically converted to Circle Segments which will modify the connector shape in some cases Keep in mind that since Gridgen Version 6 files do not contain database parametric data for Line on DB and Curve on DB segments no con nectors in Version 6 files will be constrained to the database 4 2 Quick Import The Gridgen Quicklmp menu button allows you to perform a quick import of your Gridgen restart file Gridgen assumes that nothing has changed in the grid to database associativity and therefore does not re compute the x y z coordinates of any database constrained points Gridgen also does not check for proper node linkages Quicklmp should only be used when 1 The Gri
357. s software package It is only available if the current analysis software package allows for separate boundary condition and grid files See Section 17 8 for more information 4 11 Export Analysis Data The Export Analysis Data command allows you to write to a file the current grid boundary condition volume condition and other data formatted for the current analysis software package See Section 17 8 for more information 4 12 Export FIELDVIEW Boundary Surface File For structured grids the Export FV Bndry Surf File command allows you to write a FIELDVIEW bound ary surface file that may be imported by the FIELDVIEW visualization software Reference 43 The con 4 19 Importing and Exporting Files tents of the file include the index ranges of all of the surfaces in your grid grouped according to their boundary condition Once imported into FIELDVIEW along with your grid this data allows you to easily turn on the display of common surfaces such as walls or symmetry planes 4 13 Incorporate Volume Grid The Incorporate Volume Grid command in the INPUT OUTPUT menu is used to merge the structured volume grid results of Gridgen s application of elliptic PDE methods with the rest of the Gridgen system This command would be used when the entire volume grid must be assembled in Gridgen for subsequent export using the analysis software commands Otherwise there is no strict requirement for incorporating the final volume grid with the Gridgen fi
358. s that might poten tially delete many higher level elements The figure below shows the effect of modifying by translating upward a connector that is linked to a domain and a block the horizontal connector at the upper left of the block In this case no matter what but ton you press the grid entities will remain linked Modifying Entities i d II um EN ass a rj zz jf Connectors are also linked to domains and blocks by their grid points Changes in a connector s grid points whether through a connector shape change or a distribution change Section 11 3 are propagated automati cally to the domains and from the domains to the blocks The effects on the grids are as follows 1 For structured domains and blocks a If the grid has been locked via application of the elliptic PDE solver the extrusion solver trans formation or copying off a database surface import from a grid points file a small perturbation technique is applied to the grid blending the connector s change into the grid s interior This tech nique attempts to preserve the current grid s qualities subject to the connector change However this technique works best if the changes to the connector are small Large changes in shape or dis tribution may require re application of one of the solvers b If the grid has only been initialized via one of the algebraic methods then that algebraic method will b
359. se the command corresponding to entity type you wish to edit via the row of buttons labeled Edit 2 22 Display Editing Display Style Dspla DB database entities Dom domains or Face block faces Select the entity or entities to edit Display style is an option for sorting the Browser list Select attributes from the DISPLAY ATTRIBUTES menu Press the Done button The selected attributes will be applied to the selected entities Repeat as necessary Press the Abort button to return to the DISPLAY COMMANDS menu E c ue DISPLAY ATTRIBUTES o Wireframe w Solid s Shaded h Solid Wireframe d Shaded Wireframe e Hidden Lines Removed i Outline n gt Intrvls 1 Isolines c Triangles t Curvy Render Density t ob 11oM 21oM a om 4 oz afom som 7 o ais om 1 Of 12 oMs3 a El oLb15 om 6 oM 7 o ars Done Apply Atts ent The following sections describe each category of display attribute that may be applied to surface grids and database entities 2 10 1 Display Style O Off o o Wireframe w Solid s Shaded h Solid Wireframe d Shaded Wireframe e Hidden Lines Removed i Off The entity will not be displayed For domains and block faces this turns off the display of interior grid points but the bounding connectors will continue to be displayed Off is not a display style for database enti ties To eliminate the display of databas
360. sion is an algebraic method that sweeps the grid in a circular path around a pre scribed axis 8 2 Running the Extrusion Tran The translational extrusion is an algebraic method that sweeps the grid in a linear path in a prescribed direction Path The path based extrusion is an algebraic method that allows you to sweep the grid along a path defined by a connector that you select The extrusion types are illustrated in the following figure top left the original connector top center normal top right hyperbolic e bottom left translation in the vertical direction bottom center rotation 20 degrees about an axis not shown to the left of the lower left node in the grid bottom right path along the curve connector on the right side IM SS DIT ROH ALU AS LAA UHR Qu Once you have selected an extrusion type you apply it to the grids you selected by running the required number of marching steps The extrusion methods are a process by which the initial grids you select are marched outward step by step according to the current attributes Each step results in a new layer of grid cells whether they re quadrilaterals prisms or hexahedra The Display window is updated after each marching step so you can monitor the extrusion process Controls for the extrusion process are described below Pause Pressing this button causes the extrusion process to stop Run Pressing this button
361. structure you are warned and can select another domain For 3D blocks it 1s not possible to save the face until it fully encloses a volumetric region How ever once the face is fully closed and no yellow free edges appear in the Display window the face may be saved and the Display window shows in orange the face s normal vector as illustrated below 10 3 Creating Blocks Block 1 Note that this normal vector should point into the volume to be gridded If Gridgen does not choose the cor rect normal vector you may flip the normal by using the Reorient Face command Section 10 5 10 4 Assembling a Hybrid Unstructured Block A hybrid unstructured block consisting of pyramid cells near the quadrilateral boundaries and tetrahedral cells elsewhere 1s assembled in the same manner as an unstructured block Section 10 3 with one excep tion both structured quadrilateral and unstructured triangular domains may be added to the faces Pyra mid cells are created in the volume grid adjacent to every structured domain on the block s faces Tetrahedral cells are created elsewhere in the volume grid Control of the pyramid cells 1s covered in Sec tion 13 10 5 Face Creation Commands Commands used during face creation include the following Pick Multiple Doms m All Domains 1 Adjacent Doms j Wf Struc 7 MUnstr 8 Pick Multiple Doms m MNonMnfld Cnnct 1 All Domains 1 Join Ang Any e Adjacent Doms j EraseDom I P
362. t Gridgen will not allow the connection to take place These situations usually arise when none of the linkages maintains the rectangular alignment of the computational domain 10 7 Structured Block Topologies and Orientations When you save the last face of the block Gridgen automatically attempts to find all distinct topologies in which the faces can be arranged onto the boundaries of a computational block 1 Ifthere are not any valid topologies you are warned the last face is removed from the block and you are returned to block creation mode Invalid blocking topologies are most often caused by having coin cident connectors along the intended block edges Any edges having coincident connectors will be highlighted in yellow when Gridgen warns of the topology problem 2 If there is only one topology the block has been constructed properly The block is saved and you may proceed with other block commands such as Name or ReSpecify amp n G 3 If there is more than one possible block topology you will be warned and Gridgen s first valid topology will be used for the block Multiple topologies usually occur when two faces in the block are defined by identical sets of domains In this case the warning raises no concern since the multiple valid topologies are in reality identical After Gridgen identifies a valid block topology a computational coordinate system 1s assigned The default n axes are chosen based on the first f
363. t is split scaled or stretched 4 aGridgen file is imported without its database 5 adomain is split Each scenario is an example of a modified segment that can no longer be represented in a Bezier form while maintaining the same shape Editing of General Segments is very similar to modifying Bezier Curve seg ments except Gridgen attempts to preserve the segment s original shape where possible Whenever the con trol point cursor 1s moved to a control or slope point that has its original shape you are warned that adjustment of the control slope point will destroy the local shape of the curve Once moved the region of the segment between the control point and its two neighbors will generally be impossible to restore to its original location 7 8 Add Segment Miscellaneous Commands 7 2 6 Miscellaneous Commands As stated previously a connector may consist of more than one segment After saving a segment you have several options according to the following menu CREATE CONNECTOR Translate t Rotate Ag Scale As 5tretch 5 Mirror m Split cl Segment Add nlInsert n Edit e Erase e ReDimension d Done Save Connectors ent Done Creating Conns esc Translate Translate the connector Section 14 3 1 Rotate Rotate the connector Section 14 3 4 Scale Scale the connector Section 14 3 2 Stretch Stretch the connector Section 14 3 3 Mirror Mirror the connector LSQ Fit Perform a leas
364. t its reference to the database surface s u v coordinates is eliminated e Removes the database link from each domain grid point The point s x y z coordinates do not change but its reference to the database surface s u v coordinates is eliminated With the linkages severed Gridgen modifies the database surface in this case by translation without chang ing the shape of the grid as shown below On the other hand you can press the Maintain Linkage button and the grid will stay linked to the database surface and update its shape after the database modification in this case translation as shown below 14 3 Modifying Entities 14 2 2 Connector Linkages You can edit Section 14 9 4 a database constrained connector and its linkage to the database will be main tained automatically For example the figure below illustrates the results of editing one connector belonging to the left most domain its linkage to the database is maintained automatically Splitting Section 14 7 and joining Section 14 8 also automatically maintain the connector s linkage to the database On the other hand the transformation commands Section 14 3 will break the linkage between a connector and the database and allow you to move the connector away from the database After the transformation is complete the connector is converted to a general type segment Section 7 2 5 4 A general type segment is a fit of the discretized shape of the co
