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1. By entering 1 you ll be able to pick another connector from which the spacing will be copied This is a 4 9 Swept Ramp Basic Multi Block Structured Grid handy feature to ensure you have the same spacing on either side of a break point 2 3 Move the mouse and position the cursor over the pink image of the connector from which you want to copy the spacing 4 When the cursor is over the connector s image the pink color will change to salmon 5 Press and release the right mouse button The hand with pointing finger cursor is a reminder that Gridgen is expecting something to be picked The candidate items are those colored in pink in this case connectors sharing a common node The salmon highlight confirms the item under the cursor is pickable Pressing and releasing the right mouse button picks the connector The image of the grid points in the Display window has now changed to reflect the new clustering Also note the Browser window Connector Segments 1 Connector Dimensions 17 SubConnector 1 info Dimensions 17 Spline Linear on S Distribution TANH beg As input 1 0000E 02 As actual 1 0000E 02 end As input 0 0000E 00 As actual 3 1690E 01 As 14 15 1 85405E 01 Cursor Position x 1 375000E 00 y 2 500000E 01 z 0 000000E 00 It now also reflects the fact the As specified at the beginning of the connector is 0 01 Complete this connector as follows 1 Ending A 2 O01 3 Done ReDi
2. To compact the layer Browser list turn off the Show Empty list filter in the List Filters section of the Layer Manager panel 1 Show Empty This removes all empty layers from the layer Browser list giving you a nice condensed list of all layers that contain enabled and or disabled entities The reduced layer Browser list is shown in the next figure raver entorno E Construction All 10 Sphere Medium 15 Sphere Large 20 Cube Small 25 Cube Medium 30 Cube Large zl You now have a hint as to where that missing sphere is located Layer 831 although not labeled apparently contains some disabled entities Isolate that layer now and then enable all entities to determine what it con tains 2 Place the mouse cursor over layer 831 in the list and left click to select it It will now be highlighted in blue 3 Isolate This turns off all other layers indicated by their text in the layer Browser turning from red on to black off This command also sets layer 831 to the current working layer meaning if any new database entities were now created they would automatically be placed in layer 831 Also note that no entities are shown in the Display window since all other layers are off and apparently everything in layer 831 is disabled Now from the MAIN MENU in Gridgen proceed to the DATABASE COMMANDS menu 1 Database 2 En Disable You can now see the disabled small sphere in the DB ENABLE STA
3. 10 4 Geometry The droplet in a cylinder configuration you will use for this tutorial is shown in Figure 24 1 10 1 Droplet in a Cylinder Hybrid Grid Figure 24 1 Droplet in a Cylinder Geometry The geometry you will use to create the hybrid grid topology consists of a spherical droplet of diameter 15 0mm suspended in a cylinder of diameter 128 0mm and a height of 200 0mm The block topology is shown in Figure 24 2 The topology consists of both structured and unstructured blocks with pyramid transition cells between the structured and unstructured volumes 10 2 Getting Started Figure 24 2 Hybrid Grid Topology for Cylinder and Droplet The droplet has an unstructured surface grid from which prism cell layers are extruded into the interior of the droplet and outward into the cylinder with clustering of the grid points close to the droplet surface The remaining core volume is filled in with tetrahedral cells The cylinder has a structured surface grid from which hexahedral cell layers are extruded inward into the cylinder The ends of the cylinder are capped off with an unstructured surface grid and finally the volume between the cylinder and droplet is filled with tetrahedral cells For convenience only half of the geometry will be modeled to take advantage of symmetry 10 5 Getting Started Start Gridgen by either typing the string gridgen on Unix workstations or simply double clicking the Gridge
4. The Message window will display TRANSLATE Move the handle point with the mouse or select from the options below Solid Square is initial handle location Move the point by moving the mouse to the right while holding down the right mouse button You should see the entire connector move as you move the mouse When the 3D cursor the is over point D select Set Handle by Picking to finish moving the con nector 2 7 2D Bump Basic Skills 3 Done Translate 4 Press the Done Save Connectors button to return to the CONNECTOR COMMANDS menu If everything is going well your Display window should look like Figure 18 5 a Figure 18 5 Three Connectors form the Bottom Edge of the Bump Starting from the Connector menu create connector BG by a Create Add Segment 3D Space Line Position the 3D cursor over point B Add CP O by Picking Add CP O via Keybrd Enter the coordinates of point G 20 20 0 Done Save Segment 49 o9e de OX OE UE cbe ReDimension jmi From keybrd 11 Enter 21 12 Done ReDimension 13 Done Save Connectors 14 Done Creating Conns Connector EF is identical to connector BG so you can copy BG and translate it to the position of EF 1 Copy 2 Position the cursor over connector BG 3 Press and release the right mouse button 4 Done 5 Select the bottom end of connector BG as the translation control point the handle by positioning the
5. 1 Input Output 2 Database Export 3 composite 4 Done 5 Type In Name 6 elbow Note that Gridgen will automatically append the correct file extension dba 7 Done This completes the database creation portion of this tutorial Next we will begin creating our connectors 9 7 Creating Connectors Gridgen s one dimensional grid elements are referred to as connectors The connectors will determine the shape of your grid and the basis for its dimension and grid point distribution Before you begin creating the connectors you should use the Defaults command Section 3 1 2 of the User Manual to set an average grid spacing which will be applied to all of the new connectors you create 1 Defaults 2 Con Dim avg As 3 3 4 Done Now you are ready to begin connector creation We will begin with Gridgen s easiest connector creation tool the On DB Entities command Section 6 4 of the User Manual This command will simply take all of the database entities that you select and outline them with new connectors Curves will become single connectors and surfaces will have a new connector representing each edge of the surface Begin creating connectors now Il Connectors Create On DB Entities Select all of the entities except the first two which are the axes used for the surfaces of revolution wv ge oem Done A little additional connector clean up is necessary The circular connector MF needs to be broken at points J
6. 14 9 Domain Decimation There are many planar domains in this model but three particularly large ones on the base of the model have significantly denser triangulation than necessary We will use the domain unstructured solver to deci mate these domains 1 Run Solver Unstrctrd Select domains 1 2 and 52 Done Set Solver Attribs Grid Control Params 2 3 4 5 6 Triangle Min Size 7 0 01 8 Triangle Max Size 9 Qi 10 Done Setting Attributes 11 Tri Solver Decimate 12 Done Save The three domains should now be substantially coarser on the interior which will allow a savings on tetrahe dra count in the eventual volume grid Your grid should now appear similar to the one in Figure 26 5 14 7 Mechanical Part Basic FEA Mesh Figure 26 5 Domains After Decimation Pass 14 10 Completing the Grid Completing the grid for this part simply involves creation of a single unstructured block and using the block unstructured solver to initialize the interior with tetrahedra Create the block starting from the BLOCK COMMANDS menu 1 Create 2 Cell Type unstructured 3 Assemble Faces 4 Add 1st Face 5 Pick All Domains Note there are no bold yellow outlines of domain edges which are used to indicate the boundaries of an incomplete face 6 Savethe Face Now note the arrows rendered pointing away from the domains making up the block s face These represent the face normals and should always point into the in
7. 9 4 Geometry The pierced elbow configuration you will use for this tutorial is shown in Figure 22 1 Presumably this grid will be used with a computational fluid dynamics code to compute the flowfield inside the elbow The CFD solver is not part of Gridgen 9 1 Pierced Elbow Basic Unstructured Grid SIDE D PERSPECTIVE p FRONT Figure 22 1 The Pierced Elbow Configuration To Be Gridded The grid you will generate consists of one block filling the entire elbow excluding the region of the piercing shaft as shown in Figure 22 2 For clarity the image only shows a surface grid for the elbow itself and the shaft surface grid has been shaded Symmetry plane surface grids and inflow outflow surface grids are not displayed The choices of blocking system and grid topology are up to you this particular blocking system is only one of many that could be used for this elbow geometry The requirements of the particular analysis software you are using should be considered when planning any grid A DA XS dun PM AE ERA X Y X at FA Fe LY 2 MUR RE iN 22 ross RS pd R Nen eS Serer Ree Cc NI eec ANE ND Figure 22 2 The Single Block System To Be Used In the Elbow Now that a topology for the blocking system has been chosen we can begin creating the grid For conve nience we have assigned a naming convention to important points in the grid The points labels and coordi nate va
8. Gridgen Journal Variable ri set ri 2 66 Gridgen Journali Variable re set re 2 19 Gridgen Journal Variable ro Figure 28 5 Excerpt From File nozzle glf In order to see the grid being regenerated you should clear everything from Gridgen From the MAIN MENU press Restart Gridgen followed by Restart Go to the GLYPH COMMANDS menu and press Execute Script Use the Browser to select the file nozz1e g1f and the script will be rerun Notice the smaller nozzle exit You can experiment with changing other variables in nozzle glf to make changes to the grid You may press the Re execute Last Script button to bypass having to select the file name using the Browser You do not have to Restart Gridgen each time because of the restart commands that are included at the top of nozzle glf 13 9 Completing the Grid Completing the grid for this nozzle involves using rotational extrusion setting boundary conditions and exporting the files Before continuing you should start journaling again by pressing Append to Journal from the GLYPH COMMANDS menu and selecting the file nozzle glf Create the 3 blocks starting from the BLOCK COMMANDS menu 1 Create Cell Type structured Extrude From Doms Pick All Done Type Rot Set Attributes 9e deb Oy On a Ib Total Rotation Angle 13 6 Completing the Grid 9 Enter via Keybd 10 90 0 11 Set Rotation Axis 12 Use X Axis 13 Done 14 Run N 15 31 16 Done Next go to
9. and Angle refer to the foreground control functions influencing the angle of intersection and spacing of transverse grid lines at the four edges Notice there are four color coded fields in the foreground control function table corresponding to the same colored edges in the Display win 4 16 More Connectors and Domains dow Also note the line containing Relaxation Gridgen solves the elliptic PDEs using an explicit SOR algorithm The Browser window indicates we are using an optimal relaxation parameter by default Change the relaxation parameter and continue the solver 1 Relaxation Parameter Use Nominal Relax 0 7 Done Setting Attributes gru gp Elliptic Slvr Run When ready stop the solver and save the Gridgen file 1 Done Save 2 Done 3 Input Output 4 Gridgen Export Since the file already exists in the current directory you saved one before you can pick the name from the Browser 1 Position the cursor over the entry for ramp gg in the file Browser Press and release the right mouse button Open Yes overwrite file A oe Done Gridgen makes you confirm your file name choice when exporting to a file already existing just in case you inadvertently picked the wrong file name 4 9 More Connectors and Domains So far you have made one domain corresponding to one face of one of the blocks in the system in Figure 19 2 You can use some of Gridgen s higher level commands to speed up the remainder o
10. 1 Database 2 Modify 3 Select the intersection curve in the Display window or in the Browser list entity 11 4 Done 5 Maintain Linkage 6 Split 7 Move O via Keybrd 8 0 3 9 Splitat Hiliter 10 Select Split It 11 Modify 12 Select the remainder of the intersection curve from the Browser list entity 12 13 Done 14 Split 15 Move O via Keybrd 16 0 6 17 Split at Hiliter 18 Select Split It 19 Done Now that the intersection curve has been split into three sections you will need to create a connector of dimension two on each section At the beginning of this tutorial you set the default connector dimension to 2 so now when you create your three new connectors they will already be dimensioned for you From the MAIN MENU 1 Connectors 2 Create 3 OnDBEntities 4 Select the intersection curves three database entities from the Display window or from the Browser list entities 11 12 and 13 5 Done 6 Done The three new connectors should now appear in green along the intersection curve as seen in the following figure 6 14 Building H Block for Branch Pipe Figure 20 14 Intersection Curve Connectors Now that connectors FJ J K and K G have the same dimension as connectors FJ JK and KG you can connect their nodes so that they will be automatically merged together by Gridgen Since you want the H Block to conform to the shape of the branch pipe you will need to move poin
11. 11 Save the Face The final face corresponding to the ramp surface is comprised of two domains 1 Position the cursor over connector AH 2 Without moving the cursor press and release the x key Repeat this procedure several times Each time the x key is pressed Gridgen moves to the next candidate item under the cursor and makes it pickable Continue this process until domain AHIBA is highlighted 1 Make sure the correct domain is highlighted 2 Press and release the right mouse button 3 Move the cursor off the connector Remember this domain is only part of the face of the block Before saving the face we must pick the other domain 1 Position the cursor over connector IJ Without moving the cursor press and release the x key Make sure the correct domain is highlighted Press and release the right mouse button QW oue oe Move the cursor off the connector Examine the schematic of this face in the Browser window It shows how the two domains will be combined into a single face Figure 19 12 shows how your screen should look 4 26 Creating a Block 0 Blocks 7 Domains 15 Connectors 10 Nodes 0 DB ents STAR CD 3D ASSEMBLE 1ST FACE OF THE BLOCK Use the cursor to add a domain to the face or choose from the menu options below use x to cycle picks ASSEMBLE 1ST FACE Pick Multiple Doms m All Domains 1 Adjacent Doms j MDomain Once 1 EraseDom L P i kd 9 Last del Merge Nodes
12. 14 11 15 Done 16 Done Creating Conns The airfoil length is one unit 1 0 so entering 11 for the length of the wake connector puts the exit boundary at 10 body lengths downstream This distance is a typical value for many analysis problems Also when you entered only a single number 11 Gridgen used this as the x coordinate and assumed the default values for y and z To change only the y coordinate value you would enter 11 so that Gridgen would use the default x and z Likewise for updating the z coordinate enter 11 Your final connector work involves this last wake connector At its beginning it has the default spacing you setearlier You really want it to match the spacing at the TE of the airfoil connectors You can Modify it to make this change 1 Modify 2 Pick the wake connector 3 Done 4 ReDistribute 5 Begin A 6 1 Entering negative one 1 instructs Gridgen that you wish to copy a spacing from the other side of this par ticular BreakPoint It highlights in a deep pink color the candidate connectors for you to select one from The spacing from the end of the candidate connector you choose will be copied to the connector your are currently modifying 7 Pick either airfoil connector since both have the same TE spacing 3 3 2D Airfoil Re Extrude 8 Done ReDistributing 9 Done Replace Connectors This completes the connector creation phase of this tutorial Use the r hot key on the keyboard