365. t squares fit of the connector s grid points Project Project the connector onto the database Section 14 4 Add Add another segment to the end of the connector Section 7 2 Insert Insert a segment in front of a segment already in the connector Edit Modify the control points of a segment already in the connector Section 14 9 Erase Remove a segment from the connector definition ReDimension Change the number of grid points on the connector Section 11 1 ReDistribute Change the distribution of grid points along the connector Section 11 3 Done Save Connectors Save the current connector definition Done Creating Conns Abort the connector creation process without saving the current connector Several commands are available when creating and editing segments for adding control points and manipu lating Gridgen s 3D cursor These commands include Erase Last Point del Edit Existing Curve al Cnurt tojLine l Akima 4h Movement Restrictions m Sensit Decr lt Reset Incr gt Move to Screen Center c Move Rotation Pt To t Done Save Segment ent Abort Dont Save esc 7 9 Creating Connectors Erase Last Point Remove the control point most recently added to the segment definition The cursor is moved to the deleted control point s location Edit Existing Curve Save the current segment definition and invoke the Edit command Section 14 9 Cnvrt to Change the segment s type to the chosen ty
366. t surfaces and re feature extracting the original shells This would be used if you wanted to feature extract using a different split angle Continue After the feature extraction process has been paused pressing the Continue button will re start the process from where it was stopped If you change the split angle and then press continue the new split angle will only be applied to shells remaining to be extracted after the Continue button was pressed Pause Pressing this button will stop the feature extraction process Select Entities ReSelect Entities Invoking this allows you to select a set of database shell entities for feature extraction Set Split Ang After pressing this button you will be prompted to enter an angle in degrees If the angle between two adjacent triangle facets in a shell is greater than the angle you type here the edge between them will be a candidate feature Whether it is actually extracted as a curve or surface edge depends on the setting of the Extract Surfaces and Extract Curves toggles Extract Surfaces If this button is selected Gridgen will look for closed boundaries of features that can be used to subdivide the input database shell entity The shell will subdivided if the features form a closed loop or a loop that closes with the boundary of the shell Extract Curves If this button is selected Gridgen assemble features into database curves polylines Contiguous features are joined into a single cur
367. t this toggle is enabled the menu is on the left Menu QukMnu This toggle button indicates whether or not the Quick menu Section 2 3 7 is displayed By default this toggle is off When the Quick menu is not displayed the Quick Keys Section 2 3 6 are dis played instead Menu Warp This toggle button allows you to disable Gridgen s mouse warping whereby the cursor is sometimes moved for you to certain buttons By default this toggle is enabled Wndw WhiteBG This toggle button will change the background color in the Display and Browser win dows between white and black The default background color is black Wndw Ortnrml This toggle button changes the Display window view between perspective and orthonor mal viewing transformations In a perspective transformation the image will be rendered with a vanishing point so that distant parts of the image in the screen z direction will appear smaller than close parts An orthonormal transformation does not scale the image based on distance When using the zoom box Section 2 7 5 we recommend that you use an orthonormal transformation Wndw VueLims This command tells Gridgen to compute the size of the 3D viewport for the objects in the Display window The current viewport is based on the dimensions of the displayed objects As new items are added to the display it may be necessary for you to reset the viewing transformation using this command to take into account the new size of the total
368. take great care in constructing domains to insure new domains do not overlap 9 8 5 Prohibited Despite the general nature of domains that can be created in Gridgen there are a few types that still should not be constructed These domain types are illustrated below 9 12 Bad Domain Types Prohibited REL The domain in the left of the figure contains a circular arc connector that begins and ends at the same node a self connecting connector Domain s containing self connecting connectors should be avoided This topology can be corrected by dividing the self connecting connector into two or more connectors The domain in the center of the figure illustrates a domain that does not trace a loop in physical space but represents a surface of finite area The topological problem here is that a rectangular domain is folded in half The correction would simply require splitting the domain at the fold The domain in the right of the figure illustrates a zero area domain that doesn t contain any poles This topo logical problem involves a domain that is sheared until it collapses onto itself leaving only two unique edges It is possible to arrive at other domain topologies possibly combinations of the three examples above that are not possible to generate or more likely ones that are of no use in block construction In most of these cases the solution will be to further divide the surface into smaller domains so the topology conforms to G
369. tance within which a node and a connector must lie in order to be candidates for merging After you enter this value Gridgen lists in the Browser all node connector pairs that are within this tolerance Each Browser item consists of three bits of information The two integer numbers separated by dashes are the node and connector numbers respectively The real number on the right is the actual maximum distance between the node and connector To merge the node and connector select the pairs to be merged from the Browser and press Done The connector is split at the location closest to the node and the new node on the connector is merged with the node 15 13 Miscellaneous For example consider the grid below with two connectors a circular arc and a vertical line The lower end point of the vertical line is very close to the circle and we wish to make the two connectors intersect Per haps the gap resulted from a sloppy database model from which the connectors were originally created After pressing the Merge Nodes and Conns button we enter a tolerance of 0 2 which is large enough to locate the connector and node we wish to merge in this example the horizontal distance between the circle s end points is 1 0 Enter a tolerance for which node connector pairs will be listed 1 nod 2 con tol e tol default 0 200000 The Browser then lists all node connector pairs that fall within the specified tolerance In this case it f
370. tate of the selected layer s All On turns on the display of all layers All Off turns off the display of all layers with the exception of the current working layer which is always displayed On turns on the layers currently selected in the Browser list Off turns off the layers currently selected in the Browser list Toggle toggles the on off state of all layers 5 9 9 Saved Layer Sets The Saved Layer Sets tool allows you to store and later recall the on off state of all layers as well as the des ignated current working layer Saved layer sets do not preserve any filter settings 5 7 Layer Manager Saved Layer Sets hub isolated Save nacelle isolated Restore Delete Ed Save opens a dialog panel shown below where you can type in the name of your new saved layer set BH Layer Set Name eee E ete Cancel OK Restore restores the layer set that is selected in the Saved Layer Sets Browser You can also double click a layer set in the Browser to restore it Delete removes the layer set selected in the Saved Layer Sets Browser 5 5 6 Special Features A tool tips field is provided at the bottom of the Layer Manager panel as shown below As you pass the cursor Over any command Browser entry or text field helpful text will be displayed in this field to assist you There is a Close command to close the Layer Manager panel completely To reopen return to the MAIN MENU and use the La
371. te direction This command is available for unstructured blocks only 10 6 Linkages The manner in which a domain attaches to a face during face creation is called the linkage Sometimes a domain being added to a face has more than one linkage In the example below suppose the vertical domain on the left of the Display window is being added to the face It can connect to the face in either of two places Gridgen determines all of the possible linkages and highlights in pink the first of them in both the Structured Block Topologies and Orientations Adding Faces to an Unstructured Block Display and Blackboard windows Three menu buttons are available for you to choose how to proceed Selecting the proper linkage is generally only an issue when you have a self connecting face in a structured block such as a face consisting of an upper and lower half cylinder Here you should select the proper link age so the face s computational extremes lie at the intended physical locations DETERMINE DOMAIN LINKAGE Link Doms at Hilite 1 Display Next Linkage n Abort Do Hot Link esc Link Doms at Hilite Press this button if the highlighted linkage is the one you want Display Next Linkage Press this button if you want to see the next possible linkage Abort Do Not Link Press this button if the linkage problem was caused by picking the wrong domain You may encounter situations when the domain to be added clearly attaches to the face bu
372. ted throughout the grid causing domain and block grids to be updated The ImmdRegen toggle button determines whether or not your spacing constraint changes cause immediate regeneration of surface and volume grids enabled by default or whether the surface and volume grids are only regenerated when you exit the command Spacing constraints may be picked from either the Browser or Display window When picking from the Dis play window the first and last 10 of each subconnector s length is pickable corresponding to the region close to the break point All picked spacing constraints are shown in the Display window as the connector s 1096 of length with an arrow head pointing toward the constraint location The Browser lists each spacing constraint as shown below pP Py PI PS PS P PPS AA AAA coco ococecedc Jj 1 0 CN CS DS CIS D CIS I 6 0 60 0 00 CO M CU D 0 O DO 0 0444 The first number listed in each entry is the connector number If subconnectors are present then they are listed to the right of the decimal point Therefore 2 2 in the example above refers to the second subconnec tor of connector number 2 The B and E refer to the beginning and ending break point of the subconnector respectively The next field lists the distribution function if it is not hyperbolic tangent TANH The possible values of this field are blank hyperbolic tangent 11 13 Grid Methods for Connectors mrqs monotonic rational quadratic sp
373. tes that is between 10 and 2000 the approximate upper limit of memory addressable by a 32 bit address The default value is 64 MBytes 3 3 2 2 Tetrahedral Mesh Size Factor The default size factor qualitatively controls how far into the grid s interior the boundary cell size affects the interior cell size A value of 0 means there is no influence whereas a value of 1 provides full influence The initial value for this default is 0 5 To change it press the SizFac button and type in a value in the range 0 1 3 3 2 3 Minimum Pyramid Height The height of the shortest allowable pyramid in a hybrid unstructured block is specified by pressing the Min Pyr button and typing in the desired minimum height By default this value is not explicitly set 3 3 2 4 Maximum Pyramid Height The height of the tallest allowable pyramid in a hybrid unstructured block is specified by pressing the Max Pyr button and typing in the desired maximum height By default this value is not explicitly set 3 3 2 5 Pyramid Aspect Ratio The aspect ratio from which pyramid height 1s derived in a hybrid unstructured block is specified by pressing the Pyr AR button and typing in the desired value which must be a positive number By default this value is set to 0 5 3 4 Domain Topology Controls 3 4 1 split Angle The default split angle controls how triangular surface grids will be subdivided when they are imported into Gridgen This default applies whether they are
374. tes your acceptance of all the Right to Use License Pointwise Gridgen and Get the Point are registered trademarks and GridgenGlyph is a trademark of Pointwise Inc FIELDVIEW and FVX are trademarks of Intelligent Light FIELDVIEW Unstructured format Copyright 1996 2002 by Intelligent Light Used by permission FIELDVIEW Unstructured format is intended for the exclusive use of the licensors of FIELDVIEW from Intelligent Light Silicon Graphics IRIX and OpenGL are registered trademarks and SGI and GL are trademarks of Silicon Graphics Inc Hewlett Packard HP and HP UX are registered trademarks of Hewlett Packard Inc IBM AIX and RS 6000 are registered trademarks of IBM Corporation Compaq and Tru64 are registered trademarks of Compaq Computer Corporation Sun Sun Microsystems and Solaris are trademarks or regis tered trademarks of Sun Microsystems Inc LINUX is a trademark of Linux Torvalds REDHAT is a registered trademark of Red Hat Inc FLEXIm and Flexible License Manager are registered trademarks of GLOBEtrotter Software Inc All rights reserved Gridgen uses the TetMesh GHS3D tetrahedral mesher copyright O SIMULOG S A 1999 PATRAN is a registered trademark of The MSC Software Corporation NASTRAN is a registered trademark of NASA VSAERO copyright 1985 Analytical Methods Inc INCA is a trademark of AMTEC Engineering Inc UNIX and XWindow System are registered trademarks in the U S and other countries licensed exclusivel
375. the actual splitting A necessary side effect of splitting a domain is that the two connectors on the domain s edges that are opposite the split direction will also be split SPLITTING A DOMAIN I Lines o J Lines H Move via Keybrd pad Done Split at Hilite ent Abort Dont Split esc The Move O via Keybrd button may be used to type in the index of the grid line to which the hiliter should be moved The figures below illustrate the before during and after stages of a domain being split from left to right respectively EO a FUERAT ES ae SSS end a 2 t d See zr rr i EIER NE XN TC me mon ES ae ee s a X UR Rc Only structured domains can be split The equivalent functionality for an unstructured domain is illustrated in the figure below From left to right 1 Start with the original unstructured domain 2 Delete the unstructured domain but not its connectors 3 Split the connectors and create new nodes at either end of the split line the two vertical connectors in the example 4 Create a new connector for the split line in this case the line slanting downward and to the right 5 Create two new unstructured domains by assembling the edges APKE P ibaa 14 7 4 Blocks When the Split command is invoked for a structured block the highlighter appears in the Display window The hgihlighter location is the split location The highlighter can be moved
376. the Browser is first invoked Show Proj DBs This toggle button controls whether or not the database entities being projected onto will be highlighted in the Display window Turning off this toggle will un clutter the display Show Proj Vector This toggle button controls whether or not the projection vector with which grid points are projected onto the database entities is rendered in the Display window Turning off this toggle 13 4 Relaxation Parameter Attribute DB will un clutter the display Align View w Proj Vector This command changes the orientation of the Display window image so that the focus grid s projection vector is parallel to screen z 13 4 Relaxation Parameter Attribute The unstructured solver s relaxation parameter is the coefficient to be applied to a smoothing sweep through the grid points which is performed after all grid point insertion is completed Relaxation is only available for domains The smoothing algorithm works as shown below smooth 7 1 0 Y original 0 average Where Faverage 1S the average value of all of the grid point s neighbors The value of the relaxation parameter Q is limited to values between 0 no smoothing and 2 0 since values greater that 2 0 can introduce numerical instability Use Nominal Relax 0 1 3 Enter Relax via Keyboard 1 Use Nominal Relax This button sets the value of the relaxation factor to Gridgen s default value which has been deemed nominal Enter Relax via K
377. the entities For example network files may only contain bilinear surfaces The database file types supported by Gridgen are described below 4 4 4 1 Network Network files contain any number of bilinear surfaces The data in a network file is described in Section 18 4 Each network is similar to a surface grid in that it consists of an ordered M x N array of points Note that Gridgen does not fit a smooth surface through a network s points the surface will be faceted If you want to create a smooth surface from the faceted surface obtained from a network file you should use the Fit command Section 6 5 5 in the DB CREATION menu 4 6 Importing Database Files File Type 4 4 4 2 Gridgen Segment A segment file contains any number of linear curves The data in a segment file is described in Section 18 5 A segmented curve consists of an ordered string of discrete points Segment files are the same as those used in connector creation under the Import segment type Note that Gridgen does not fit a smooth curve through a segment s points the curve will be faceted If you want to create a smooth curve from the faceted curve obtained from a segment file you should use the Fit command Section 6 3 8 in the DB CREATION menu Gridgen automatically removes any consecutive coincident points from segment files to make sure that the segment is single valued 4 44 3 Gridgen Composite File A composite file contains any number of any of the entities su
378. the following list 1 Parametric TFI Gridgen will apply Parametric TFI if the domain s connectors have been defined in terms of one and only one database entity The connector s may have been created directly on the entity for example DB cnstr Line segment type or may have been projected onto the database Parametric TFI ensures the grid will conform to the database shape 2 Parametric Fit TFI If Gridgen cannot apply Parametric TFI it tries to apply Parametric Fit TFI In order to apply Parametric Fit TFI a certain percentage of the domain s connectors must have been defined in terms of any database entity the connector s grid points must lie within the bounding box of a single database surface entity and the distance from the connectors to the database must be less than a tolerance If these conditions are met the domain s connectors grid points are projected onto the data base and the parametric coordinates obtained from the projection are used to apply Parametric TFI 9 3 Creating Domains This will ensure that the interior grid points will conform to the database shape 3 Standard TFI If neither of the two methods above can be applied Gridgen applies Standard TFI A Standard TFI grid will not adhere to the database You must modify the domain via projection Section 14 4 if you want the grid to lie on the database Gridgen color codes newly created domains to show you which TFI method was used for the initial domain
379. the grids selected for the solver The focus grid 1s the grid whose attributes are listed in the Blackboard and whose image is highlighted in the Display window Focus Prev Moves focus to the previous grid in numerical order of the grids selected for the solver The focus grid is the grid whose attributes are listed in the Blackboard and whose image is highlighted in the Dis play window Apply to Focus This radio button specifies that the selected attributes are to be applied to the focus grid only Apply to All This radio button specifies the selected attributes are to be applied to all grids currently selected for the solver Surface Shape Params These attributes define how the shape of the selected surface grids is to be maintained by the solver These settings are not available for blocks Relaxation Parameter This attribute controls the coefficient for the smoothing to be applied to the grid Smoothing is not available for blocks Grid Control Params These parameters allow you to control the criteria for point insertion into the grid Two other commands come into play when you are setting attributes The following two buttons appear within each of the specific attributes menus Set Other Attributes esc Done Setting Attributes ent Set Other Attributes Pressing this button will invoke the main unstructured attributes menu so that you may select a new attribute type to set Done Setting Attributes Pressing this b
380. the grids to which TFI is to be applied from either the Browser or Display window The TFI method last applied to each grid is listed in the Browser window s second column after the grid number The appearance of an plus sign or an asterisk after the algebraic method type indicates the following a Aplus sign indicates a grid that has been locked by application of the elliptic PDE solver b Anasterisk indicates a grid that has been locked by application of the hyperbolic solver by importing the grid from a file or by projection scaling or stretching 12 1 Grid Methods for Structured Domains and Blocks stndr 2 stndrd T2123 3 ortho T2123 4 stndrd T8M f 1234 5 stndrd b T8M f 1234 46 stndrd T8M f 1234 7 stndrd tb T8M f 1234 8 prfit 7 b T8M f 1234 9 prfit 10 b T8M f 1234 10 prfit 4 b T8M f 1234 1l param 5 b T M f 1234 12 prfit 3 b T8M f 1234 13 stndrd b T8M f 1234 2 To re apply the last TFI method used for each selected grid a Press the Initialize via TFI button 3 Toapply a new TFI method a Press the Set Solver Attributes button b Press TFI Methods button c Press the button for the specific TFI method to be applied d Press the Done Setting Attributes button e Press the Initialize via TFI button 4 Select other grids to run or press the Done button All TFI methods in Gridgen are based on a set of closed form algebraic equations that use the grid points on the boundaries
381. the solid filled blue or red slope point which you can adjust in the same manner as regular control points Editing of Bezier curves is described in more detail in Section 14 9 7 2 5 3 Bezier on DB This segment type is the surface equivalent of the Bezier segment Section 7 2 5 2 All control points are constrained to database entities and the resulting segment shape will lie exactly on the entity s Like the Bezier Curve segment this type of segment can only be formed by editing an existing segment and by con verting it to the Bezier form Editing of Bezier curves is described in more detail in Section 14 9 7 2 5 4 General Segment General segments are never constructed explicitly but come about whenever a segment is modified in a way that destroys the Bezier properties of the segment For example if a connector on a database entity is trans lated off the entity the Bezier properties formerly defined in terms of the parametric u v coordinates will no longer hold since u v are defined only on the entity In order to preserve the shape of the original seg ment after translation that 1s Gridgen stores the original segment shape discretely and uses it to define the new segment General Segments will arise under these circumstances 1 adatabase constrained segment is translated stretched scaled or rotated from its original position 2 asegment is projected onto database entities 3 acircular arc or conic section segmen