13. DOMAIN COMMANDS menu 1 Copy 8 9 LDI Combustor Advanced Structured Grid Pick All Done Abort Don t Translate Rotate Enter Axis_1 via Keybrd On 2 55 0 Use Z directed Axis 9 Enter Rotation Angle S31 9A FON 10 45 11 Done Rotate 12 Save Domains 13 Done Repeat steps 1 13 for 90 and 180 angles of rotation each time selecting all domains The Display window should look like Figure 22 14 on the next page Figure 22 14 Copied Domains Between Passages You are now ready to proceed to the next phase of the grid construction process 8 11 Creating Boundary Topology You are now going to create the connectors defining the topology around the swirler passages and the burner boundary We will be referring to the labeling conventions shown in Figure 22 15 Figure 22 15 Labeling Convention for Boundary Domains First set a new default number of grid points from the MAIN MENU 1 Defaults 2 Con Dim dimen 35 410 4 Done Now begin creating the connectors 1 Connectors 2 Create 3 2 Point Connectors Connector GH 1 Place the 3D cursor over point G 2 Add CP O by Picking 3 Add CP O via Keybrd 4 0 Connector HI 1 Place the 3D cursor over point H 2 Add CP O by Picking 3 Add CP O via Keybrd 4 0 2 Connector GJ 1 Place the 3D cursor over point G 2 Add CP O by Picking 3 Add CP O via Keybrd 4 2 Connector IJ to close domain GHIJ 1 Place the 3D
14. Done Save Connectors You have now completed a parametrically defined connector that spans two different database entities In order for these DB Cnstr segment types to be successful a minimum of two control points must be saved on each database entity The small piece of the connector you made approximately 0 1 in length is referred to as a branch segment Section 6 2 2 of the User Manual That portion of the connector is not constrained to either database entity and must have a small but finite length in order for Gridgen to not convert it to a pole segment or singularity Next make a connector that goes around the centerbody from the top to the bottom 1 ph Oy Us ee 9 Add Segment DB Cnstr Line Add CP O by Picking Position the 3D cursor at the back bottom corner of the same surface Add CP O by Picking Done Save Segment Done Save Connectors Make database constrained connector EI in the same way Decem m9 Add Segment DB cnstr Line Add CP O by Picking Position the 3D cursor at the front bottom corner of the same surface 7 9 B 747 Nacelle Working With An IGES Database 5 Add CP O by Picking 6 DBEnt Pick 7 Select the lower centerbody nose surface 8 Move the 3D cursor slightly forward until the Distance to Last Point is approximately 0 1 9 Add CPO at 10 Position the 3D cursor at Point E 11 Add CP O by Picking 12 Done Save Segment 13 Done Save Connectors 14 Done Creating Conns
15. Figure 19 2 The Two Block System to be used for the Swept Ramp Now that a topology for the blocking system has been chosen we can begin creating the grid For conve nience we have assigned a naming convention to important points in the grid The point s labels and coordi nate values are shown in Figure 19 3 and followed by a tabular list Note these particular locations for the outer boundary points may not be adequate for a CFD simulation the outer boundary may need to be farther away from the ramp in order to minimize the boundary condition s influence on the flow 4 2 Getting Started Figure 19 3 The Ramp s Labeled Coordinates List of Swept Ramp Coordinates Label X Y Z a 0 00 0 00 0 00 b 0 75 0 00 0 00 c 2 00 0 50 0 00 d 3 00 0 50 0 00 n 0 00 12 50 1 00 45 Getting Started Begin by starting Gridgen presumably by typing the string gridgen on Unix or by simply double click ing the Gridgen shortcut on your PC s desktop The Gridgen logo will disappear after a few seconds or as soon as you invoke your first menu command The first step in running Gridgen is to select the software Section 17 1 to be used in the analysis This will ensure the grid generated by Gridgen is consistent with 4 3 Swept Ramp Basic Multi Block Structured Grid the capabilities of the analysis software For this analysis we will be using the STAR CD flow solver by default Gridgen selects the generic sol
16. Now note a few aspects of these 58 domains First there are three areas where Gridgen followed the topol ogy of the underlying database and created two separate domains rather than a single 360 degree domain wrapping around the geometry In terms of defining the shape properly a single domain would have been sufficient in each case To observe the second more serious issue proceed to the CONNECTOR COMMANDS menu 1 Merge Conns 2 0 01 Note there are several pairs of coincident connectors in the Browser list It means that the mesh is not closed due to gaps in the database Normally this kind of issue only becomes evident or a problem at the block face creation stage of the grid However these could have been eliminated at the domain creation step as you will see in the next section allowing the problem to be avoided altogether While in the MERGE CON NECTORS Browser note some pairs of connectors are listed with a dash between them and some with an exclamation point Dashes indicate connector pairs with equal number of grid points exclamations indicate nonequal connector dimension Simply Abort from the MERGE CONNECTORS Browser since we will not be continuing with these domains 14 8 Creating Unstructured Domains Second Pass Now we will restart this Gridgen session and create the domains again using some additional functionality From Gridgen s MAIN MENU Restart Gridgen 2 Turn off the Clear DB toggle since we wish t
17. This sample session is a short introduction to using feature extraction Basic Gridgen skills you will learn are importing STL shell surfaces into Gridgen using the Database Import command using the Feature Ext command to split the shell surfaces into discrete database entities automatically create domains using Con Split and Set Angle commands to ensure that nodes and con nectors are created at feature lines creating blocks from the domains to form the structured volume grid 11 3 Background You should complete all previous tutorials before attempting this session since it assumes you already have the skills covered in them 11 4 Geometry The geometry to be meshed is a 3D tension bar shown in Figure 25 1 The tension bar geometry is provided in STL format and is comprised of triangular faceted shells that form the model The grids will be generated by first splitting the model into discrete database entities and then applying Gridgen s On DB Entities tool to generate the surface grid 11 1 Tension Bar Feature Extraction Figure 25 1 Tension Bar Shell Geometry 11 5 Getting Started Start Gridgen by typing the string gridgen on Unix workstations or by simply double clicking the Gridgen shortcut on your PC s desktop 11 6 Import Shell STL Model The first step in this tutorial is to import the shell model The tension bar geometry you will use for this tuto rial is an STL file named tension stl Itis located in th
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19. 4 Swept Ramp Basic Multi Block Structured Grid 4 1 4 1 IBIFOGUCHOIO soe 4 1 4 2 TODICS COVO ed ERO RD a aa E uL 4 1 Bid Background iiie oit ioo ot ot o od o Mes ederet AM petu danas 4 4 1 LI EC iii EC 4 1 45 Gelling Started eo dp e ote trapo ate Eee abate doqe Deep treo Mase 4 3 4 6 Drawing Connectors 4 e tie vinos biete bene tapered iedraiboc te demise bs 4 4 4 7 Creating A DOmalli eo ERR b eb Le ae ec cut etes 4 12 4 8 Running the Elliptic PDE Solver sse 4 15 4 9 More Connectors and Domains 1 11 sessi 4 17 410 Cheating a Block doc pta bestie eni boda beo atus tds 4 25 4 11 Creating the Second Block s sse 4 29 4 12 Running the Elliptic PDE Solver on Volume Grids 4 32 4 13 Volume Grid Inspection ssssssssssssssssseee enn 4 32 4 14 Customizing the Grid for the Analysis Software 4 33 5 Intersecting Pipes Pole Grid Construction Bottom Up 5 1 5 1 Introduction oo b DE IER UNE IR nes EO ESAE Mc tuned 5 1 5 2 TODIOS COVOtG U o eto iita tbe a idolo ite 5 1 5 9 BACK OFOUNG oH ME au ie aU ee MU EE 5 1 EP dcin H 5 1 5 5 Gelling Slane oo dio x obe uiid c hs ba beide 5 2 5 6 Creating a Database oe oiu tenter ip eA pA ue eed 5 2 5 7 Drawing Connectors cu i rero rit ione nea b
20. A script such as this is relatively easy to construct and essential to the process of construct ing a mesh through a top down method Of these three types of blocks offered only the H Block and the Polar block will be used for this tutorial The block topology which will note be used the T Block consists of two H Blocks which adjoin at one face to form a topology roughly in the shape of a T Please feel free once you have completed this tutorial to experiment and try this block and the others offered on other data base models For the main pipe we will want to use a polar block to create the O grid topology mentioned earlier Assuming that you have copied the file block gui glf into your current working directory from Grid gen s MAIN MENU 1 Glyph 2 Execute Script 3 block gui glf A small interface will appear as seen in the following figure Ready Made Blocks Grid Type H Block Polar C T Block Run Cancel 6 4 Building Polar Block for Main Pipe Steps 4 5 require you to make your selections from within this interface 4 Polar 5 Run 6 Done The polar block should now be loaded in the Display window as seen in the following figure Figure 20 5 Polar Block The next few steps you take will be to scale and align this block to fit the geometry The polar block created by this script is 10 units in length along each edge with the pole running from x 0 y 0 x 5tox 10 y 0 z 5 The main pipe has a
21. Add Segment 3D Space Line Add CP O by Picking Press and hold the right mouse button Dh gta Des pe Move the cursor using the mouse until the 3D cursor is positioned over the node corresponding to Point G Release the right mouse button Add CP O by Picking Done Save Segment 39 2 290 ci ON ReDimension 10 Position the cursor over the connector corresponding to connector AB Press and release the right mouse button 11 Position the cursor over the connector corresponding to connector BC Press and release the right mouse button 12 Done ReDimension 13 Done Don t Copy Dist 14 Done Save Connectors 15 Done Creating Conns 16 Done You just drew a straight connector between Points F and G told Gridgen to put as many grid points on con nector FG as there are total on connectors AB and BC and told Gridgen not to copy the distribution of points but to use the default equal spacing 4 11 Swept Ramp Basic Multi Block Structured Grid You should now see something similar to Figure 19 5 Figure 19 5 All of the Connectors for the Ramp s First Domain Usually this type of display gets too cluttered so turn off display of connector grid points again 1 Disp 2 Show Con GPs 3 Done 4 7 Creating A Domain The connectors you have drawn form the perimeter of one of the surface grids to be used in the blocking sys tem in Figure 19 2 specifically we have drawn the perimeter of the min face of the ups
22. Advanced Structured Grid Figure 22 25 Inlet Block of Burner 8 16 Creating Blocks for the Passages You now need to create the blocks for the eight elliptical passages This will be done again using the extrusion command Before you do this turn on the swirler passages database entities from the DISPLAY COMMANDS menu then from the MAIN MENU Blocks Create Extrude From Doms Pick the domain of passage entity 9 Done Type Tran Set Attributes Qoo ee iN om Total Translation Dist You are now going to pick the two endpoints which define the distance and vector direction of the extrusion operation as shown in Figure 22 26 on the following page R EP2 Figure 22 26 Endpoints for Translation Extrusion Operation From the TRANSLATION DISTANCE menu 1 Pick Endpoints 8 20 2209292070 PY DN 0 1 i25 13 Pick Endpoint EPI Pick Endpoint EP2 Done Setting Distance Set Translation Vector Pick Endpoints Pick Endpoint EPI Pick Endpoint EP2 Done Setting Vector Done Run N 10 Done Creating Blocks for the Passages Zoom and reorient the view around passage entity 9 the Display window should now look something like Figure 22 27 on the following page You will now copy and rotate the passage entity 9 block 1 2 3 4 5 6 8 9 1 0 Copy Pick block of passage 9 Done Abort Don t Translate Rotate Enter Axis 1 via Keybrd 0 5 22 5 0 Use Z directed Axis Enter Rotation Angle
23. Because we are using linear projection we need to align the view with the direction in which we want the grid projected An easy way to get the right view is to first hit the r hotkey to restore the default view Then while holding down the Page Down key press the Pad key to get a 90 degree rotation about the y axis Done Project 10 Save Domains 7 7 B 747 Nacelle Working With An IGES Database Figure 21 4 First Two Domains of Block 1 You should now have the two domains shown in Figure 21 4 Rotate the view to verify that the grid points and connectors of the domain you projected are on the database surface The procedure you just went through is one of the ways that you can conform the grid to the shape of the geometry We will look at some others during the construction of the second block You are on your own for the remainder of the construction of the first block You should have already com pleted the previous tutorials Create the four remaining connectors for this block AE BF CG and DH as 2 Point Connectors Use them to create the four other domains ABEF BCGF CDHG and DAEH Finally put the block together using one domain for each face Save the grid after you complete the first block 7 8 Creating Block Two Now you are ready to begin the construction of the second block Before beginning turn off the display of the domains in Block 1 so that the Display window is less cluttered 1 Disp Edit Dspla
24. Me ooo c ON IONS ES OA a Done Project ja Replace Domains ae Maintain Linkage Figure 21 5 Centerbody Domain Before Projecting Now when you rotate the image you should see that the grid is on the database The domains on the centerbody can be improved by refining them with Gridgen s elliptic PDE methods We will modify some of the elliptic solver attributes to ensure that the domains stay on the database surfaces and to let the boundary between the two domains on the centerbody float to a new position resulting in higher grid quality Run Solver Structured Select the two domains on the centerbody surface domains 2 and 7 Done Set Solver Attribs Apply to All Solver Bound Conds Floating Done Setting Attributes x oe c NY Ux gRO to R9 Elliptic Slvr Run N Iters 7 11 B 747 Nacelle Working With An IGES Database 10 30 11 Done Save Your grid should now look like the one in Figure 21 6 Note that the connectors between the two domains are a different shape now than they were before running the elliptic solver By setting the Floating bound ary condition you told Gridgen to let their shape be computed as part of the PDE solution just like they were interior grid lines Not all of the connectors moved even though we used Apply to All for the floating boundary condition because it only applies to conn
25. Now the Saved Layer Sets Browser should be updated as below m Saved Layer Sets Construction Save Restore Delete X Spheres To restore a saved set select it in the list and use Restore or simply double click the entry in the list You can remove a set by selecting it and choosing the Delete command Note that the save sets you have made also include the current working layer layer 0 Verify this by setting some other layer as current and then restoring one of the saved layer sets Congratulations You have completed this tutorial While you have not used all of the Layer Manager commands and capabilities in this tutorial you have used nearly all of them and certainly the most fre quently used Feel free to experiment further with this model and the layering changes you have made Other tutorial database models that would make interesting cases for layer experimentation would be the intersecting pipes model in Section 5 the 747 Nacelle model in Section 7 the LDI combustor model in Sec tion 8 and the mixer model in Section 12 1 12 2 2D Bump Basic Skills 2 1 Introduction This section includes a brief tutorial to help you become familiar with the basic operations of Gridgen If you have never used Gridgen before you should work through this and the other tutorials before applying Gridgen to actual problems 2 2 Topics Covered This sample session is a short introduction to using Gridgen Ba
26. Pick the connector corresponding to connector GN in Figure 19 3 Pick the node corresponding to Point G in Figure 19 3 Press and hold the right mouse button Move the cursor over the node corresponding to Point F in Figure 19 3 Release the right mouse button Set Handle by Picking Done Copy Connector Copy Break Point Info Done Save Connectors 4 21 Swept Ramp Basic Multi Block Structured Grid 22 Add Segment Others Copy Pick the connector corresponding to connector FM in Figure 19 3 Pick the node corresponding to Point F in Figure 19 3 Press and hold the right mouse button Move the cursor over the node corresponding to Point C in Figure 19 3 Release the right mouse button Set Handle by Picking Done Copy Connector Copy Break Point Info Done Save Connectors The final connector connector BI corresponding to the leading edge of the ramp will be drawn using a straight line segment OOO sed UON S des s B e n Ny oc 13 Add Segment 3D Space Line Position the cursor over the node corresponding to Point B in Figure 19 3 Add CP O by Picking Position the cursor over the node corresponding to Point I in Figure 19 3 Add CP O by Picking Done Save Segment ReDimension From keybrd xd Done ReDimension Done Save Connectors Done Creating Conns You should now have all the connectors shown in Figure 19 10 4 22 More Connectors and
27. The green dots at either end of the connector are the nodes Recall nodes are the control points at the ends of a connec tor Create another connector and this time we will look more closely at what Gridgen is doing The second con nector to draw is connector AB in Figure 19 3 the horizontal connector from the leading edge of the grid to the leading edge of the ramp We will begin by doing the following 1 Create 2 Add Segment 3 3D Space Line Gridgen is now in segment drawing mode The first item you should identify is the small white cross in the Display window This cross is Gridgen s 3D cursor and is used to define the control point locations Also identify the Browser window on the left side of the screen It will be displaying information about the con nector segment and control point you are currently creating In fact it should currently look like Connector Segments 1 Connector Dimensions 0 Cross Position x 0 0000000E 00 y 1 5000000E 00 z 0 0000000E 00 The Display window and Browser window both reveal the 3D cursor is located at point G from Figure 19 3 However we are drawing connector AB Instead of typing in the control point coordinates as we did on the previous connector this time we will use another control point method Specifically we will tell Gridgen to place a control point at the node corresponding to Point A Do the following 1 Press and hold the right mouse button 2 Move the mou
28. We are almost ready to make another domain First we need to redimension some connectors in the first block 1 Redimension Grids Select connector EF 8 Select connector FG 16 De ape dues oS Done Apply New Dims Now make the domain 1 Doms 2 Create 3 Assemble Edges 4 Make sure Auto Next Edge and Auto Complete are toggled on 5 Pick connector HJ 6 Pick connector JI Gridgen will recognize that connector IE is the next edge and will add it to the domain 7 Pickconnector EF Gridgen will recognize that connectors FG and GH are needed to complete the domain and will add them 8 Done The Display window should now look like Figure 21 5 Rotate the image and note that the domain does not lie on the database surfaces It is actually easy in Gridgen to know immediately upon creation which domains are database constrained automatically and which are not When they can be constrained automati cally Gridgen renders them in a purple color if not they are green See the end of Section 7 2 of the User Manual for more details regarding the algebraic methods used to initialize structured domains Gridgen was not able to automatically constrain this domain because it spans multiple database surfaces Before proceed ing put it on the database by projecting it 1 Modify 7 10 Creating Block Two Select the newly created domain domain 7 Done Project Cylindrical Use X principal Axis Proj Out Int Pts
29. n Conns c Nod Con 2 Auto a Pick k Update d TopoF ltr 4 A11 3 OoFree 4 ONonMnfldtFree 5 FaceFltr A11 6 OBndry y Outsd d Save the Face ent AutoSave e Off o Face c Abort esc Help Figure 19 12 The Browser Shows How the Two Domains Form One Face of the Ramp s First Block 1 Save the Face When you save the sixth face Gridgen assembles all of the domains and places their surface grids on the exterior of a volume grid Gridgen also chooses a default orientation of the computational axes which are displayed according to a red E orange n yellow C scheme Since Gridgen s selection of computational axes may not be what you wanted it lets you manually redefine the axes if you want In this block we want to run in the x direction n in y and Gin z Try this now 1 ReSpecify n G Position the cursor over any of the four block edges that run in the direction Press and release the right mouse button amp direction Position the cursor over any of the four block edges that run in the y direction Qv Uv xb c bs Press and release the right mouse button 4 27 Swept Ramp Basic Multi Block Structured Grid 7 1 direction 8 direction It is hoped you noticed each of the color coded connectors has an arrow pointing in the positive index direc tion Each block must be given a unique name when using the STAR CD analysis software Do that now 1 ReName 2 upstream 3 Do
30. 12 More Descriptions iridis conos locas cerra su qU RU RD 3 o ayaa eens 1 10 1 13 Saved Sets MM ee ee 1 11 2 2D Bump Basic Skills 00 0 0 cece ceeseteteesesseseeecseeecaeeaseeeeseesaeaeaeees 2 1 Ego 2 1 2 2 Topics Covered 2 1 2 3 BaCKgr Nd pasene EE EE A EREE REEE EEA 2 1 24 GEOmMetry SE 2 1 PASE CE eeen 2 2 2 6 Draw Connectors MM I 2 2 2 7 Create a Structured Domain sss 2 10 2 8 Refine the Structured Domain Grid ssssssssssssss 2 11 2 9 Create an Unstructured Domain sss 2 12 2 10 Tutorial Wrap up io ene c cis icd acid oiu ds acaba oca tuc od rdi ap edu d da Ge 2 13 3 2D Airfoil Re Extrude sida oet od s ocu n Ge pa ean UR qud nes 3 1 KE pes mm 3 1 3 2 TODICS Cov ed M 3 1 EN E LebQp M 3 1 EN cou P EE Oe an ere E re ere 3 1 3 5 Start Gridgen ice E 3 2 3 6 Database Model Import ssssssssssee rne 3 2 37 Sel Defallls uo or SERE dte d e end 3 2 3 8 Connector Creation srs evinces e wt RE Ru eas ee 3 2 3 9 Domain Extrusion orci oerte ER epis tata Ring ti etui 3 4 3 10 RHe EXITUUe oe Suede veins baits ira eR desea asus 3 6 3 11 2D Block Creation and ASW Settings sssssssssus 3 8
31. 14 1 14 4 14 6 structured example use 2 0 4 12 unstructured example use 2 2 9 9 project example use 7 7 domains create On Database Entities example use 71 5 Droplet in a Cylinder 0 E elliptic PDE solver attributes boundary condition floating example use 7 17 example use 73 5 running example use 4 5 Examine example use 9 4 14 9 F Feature Extraction feature extraction example use 71 1 Finite Element Analysis example use 74 1 G Glyph example use 3 Add Variable 3 3 Append to Journal 73 2 grid extrusion hyperbolic Hyp example use 70 14 normal Nrml example use 10 7 10 11 rotational extrusion example use 3 6 translational Tran example use 8 19 H Hybrid Grid 70 7 hybrid grid example use 70 1 I Import working with an IGES database 7 7 L Layer Manager tutorial M merge connectors example use 72 5 Mixer 2 Multi block Structured Grid 4 7 P picking example use 5 4 Pierced Elbow 9 7 R Re Extrude 3 S Set BCs example use 9 16 12 7 Set As Values example use 13 4 Swept Ramp 4 7 T Tension Bar U Unstructured Grid 9 7 unstructured grids block create example use 4 8 solver example use 9 13 14 7 14 8 unstructured solver example use 9 13 14 8 Using Baffles 2 Using Glyph Scripting 3
32. 19 7 Gridgen Automatically Creates the Ramp s Domain Mesh When You Close its Perimeter By examining the Browser and Display windows you can see we have defined the perimeter of a surface and mapped the surface into a four sided region with 31 x 21 grid points Furthermore in the connector cre ation process we distributed grid points along each of these connectors which provided the input for generat ing the surface grid We recommend you get in the habit of saving your work to a file at regular intervals in case there s a hard ware problem Let s do that now 1 Done 2 Done 4 14 Running the Elliptic PDE Solver 3 Input Output 4 Gridgen Export 5 Type In Name 6 ramp 7 Done You just exported a Gridgen file called ramp gg gg is the default extension The Gridgen file is the main file type used by the code and contains everything from nodes through blocks and display information Every grid you make will have a Gridgen file This file can be used to restart the work to continue construc tion of a grid or to modify an existing grid 48 Running the Elliptic PDE Solver As mentioned during the domain creation discussion an algebraic method specifically transfinite interpola tion is used to initialize the grid points within a domain This grid may not be acceptable for your analysis code due to skewness or clustering problems Because of this Gridgen provides elliptic PDE methods to allow you to make the domain grid
33. Browser or graphically multiple break points at once and set them to the same spacing constraint value Since you have three spacing variables to apply you will only need to select and specify three groups of break points D5w DS5u Figure 28 3 Locations to Apply Variables Start with break points corresponding to DSi Beginning on the CONNECTOR COMMANDS menu 1 Set As Vals 2 Selectthe two break points corresponding to DSi in Figure 28 3 3 Done Note that the text input window is hilighted and expecting you to type in the desired spacing value Also note that the Browser contains a list of all variables defined by the journaled script and the three you just cre ated 4 Select DSi from the Browser and enter 5 Use Figure 28 3 to apply spacing constraints all around the rest of the grid 6 Done When you are done the grid should look like the one shown in Figure 28 4 13 4 Script Editing and Playback Figure 28 4 Spacing Constraints Applied To complete the symmetry plane grid you should run the elliptic PDE solver on the domain representing the nozzle s interior Proceed to the DOMAIN COMMANDS menu O Run Solver Structured Select the interior nozzle domain ABFEDC Done Set Solver Attribs Foreground Cont Funcs Select edge BF by filling the colored square corresponding to that edge Edges Set aCalc Interpl We coe cL ON Ue Ee o9 S Done Setting Attributes Note that because you a
34. Extraction You are now going to use the Feature Extraction tool to extract geometry from the shell surface From the MAIN MENU DATABASE COMMANDS Import i Expor t FEATURE EXTRACT Create n Modi y Copy c Delete Feature Ext Select Entities 1 Debug b Set Split Ang 2 Name Extract MSurfaces 3 Group MCurves 4 Exam ine e En Disable Done ent Abort esc Cons C Doms D DB Dflt T 1 o E AS W A GlyphY Quit a Disp a Help 1 Database 2 Feature Ext 3 Select Entities 4 All 5 Done 6 Set Split Ang du 45 8 Turn the Extract Curves toggle off 9 Run The original shell surface has now been split into ten discrete surfaces as shown in the Browser on the next page 11 4 Creating Structured Surface Grids FEATURE EXTRACT Paused Selected 1 entity Split Ang 45 0 deg 100 X 1 shell split into surfaces 10 FEATURE EXTRACT ReRun s ReSelect Entities 1 Set Split Ang 2 Extract MSurfaces 3 Curves 4 Done ent Abort esc The Display window should look like Figure 25 3 The thick yellow lines in the Display window indicate the boundaries of the new shell surfaces resulting from the splitting operation Figure 25 3 Feature Extraction 10 Done 11 Done To view the individual shell database entities you can change the display style in the DISPLAY COM MANDS menu 11 9 Creating Structured Surface
35. Glyph file should be available in your Gridgen installation directory under gridgen home path exam ples tutorial glfnoz Since journaling using the Append to Journal feature will modify the selected file you must create a copy of the original Glyph file nozzle g1f and append to the copy It is not likely that you would have write permission where the original is installed and the original should be preserved for other users who wish to work this tutorial Another Glyph script file noz all glf is included that generates the entire grid for this tutorial From the MAIN MENU 1 Glyph 2 Append to Journal 3 Use the Browser to navigate to the directory containing the copy of nozzle g1f and select it 4 Open Watch as Gridgen builds the connectors and domains on the symmetry plane Note the orange text JOUR NALING TO nozzle glf inthe Display window s upper left corner This is a reminder that the script equivalents of commands you execute will be appended to the file nozzle g1f and will continue to be journaled until you use End Journaling in the GLYPH COMMANDS menu There is a small percentage of Gridgen s commands that cannot yet be journaled Commands not available for journaling will be grayed out in the Gridgen interface 13 2 Setting Variables for Spacing Constraints Figure 28 2 Connectors and Domains After Script Execution As you can see in Figure 28 2 the spacing constraints on the connectors have not been set This is what
36. Gridgen User Manual before attempting this one since it cov ers advanced topics and assumes you already understand the basics covered in previous Gridgen tutorials You should also read Section 12 and Section 13 to familiarize yourself with the advanced topics covered in this tutorial 8 4 Geometry The multi point LDI combustor as shown in Figure 22 1 has a rectangular inlet section 0 5 inches long and is upstream of nine groups of swirlers arranged in a 3 by 3 pattern Each group of swirlers comprises eight passages all co rotated at 35 in the tangential direction A 7 5 inches long rectangular burner duct is downstream of swirler section The combustor has a cross section of 3 inches by 3 inches as indicated by a square box placed around the swirlers 8 1 LDI Combustor Advanced Structured Grid Figure 22 1 The Multi Point LDI Combustor Geometry For simplicity you do not have to model the whole combustor since the geometry can be considered as a grouping of nine sets of identical discrete combustors The topology is divided into a single combustor section consisting of an inlet section eight passages and a burner section as shown in Figure 22 2 The blocks I J and K directed grid lines will align in the positive x y and z directions respectively This tutorial will guide you through creating the inlet section block and the passages but leave the burner section for your own practice Inlet Block Passages Burner
37. Gridgen by typing the string gridgen on Unix workstations or by simply double clicking the Gridgen shortcut on your PC s desktop After a few seconds Gridgen will start and you will see the Gridgen logo in the Display window The logo will disappear after a few seconds or as soon as you select your first menu button 3 6 Database Model Import To begin the tutorial import the composite geometry file reext dba This file should be available in your Gridgen installation directory under gridgen home path examples tutorial reext You may wish to copy the file to some other working directory before proceeding From the MAIN MENU 1 Input Output Database Import Use the Browser to navigate to the directory containing the copy of reext dba and select it Jet pas Ib2 Done In your Display window you should now see the database model as displayed in the previous figure 3 7 Set Defaults Before creating your initial connectors you can save some time later by setting a few connector defaults now From the MAIN MENU 1 Defaults 2 Con Dim dimen 3 31 4 Con Dist Bgn As 5 0 01 6 Done All newly created connectors will now have a default dimension number of grid points of 31 They will also each have a spacing constraint of 0 01 at their beginning See Section 3 1 of the User Manual for more details 3 8 Connector Creation You will now create three connectors that will eventually be extruded into your new C style grid The f