382. ther hand if a block connects to itself then one domain can be used twice in the same block 3D case only Domains can be added to a face and faces can be added to a block without regard for the structured block s eventual computational coordinate system Section 15 7 Begin block creation by going to the Block Commands menu and pressing the Create button Then begin assembling the block face by face by first pressing the Assemble Faces button and then the Add 1st Face button Repeat the face assembly process described in the following section for each of the block s faces 10 2 1 Adding Faces to a Structured Block A block face consists of one or more domains After the Add 1st Face button is pressed you select the first domain to be added to the face by positioning the cursor near one of the edges of the domain until it high lights and pressing the right mouse button The pickable part of a domain during block face assembly is the first row of cells along its boundary If the wrong domain highlights try moving the cursor to lie only over the desired domain or use the x hot key to cycle through the available choices until the one you want is high lighted The edges of the developing face are highlighted in the Display window A schematic representation of the face in computational space is drawn in the Blackboard with the composing domain numbers drawn in the center of each domain The Display window and Blackboard images are color coded conne
383. til all desired items are queued and then press the Done button 2 4 2 Selecting From The Browser Commands that allow picking via the Browser will present a single or two column list of entities from which you may pick The Browser text for each entity depends on the command and the entity type being picked When the list of items exceeds the Browser s capacity Gridgen will create a multi page Browser list You may scroll through the entire list using VCR menu buttons Section 2 3 5 When picking from both the Browser and Display windows and when the Browser contains a multi page list picking an item s graphical display will cause the Browser list to be repositioned so the item s list entry is visible 2 4 2 1 Selecting Entities One At A Time To select entities from the Browser window follow this procedure 1 Position the cursor over an entity s text in the Browser window The text will be highlighted 2 Press and release either the left or right mouse button The text will now be white 3 Ifthe command can only operate on a single entity it will begin operating on the picked entity now 4 Ifthe command allows multiple entities repeat the selection process until all desired entities are queued and then press the Done button 2 4 2 2 Selecting Several Entities At Once To select several entities from the Browser window follow this procedure 1 Position the cursor over an entity s text in the Browser window The text will be h
384. ting connector or domain and trans form it via translation or rotation respectively so that future changes transformations editing dimension 15 8 Periodicity Blocks distribution to the original grid are automatically made to the periodic copy and vice versa Please note that periodicity is only enforced in pairs no more than two grids or two domains may be periodic with each other Periodic Trans Pressing this button lets you pick an existing connector or domain that is then copied and transformed using Gridgen s translate Section 14 3 1 command Any subsequent changes to either grid will be reflected in the other Periodic Rotate Pressing this button lets you pick an existing connector or domain that is then copied and transformed using Gridgen s rotate Section 14 3 4 command Any subsequent changes to either grid will be reflected in the other Periodic Break This command invokes the Browser with a list of every periodic connector or domain pair You then select the periodic pair that you wish to break delete Pressing the Done button then separates the pair and each grid may then be modified independently A sample implementation of periodicity is described below Consider the two dimension blade centered pas sage shown below on which we want to generate a simple blade centered H mesh First using Gridgen s normal tools we can create the connectors shown below The goal is to ensure that the lower connector is
385. tion to delete the blocks domains Delete Domains Also Should you choose to delete domains then only the domains unique to the deleted blocks will be deleted Delete Connectors Also y Only Block and Domains m 15 5 Sort Sort Ag The Sort command is used to arrange the numerical sequence of the blocks in the system This command is useful for arranging the grid in a manner that will be better suited for the analysis software Sorting is also useful for examining the block sizes in a large grid The first step after pressing the Sort button is to select from the Display window or Browser the block s to be moved in the numerical sequence Once these blocks are selected they can then be arranged using one of the following sorting criteria 15 5 Miscellaneous Hove to Top of List t Move to Bottom of List b Alphabet ize Aq Reverse the Order Ar Sort by Block Dimens 5 Move to Top of List This will move all selected blocks to the top of the overall block list If 6 of 10 blocks were selected for example they will occupy the first six out of 10 positions in the block list Move to Bottom of List This will move all selected blocks to the bottom of the overall block list If 6 of 10 blocks were select for example they will occupy the last six out of 10 positions in the block list Alphabetize This will alphabetize the selected blocks and rearrange them relative to one another keeping all non queued blocks in their original position
386. tional index After the direction is set the selected connectors are redrawn using the following color code Computational coordinate color scheme computational coordinate Next select one of the two remaining edge groups with the right mouse button and select its computational coordinate from the menu The connectors are again redrawn to reflect their new orientation The last step is to select from the menu the computational coordinate of the third and final edge group 15 8 Align n Align Ax The Align n G command in the Modify Blocks menu allows you to specify the computational coordinate axis systems of one or more structured blocks so that where possible they are aligned with the n G axes of a block of your choosing You might use this command if your chosen analysis software package restricts the type of inter block connections For this command to function properly all of the selected blocks must be connected to one another so that the coordinate system from the chosen block can be propagated throughout the blocks Any physically iso lated blocks will not be affected by this command Also the master block must be selected in the group for modification 15 9 Periodicity The Periodic commands may be used to slave two connectors or two domains together to ensure periodicity in your grid Periodic Trans a Rotate 1 Break b The Periodic Trans and Rotate commands allow you to copy an exis
387. tions and the anchor point to find the new point locations The Enter Scaling Factors command allows you to type in the coefficients for each of the x y and z directions Other scaling commands are described below Repick Handle Point n Set Handle by Picking pad via Keybrd pad Axyz via Keybrdo Acp via Keybrd o by Linear Proj at Clsest DB Pt Enter Scaling Factors e Original Location 1 Movement Restrictions m Sensit Decr lt Reset Iner gt Hove to Screen Center c Rotation Ft To Cross t Done Scale ent Abort Dont Scale esc Repick Handle Point Lets you pick a new handle point if you picked the wrong one the first time Set Handle The buttons following this label are the standard mechanisms for selecting the final location of the handle Original Location Move the handle back to its position prior to movement The entity is not copied prior to scaling Use the Copy command first if that is what you want In fact after copying the entities the Copy command will invoke the Modify menu for the copies The scaling is not saved until the Done Replace button is pressed 14 3 3 Stretch The Stretch command is used to alter entities by scaling along a defined vector Multiple entities can be stretched at one time The figure below illustrates stretching the domain with the lower left corner fixed and the upper right corner used as the handle 14 9 Modifying Entities After the entities are se
388. to the unspecified state 17 7 Mirror Blocks for Export Mirror Blks for Export b The Mirror Blks for Export toggle when enabled instructs Gridgen to mirror selected blocks only on export for your analysis software This setting the selected blocks for mirroring and the chosen mirror plane only persist while the user is in the ANALYSIS S W COMMANDS menu Once the menu is exited or the Mirror Blks for Export toggle is turned off all settings related to this command are cleared from memory Turning on this toggle immediately places you in the block Browser to select the blocks you wish to mirror on export Once the blocks are selected you are placed in a final menu used to determine the mirror plane See Section 14 3 5 for more details on the mirror plane selection 17 8 Export Analysis Data Grid and BCs These commands allow you to export analysis software data to a file or files including boundary condition volume condition and grid data Analysis software requiring a boundary condition file and a grid file will be supported by the command pair Export Analysis BCs and Export Analysis Grid Analysis software requiring exactly one comprehensive data file or more than the customary two grid and BC files will be sup ported by a single command Export Analysis Data 17 7 Analysis Software Interfaces See Section 2 5 for additional information regarding use of the file Browser These commands may also be invoked via a button or bu
389. to 2 2 simply enter 2 2 note the commas The x and y coordinate values will be set to the cross s x and y values 2 8 2 4 Via Offset A fourth method of choosing a control point is selected with the Add CP O via Offset button A prompt appears in the Message window and the program waits for the numerical input to be typed in the Text Input window You will be expected to input Ax Ay Az values if the current segment is not database con strained and parametric Au Av values if the segment is surface constrained The offsets are measured relative to the current cross location 2 8 2 5 By Linear Projection You can add a control point on the database where no pickable database point exists using the Add CP L1 by Display Commands Menu Miscellaneous Controls Linear Proj command A ray is cast in the screen z direction through the current cursor location and into the database The control point is added if and where the ray intersects the database 2 8 2 6 By Closest Point Projection You can also add a control point on the database where no pickable database point exists using the Add CP O at Closest DB Pt command When this button is pressed Gridgen adds a control point at the point on the database that is closest to the current cursor location 2 8 3 Miscellaneous Controls Various buttons listed below allow you to fine tune control of the cross during 3D cursor manipulation Sensit Decr lt Reset Incr gt Move
390. to Screen Center c Move Rotation Pt To t Sensit Decr The sensitivity of the cross s response to mouse movement is decreased by a factor of ten Sensit Reset The sensitivity of the cross s response to mouse movement is re initialized Sensit Incr The sensitivity of the cross s response to mouse movement is increased by a factor of ten Move to Screen Center The cross will be positioned at the center of the Display window at the zoom dot Move Rotation Pt to The rotation point the graphical origin of the body axis system rendered in the Display window is moved to the current cross cursor location Thereafter all image rotations using the key pad take place about this point The rotation point is reset to the centroid of the viewport containing the grid and database whenever the original view orientation body x aligned with screen x body y aligned with screen y is restored by pressing the r hot key 2 9 Display Commands Menu This menu will be displayed when the Display Commands button which is available from almost every menu in Gridgen is pressed 2 19 Graphical User Interface Edit Dspla DB d Dom s Fac b En Disable DB h Dom j Blk n IShow LIDsbldDB e MEnb1dDB 4 Con GPs c Iv Nods 1 vf Cons 2 MDoms 3 MRotAxs a LIXYZAxs X Menu O SmalTxt 7 MOn Left 5 O QGukMnu q Iv Warp W Winch 4 Wh i teBG k L10rtnrml V YueL ims lilLinewid 41 Rot Pnt miFramBuf f Mous MGlide m D LeftPk 6 Demote0 0 8
391. to Section 7 2 1 for more information on creating Lines 6 3 2 Curve Creation of Curve database entities is similar to creation of Curve connector segments Please refer to Sec tion 7 2 1 for more information on creating Curves 6 3 3 Akima Curve Creation of Akima Curve database entities is similar to creation of Akima Curve connector segments Please refer to Section 7 2 1 for more information on creating Akima Curves 6 3 4 Conic Section Creation of Conic Section database entities is similar to creation of Conic Section connector segments Please refer to Section 7 2 3 for more information on creating Conic Sections 6 3 5 Circular Arc Creation of Circular Arc database entities is similar to creation of Circular Arc connector segments Please refer to Section 7 2 3 for more information on creating Circular Arcs 6 3 6 Offset Offset curve entities can be added to the database using the Curve Offset button in the DB Creation menu Offset curves are the result of moving a curve called the generatrix a specified distance normal to itself You have two controls during offset curve creation the normal direction and the offset distance Because in general a 3D curve does not have a unique normal direction Gridgen constrains the normal direction to the plane of the Display window Therefore the orientation you choose for the Display window image helps define the offset direction An additional control is provided by the command Reve
392. to be hand edited to ensure that the correct values have been written Therefore always inspect your Glyph files before running Gridgen 4 21 Importing and Exporting Files 4 22 5 Layer Manager 5 1 Overview Gridgen s layer manager gives you flexible control over what portions of your database model are displayed Gridgen s layer manager is implemented in a very similar style to that of common computer aided design CAD software packages Gridgen supports 1024 layers numbered O through 1023 An entity must exist in exactly one layer Layers can be likened to drawing on transparencies that overlay each other You choose which layers are visible Layers are designed for display management only There are other tools En Disable see Section 15 6 and Group see Section 15 2 providing additional control over database entity display and use This sec tion of the User Manual describes in detail commands associated with and the operation of the layer man ager All layer information is saved in your Composite dba database file see Section 4 5 5 2 Database Groups and the Layer Manager Two points of consideration regarding database groups should be made First database groups are a picking mechanism only and as such do not belong to a layer Second if any child of a group is disabled or is in a layer that is off the group itself will be unavailable for picking or selection For more information about database groups see Sectio
393. ton lets you type in the limit on cell aspect ratio 8 2 9 Copy Attributes For hyperbolic and normal extrusions users can copy the extrusion attributes of an already extruded domain or block to use for the extrusion of a new domain or block Using Copy Attributes sets the initial spacing and other extrusion attributes for a new extruded domain or block so that the grid characteristics of the previ ously extruded domain or block are maintained across their interface Grid Extrusion Methods Copy Attributes h Copy Attributes is only available for certain criteria Extrusion must be of type Nrml or Hyp Extrusion must be From Cons or From Doms e Selected extrusion type must match type of previously extruded domain or block e Selected connector or domain must be the last entity created from a previous extrusion e Selected domains are the top faces on the same block prism blocks only Please note that Copy Attributes is currently not allowed for creating extruded domains or blocks From An Edge or From A Face 8 2 10 Heset Attributes For all types of extrusion users may reset the extrusion attributes to the default values before they extrude a domain or block Reset Attributes m In cases where an already extruded domain or block exists users can remove the extruded grid see Section 14 6 select Reset Attributes and restart their extrusion 8 14 9 Creating Domains 9 1 Overview Domains are Gridgen s mid level grid
394. tons enables the hiliter on n and G constant planes of a structured block respec tively X Y Z Pressing these buttons enables the hiliter on x y and z constant planes of block respectively O kbrd Move the hiliter to the typed in point X kbrd Move the unstructured block hiliter by entering a the x y or z constant plane value Rot Pt O Move the rotation point to the current hilited point O to min Move the hiliter to the location of the minimum value of the current diagnostic function if appropriate O to max Move the hiliter to the location of the maximum value of the current diagnostic function if appropriate An example of the hiliter for a curve entity with Blackboard information is shown below 16 12 db entity 1 of 1 name GG pcurve 1 type parametric curve intervals degree 3 Q entity 1 intervalit 3 e eaves Ha 0 00000000E 00 3 774 1 3 1 x CL NY doms 1 1 points 961 of 961 dimension max imum 961 A 1 average 961 minimum 961 A 15 NN zh Yes AW quads 900 of 900 tris 0 of O entity 1 grid point NN y z db ent LI blocks 1 1 points 18750 of 18750 dimension maximum 18750 average 1875 minimum 18750 O entity 1 GP 10 11 5 x 6 7739575 y 1 1285714 z 5 1067017 m i 10 382234 j 11 361232 Ei An example of the hiliter for an unstructured block with Blackboard inf
395. tor Section 11 1 distribution the distribution of grid points along a connector Section 11 3 As described in the list above a connector s shape is defined by its segments A segment is a specific math ematical curve type Therefore a connector is what computer aided design CAD software would refer to as a composite curve Some important connector terminology is defined in the following list connector a point wise CO continuous series of segments segment a specific type of curve that defines how the curve shape is derived from the control points control point a 3D location in x y z space through which a segment will pass node the control point at either end of a connector displayed as a filled circle Connectors are color coded according to their current state in the grid as listed in the following table Con nector colors are not user definable Connector color scheme color meaning bright green light green light blue dark blue Create a connector by selecting the Create command from the Connector menu There are three methods for creating connectors as shown below Add Seqment n 2 Point Connectors 2 On DB Entities 3 Add Segment You create one connector by creating each of its segments individually 7 1 Creating Connectors 2 Point Connectors You create connectors rapidly by defining two control points If the two points lie on the same database entity the connector s shape is snapped
396. tors ooocccocccccoccnccoccnonocnncnoonononononanonos 11 5 1131 Denon PEN T T T E ea a 11 6 11 3 2 Distrib tion Parameters oet ra 11 6 11 3 3 Break Points and Subconnectors eesseeesssssuss 11 10 11 3 4 Miscellaneous Controls oocccconnccocccoccncccncccononocnoncnnnnonnononnnnonnnonnonanoss 11 12 11 4 SeE S Valles cr o oou MR dedu ea oe DU ee 11 13 12 Grid Methods for Structured Domains and Blocks 12 1 12 1 PIGEDIAIC Method S ei oc 12 1 12 Ercole 12 2 T2 T2 bane dr nen E dn eas abared Farbe tue oed iae Bs 12 2 T2 1 9 Polar Elson Ni doe a anata d dcscaiLd dua CO adenine 12 3 2 1 ORDOLTE boe eet ans heater e tete itte se Ho ode dau 12 3 LEER ES Paame ie eer 12 3 126 Parametric PIE TF boortoren EE aA 12 4 LE O E E E E E E A E I A EE E NE N S eee A E 12 4 12 2 Elliptic PDE Methods 0000 din 12 4 122271 RUNAMO The Sol ai a 12 4 12 2 2 SeN AETHDULGS bici see Dus a ru utu desde i ud 12 6 12 2 3 Relaxation Parameter esses nennen nennen nennen renean 12 7 12 2 4 Background Control Functions leeren enne 12 8 12 2 5 Foreground Control Functions cooocccoccccccnnnocncnononnnonconnnonannnncnonannnnanoos 12 9 12 2 6 DU ace old DO eter adu aset iii 12 11 12 27 Boundary GoFdiILIIOriS sci niae lid 12 13 12 3 Structured SUDGHIOS iei teret ihid tease eLetters ode 12 14 12 9 T POGING d HDC IC coca iad Oo 12 14 123 2 Deleng SUDGINGS ases
397. tructured domain is not deleted An Aligned triangulation below right triangulates each quadrilateral cell along the diagonal from its i J min Comer to the i 3 max corner A Best Fit triangulation below left triangulates each quadri 9 8 On Database Entities lateral cell along the diagonal maximizing the minimum included angle of the resulting triangles BEEN NND RRA AAN ARA AA RRA AAA RON RARA NA Dl A pa A AA of ARA es ERR RSS V ANS I y ERE RIA ERHOBEN ARA RRR ARIA SAUTER Rae zal Pal A PRA ey ADA RARI RSS NAVI NAVAS STRIS ISTIS TRAE Esp OI RRA o PERRERA ERRE AAA ABRAN FERRER ARRAS EASES 9 6 On Database Entities The On DB Ents command for creating domains is the surface grid analogy of the same named command for creating connectors Section 7 4 It allows you to very rapidly create surface grids for each database sur face entity you select This command is not available unless you first set a default connector dimension in the Defaults Menu Gridgen performs the following steps 1 Executes the On DB Ents command creating connectors resulting in dimensioned and distributed con nectors joined in a domain around the perimeter of each trimmed and untrimmed database surface you select 2 The Merge command is applied with the default tolerances to remove coincident and overlapping con nectors between adjacent domains 3 The default Alge
398. tton 11 7 Grid Methods for Connectors Equal Spacing TANH Function Copy From Network Mono Rat Quad Spln Geometric Progression Copy From SubConnects Max Dev Max Ang OO O75 23 O0 Equal Spacing This is not a true distribution function This is a shortcut command to convert the distri bution function to hyperbolic tangent and unconstrain both the beginning and ending spacing constraints TANH Function Gridgen s default distribution function is the hyperbolic tangent Reference 36 If the spacing is unconstrained at both ends grid points will be distributed uniformly using a simple uniform inter polation scheme If the spacing is unconstrained at only one end an alternative one sided hyperbolic tangent distribution function is used Hyperbolic tangent works very well for the majority of cases and for that rea son it is the default distribution function Copy From Network This distribution function positions the grid points so they lie exactly on the inter vals of a database bilinear surface entity network This distribution will not be available for selection unless four criteria are met All segments in the connector are Line on DB segments and all segments lie on the same database bilinear surface network Each control point lies exactly on a network interval s corner All control points share either a u or a v parametric database coordinate The dimension of the connector is equal t