38. Grids You are now ready to create structured domains on the shell database entities From the MAIN MENU 1 Domains 11 5 Tension Bar Feature Extraction Create Cell Type structured Turn the Con Split toggle on Set Angle 45 On DB Entities Pick All Done oo Oe Oyo eS The connector split angle ensures connectors are split at feature edges and nodes are correctly created at the ends of these edges Note only eight domains are created automatically The Display window is shown in Figure 25 4 Figure 25 4 Domains on Database Surfaces You now need to create manually the remaining domains defined in Figure 25 5 These close off the sides of the tension bar to form the faces defining the volume of the block Figure 25 5 Domain Labelling on Tension Bar 11 6 Creating Blocks You may want to orient your view as shown in Figure 25 5 as you will be creating the domain nearest to you defined by connectors ABCDEFG From the DOMAIN COMMANDS menu Create Assemble Edges Turn the Auto Next Edge toggle off and turn the Auto Complete toggle on Pick connectors AB CB then CD Next Edge Pick connector DE Next Edge Pick connectors EF then FG SO toon I IOS C CAI spe Xx LES Pick connectors that form the opposite face of the tension bar 10 Done Turn off the database entities to more easily view the surface grid From the MAIN MENU 1 Disp 2 Turnthe Show EnbIdDB toggle off 3 Done The s
39. The Text Input window is the bar immediately above the Blackboard window Add CP O Axyz via Keybrd will allow you to type offsets of the current 3D cursor x y and z coordi nates to position the new control point 2 4 Draw Connectors Add CP O by Linear Proj will add the point by projecting from the current 3D cursor location in a direc tion normal to the plane of the screen until a database entity is hit Add CP O at Clsest DB Pt will add the point by projecting from the current 3D cursor location to the closest point on a database entity For this tutorial 1 Select Add CP O via Keybrd 2 Enter 10 0 O After entering point C s coordinates look at the Blackboard window It should indicate that there is 1 control point and the cross position is C10 0 0 The Message window should be prompting you to enter the end ing point of the circle CIRCLE Enter the ending point of the circle 1 Select Add CP O via Keybrd 2 Enter10 O0 0 Now the Message window should display EDIT CIRCLE POINT ove the selected point and select from the options below This is your indication that a third point is needed to define the circular arc You have a choice of entering a point that lies on the arc or entering the center point of the arc Since you know the circular arc center point you may enter its coordinates using 1 Select Store Center via Kbrd 2 EnterO 8 O0 The Gridgen Display window should now l
40. become familiar with creating basic 2D extruded grids as well as with Gridgen s Re Extrude capability This capability allows you to return to a previously saved extrusion and make changes to it These possible changes are backing up continuing from the previously saved final step and changing attributes 3 2 Topics Covered This sample session is a short introduction to using Gridgen Basic Gridgen skills you will learn are importing a database model using Database Import setting connector defaults using the SET DEFAULT VALUES menu connector creation using 2 Point Connectors creating a C style airfoil grid using hyperbolic domain extrusion changing a saved extrusion using Modify Re Extrude 3 3 Background You do not need to run any other tutorials before running this one However please read Section 2 of the User Manual to familiarize yourself with the operation of the Gridgen user interface before attempting to run this tutorial 3 4 Geometry For this introduction to Gridgen s Re Extrude command we will work with a geometry model consisting of two curves forming a simple 2D airfoil Our final grid will be a C style 2D mesh The model is shown in Figure 1 10 below Figure 1 10 Database Geometry Model 3 1 2D Airfoil Re Extrude This is purely a contrived problem for demonstration purposes however the operations to be demonstrated will be common to any models you work with in Gridgen 3 5 Start Gridgen Start
41. button to swap the direction of the string of connectors Done ReDimension Done Don t Copy Dist Done Save Connectors Done Creating Conns This is the last connector you need to create Let s turn on display of the connector grid points so you can see how the grid points are distributed 1 2 3 Press Disp in the Quick Keys Show Con GPs Done 2 9 2D Bump Basic Skills The Display window should look like Figure 18 6 on the following page Figure 18 6 Grid Points are Distributed on the Bump s Connectors 2 7 Create a Structured Domain You will now tell Gridgen how to make a surface grid from the connectors you just created 1 Select the quick key Doms from the bottom of the Menu window to go to the DOMAIN COMMANDS menu 2 Select Create to start making a domain The Message window will change to CREATE A DOMAIN Specify the cell type and then select a technique below for constructing a domain and the CREATE DOMAIN menu will appear Make sure that the Cell Type structured radio button is selected Then begin the domain creation process by selecting the loop of connectors that form the perimeter of the domain 1 Select Assemble Edges 2 Check the Auto Complete box The corners of the domain will be at points B E F and G so you can pick any connector except CD as the first one For this sample start with connector EF 3 Position the cursor over connector EF 4 Press and release the ri
42. cursor over point I 2 Add CP O by Picking 3 Place the 3D cursor over point J 4 Add CP O by Picking Connector AK 1 Place the 3D cursor over point A 2 Add CP O by Picking 3 Add CP O via Keybrd 4 2 Connector JK to close domain ADEFJK Creating Boundary Topology 8 11 LDI Combustor Advanced Structured Grid 1 Place the 3D cursor over point J 2 Add CP O by Picking 3 Place the 3D cursor over point K 4 Add CP O by Picking Connector NL 1 Place the 3D cursor over point N 2 Add CP O by Picking 3 Add CP O via Keybrd 4 2 Connector KL to close Domain AKLNMB 1 Place the 3D cursor over point K 2 Add CP O by Picking 3 Place the 3D cursor over point L 4 Add CP O by Picking Connector NO 1 Place the 3D cursor over point N 2 Add CP O by Picking 3 Add CP O via Keybrd 4 1 Connector OP 1 Place the 3D cursor over point O 2 Add CP O by Picking 3 Add CP O via Keybrd 4 2 Connector LP to close domain LNOP 1 Place the 3D cursor over point L 2 Add CP O by Picking 3 Place the 3D cursor over point P 4 Add CP O by Picking Connector RQ 1 Place the 3D cursor over point Q 2 Add CP O by Picking 3 Add CP O via Keybrd 4 0 Connector HR Structured Domains on Inlet Plane 1 Place the 3D cursor over point H Add CP O by Picking Place the 3D cursor over point R Add CP O by Picking Done oa FY N Done Creating Conns You can turn off the data
43. do the same for new surface grids 6 UnstrDom MaxAng 7 10 0 Now Gridgen will calculate the difference in angle between a new unstructured domain s cell normals versus the underlying database normals at the cell vertices If larger than 10 degrees additional points will be inserted into the surface grid until the maximum angle criteria is met These angle criteria will allow us to 14 3 Mechanical Part Basic FEA Mesh better capture the shape of the tight radius surfaces in this model 8 Done 14 7 Creating Unstructured Domains First Pass Since the purpose of this tutorial is to illustrate the use of Gridgen s On DB Entities command the domains will be created twice First the basic command will be used with no additional clean up enabled Once created we will look at some of the issues in the resulting domains From the DOMAIN COMMANDS menu 1 Create 2 Cell Type unstructured 3 On DB Entities 4 Pick All 5 Done To make the new domains more visually accessible change some of their display attributes in the DISPLAY COMMANDS menu Disp Edit Dspla Dom Pick All Done display style Shaded Wireframe wireframe color red solid shade color purple Done Apply Atts Abort 10 Done e E SOY a pA dq When you are done the grid should look like the one shown in Figure 26 3 14 4 Creating Unstructured Domains Second Pass Figure 26 3 All Domains After Changing Display Attributes
44. done use Quit Gridgen from the MAIN MENU to exit the program Tutorial Wrap up 8 23 LDI Combustor Advanced Structured Grid 8 24 9 Pierced Elbow Basic Unstruc tured Grid 9 1 Introduction This tutorial will give you a guided tour of the Gridgen process for creating a simple single tetrahedral vol ume grid for the flow field inside a 90 degree pierced elbow We encourage you to complete this tutorial and then begin making your own simple grids 9 2 Topics Covered This tutorial covers basic and advanced features of Gridgen Gridgen skills you will learn during this tuto rial session are setting Defaults appropriate for an unstructured grid creating various database entities using the DB CREATION menu creating connectors with the 2 Point Connectors and DB cnstr Line commands projecting connectors onto a database surface using Modify creating unstructured domains using Assemble Edges creating an unstructured block using the Pick All feature initializing the tetrahedral volume grid with the Run Solver Unstrctrd using Examine to visualize the interior of the volume grid setting boundary conditions for flow solver export with Set BCs 9 3 Background You should work through the 2D Bump on a Wall tutorial Section 2 to get a feel for Gridgen basics You should also read Section 2 of the User Manual to familiarize yourself with the operation of the Gridgen user interface before attempting to run this tutorial
45. into the volume of the core if not you can use the command 1 Reorient Faces Otherwise 1 Done Save Blocks Now you have successfully created and saved the block with the surface normals pointing into the interior of the core Tetrahedral cells may now be generated within the core block 10 9 3 Initializing the Tetrahedral Volume Grid Now that the core block has been created you can initialize the interior tetrahedral volume within the core of the droplet From the BLOCK COMMANDS menu initialize the tetrahedral volume by 1 Run Solver Unstrctrd 2 Pick the core block from the Browser 3 Done 4 Initialize 5 Done Save 6 Done You now have a complete volume grid of the droplet interior consisting of prism cells extruded from the unstructured surface grid and tetrahedral cells initialized in the core You may wish to examine the volume grid using the Examine command in the BLOCK COMMANDS menu 10 10 Droplet Exterior Prism Extrusion You are now going to extrude prism layers from the exterior of the droplet into the cylinder The method is similar to the one described in Section 10 8 of this tutorial From the MAIN MENU 1 Blocks 2 Create 3 Extrude From Doms 4 Pick the spherical unstructured domain Entity 1 from the Browser on the surface of the droplet 5 Done You are going to extrude the prisms normal to the droplet domain Therefore you will have to set the normal extrusion attributes 10 11
46. key until the pole connector CC highlights 5 14 Creating Blocks 7 Press theright mouse button 8 Position the cursor over connector CH and when it highlights press the right mouse button Gridgen will then recognize that connectors HL and LN are needed to complete this domain and will add them The remaining domains are all pretty easy They each have only one connector per edge Hopefully you can tell which domains are left by looking at the Display window Just in case you need help here are the remaining domains AMNC EFJI FGKJ GHLK FGPO GKSP JKSQ FJQO and OPSQ Create them now Note that some of your new domains are rendered in purple and some in green Purple domains have been initialized using either Parametric or Parametric Fit TFI and green domains have been initialized using Grid gen s Standard TFI method Parametric domains automatically take the shape of the underlying database surface Standard domains do not Various criteria must be met for a domain to be initialized using a para metric method See Section 10 1 of the User Manual for further details Domain color is only relevant at the time of initialization The color will not be changed automatically to reflect later modifications to a domain 5 9 Creating Blocks Finally we are ready to create blocks We will create the main pipe block first Remember that it uses an O type topology with a pole at the center line of the pipe Go to the BLOCK COMMANDS m
47. license receipt or use of the softwrae constitutes 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 SIMULOG S A 1999 PATRAN isa registered trademark of The MSC Software Corporation NASTRAN is a registered trademark of NASA VSAERO copyright O 1985 Analytical Methods Inc INCA is a trademark of AMTEC Engineering Inc UNIX and XWindow System are registered trademarks in t
48. more isometric view again to make the remaining operations easier Use the following procedure from within the DB CREATION menu to create the first surface 1 Surface Revolution 2 Select arc EGF 3 Select line AB 4 Re Set the Angle 5 90 6 Done Save Surf of Revol 9 5 Pierced Elbow Basic Unstructured Grid And now for the piercing shaft use the same procedure 1 Surface Revolution Select line IN Select line CD Re Set the Angle 180 Done Save Surf of Revol pl Oy CO Spe Spe P9 Done The following figure shows all of the entities you have already created plus the intersection curve which you will compute next Figure 22 4 A Complete Database Model For the Elbow To complete the database you will now create the intersection of the two surfaces of revolution For this pro cedure Gridgen will put you into Browser mode twice You will do this to select two groups of entities to intersect with each other For this tutorial you will only have one entity in each group Intersect Select Group A Select the elbow surface of revolution Done Select Group B Select the piercing shaft surface of revolution pi cy cUm de Cen Do Done 9 6 Creating Connectors 8 Run 9 Done 10 Done You should now see a yellow database curve at the intersection of the elbow and the shaft Itis a good idea to save your work frequently so export your database now in Gridgen s composite database file format
49. must create blocks domains alone are not sufficient Starting from where you left off in the DOMAIN COMMANDS menu 1 2 3 4 5 6 AS W Select Analysis S W 2D FLUENT Next Page Done It was necessary for you to make this setting first so that Gridgen is now in 2D mode and will allow creation of a 2D block from your single domain 7 8 9 10 11 12 Blks Create Cell Type structured Assemble Faces Add 1st Face Pick the domain 2D Block Creation and AS W Settings 13 Save the Face 14 Done Save Blocks Now you are ready to set BC s and export your analysis data 15 AS W 16 Set BCs Note that the wake connector is in the list twice and has already been set as a Type 1 block connection which is an inter block connection No further settings are necessary for that part of the boundary 17 Select the two outflow connectors 18 Done 19 Next Page 20 Outflow 21 Select the C boundary connector 22 Done 23 Velocity Inlet Note there are only two BC s left to set Those obviously correspond to the airfoil connectors 24 Select the remaining unset edge connectors from the Browser list 25 Done 26 Wall 27 Done Your new grid is ready for export to a Fluent case file 28 Export Analysis Data 29 Type In Name 30 airfoil You now have a new analysis data file airfoil cas ready to run Congratulations You have com pleted this tutorial 3 9 2D Airfoil Re Extrude 4 S
50. second column of information shows the face number for that block After the face number in parentheses is the domain number associated with that boundary patch The blank space after the parentheses is where the name of the boundary condition you apply will be displayed Set the boundary conditions as outlined in the following steps 9 16 Saving Your Model and Export to Solver SELECT DOMAINS FOR BC seouT T T T T7 Pick All a None n Tog t in Box on Box ByText 1st o last o of F O Aon tog num2 o BC s u rev4 Pick by expression x Done ent Help abort esc Select the shaft and elbow domains Done Wall Select the two symmetry plane domains Done Symmetry 49200 c CON GAP Bee du Select the elbow opening which lies in an x constant body coordinate plane 10 Done 11 Velocity Inlet 12 Select the elbow opening which lies in a y constant body coordinate plane 13 Done 14 Outlet Vent 15 Abort Your boundary conditions are now set and you are ready to export your flow solver file While still inside the ANALYSIS S W COMMANDS menu proceed to export the file 1 Export Analysis Data 2 Type In Name 3 elbow Note that Gridgen will automatically append the default file extension cas 4 Done Now export your Gridgen restart file once more to preserve your boundary condition settings in the restart 9 17 Pierced Elbow Basic Unstructured Grid file Congratul