399. tton Gridgen saves the domain and automatically generates its interior grid points unless explicitly disabled as described in Defaults Section 3 3 1 FAC LE a Ta x c x E SE e s mS Es A A s as E Es ma Bear m LT X ES AAA p P I EE p L x al A Ty ne E me ZA mr E z e Ql c inr CE KR Defining the Outer Edge TU ES mia E AS Vu A EP E EDS mM Ee T etas Ts ERIS Pts J T ral ADE m A 7 Punto ERE EA UA ihn EY Ac J Ad LX ES B cz n EN y iz Ty E val Assembly of a domain with multiple edges internal holes proceeds in much the same manner The first edge must always be the outer boundary of the domain Make sure that Auto Save is toggled off Other wise Gridgen will save the domain and put triangles on the interior as soon as the outer edge 1s complete and before you have had a chance to define the interior edges As shown below the process begins with the selection of the initial edge of the outer boundary Creating Domains Defining the Outer Edge Connector selection continues around the entire perimeter of the outer boundary Defining the Outer Edge When the outer boundary closes on itself press the Next Edge button to begin defining the inner boundary Be sure to select the inner loop s connectors in an or
400. ttons in the INPUT OUTPUT COMMANDS menu The following sections describe the analysis data export in the context of specific analysis software pack ages 17 8 1 generic Gridgen s generic ASW is not really a software package at all but a facsimile of one that is included in Grid gen to give you the ability to create and export grids and boundary conditions in a generic format Using the file descriptions in Section 18 you may then write your own translator to convert from the generic format to your own format Gridgen s generic solver has been patterned after a computational fluid dynamics CFD code and supports hybrid grids The generic ASW supports both structured and unstructured grid output formats with the exception of 2D unstructured The structured grid output maintains the computational coordinates of the grid whereas the unstructured grid output format breaks the entire grid into a list of points and element connectivity The generic structured format allows you to export separate grid and boundary condition files The format of the generic structured BC file may be found in Section 18 8 The generic structured grid file only sup ports quadrilateral and hexahedral grid cells and is a structured multi block grid with Gridgen style ASCII binary or unformatted format and double precision as described in Section 18 10 The generic unstructured format includes the grid and the boundary conditions as named regions exported in FIELD
401. u specify The surface grid method is a modified Delaunay method since LaPlace smoothing is applied to the grid whereas the volume grid method is strict Delaunay 13 1 Running the Solver LlIList By BCs Unstretrd At The Run Solver Unstrctrd menu button is used to apply a triangulation method to one or more unstruc tured grids The first step in running the unstructured solver is to select from either the Browser or the Dis play window the grids to be run During selection of the grids a terse description of the current unstructured solver attributes Section 13 2 will be displayed for each grid in the Browser For example in the sample shown above grid number 6 has 227 points and is constrained to the database DB The List By BC menu button instructs Gridgen to list domains in the browser by their boundary con dition defined using the ANALYSIS S W COMMANDS menu Section 16 2 If a grid s Browser text contains a plus sign this indicates that the mesh has been run in the solver and is locked An asterisk in the Browser text indicates a mesh locked by another action such as copying and translation off the database Also running the tetrahedral solver on a block locks all domains used on the block s faces When you have selected any number of grids the unstructured solver is invoked and immediately enters the paused state with the menu shown below for domains 13 1 Grid Methods for Unstructured
402. uctured Grid Gener ation System NASA CP 3142 Software Systems for Surface Modeling and Grid Generation ed by Smith R E NASA Langley Research Center Apr 1992 pp 253 271 Steinbrenner J P Chawner J R and Anderson D A Enhancements to the GRIDGEN System for Increased User Efficiency and Grid Quality AIAA paper no 92 0662 AIAA 30th Aerospace Sciences Mtg Reno NV Jan 1992 Steinbrenner J P and Anderson D A Grid Generation Methodology in Applied Aerodynamics from Applied Computational Aerodynamics ed by Henne P A AIAA 1990 pp 91 130 Steinbrenner J P Chawner J R and Fouts C L The GRIDGEN 3D Multiple Block Grid Generation System WRDC TR 90 3022 Vols I and II Wright Research and Development Center Wright Patter son AFB OH Jul 1990 and Oct 1990 Steinbrenner J P Chawner J R and Fouts C L Multiple Block Grid Generation in the Interactive Environment AIAA paper no 90 1602 AIAA 21st Fluid Dynamics Conference Seattle WA Jun 1990 Steinbrenner J P Chawner J R and Fouts C L A Structured Approach to Interactive Multiple Block Grid Generation from AGARD CP 464 Applications of Mesh Generation to Complex 3 D Configurations Mar 1990 pp 8 1 8 12 Steinbrenner J P and Anderson D A Three Dimensional Parametric Block Grid Regeneration With Localized Solution Adaption from Numerical Grid Generation in Computational Fluid Dynamics 88 ed by Sengupt
403. uld probably enable this radio button Otherwise your Line on DB segments will be replaced by General segments Section 7 2 5 4 Cons Too Nods Too The boundaries of the domain or connector are also projected in addition to the interior points This would be useful for example if you have imported a domain from some external source and want to project the entire entity onto an IGES database Four different projection methods are available each with its own advantages as described in the following sections The naming convention for the projection methods is based loosely on analogies with coordinate system types Each method however is simply a ray surface intersection calculation The methods differ in how the rays are cast e Spher i cal Cylindrical Linear Closest Pt In the following subsection the projection type will be illustrated by showing the effect of projecting the square grid onto the spherical database as shown below C fh 14 4 1 opherical Enter Source via Keybrdpad Spherical projection is named for its analogy with a spherical coordinate system This method projects grid points along rays relative to a user defined point The projection rays emanate from the point and pass through each grid point After pressing the Spherical button you define the projection point either by pick ing a point from the Display window or choosing the Enter Source via Keybrd button and typing the coordinates of a p
404. ursor displayed as a pair of scissors over the segment to erase and hit the right mouse button Once a segment is erased it cannot be restored so caution is advised If the segment after the erased one 1s not a database segment its first control 14 20 Connector Segment Modification Edit point will be moved to the end of the previous segment to maintain continuity If the following segment is a database segment the last point on the segment in front of the erased segment will be moved to the first point on the segment beyond the erased segment If the segments on both sides of the erased segment are differing surface segments they will be connected by a branch segment 1494 Edit The Edit command is used when individual control points of a segment need to be re positioned If there is more than one segment in the definition first pick the segment to edit Then pick the control point to edit via the mouse Once a point is picked it may be moved via mouse control in the same manner as during the segment s creation However the edited point need not be saved explicitly since the edit point is constantly replaced in permanent memory with the cursor location Thus when editing 1s exited the edit point will be stored in the existing cursor location If the point being edited is a segment end point adjacent to another segment the adjacent segment will be modified when edit mode is exited or when another point is edited whichever comes first
405. used in their creation The dimension of unstructured domains and blocks is also determined by point insertion during application of the unstructured grid methods Section 13 Only connectors that are not used in structured domains may be redimensioned using this command Connectors belonging to structured domains must be redimensioned using the ReDimension Grids command Section 11 2 The change in number of grid points is propagated throughout the multi block grid topology After a connector is dimensioned its Display window image changes from a bright green color meaning undimensioned to a light green color meaning dimensioned If the connector being redimensioned already has a dimension and a distribution of grid points Section 11 3 the distribution will be updated automatically to match the new dimension using the current distribution constraints Three interrelated controls allow you to specify a connector s dimension 1 Specify a number of grid points or an average spacing along the connector 2 Type in a number of grid points or select a string of connectors with the desired dimension from the Dis play window You can also copy the distribution of grid points 3 Add additional grid points to further resolve the connector s shape Using this option changes the con nector s dimension and distribution Each of these three controls is illustrated in the figure below and described in the following sections Apply Oavg As
406. uses the extrusion and invokes the main extrusion menu so that you may change extrusion attributes to obtain a grid that meets your criteria or to relax your stop criteria The various stop criteria are described below L pos skew 1 zero 2 neg skew 3 neg 4 Total Height 5 Set 5 Skewness 6 Set 6 Aspect Ratio T Set 7 Jacobian pos skew Enabling this toggle button will cause Gridgen to pause the extrusion process when a grid cell with a positive skewed Jacobian is computed Jacobian zero Enabling this toggle button will cause Gridgen to pause the extrusion process when a grid cell with a zero Jacobian is computed Jacobian neg skew Enabling this toggle button will cause Gridgen to pause the extrusion process when a grid cell with a negative skewed Jacobian is computed Jacobian neg Enabling this toggle button will cause Gridgen to pause the extrusion process when a grid cell with a negative Jacobian is computed Total Height Enabling this toggle will cause Gridgen to pause the extrusion process when the total dis tance marched by any grid line exceeds the value you type in by pressing the Set button in the same row Set Pressing this button lets you type in the limit on extrusion height Aspect Ratio Enabling this toggle will cause Gridgen to pause the extrusion process when a grid cell exceeds the aspect ratio value you type in by pressing the Set button in the same row Set Pressing this but
407. uted relatively quickly Elliptic PDE methods in Gridgen are based on iterative solution of the elliptic partial differential Poisson s equation You may apply the elliptic PDE methods to any grid at any time in order to improve the smooth ness clustering and orthogonality of the grid The elliptic PDE method s default controls have been estab lished to give you the best possible grid Additionally a wide variety of controls are available for fine control over the grid characteristics The algebraic and elliptic PDE methods are both available via the Run Solver Structured command in both the Domains and Blocks menus The following sections describe in detail how to apply each grid method If you select the List by BC toggle in the Domain Commands menu Gridgen will display the boundary condition set on each domain when you are selecting domains to run in the solver This may make it easier to select the domains you want to elliptically refine 12 1 Algebraic Methods The Initialize via TFI command in the Run Structured Solver menu for both domains and blocks is used to modify grid point locations on the interior of selected grids through application of one of several algebraic transfinite interpolation TFI Reference 9 Reference 17 Reference 19 methods TFI is automatically applied to a grid when it is first generated but can be applied manually any time thereafter as well Running the algebraic solver proceeds in three steps 1 Select
408. utton will invoke the solver and enter pause mode You may then apply the solver with the new attributes using the buttons on that menu 13 3 Grid Methods for Unstructured Domains and Blocks 13 3 Surface Shape Attributes Gridgen s unstructured solver for domains is a true surface solver in that grid points may be inserted directly on a specified geometrical shape the database This attribute is used to specify the manner in which that shape is maintained during solution The following two techniques are available Shape Free u DB d Proj Typ Lin Def 1 Lin Cur 2 ClosePt 9 Proj DBs Default 3 Picked 4 MM Show Proj DBs 7 MM Show Proj Vector 8 Align View w Proj Vector 6 Surface shape attributes are only available for domains 13 3 1 Free The shape 1s computed implicitly as a result of the triangulation method for the Cartesian coordinates x y z If the grid is constrained to the database and you run the solver with the free shape attribute then the grid will no longer conform to the database Free is the default shape attribute unless Gridgen has auto matically applied either Parametric or Parametric Fit Triangulation when the domain was created Section 9 3 In this case the default shape attribute is database 13 3 2 DB This method is used to have the grid conform to one or more database entities For best results the starting grid should already lie on the database entities which can be
409. utually exclusive When the average spacing default is set all new connectors will be dimensioned so grid points are spaced along them at arc length increments approximately equal to the value of the average spac ing default The initial value of this default is O 0 meaning this default will not be applied To change the value of the default press the Con Dim avg As button and type the new value in the Text Input window Setting the average spacing is very useful when creating unstructured grids because it allows a large number of connectors to be created and dimensioned at one time when used with the On DB Entities Section 7 4 and 2 Point Connector Section 7 3 commands The same holds true for the On DB Entities domain 3 1 Setting Defaults creation command Section 9 6 Conn Dimens Tanh Bckgr ConFun Thom amp Mid Forgr ConFun Hilgenstok UDom Min Eda from Bdry Max Eda from Bdry Max Dev n a Max Ang n a Decay 5 uie aie UBlk Max Mem Bytes SizeFac 65 0000E 01 Pyr AR 5 0000E 001 Split n le HM Join Angle DB Coord Display U QuickSave quic nue ga SET DEFAULT VALUES Con Dim Odimen Oavg s Max Ang Max Dev Con Dist Bgn As 1 End As 1 Tanh h OMR S m Bckgr CF OLaP1 1 TM 2 OFixd 3 Forgr CF None 4 OSrns 5 6 Hlgn 6 UnstrDom 4 IntPt s Decay y HinEda 7 MaxEdg 8 HaxAng 9 MaxDev 1 UnstrB1k MaxMem A2 Si zF ac 7 MinPyr 4 MaxPyr 5 Pyr AR A
410. ve Section 7 2 5 that retains its smoothness during editing 14 23 Modifying Entities 14 24 15 Miscellaneous 15 1 Name Names can be assigned to database entities and blocks Gridgen uses database entity names to associate grid with the database When you create a connector on a database entity or project grids onto the database each grid point is tagged with the name of the database entity it is on and its parametric coordinates Block names are used to identify particular blocks and for sorting Block sort order is used to determine the order in which blocks are exported The blocks at the top of the sort list are exported first The naming processes for database entities and blocks are slightly different They are each described in the following sections 15 1 1 Database Entities Each entity in the database will be assigned a unique name by Gridgen at the time of import or creation You can also assign a name to an entity via the Name command Having unique entity names is important because Gridgen associates grid elements connectors domains and blocks with the database entities via the entity name It is always necessary for the database file to be imported before the corresponding Gridgen file Gridgen will look for the database entity name that matches the entity name stored in the Gridgen file The grid database associativity via name also allows portions of the database to be varied easily For exam ple a new b
411. ve and surface entities O kbrd Move the hiliter to the typed in point Rot Pt O Move the rotation point to the current hilited point O to min f Move the hiliter to the location of the minimum value of the current diagnostic function if appropriate O to max f Move the hiliter to the location of the maximum value of the current diagnostic function if appropriate 16 5 2 Domains on h o off Ah Okbrd pad Rot Pt m O to min f O Oto max f 1 For structured surface grids and database surfaces two isolines lines of constant computational grid or parametric database coordinate are drawn through the circle hiliter glyph The glyph used for the hiliter depends on whether the current diagnostic function is point or cell based Point based diagnostic functions utilize an open circle O Cell based diagnostic functions use a glyph that outlines the cell The hiliter controls for domains are similar to those for connectors Reference 16 5 1 16 5 3 Blocks Two types of hiliter are available for volume grids topological Topo and physical Phy For structured volume grids the topological hiliter displays a constant computational coordinate plane 8 n or on which the hiliter isolines and circle glyph are drawn The glyph used for the topological hiliter depends on whether the current diagnostic function is point or cell based Point based diagnostic functions utilize an open circle O Cell based diagnostic functio
412. ve for easier reference during grid construction and other database operations 15 18 16 Diagnostic Functions EXAMINE Focus Next n Prev n Function ion None f Di Display SolidtrWire t m OLocal _0 Global 4o Hiliter ooff Le tena Topo og ilon iot Phy Jex silor sjloz m Exam ine e Y bal ae ALTI X kbrd pad Rot Pt ATM Ref Surf MPermanent crinkle c Flat liCells 5 Erase Cur djErase All d Fick Hore ent labor t esc The Examine command provides you with three sets of information regarding the selected entities and function 1 acolored display in the Display window 2 atabular listing in the Blackboard and 3 the hiliter Gf enabled When the Examine command is invoked it automatically displays the diagnostic measure you last examined or a simple listing of entity attributes if this 1s the first time the command has been invoked 16 1 Focus Entity The focus entity is the entity that is emphasized and hilited if the hiliter is enabled in the Display window If either Local mode Section 16 4 or the hiliter Section 16 5 are enabled the focus entity is also the entity to which the Blackboard text corresponds Focus Next n Prev n Focus Next Moves the hiliter if enabled and the Blackboard text 1f in Local mode to the next selected entity in numerical order If focusing on the last selected entity focus will be moved to the first selected entity Focus P
413. will be converted to a Line segment If the segment is a Bezier type you will be asked to confirm the request since all previously set slope conditions on the segment will be overwritten In the figure below the upper left connector uses linear slopes Cnvrt to Curve not for Circles or Conics The current segment will be converted to a Curve segment If the segment is a Bezier type you will be asked to confirm the request since all previously set slope condi tions on the segment will be overwritten In the figure below the upper right connector uses curve slopes Cnvrt to Akima not for Circles or Conics The current segment will be converted to an Akima Curve segment If the segment is a Bezier type you will be asked to confirm the request since all previously set slope conditions on the segment will be overwritten In the figure below the lower left connector uses Akima slopes Cnvrt to Bezier not for Circles or Conics The current segment will be converted to a general Bezier seg ment In so doing you will be asked to decide whether or not to remove all slope constraints on the segment A yes response will set the slope condition on all slope points on the segment to free so that further modification of the control point will maintain the same relative tangent vector A negative response will maintain either all Linear or cubic slope conditions on all slope points depending on the segment type before conversion
414. will then create the inter block connection To import grid points from a file and have Gridgen build a grid system connectors domains and blocks around them follow the procedure below starting from the INPUT OUTPUT menu 1 Press the Grid Pts Import button 2 Select the type of grid element connector domain or block for which you will importing grid points from the SELECT GRID ENTITY menu 4 13 Importing and Exporting Files SELECT GRID ENTITY Connector Curves 1 Surfaces 2 Yolumes 4 Abor t esc Help 3 Select the name from the Browser The default extension for the file name is grd 4 For domain and block import select file attributes from the FILE ATTRIBUTES menu below L FILE ATTRIBUTES style j OGridgen 1 PLOT3D 2 PATRAN 3 NASTRAN 4 NASTRAN L 5 o UCD 6 0 VRML 1 0 7 OSTL 2 OoFV UNS 3 QXPATCH 4 format ASCII a o binary b unfrmtd n precision single s double d O Split Ang Off b Done ent Abor t esc Help 5 Press the Done button 4 6 1 otyle The file style attribute pertains to the particular formatting of certain file types containing discrete data For grid point import Gridgen reads the following style attributes style j OGridgen 1 PLOT3D_ 2 OPATRAN 3 ONASTRAN 4 O NASTRAN L 5 UCD OVRML 1 0 7 STL O OFV UNS 43 OXPATCH 4 Gridgen style refers to
415. x for picking multiple entities at a time from the Display window is described in Section 2 4 1 2 By Text Pressing this button allows you to type in a text string and all items having your string in their Browser text will be picked get 1st When multiple pickable entities lie beneath the current cursor location the entity with the lowest entity number 1 e the first one in numerical order is highlighted Pressing the x key moves to the next in numerical order pickable entity at the cursor location default get last When multiple pickable entities lie beneath the current cursor location the entity with the highest entity number i e the last one in numerical order is highlighted Pressing the x key moves to the previous in numerical order pickable entity at the cursor location Set to off This radio button causes Gridgen to un pick the entities you select Set to on This radio button causes Gridgen to pick the entities you select Set to tog This radio button causes Gridgen to toggle the pick status of the entities you select default oort By By default entities are listed in the Browser in numerical order from first to last The radio but tons labeled Sort By provide additional context sensitive sort criteria to aid in the selection process by grouping like entities in the Browser The Sort By rev toggle button provides even further control by allow ing you to reverse the order of the current list For example in th