51. select WIND do the following 1 Analysis S W Select Analysis S W Next Page WIND 3D Next Page Done 9o pw wr eS 9 Done 7 6 Importing the Database The 747 inlet geometry we will use for this example is in an IGES file named 747 new iges It is located in the gridgen home path examples tutorial 747 directory You may want to copy it to a local directory before trying to import it into Gridgen Assuming that you have copied 747 new iges to your current working directory the procedure to read it in to Gridgen starting from the MAIN MENU is 1 Input Output 2 Database Import 3 Select 747 new iges from the Browser 4 Open 5 Done 7 3 B 747 Nacelle Working With An IGES Database After the file is read rotate the image in the Display window until the model orientation is similar to that in Figure 21 2 To remove some clutter from the display we will disable database entities that will not be nec essary for this tutorial There are other advantages to disabling unnecessary database entities Gridgen s rendering speed will be improved There will be fewer items to pick from when creating connectors on data base entities And domain projections will be more efficient since Gridgen will not attempt to project onto disabled entities To disable the database surfaces on the exterior of the nacelle 1 Database 2 En Disable 3 Select or toggle entities 3 4 6 and 7 4 Done 5 Done To simplify connector
52. the ANALYSIS S W COMMANDS menu and choose your solver and set some boundary condi tions 1 Select Analysis S W 2 FDNS UNIC 3 Next Page 4 Done 5 Confirm Make Changes Using the Set BCs command apply boundary conditions for the CFD solver Finally export your grid and boundary condition data for FDNS 1 Export Analysis BCs 2 Type In Name 3 noz fdns Note that Gridgen will automatically append the correct file extension 4 Export Analysis Grid 5 Type In Name 6 noz fdns The grid is now complete so go to the GLYPH COMMANDS menu and End Journaling It is worth not ing you do not need to save a Gridgen gg restart file since this grid can be re created entirely from the Script 13 7 Converging Diverging Nozzle Using Glyph Scripting AE NV anes WV eH NW he im SM NE SN V N Figure 28 6 Completed Grid M V SN M j NN NN S 13 8 14 Mechanical Part Basic FEA Mesh 14 1 Introduction The purpose of this tutorial is to introduce you to Gridgen s On DB Entities domains command for unstructured surface grid creation 14 2 Topics Covered Gridgen skills you will learn during this tutorial session are setting defaults appropriate for unstructured grids using the Defaults command using the On DB Entities domains command to create unstructured domains using Auto Join and Auto Merge with On DB Entities to improve do
53. the connector tolerance 7 7 Creating The First Block The first connectors you will create correspond to lines AB BC CD and DA in Figure 21 2 Their shapes will different than those in the figure when you first create them We will take care of the shape later Starting from the MAIN MENU A Connectors Create 2 Point Connectors Add CP O via Keybrd Oy Ou 76 Add CP O via Keybrd 0 6 6 Add CP O by Picking Add CP O via Keybrd 0 6 6 11 Add CP O by Picking 12 Add CP O via Keybrd 13 10 0y 6 14 Add CP O by Picking NO 600s e TON T do dob 15 Position the 3D cursor over Point A 16 Add CP O by Picking 7 6 Creating The First Block 17 Done 18 Done Creating Conns We have four connectors so go ahead and create a domain 1 OFERTE Ox NG Re R SNS Doms Create Cell Type structured Assemble Edges Toggle on Auto Next Edge and Auto Complete Pick connector AB Pick connector BC Gridgen will then automatically complete the domain Done This domain will be the front face of the first block of our grid The back face will be similar to the front but projected onto the centerbody Copy the first domain and project it onto the surface by starting from the DOMAIN COMMANDS menu and 9 PS cL OY pM cbe Shed Copy Select the domain Done Abort Don t Translate Project Linear Cons Too Rotate the image in the Display window so that you are looking down the x axis
54. the end of the main pipe pole Set Handle by Picking Done Translate Rotate Use X principal Axis Enter Rotation Angle s 590 Done Rotate Done Replace Blocks Maintain Linkage The polar block should now appear as to contain the main pipe of the intersecting pipes as seen in the fol lowing figure Figure 20 6 Main Pipe Polar Block In Figure 20 6 the block nodes have been labeled for reference in the block s fit to the geometry To fit the block to the geometry you will need to split domain EILH into three domains in the area of the intersection curve seen in the following figure 6 6 Building Polar Block for Main Pipe Figure 20 7 Intersection Curve Computed by Gridgen The middle domain formed from the domain split will eventually form the end of the branch pipe block Splitting the domain EILH will require Gridgen to also split the domains connectors In Gridgen a connec tor must have three or more points before it can be split Because the default connector dimension was set to 2 the connectors running the length of the pipe were created with a dimension of 2 All four of these con nectors need to be re dimensioned to a larger value before domain EILH may be split We will re dimension them to a value close to their final dimension Before redimensioning these connectors it is important to understand how the Redimension Grids button works when selecting a connector that is already a part of a struct
55. the surface of the droplet Entity 4 from the Browser 10 5 Droplet in a Cylinder Hybrid Grid Done render mode Isolines 55 Done Apply Atts Abort Done Ne o c 9v UO GRE You can zoom into the area around the droplet for the next step of the grid generation process If everything is going well your Display window should look like Figure 24 4 Itis a good idea to save the database as a Gridgen Composite file before proceeding further 1 VO Database Export Type composite Done Type In Name hybrid pl gy cs sp does S Done Figure 24 4 Surface of Revolution for the Droplet 10 7 Unstructured Surface Grid on Droplet You are now ready to create an unstructured surface grid on the surface of the droplet The number of grid points on the droplet surface is based on the avg As grid point spacing parameter defined in Section 10 5 From the MAIN MENU 1 Domains 2 Create 10 6 Sl LD me S Cell Type unstr On DB Entities uctured Pick the surface of the droplet Done Done Droplet Interior Prism Extrusion You have now created an unstructured surface grid on the droplet surface For the purposes of the tutorial we will only create half of the droplet and utilize the symmetry of the geometry The surface grid should look like Figure 24 5 on the following page 10 8 Droplet Interior Prism Extrusion Figure 24 5 Surface Grid around Droplet Surface You are now ready to extrude a layer of pri
56. unstructured grid Building triangulated unstructured domains is much simpler than building structured quadrilateral domains since there are few restrictions on the topology of the domain it can have any number of edges Begin by constructing one of the simplest domains for this grid the triangular shaped symmetry plane domain IKF 1 Doms 2 Create 3 Cell Type unstructured 4 Assemble Edges 5 Toggle on Auto Save 6 Pick in order edge connectors IF FK KI Since you turned on the Auto Save feature Gridgen detected automatically that you had completed the loop with the three connectors and paused to save and initialize the domain immediately Your model should now look like the one shown in Figure 22 6 9 9 Pierced Elbow Basic Unstructured Grid Figure 22 6 The First Domain Continue creating the remaining five domains while still in the CREATE A DOMAIN menu by simply selecting the connectors as directed below and pausing to allow Gridgen to initialize the completed domains Pick IF 2 Pick FE 3 Pick EH 4 Pick HI 5 Pause for initialization 6 Pick HI 7 PickIK 8 Pick KJ 9 Pick JH 10 Pause for initialization 11 Pick JH 12 Pick HE 13 Pick EL 14 Pick LM straight line 15 Pick MJ 16 Pause 17 Pick LM straight line 18 Pick ML arc 19 20 21 22 23 24 25 26 27 28 Creating Domains Pause Pick ML arc Pick LE Pick EF Pick FK Pick
57. use Gridgen s On DB Entities command to create essentially all of the topology for this tutorial Once created we will look at some of the issues with the resulting connectors Beginning on the DOMAIN COMMANDS menu 1 Create 2 Cell Type unstructured 3 Turn on the Auto Merge toggle to have coincident connectors merged automatically 4 Set Toler on 30 5 Note that Gridgen will use an iterative process to merge connectors during the On DB Entities command execution Merging will start with the default connector tolerance as shown in the SET TOLERANCE VALUES Blackboard and will gradually increase to the tolerance value specified here Therefore relatively large values of merge tolerance can be specified without worry of topology destruction 6 On DB Entities 7 Pick All 8 Done To make the display of the grid less cluttered change the render attributes of the domains in the DISPLAY COMMANDS menu 1 Disp Edit Dspla Dom Pick All Done display style Off Done Apply Atts Abort Done 96 c0 ON Oe deo DA oE When you are done the grid should look like the one shown in Figure 27 3 12 4 Additional Connector Merging Figure 27 3 All Domains After Changing Display Attributes 12 8 Additional Connector Merging Proceed to the CONNECTOR COMMANDS menu set TopoFItr to NonMnfld Free and use the Merge Pick command to note that the baffle domains have connectors overlapping those from the cylinder domains These were no
58. you will do by creating and using variables 13 6 Setting Variables for Spacing Constraints You are going to set three variables for the values of the grid clustering at various locations in the grid Vari ables will make it easy to edit the journaled script and change the value of the clustering for generating another grid The spacings you will set are wall spacing DSw inlet spacing DSi spacing at node D DSd A Gridgen variable can have any value scalar vector integer floating point or character You can define the variable using any valid Tcl expression including arithmetic operations For this tutorial the three vari ables you create will be floating point scalars While still in the GLYPH COMMANDS menu 1 Add Variable Note that the Browser lists variables that have already been defined These came from the script you started with nozzle glf 2 DSw Now the ADD VARIABLE menu shows the seven methods for setting a variable s value 3 Enter Tcl Expression 4 0 2 5 Add Variable 6 DSd 7 Enter Tcl Expression 13 3 Converging Diverging Nozzle Using Glyph Scripting 8 1 0 9 Add Variable 10 DSi 11 Enter Tcl Expression 12 1 5 13 7 Using Variables You may now go to the CONNECTOR COMMANDS menu and use these variables to set the clustering at the break points according to Figure 28 3 You will use the Set As Vals command This command conve niently allows you to select either in the
59. 2 8 Draw Connectors cursor over the bottom and pressing and releasing the right mouse button Translate the connector copy to its new position by moving the mouse with the right mouse button pressed Set Handle by Picking Done Translate Done Save Connectors The final connector is GE Starting from the CONNECTOR COMMANDS menu E a A oA oo Dog C 10 11 12 13 14 15 16 17 18 Create Add Segment 3D Space Line Position the cursor over point G Add CP O by Picking Position the cursor over point F Add CP O by Picking Done Save Segment ReDimension to assign a number of grid points to connector GE Since connector GF will be opposite connectors BC CD and DE in the final structured grid it must have the same total number of grid points Position the cursor over connector BC Press and release the right mouse button Next position the cursor over connector CD Press and release the right mouse button Note how the Blackboard window changes when you do this Finally position the cursor over connector DE and press and release the right mouse button Note that connector GF and the string of connectors BC CD DE have colored triangles at their end points The color of the triangles provides a directional reference for copying the distribution of grid points For this symmetric problem it does not matter which direction the curves are running If it did you could use the Reverse the Direction
60. 45 Figure 22 27 Extruded Block for Passage Entity 9 8 21 LDI Combustor Advanced Structured Grid 11 Done Rotate 12 Done Save Block Repeat steps 1 13 for 90 and 180 angles of rotation each time selecting the newly copied domains You may want to turn on the Hidden Line Removed toggle from the DISPLAY COMMANDS menu and reorient the Display window as shown in Figure 22 28 Figure 22 28 Passages Created Using Copy and Rotate You now need to align the computational axes with the model axes In all of the blocks you want amp to run in the x direc tion 1 in y direction and G in z direction From the BLOCK COMMANDS menu Modify Pick any rectangular block in the Inlet section Done ReSpecify 6 n G Select one of the block edges that run in the positive x direction amp direction Repeat steps 5 and 6 for the y direction and z direction pressing the n and G direction buttons accordingly Done Replace Blocks Modify 10 Pick AII 11 Done 12 Align amp n G 13 Pick the rectangular block in step 2 0 0 200 FR wON za 14 Done Replace Blocks 15 Done 8 17 Tutorial Wrap up This completes the Gridgen tutorial You may proceed to generate the grid for burner section in a similar way If you want to save this grid 1 Select I O from the Quick Keys 8 22 Gridgen Export Type In Name Enter the file name top swirler gg a LW Done When you are
61. AIN MENU 1 Domains Run Solver Structured Select domains OQSP and FJKG Done Run N Iters 11 Done Save 99 ub Ow Oe ups P9 Done Your grid is now complete To examine the grid you will want to turn on the display of your domains and edit their display attributes From the DISPLAY COMMANDS menu 6 18 Connector and Domain Projection 1 Toggle on Show Doms 2 Edit Dspla Dom 3 Pick All 4 Done 5 display style Shaded Wireframe 6 solid shade color All 7 Done Apply Atts 8 Abort 9 Done The intersecting pipes grid you have constructed should now appear as in the following figure Figure 20 17 Completed Intersecting Pipes Grid Before you finish the tutorial you will want to save your work To save your database dba and gridgen restart gg files you will need to go to the INPUT OUTPUT COMMANDS menu accessible from the MAIN MENU Input Output Database Export Make sure composite is selected Done Type In Name pipestd Gridgen Export Type In Name NE e mE CON OE CA 9 pipestd Please note that due to database references in the Gridgen restart file itis always a good idea to export your database model prior to exporting your Gridgen restart file 6 19 Intersecting Pipes Pole Grid Construction Top Down You have now completed the tutorial You should be able to use the techniques and methods you have learned in this tutorial for your own geometries For practice yo
62. Adele tse 14 3 14 7 Creating Unstructured Domains First Pass suessssss 14 4 14 8 Creating Unstructured Domains Second Pass 1 14 5 14 9 Domain Decimation sss eene 14 7 14 10 Completing the Grid 5 eei rtt drea eot esddons 14 8 TO SINON o oet uet aL ftm M E e Pais EE 15 1 1 Cubes and Spheres Layer Man ager 1 1 Introduction This section includes a brief tutorial to help you become familiar with the basic operations of Gridgen s Layer Manager It will also introduce you to the database pick masking capability available in all database entity browsing operations There will be no actual entity creation in this tutorial Only database model manipulation will be covered as an introduction to how the Layer Manager gives you ultimate control over your database model and its display 1 2 Topics Covered This sample session is a short introduction to using Gridgen Basic Gridgen skills you will learn are assigning entities to certain layers using the Assign Layer command e manipulating layers using the layer Browser list manipulating the layer Browser list using filters changing the display state of certain layers using Isolate All On and All Off creating saved layer sets using the database Browser command DB Pick Mask 1 3 Background Work through this tutorial to familiarize yourself with the basic operations of Gridgen s Layer Ma
63. Block Figure 22 2 A Single Combustor Divided into Ten Blocks 8 5 Getting Started Start Gridgen by typing gridgen on Unix workstations or by simply double clicking the Gridgen shortcut on your PC desktop For this tutorial we will not be performing any analysis using this grid so it will not be necessary to select a par ticular solver from the Analysis Software menu 8 6 Importing a Database You will need to import a database file for this geometry This will normally be located under gridgen home path examples tutorial ldi Load it into Gridgen as follows starting from the MAIN MENU 1 Database 2 Import 3 Select 1di dba from the Browser window 8 2 Setting Defaults 4 Open 5 Done 6 Done After importing the file the Display window should look like Figure 22 3 Figure 22 3 Default View of the LDI Combustor Database 8 7 Setting Defaults Since you will be creating a structured grid you will begin the process by first setting up default values for the number of grid points and connector tolerances From the MAIN MENU Defaults Con Dim dimen 3 Tolerances Connector 0 01 Done 2 No Qu So YS Done You have now set up the grid attributes which will be used throughout this session unless otherwise stated 6 8 Displaying Swirler Passages You will only create a one inch square grid for the combustor at the lower left corner To simplify the geometry we want to only display the database curves in the are
64. C 13 Pick domain CGFB 14 Pick domain AEFB 15 Save the Face 16 Pick domain OSKABCD 17 Save the Face 18 Pick domain QRNM 19 Pick domain PQTU 20 Pick domain UTML 21 Pick domain OPUS 22 Pick domain SULK 23 Save the Face 24 Done Save Blocks The block is complete and you have completed this tutorial Save a Gridgen file before doing anything else After that you can examine the two blocks you have created See if you can think of any ways to improve this grid 7 18 8 LDI Combustor Advanced Structured Grid 8 1 Introduction This tutorial will give you a guided tour of the Gridgen process for creating a grid for a lean direct injection LDI com bustor with discrete jet swirlers The original tutorial was provided by Dr S L Jason Yang and Chen Yen Teo Mechanical Engineering Engineering Mechanics Department Michigan Technological University 8 2 Topics Covered This sample session is a short introduction to using Gridgen Basic Gridgen skills you will learn are e Creating database constrained connectors using On DB Ents command e Creating connectors using 2 Point Connector command e Creating domains using Assemble Edges e Copy and Rotate topology e Hlliptically smooth domains using Run Solver Structured command Use the Extrude command to create blocks e Use the ReSpecify n C to align the computational axes 8 3 Background We encourage you to complete all previous tutorials in the
65. Copy Creating the Second Block 22 Pick the connector corresponding to connector ML in Figure 19 3 23 Pick the node corresponding to Point M in Figure 19 3 24 Move the 3D cursor to Point J in Figure 19 3 25 Set Handle by Picking 26 Done Copy Connector 27 Copy Break Point Info 28 Done Save Connectors 29 Done Creating Conns 30 Done Create four new domains ja Domains Create Assemble Edges If Auto Next Edge and Auto Complete are not enabled then enable them now Pick connector CD Pick connector DE You should see domain CDEFC appear now Pick connector CD Pick connector DK You should see domain CDKJC appear now 19 2700 cip Oy con a Pa Da Pick connector JK 10 Pick connector KL You should see domain J amp LMJ appear now 11 Pick connector LM 12 Pick connector MF You should see the domain LMFEL appear now 13 Done 14 Done Create the new block em Blocks Create Assemble Faces Add 1st Face Turn on the AutoSave Face toggle Pick domain CDEFC Pick domain DKLED Pick domain DKJCD Pick domain CJMFC 10 Pick domain JKLMJ NOOO l AI ON OO dix Os c9 4 31 Swept Ramp Basic Multi Block Structured Grid 11 Pick domain ELMFE 12 ReName 13 downstream 14 Done Save Blocks 15 Modify 16 Pick All 17 Done 18 Align amp n G 19 Pick the upstream block with the right mouse button 20 Done Replace Blocks 21 Done Save the two bl
66. D cursor the white in the Display window The cursor can be moved by hold ing down the right mouse button and moving the mouse assuming that Left Pk has not been set in the DIS PLAY COMMANDS menu As the 3D cursor moves its coordinates listed in the Blackboard window are updated 2 3 2D Bump Basic Skills 0 Blocks 0 Domains 0 Connectors 0 Nodes 0 DB ents generic 3D CIRCLE Enter the starting point of the circle Connector Segments Connector Dimensions Cross Positi CIRCULAR ARC Add CP lat padEnt by Picking pado via Keybrd pad Axyz via Keybrdo Movement Restrictions m Move to Screen Center c Rotation Pt To t Sensi t Decr lt jReset Incr Abort Don t Save esc Display Commands d Help Figure 18 3 The Gridgen Window is Divided into Several Subwindows Above the Blackboard window is an area called the Message window This is where Gridgen provides cues for the input it expects from you In this instance it should say CIRCLE Enter the starting point of the circle You have six options for entering the location of the starting point Add CP O at will add the point at the current position of the 3D cursor as shown in the Blackboard win dow Add CP O by Picking will add the point at the pickable grid or database point underneath the 3D cursor Add CP O via Keybrd will allow you to type the x y and z coordinates of the point in the Text Input window
67. Dom Pick All Done display style Off Done Apply Atts Abort Done ON GUN cB sd Now you are ready to begin creating some more database constrained connectors This time you will use the DB cnstr Line segment type to create some connectors that span multiple database entities on the center body surface 1 Cons 2 Create 3 Add Segment 7 8 Sys ae uE Creating Block Two DB cnstr Line DB Ent Pick Select the centerbody upper nose surface Position the 3D cursor over Point H If you are having trouble moving the 3D cursor try rotating the view Gridgen converts your mouse movements into database constrained screen movements of the cur sor This works best when the database surface at the cursor location is approximately in the plane of the screen It can have trouble when the surface is perpendicular to the view Add CP O by Picking Position the 3D cursor at the top back corner of the surface at u v 0 0 Add CP O by Picking DB Ent Pick Select the main aft surface of the centerbody Note that the 3D cursor is now on the new database surface but it is still at the same physical location The Distance to Last Point shown in the Blackboard window should be 0 Move the 3D cur sor a slight distance aft until the Distance to Last Point is approximately 0 1 Add CP Dat Position the 3D cursor at the top back corner of the surface at u v 1 0 Add CP O by Picking Done Save Segment
68. Domains X te O_O ERE OUA Oe VS S TEATS ARERR LOE TRA FAIA VRQ iS SK Ce p CN NE SS Ad at TSS none eas SEE S RO A A AANA SNN AN N CORNER CONS C S amp T SSVOCNNNNNS D SEEN Figure 19 10 Copying and Translating Connectors Speeds the Ramp s Grid Generation Process Now that all of the connectors relevant to the upstream block have been created you can continue with the domain creation process Start with the upstream and far field Gimax domains Done 1 Domains 2 Create 3 4 Assemble Edges Auto Next Edge 5 6 Pick connector AH Pick connector HN At this point Gridgen should automatically create domain ahng T Pick connector GN 8 9 Pick connector NM This completes domain GNME 10 Done The Display window is getting pretty cluttered It is a good idea to turn off the display of the domain grids to make the new grids easier to see Disp 2 Edit Dspla Dom 1 4 23 Swept Ramp Basic Multi Block Structured Grid 3 Pick All 4 Done 5 Off 6 Done Apply Atts 7 Abort You should now see only connectors as shown in Figure 19 11 Figure 19 11 Turning Off the Display of Existing Ramp Domains Reduces Screen Clutter The three domains that still need to be created are the outflow domain and the two domains on the ramp sur face 1 Done Create Assemble Edges Pick connector FM Pick connect
69. Droplet in a Cylinder Hybrid Grid 1 Type Nrml 2 Set Attributes This should take you to the NRML EXTRUSION ATTRIBS menu 3 As Init 4 0 1 5 Boundary Conditions 6 Turn on the Constant Z Plane toggle Since you will be extruding a second prism layer outward into the cylinder you must reorient the normals so that they face outwards away from the droplet surface 1 Set Other Attributes 2 March Flip 3 Done Now create the prism layer From the BLOCK EXTRUSION menu 1 RunN 2 10 3 Done 4 Done This completes the hybrid mesh on the droplet Set all faces on the blocks to hidden line the Display win dow should then look like Figure 24 8 on the following page Notice the grid spacing on the prism layers is clustered close to the surface of the droplet The grid spacing then becomes progressively coarser away from the droplet surface Figure 24 8 Prism Layers Extruded Outward into the Cylinder 10 12 Structured Surface Grid on Cylinder Initializing the Tetrahedral Volume Grid 10 11 Structured Surface Grid on Cylinder You are now ready to create a structured quadrilateral surface grid on the surface of the cylinder From this you will extrude a layer of hexahedral cells inwards into the cylinder To speed up construction you will set defaults values for connector dimensions using the Defaults menu option To set the defaults from the MAIN MENU 1 Defaults 2 Con Dim dimen 3 35 4 Done Any connecto
70. Dspla DB Pick AII Done render mode Outline Done Apply Atts Abort oe i gv CA dO 9 9 If you chose the first option for importing the database into Gridgen you may have to rotate the image to get it to the orientation seen below Section 2 7 3 of the User Manual If you chose the second option for load ing the database the model should already be in this orientation Figure 20 3 Pipes database 6 7 Building Polar Block for Main Pipe The geometry you just imported will be used to determine the shape of the grid you will create next Before starting to build the grid set a default number of grid points to put on each new connector created For con venience we will specify a grid size of 2 From the MAIN MENU 1 Defaults 2 Con Dim dimen 6 3 Intersecting Pipes Pole Grid Construction Top Down 3 2 4 Done The blocks you will create are shown labeled in Figure 20 4 The below figure is an exaggerated version of the blocks and the topology This will be used for reference in the discussion that follows Figure 20 4 Block Topology Labels You will create a polar block for the main pipe by running the glyph script block gui glf Itis located in the gridgen home path examples tutorial pipestd directory You may want to copy it to a local directory before trying to execute it in Gridgen The script was designed to offer three different types of block topologies H Block Polar and T Block for block creation
71. EATE OFFSET CURVE Store Pnt Jat padEnt by Picking pado via Keybrd pad Axyz via Keybrdo Acp via Keybrd o by Linear Proj at Clsest DB Pt Sensi t Decr Reset Iner gt Move to Screen Center e Rotation Pt To t ReDef ine Generatrix del Set Fit Tolerance 2 Reverse the Offset s Enter Offset Distance d Abort esc Help Creating a Database Next you will create an edge curve for each pipe by creating offset curves from the two existing curves The edge curves are offset from the center line by the pipe radius Itis important to remember when using the Offset command that the offset operation is performed in the plane of the screen Therefore it is essential that your view orientation be perpendicular to the plane in which you wish the offset operation to take place The radius of the main pipe is 1 0 and the radius of the branch section is 0 75 3 4 5 6 7 8 9 Curve Offset Position the cursor over line AC and press and release the right mouse button assuming you are using the default mouse button configuration Otherwise swap right mouse for left mouse in the remain der of this tutorial Enter Offset Distance 1 0 Save Curve Offset Position the cursor over line Enter Offset Distance 0 75 10 Reverse the Offset 11 Save BD and press and release the right mouse button 5 5 Intersecting Pipes Pole Grid Construction Bottom Up Figure 20 4 Database Curv
72. KJ Pick JM Pause Done Done The domains rendered in purple have been initialized parametrically Section 11 of the User Manual This means the domains grids have been initialized in the parametric space of the corresponding underlying data base surface and will not require projection in order to make them assume the shape of the surface The pur ple color is used as a visual cue to let you know this has taken place Your model should now look like the one shown in Figure 22 7 Figure 22 7 All of the Domains Created Your rendered model in the Display window is quite a cluttered mess with all of the triangular surface grids being displayed In order to remove some of the clutter in the Display window to make later work a little easier again return to the DISPLAY COMMANDS menu Section 2 9 of the User Manual to change some display attributes of the domains and turn off display of the connector grid points l 2 3 Disp Toggle off Show Con GPs Edit Dspla Dom 9 11 Pierced Elbow Basic Unstructured Grid 4 Pick All 5 Done 6 Off 7 Done Apply Atts 8 Abort You also really do not need to use the database entities any more for the remainder of the tutorial Disabling the database entities will remove more clutter from your display The difference between changing the dis play attribute to off as you did for the domains and disabling as you are about to do for the database enti ties is disabled objects can
73. Multi Block Structured Grid 2 Point Connectors Add a control point by positioning the 3D cursor and picking the node corresponding to Point C Add a control point by positioning the 3D cursor and picking the node corresponding to Point D Done Done Creating Conns Set As Vals Pick the end of connector CD at Point C Done 9 OT Abort Note a new command Set As Vals was used to redistribute the grid points on connector CD Using this command you can pick multiple connector ends and set their spacing constraints all at once In this exam ple you only want to set the spacing constraints at one end of the connectors You can pick as many as you want before setting the spacing Make three copies of the original x directed connector A We OOD mA ON CUN ses err s B9 11 4 30 Create Add Segment Others Copy Pick the connector corresponding to connector CD in Figure 19 3 Pick the node corresponding to Point C in Figure 19 3 Move the 3D cursor to the Point F in Figure 19 3 Set Handle by Picking Done Copy Connector Copy Break Point Info Done Save Connectors Add Segment Others Copy Pick the connector corresponding to connector FE in Figure 19 3 Pick the node corresponding to point F in Figure 19 3 Move the 3D cursor to Point M in Figure 19 3 Set Handle by Picking Done Copy Connector Copy Break Point Info Done Save Connectors Add Segment Others
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75. Points 2 Cross Position x 7 5000000E 01 y 0 0000000E 00 z 0 0000000E 00 Distance To Last Point D 0 0000000E 00 Once you ve defined the shape of this segment we ll save it and proceed with assigning a number of grid points to it Section 9 1 1 Done Save Segment ReDimension From keybrd 15 Qu oe ie Done ReDimension Notice the Browser window now reflects the fact a number of grid points has been assigned to the connector Connector Segments 1 Connector Dimensions 15 4 7 Swept Ramp Basic Multi Block Structured Grid Finally let us proceed with grid point distribution Section 9 3 1 ReDistribute Before assigning clustering values let us take a closer look at the screen Locate a large white open circle in the Display window This is the cursor Note several menu buttons refer to the cursor they have a large white open circle on them Also look at the Browser window text Connector Segments 1 Connector Dimensions 15 SubConnector 1 1 info Dimensions 15 Spline Linear on S Distribution TANH beg As input 0 0000E 00 As actual 5 3571E 02 end As input 0 0000E 00 As actual 5 3571E 02 As 8 5 357143E 02 As 8 5 357143E 02 Cursor Position x 3 7500000E 01 y 0 0000000E 00 z 0 0000000EK 00 The coordinates of the cursor are shown at the bottom of the Browser window The 3D cursor may be moved along the connector by 1 Press and hold the right mouse b