416. y Commands menu Section 2 9 is turned on Buttons on the Quick menu are used to save and restore orientations of the Display window image unrotate untranslate unzoom and zoom the Display window image control image manipulation sensitivities e jump from your current location in Gridgen s menu structure into another menu export a Gridgen file exit Gridgen Note that the Quick Keys Section 2 3 6 are a subset of the Quick menu There are two main reasons why you might choose to enable the Quick menu Lesser used but powerful Gridgen commands are always available on the menu This allows novice users to find and use these commands by the text description that appears when the mouse is moved over the Quick menu It also allows advanced users to find these commands without searching through the DIS PLAY COMMANDS menu By moving the Quick menu commands to the bottom left corner of the Gridgen screen the main portion of the Menu window is less cluttered for ease in navigation The Quick menu commands are g Save get the current orientation as orientation 1 G Save get the current orientation as orientation 2 93 Save get the current orientation as orientation 3 94 Save get the current orientation as orientation 4 2 6 Menu Buttons Quick Menu 95 Save get the current orientation as orientation 5 gg Save get the current orientation as orientation 6 p un pan Move the Display w
417. y are created is controlled with this toggle button Initially this default is enabled and grid points are inserted into unstructured domains when they are created according to the values of the other unstructured grid attribute defaults To disable this grid point insertion thereby reducing the compute time during domain creation press the IntPt button 3 3 1 2 Decay Factor The default decay factor qualitatively controls how far into the grid s interior the boundary cell size affects the interior cell size A value of 0 means there is no influence whereas a value of 1 provides full influence The initial value for this default is 0 5 To change it press the Decay button and type in a value in the range 0 1 3 3 1 3 Minimum Triangle Area The area of the smallest allowable triangle in an unstructured domain is specified by pressing the MinTri button and typing in the desired minimum area By default this value is not explicitly set and is instead set to the area of an equilateral triangle with edge lengths equal to the smallest boundary spacing This results in interior triangles that are no smaller than the smallest triangles adjacent to the boundary Setting this attribute establishes a global minimum on the size of triangles rather than computing and using a different value in each domain 3 3 1 4 Maximum Triangle Area The area of the largest allowable triangle in an unstructured domain is specified by pressing the MaxTri but ton and
418. y default the orien tation of the body axis system relative to the screen axis system affects how the 3D cursor moves in 3D space For example when the body axes are in their default orientation body x aligned with screen x and body y aligned with screen y horizontal mouse movement will move the 3D cursor in the body x direction and vertical mouse movement will move the 3D cursor in the body y direction If you rotate the image so that body z 1s aligned with screen x and body x with screen y then horizontal and vertical mouse move ment will move the cross in the body z and body x directions respectively Finally if the body axis system is oriented such that it is not aligned at all with the screen axis system then mouse movement will result in true 3D cross movement with all three Cartesian components of the cursor position changing The cross movement can be restricted using the Movement Restrictions button It will invoke a menu allowing you to select how the movement is to be restricted The screen x and screen y option Xs and Ys is the same as the default movement Choosing any of the other options will allow only that coordinate to be changed as the mouse is moved from left to right Movement restrictions are reset with the start of every segment when creating connectors L RESTRICT 3D CURSOR AS and Ys pad A Only pacdi Y Only pad Z Only pads AS Only paca Ys Only pacds5 2s Only Apad Normal to DB Surface 0 2
419. y factor turned on fully 1 Note how the boundary decay factor allows the small cell sizes from the circular arc to influence the size of the interior triangles Zi y Y A UN AS qo SRY V a we is S pras S DO i s xU z KOS CERA PSA SA Koa CK E 13 6 Tetrahedral Mesh Attributes The unstructured solver s grid control parameters allow you to establish the criteria by which the solver decides whether a point needs to be inserted into the grid As long a cell is larger than the minimum cell size a point will be inserted into it if any of the other grid control parameter values are exceeded 13 7 Grid Methods for Unstructured Domains and Blocks SELECT GRID CONTROL PARAM n n Tetra Memory Si ze Iterations Size Factor Ds M A Pyramid Min Height 7 Max Heiaht 8 Aspect Ratio 9 M Display 0 Set Other Attributes esc Done Setting Attributes ent Help 13 6 1 Tetrahedral Solver Memory Limit The Tetra Memory Size attribute is the maximum amount of memory to be allocated by the tetrahedral solver The default value is 64 MBytes and may be set to any value greater than or equal to 10 MBytes that the hardware platform can allow Please note it is possible for a tetrahedral mesh to be returned although not necessarily a good one even if the memory limit is exceeded A rough estimate of memory usage is 1 MByte for every 15 000 tetrahedra 13 6 2
420. y splitting include the following oplit At Constant U highlight u constant lines on a database surface for splitting oplit At Constant V highlight v constant lines on a database surface for splitting Move O via Keybrd Type in the u v coordinates to which the highlighter should be moved 14 7 2 Connectors A connector is split by moving the highlighter along its length by moving the mouse with the right mouse button pressed When the desired split location has been highlighted the connector 1s split by pressing the Split at Cursor O button A new node will appear at the split location The splitting process is illustrated in the following figure From top to bottom the figure shows the original connector the connector during splitting showing the cursor over the split location the final two connectors 14 16 Split Domains LR i gt After the connector has been split once the cursor is moved to the connector that is the ending half of the original connector allowing you to continue splitting The ending half is graphically denoted by the filled blue triangle Terminate the splitting process by pressing the Abort Dont Split button SPLIT CONNECTORS Split at Cursor O padEnt Split at Picked o pad Move O via Keyboard k O to GP via Keybd Ak to Next Grid Pt n to Prev Grid Pt An Display Segment Info d Sensit Decr lt Reset Incr gt Abort Dont Split esc Other command
421. y the formatted boundary condition and inter block connection data is written by Gridgen FANS volume grid file is multi block Gridgen style Fortran unformatted and double precision Only 3D structured grids supported 17 8 17 FDNS UNIC FDNS UNIC supports 2D and 3D structured multi block grids only Two dimensional grids must be cre ated in the x y plane Place holders for each applied boundary condition are written to the boundary condi tion file However you must modify the input variables before running FDNS 17 8 18 FLUENT v4 FLUENT v4 requires that your multiple block grid fit together into one large block If Gridgen cannot assemble your multiple block grid into a single block grid when exporting data for FLUENT v4 you will receive an error message Use the Set BCs command to check for inter block connections that are not set properly FLUENT v4 does not allow poles line singularities Instead use a small cylinder of finite radius Gridgen does not detect and warn of the existence of poles during export Both 2D and 3D structured grids are sup ported 17 8 19 FLUENT FLUENT export supports 2D and 3D grids of all cell types Export format is for the most current version of FLUENT Gridgen does not write all of the data necessary for Periodic and Periodic Shadow boundary con ditions to work properly You must make modifications to these BCs if you use them Two dimensional grids are assumed to lie in the x y plane Vo
422. y through the X Open Company Lim ited PostScript is a trademark of Adobe Systems Incorporated FLUENT is a trademark of Fluent Inc Star CD is a trademark of Computational Dynamics TASCflow and CFX are trademarks of AEA Technology PHOENICS is a trade mark of Concentration Heat and Momentum Ltd GASP and GUST are trademarks of AeroSoft Inc AVS Express is a registered trademark of Advanced Visual Systems Inc ACIS and SAT are trademarks of Spatial Corp Microsoft and Windows are registered trademarks of Microsoft Corp All other registered and unregistered trademarks are properties of their respective owner 1 DEFINITIONS a Licensed Software means any com puter program s supplied by Pointwise Inc PWI to Licensee under a valid Purchase Order or Contract whether in object code reconfigurable binary or any other form video media and training aids and any backup or other copies updates derivative works modi fications enhancements and extensions thereof b Documentation means user manuals documentation binders release notes installa tion notes written utility programs and other written or graphic materials related to the Licensed Software and all copies thereof c Licensed Product s means the Licensed Software and Documentation d Maintenance Period means the first calendar year of a perpetual license or 12 months for an annual license 2 LICENSE PWI grants to Licensee a non
423. yer Manager command or use the hot key Shift m at any time Finally Gridgen s html based help feature can be opened from the Layer Manager panel using the Help button shown below Select layer set to operate on Help Double click to restore layer set Clase 5 8 6 Creating Database Entities 6 1 Overview The collection of points curves and surfaces defining the shape of the object on and around which you will generate the grid is called the database Each individual point curve or surface within the database is called an entity Furthermore each surface entity consists of a 2D array of elements called intervals and each curve entity consists of a ID array of intervals The Create command in the Database menu allows you to add enti ties to the database Keep in mind the database has no relationship to the grid other than defining its shape The number and type of entities how they are arranged in physical space and the manner in which they are created have DB CREATION Points t Note k Curve Line d Curve e Ak ima h Conic ajCircle b Offset o Extract Ax Fit f Plane X Constant x Y Constant y zZ Constant w Pt Hormal n 3 Points 3 Coefs E Surface Ruled u Polyconic l Revolution g Linear Sweepn Fit AF Coons c Rr Auto j Done ent nothing to do with the grid s topology or number of points The database entities may overlap or may con tain gaps In fact a database isn t required for
424. ynomial curves created between successive user defined control points in the two dimensional u v space of a database entity At least two control points are required to create database constrained segments The Line Curve and Akima segment types differ in how the polynomial is computed The DB cnstr Line segment above top is a piece wise linear curve a polyline It is linear in u v space and not necessarily in x y z space as you can see from the illustration This segment type should be used whenever you want to create a connector along a constant parameter line on a database entity for example a surface s boundary You should always use this segment type when creating a segment on a database curve The DB cnstr Curve segment above center is a cubic polynomial in u v space between successive con trol points The segment will not necessarily be cubic and slope continuous in x y z space The cubic polynomial is constructed so the slope at a given control point is parallel to the chord between the two adja cent control points Catmull Rom spline At the Curve segment s end points control points from adjacent segments are used to compute the slopes If no adjacent segment exists the curve slope will be tangent to the end control point and adjacent control point Do not use this segment type if your intent is to trace a constant parameter line for example a surface s boundary or a curve entity Use a database constrained Line

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