76. Surf Flat which would generate a true cut through the tetrahedral mesh This results in a flat sheet of polygons many of which are going to be slivers While this can yield useful grid diagnostic information it is likely not as useful as the Ref Surf Crinkle option The Ref Surf Cells option will instruct Gridgen to display entire tetrahedra that are intersected by the scan plane By default these reference surfaces continue to be displayed until you either Erase Cur which erases the reference surface currently under the hiliter or until you Erase All Exiting from Examine also turns off the display of any reference surfaces but their locations are stored in memory in case you return to the Examine utility At that time your previous reference surfaces are restored and updated to reflect any changes in the surface or volume grids While in examine feel free to try other Display styles as well as rendering the reference surfaces colored by some Function When you have finished using Examine press the Abort button to exit and then Done to return to the MAIN MENU 9 11 Saving Your Model and Export to Solver Hopefully you have been saving your model along the way but this is definitely a good point at which to make sure you save a good copy of your database and grid models Since you have created a database model within Gridgen you also need to be sure to save this data It will not be included in the Gridgen file you will save as well howev
77. TUS Browser list and rendered in purple in the Display window 3 Pick All 4 Done Now you see the nicely shaded display of the small sphere in the Display window Your Layer Manager panel has again been pushed to the background on your desktop due to your use of Gridgen s primary GUI Use Shift m to pop it up Take the following steps to turn on the entire model again and restore the view to original orientation 1 Status All On Cubes and Spheres Layer Manager 2 Click in the GUI and use the r hot key to restore orientation Your model should now appear as in the figure below yi a x WOM iY BU Y M VV S QS A i 1 9 Move and Description Use Shift m to pop up the Layer Manager panel Even though we have restored the display of the small sphere you can see that it is not layered consistently with the other objects in the model Since the medium sphere is in layer 10 and the large sphere is in layer 15 the small sphere likely really belongs in layer 5 Move the entity now and label the layer accordingly 1 Select layer 831 2 Move The Move dialog box pops up Info The entities in the selected layers will be 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 E IV Move the source layer d
78. a of the lower left corner From the MAIN MENU Database En Disable Pick in Box In the Display window draw a box around the swirler passages in the lower left corner Pick Tog Done NOW YD a Done Press the keyboard hotkey r to reset the view limits of the Display window The database entities of the eight passages are shown in Figure 22 4 on the next page 8 3 LDI Combustor Advanced Structured Grid Figure 22 4 Default View of the Swirler Passages 8 9 Connectors at the Inlet Plane of the Passages You will be creating a multi block structured grid for the inlet block of the burner geometry For the purposes of this tuto rial the chosen topology on the inlet plane to the swirler passages is shown in Figure 22 5 The passage entity 9 has been labeled for the first step in the grid construction process Figure 22 5 Multi block Grid Topology for the Inlet Block Now that the topology for the blocking system has been chosen you will begin by creating connectors on the swirler pas sage entity 9 These will then be copied and rotated to form the connectors for the other seven passages From the MAIN MENU Connectors Create On DB Entities Pick the database curves for the passage entity 9 Qi LE ED a Done The Display window should look like Figure 22 6 84 Connectors at the Inlet Plane of the Passages Figure 22 6 Connectors on Passage Entity 9 You must now split the connectors to create the four edges definin
79. ado via Keybrd pad Axyz via Keybrdo Acp via Keybrd o Decr jReset Incr Move to Screen Center c Rotation Pt To MKeep Pts 1 Abort esc Help Make sure that the Keep Pts toggle button is enabled and the Keep Avg toggle button is disabled Create points A B C and D now while referring to Figure 20 3 for the proper layout of the points Figure 20 3 Labels for Starting Points 1 Store Pnt via Keybrd 10 0 0 Store Pnt via Keybrd 0 0 0 Store Pnt via Keybrd SE Be cO dp9 5 3 Intersecting Pipes Pole Grid Construction Bottom Up 6 10 0 0 7 Store Pnt via Keybrd 8 5 10 0 9 Save LINE DB ENTITY at padEnt by Picking pado via Keybrd pad Axyz via Keybrdo by Linear Proj d at Clsest DB Pt Cnvrt to Curve c Ak ima h Movement Restrictions m Decr lt Reset Incr Move to Screen Center e Move Rotation Pt To 1 c CV Abort Don t Save esc Display Commands Aa Help 2 Next create the lines that define the center line of each pipe Starting from the DB CREATION menu 1 Curve Line 2 Position the 3D cursor over point A 3 Add CP O by Picking 4 Position the 3D cursor over point C 5 Add CP O by Picking 6 Save DB curve 7 Curve Line 8 Position the 3D cursor over point B 9 Add CP O by Picking 10 Position the 3D cursor over point D 11 Add CP O by Picking 12 Save DB curve 5 4 CR
80. ae n d 4 T d Tutorials Version 15 ON WIS d A i LE I CX get the Poids 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 888 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
81. al piece of the database is the intersection curve between the two branches When finding intersec tions Gridgen prompts you to pick two groups of database entities It computes the intersections of entities in the first group with entities in the second group For this tutorial the first group contains only the surface of the main pipe and the second group contains only the surface of the branch section Run s Cont inue c ReSelect Group A a ReSelect Group B b Set Tolerance As Curve Curve Intersect O Apparent t L Closest Approach h Done ent Abort esc Help Starting from the DATABASE COMMANDS menu 1 Intersect 2 Select Group A 3 4 Done 5 Select Group B 6 7 Done 8 Run 9 Done Select the surface of the main pipe from the screen or from the Browser list Select the surface of the branch section Gridgen computes the intersection curves when you hit the Run button After some image manipulations Section 2 7 you should be able to see the intersection curve in the Display window as shown in Figure 20 5 5 7 Intersecting Pipes Pole Grid Construction Bottom Up Figure 20 5 Intersection Curve Computed by Gridgen This completes the geometry creation portion of the tutorial It would be a good idea for you to save the database as a Gridgen Composite format database file before proceeding further Starting from the MAIN MENU 1 Input Output Database Export composite Done Type In Name 9
82. and K This can be done automatically using the Merge command 9 7 Pierced Elbow Basic Unstructured Grid 1 Merge Auto 2 0 5 With that done you should Delete the unnecessary connectors lying outside the boundary of the pierced elbow volume These are the three small connectors on the y max end of the shaft surface plus the one con nector traversing from J to K on the symmetry plane for a total of four unneeded connectors 1 Delete 2 Select the four unnecessary connectors 3 Done 4 Done Now finish creating the remaining connectors using Gridgen s 2 Point Connector command This com mand allows you to specify point pairs and automatically saves a new connector with each second point entered Try it now 1 Create 2 2 Point Connectors Gridgen now goes into connector segment creation mode The 3D cursor Section 2 8 of the User Manual should appear in the Display window as a small white cross The 3D cursor is positioned by holding down the right mouse button and then panning the mouse The 3D cursor will follow the motion of the mouse For each connector end point place the 3D cursor over the desired end point location and use the Add CP O by Picking option in the menu 3 Place the 3D cursor over point E 4 Add CP O by Picking 5 Place the 3D cursor over point H 6 Add CP O by Picking Gridgen should have automatically saved connector EH Now continue creating connectors on your own using this procedure for co
83. ase the pole domain is the center line of the main pipe Starting from the DOMAIN COMMANDS menu l Create Cell Type structured Assemble Edges Auto Next Edge Position the cursor over connector AC and when it highlights press the right mouse button Position the cursor over point A Hit the x key until the pole connector AA is highlighted OOS deb Quo CoA Be Qa C2 Press the right mouse button After you select the second connector Gridgen will automatically create the pole domain This is thanks to the Auto Complete feature which always tries to complete domains automatically once the first two edges are defined You will not be able to see the new domain since it has no area however it will be rendered in a light blue color indicating that it is indeed a domain Next create two of the domains on the main pipe You should still be at the CREATE A DOMAIN menu 1 Position the cursor over connector LN and when it highlights press the right mouse button 2 Position the cursor over connector NM and when it highlights press the right mouse button 3 Position the cursor over connector MI and when it highlights press the right mouse button 4 Position the cursor over connector IJ and when it highlights press the right mouse button Gridgen will then recognize that connectors JK and KL are needed to complete this domain and will add them 5 To start the next domain position the cursor over connector HC and when it h
84. at the number of DB entities in the Status window top left of the Gridgen screen as shown in the next figure Gridaer 15 00 BETA 1 0 Blocks 0 Domains 0 femectors 0 Nodes 7 DBs gener i c 3D Display Full Database Model 1 7 Display Full Database Model Noentities are displayed because all of the layers in the database model are currently turned off This is your first task turn on all layers to view the model starting from the MAIN MENU 1 Layer Manager 2 Status All On Your Layer Manager panel should appear as in the following figure 0 Construction Al A 2 3 4 5 6 8 9 Sphere Medium 3 Click in the Gridgen GUI window and use the r hot key on the keyboard to have Gridgen recalculate the viewing extent box for the model Your model in the Display window should appear as in the next figure Cubes and Spheres Layer Manager In this version of the model the small cube has been set to the Shaded display attribute so in this perpen dicular view it appears very light and almost white As you rotate your model you will see it more clearly Also of importance note that the small sphere is not visible It would appear to be missing Actually it is only disabled but is also somewhat hidden in the layer list Your next task is to find the layer it is in isolate that layer and enable the sphere 1 8 Find and Enable Small Sphere Your Laye
85. ations You have successfully exported all of your necessary files And of course this tuto rial is now complete 9 18 10 Droplet in a Cylinder Hybrid Grid 10 1 Introduction This tutorial will give you a guided tour of the Gridgen process for creating a hybrid volume grid for a flow field through and around a droplet within a cylinder The grid will consist of tetrahedral hexahedral prism and pyramid cells that form the volume of the flow field 10 2 Topics Covered This sample session is a short introduction to using Gridgen Basic Gridgen skills you will learn during this tutorial session are creating database curves using Curve Offset creating database surfaces using the Surface Revolution command using On DB Entities to automatically create connectors and unstructured domains extruding prisms using the Nrml extrusion command using the Rot extrusion command to rotationally extrude structured grids using the Hyp extrusion command to extrude hexahedral cells initializing the tetrahedral volume grid using the Run Solver Unstrctrd command exporting the hybrid grid using the Export Analysis Data command 10 3 Background You should complete all previous tutorials before attempting this session since it assumes you already have the skills covered You should also familiarize yourself with Section 7 Section 11 and Section 12 for fur ther information on unstructured meshing and extrusion methods used in this tutorial
86. base entities to view the topology from the DISPLAY COMMANDS menu The Display win dow should look like Figure 22 16 Figure 22 16 Connectors Forming the Boundary Topology Redimension the connectors to ensure a structured grid can be obtained from the connectors From the CONNECTOR COMMANDS menu Redimension Grids Select connector JK 14 Select Connector KL 14 Select Connector HR 27 Done Apply New Dims o c KD Fwy a Done 8 12 Structured Domains on Inlet Plane You will now tell Gridgen how to make a surface grid from the connectors you just created From the MAIN MENU 1 Domains 2 Create 3 Assemble Edges 4 Turnon the Auto Next Edge toggle Domain GHIJ 1 Pick connector GH 2 Pick connector HI 8 13 LDI Combustor Advanced Structured Grid Domain ADEGJK 1 Pick connector GJ 2 Pick connector JK 3 Pick connector AD Domain ABMNLK 1 Pick connector AK 2 Pick connector KL 3 Pick connector LN 4 Pickconnector NM Domain NOPL 1 Pick Connector NO 2 Pick Connector OP Domain GHRQSTU 1 Pick connector GH Pick connector HR Connector RQ is picked automatically Pick connector QS followed by ST then finally TU OQ 8 oY Done Gridgen completes the domain and initializes the surface grid using transfinite interpolation TFI Your Display window should look like Figure 22 17 YZ From the DOMAIN COMMANDS menu 1 Create 2 Assemble Edges 3 Turn off the A
87. ck faces For more control over grid point distribution Sometimes a face is broken into smaller pieces to give you more control over the grid We are free to start with any face Let s choose the face rin 1 Position the cursor over connector GF Press and release the right mouse button 2 Move the cursor off the domain Notice the Browser window contains a schematic of this face Since this face consists of only one domain save it and proceed with the second face 1 Save the Face 2 Position the cursor over connector CJ Press and release the right mouse button 3 Save the Face 4 25 Swept Ramp Basic Multi Block Structured Grid Position the cursor over connector AH Press and release the right mouse button Save the Face Position the cursor over connector NM Press and release the right mouse button Save the Face 9e uh OY COAC E Position the cursor over connector FG Notice even though this connector is part of the domain corre sponding to the Nmax face the domain GEMNG wasn t highlighted The ambiguity is caused by the fact connector FG is used in several domains and Gridgen guessed which one it should highlight When there are multiple pickable items at the cursor location as there are in this case you can use the x hot key to scroll through all of the pickable items until the one you want the top face is highlighted 9 Press and release the x hot key 10 Press and release the right mouse button
88. ckground You should complete the tutorials in Section 2 Section 4 and Section 5 before beginning this lesson since this tutorial assumes you already have the skills covered in those sections 6 4 Geometry The intersecting pipe configuration you will use for this tutorial is shown in Figure 20 1 Figure 20 1 Geometry for Intersecting Pipes Tutorial The grid you will generate consists of two blocks One block fills the main pipe The other block is in the branch section The block topology you will build is shown in Figure 20 2 Within each block one family of grid lines will run in the flow direction however the cross section grid topology will be different for the two 6 1 Intersecting Pipes Pole Grid Construction Top Down blocks In the main pipe an O topology is used with a pole running down the center of the pipe This topology makes efficient use of the cells allows you to cluster tightly in the pipe wall boundary layer and keeps grid lines normal to the walls In the branch section an H topology is used This is not as efficient as the O topology but it makes interfac ing with the main pipe grid easier Figure 20 2 Intersecting Pipes Grid Topology 6 5 Getting Started Begin by starting Gridgen either by typing the string gridgen on Unix workstations or simply double clicking the Gridgen shortcut on your PC s desktop Usually the first step in running Gridgen is to select the software Section 17 1 of
89. create a database arc and follow that with a curve offset Finally you will create two surfaces of revolution and intersect them For the first two database entities you will use the Curve Line command and these lines will later be used as the axes of rotation for two surfaces of revolution To create the first line AB do the following 1 Database Create Curve Line Add CP O via Keybrd 0 0 0 Add CP O via Keybrd 0 0 10 oe ib ION CA sho UE ES Save DB curve Now create the second line CD by the same process 1 Curve Line 2 Add CP O via Keybrd 3 BO Oy 0 4 Add CP O via Keybrd 5 50 5 0 6 Save DB curve You may not be able to see the two lines in the Display window Go ahead and zoom the model out and rotate to a more isometric view Use the pad 7 8 and 9 keys to rotate the model in x y and z screen coordi nates respectively Section 2 7 4 The r hot key will always restore the model to an orientation where the body and screen coordinate systems are aligned if you are not happy with the results of your manipulations Since the first line AB is so small relative to the red rotation axes you may wish to also move the rotation point to the y min end of the line CD Do this by holding down the Ctrl key and clicking on the y min end of line CD with the right mouse button Now you will create the two entities that will later be revolved about the lines axes of revolution just completed The first entity wil
90. creation we are going to modify the database a little bit It will keep the same shape but we are going to change its topology slightly First split the surface on the front of the centerbody by Database Modify Select the centerbody nose surface entity 2 Done Split V Move O via Keybrd 0 5 Split at Hiliter 10 Confirm the split with Split It NOU OO P ONU ON c QA a The nose surface is now split into two separate surfaces Next split the upper surface at the front of the inlet nacelle j Modify Select the front upper nacelle surface entity 11 Done Split U Move O via Keybrd 0 75 Split at Hiliter Woo pes Rex CON OO sb NS Confirm the split with Split It There is one more surface to split the lower surface at the front of the inlet nacelle 7 4 Importing the Database Modify Select the front lower nacelle surface entity 9 Done Split U Move O via Keybrd 0 25 Split at Hiliter Confirm the split with Split It 10 Done We 0 oS ON po dee we GB Notice that we split the lower and upper surfaces at very different u values because they are parametrized differently We did not split them at exactly the same location but it is pretty close These new and existing surface gaps will require us to make some adjustments to our model s tolerances in the SET DEFAULT VALUES menu Your geometry should now look like the one in Figure 21 3 Figure 21 3 Inlet Geometry Af
91. d is the cause of the inte rior point distribution problem 7 n AT EU I TT LT i L 31 pal Figure 21 7 Domain Interior Problem Caused By Database Surface Parametrization The simple fix to this problem is to elliptically refine this domain 1 Run Solver Structured 2 Select domain UTML 7 13 B 747 Nacelle Working With An IGES Database 3 Done 4 Elliptic Slvr Run N Iters 5 30 6 Done Save There are only four connectors left to create OD RJ AK and IN Go ahead and create them now on your own as 2 Point Connectors Turn off display of all the domain interior grids to reduce the clutter on the screen 1 Disp Edit Dspla Dom Pick All Done Off Done Apply Atts Abort Done 99 b Gv oe B dg Now your Display window should look like Figure 21 8 Figure 21 8 All Connectors for the Two Blocks We have four domains left to create so finish them now We will redimension a couple connectors before starting 1 Doms 2 Redimension Grids 3 Select connector PQ 4 11 5 Select connector QR 7 14 Creating Block Two 20 Done Apply New Dims Create Assemble Edges Make sure Auto Next Edge and Auto Complete are toggled on Pick connector JR Pick connector RN Gridgen will complete doma
92. dow that A total of 1 closed sur face faces and 4 baffle faces were assembled into the block After hitting any key to continue note that the closed face has normals rendered as shown in Figure 27 4 which correctly point into the interior Therefore it is not necessary to use Reorient Faces 8 Done Save Blocks Figure 27 4 Block Face Normals Also in the BLOCK COMMANDS menu 1 Run Solver Unstrctrd 2 Pick AII 12 6 Setting Flow Solver Boundary Conditions 3 Done 4 Initialize 5 Done Save Now use the Examine command to have a look at the interior of your new unstructured block Move a Phy X Y or Z Hiliter plane to any position along the model and have Gridgen calculate a Ref Surf Crinkle ref erence surface for instance Try to produce reference surfaces that reveal the presence of the interior baffle surfaces 12 10 Setting Flow Solver Boundary Conditions To finish this tutorial we will set Fluent boundary conditions From the ANALYSIS S W COMMANDS menu 1 Set BCs Note there are Type 1 interfaces specified automatically as shown in Figure 27 5 These correspond to both sides of each of the baffles so each corresponding domain number in parenthesis is shown twice once per side Placing the cursor over each side to hilite it will result in Gridgen hiliting the domain while render ing the normals for that side in the Display Window Since Gridgen intends to treat these baffles as connec tions by defau
93. e 19 6 The Browser Shows a Schematic of the Ramp s Domain Being Created This schematic represents the four sided computational space of the domain you create in the Display win dow It will help you keep track of which of the four edges you are defining and how many grid points are on each edge As you add connectors to the domain definition there is also a color coding scheme for the edges Since the domain is defined by the closed loop of connectors forming its perimeter you must choose two things before starting the node at which the perimeter is to begin and end and the direction of the loop These two choices are irrelevant to the eventual grid index orientation they are only used in the creation pro cess For this domain we will start at the node corresponding to Point A in Figure 19 3 and proceed in a counterclockwise direction 1 Position the cursor over the connector corresponding to connector AB 2 Press and release the right mouse button 3 Move the cursor off the connector Take note of the Browser window It indicates you are Defining the First Edge of the domain and the edge has 15 points The yellow line in the Browser window corresponding to edge 1 represents the mapping of the yellow connector in the Display window to physical space However this connector is not the only connector that is part of edge 1 To complete the first edge do the following 1 Position the cursor over the connector corresponding to connec
94. e Constant Z Plane toggle 7 Done Setting Attributes Now create the prism layer From the BLOCK EXTRUSION menu 1 RunN 2 10 3 Done 4 Done You have now created a layer of prism cells from the triangular surface grid into the interior of the droplet 10 8 Droplet Core Volume Close the Core of the Droplet By default the rendering of the domains of the extruded prism layers has been turned off To display the domains on the symmetry plane and interior surface of the extruded prism layers do the following 1 Disp 2 Edit Dspla Fac 3 Pick All 4 Done You are now in the DISPLAY ATTRIBUTES menu 1 display style Hidden Lines Removed 2 Done Apply Atts 3 Abort 4 Done The rendered domains are shown in Figure 24 6 Figure 24 6 Extruded Prism Layers Inwards into the Droplet 10 9 Droplet Core Volume You now have to create the interior tetrahedral mesh forming the core of the droplet This will complete the hybrid mesh on the interior of the droplet consisting of prism and tetrahedral cells 10 9 1 Close the Core of the Droplet You must first create an unstructured domain at the symmetry plane of the droplet core This will close the core to form an enclosed shell within which a tetrahedral grid can be generated From the MAIN MENU 1 Domains Create Cell Type unstructured Pa a Assemble Edges 10 9 Droplet in a Cylinder Hybrid Grid 90 c OS OA Turn on the Auto Save toggle Pick the
95. e domain that has linkages to the main pipe and branch pipe blocks For your grid connector TU will also need to be re dimensioned to maintain computationally balanced sys tem To re dimension connectors JK FG and TU from the MAIN MENU 1 Connectors Redimension Grids Select connector JK 2 Select connector TU 93 Done Apply Dims OO coh CONI X be DAL SES Done 6 8 Building H Block for Branch Pipe Generating the H block for the branch pipe will require you to run the glyph script block gui glf once more From the MAIN MENU 1 Glyph 2 Re execute Last Script 6 9 Intersecting Pipes Pole Grid Construction Top Down Steps 3 4 should be completed from within the Ready Made Blocks interface 3 H Block 4 Run 5 Done You should now have an H block positioned at the origin You will be connecting one face of this H block to the end of the branch pipe and the opposite face to domain FJKG Figure 20 10 illustrates the points that will be referenced when connecting a face of the H block to the end of the branch pipe Figure 20 10 H Block for the Branch Pipe To attach the domain OQSP to the end of the branch pipe you will need to translate point O to point O point Q to point Q point S to point S and point P to point P You will then need to scale the H Block to fit the branch pipe Since the H Block is 4 units in length along any edge and the branch pipe has a radius of 0 75 units you
96. e gridgen home path examples tutorial fe directory You may want to copy it to a local directory before trying to import into Gridgen Assuming that you have copied the file tension stl into your current working directory from Gridgen s MAIN MENU 1 Input Output 2 Database Import 3 Select tension st1 from the Browser 4 Open 5 Done Orient the view in the Display window as shown in Figure 25 2 You will notice that you have imported a single shell database entity made up of triangles defining the tension bar s geometric shape When feature extraction is applied the imported model is automatically divided into shells and is much more amenable to meshing 11 2 Setting Defaults Figure 25 2 Shell Model 11 7 Setting Defaults For the purposes of this tutorial you are now going create a structured surface grid You will need to set a default number of grid points to 15 for all of the connectors p ET From the MAIN MENU 1 Defaults 2 Con Dim dimen 3 15 4 Done Note setting the Split Angle default prior to importing the shell surface will result in the surfaces being 11 8 Tension Bar Feature Extraction split automatically This is useful if there are discrete angles in your model that can be split into definite fea tures However for more complex models it is recommended you extract features from the shell surfaces via the Feature Ext command in the DATABASE COMMANDS menu 11 8 Feature
97. e how the boundary condition you just set is now reflected in the Browser To set the rest of the bound ary conditions 4 34 Customizing the Grid for the Analysis Software Pick the three Browser entries that contain the text nmin Done Wall Pick the two Browser entries that contain the text nmax Done Free Stream Pick the Browser entry that contain the text 1 Emin Done 19 1907 ci ON con ees c LO Inlet 10 Pick the Browser entry containing the text 2 Emax 11 Done 12 Outlet 13 Done 14 Done Now you can save another Gridgen file 1 Input Output Gridgen Export Pick file name ramp gg Open Yes overwrite file eno me R cb Done Finally export the files needed to run the STAR CD code 1 Analysis S W 2 Export Analysis Data 3 Type In Name 4 ramp 5 Done 6 Quit Gridgen 7 Quit Gridgen At last you are ready to run the STAR CD code using the files ramp inp ramp bnd ramp cel and ramp vrt The grid including nodes connectors domains blocks surface and volume grids display set tings and analysis software boundary conditions is saved in file ramp gg 4 35 Swept Ramp Basic Multi Block Structured Grid 4 36 5 Intersecting Pipes Pole Grid Con struction Bottom Up 5 1 Introduction This tutorial will introduce you to several special Gridgen capabilities while you build a grid for two pipes intersecting in a Y junction 5 2 Topics Cove
98. e main pipe From the MAIN MENU 1 9v Ee ow EB Domains Modify Select domain EIKG from the Display window or from the Browser list entity 9 Split I Lines Move the Hilite in the Display window to a point just to the left of where the branch pipe intersects the main pipe Done Split at Hilite The three new domains EIJF FJKG and GKLH should now appear as in Figure 20 9 6 8 Building H Block for Branch Pipe Figure 20 9 Split Domains of Main Pipe Polar Block You now need to prepare domain FJKG for the next block you will create with the block creation glyph script Section 6 8 This next block will be fit over the branch pipe which will require domain FJKG to be one of its faces To accomplish this you will need to take advantage of the manner in which Gridgen treats connectors and domains If two connectors in Gridgen have the same endpoints number of grid points and distribution those connectors are considered identical One of the connectors is thrown away and the remaining connector assumes the linkages of both connectors Gridgen treats domains in a similar manner Changing the dimension of connectors JK and FG to 2 will make all of domain FJKG s connectors match those of the corresponding face of the new branch pipe block once the four corners of the block s face have been moved to the points F J K and G This means that Gridgen will consider those connectors and domains identical which will result in on
99. e of coordinates you see this line spans from a 0 0 0 tog 0 1 5 0 It is hoped you can also see this particular line may be created with one connector consisting of one Line segment To draw this connector do the following Connectors Create Add Segment 3D Space Line Add CP O via Keybrd 0 0 0 Add CP O via Keybrd O 1 5 0 wo 90 cL OON CA fO ow d Done Save Segment You have just completed one third of the connector creation process shape definition The connector shape 4 4 Drawing Connectors consists of one segment Line The segment was defined by two control points 0 0 0 and 0 5 0 The image on the screen is probably small because Gridgen s default viewport size is larger than the particu lar grid we are creating To get a better look at the grid zoom in on the connector 1 Press and hold the middle mouse button 2 Move the mouse toward you south on the mouse pad 3 Continue until the connector is comfortably sized in the screen 4 Release the middle mouse button You should have noticed while the middle mouse button was pressed the cursor looked like a small magnify ing glass reminding you that you were zooming the image Let us continue with the second step of connector creation assigning a number of grid points Section 9 1 From Figure 19 2 you can see you need to put 21 grid points on this vertical connector To enter this infor mation in Gridgen do the following 1 ReDime
100. eating Block Two Now you have a lot more connectors and five more domains Note the purple color of the domains indicat ing they were automatically database constrained However the domain on the aft most surface QRNM has the same dimension on all edges as the forward four domains just as we instructed Gridgen Since the interfacing connectors along the boundary between QRNM and PQTU UTML do not match dimensionally Gridgen does not automatically merge them Therefore we now have coincident connectors along this cir cumferential boundary between the larger QRNM and the two domains in front of it Make the necessary dimension changes and Merge the coincident connectors now Redimension Grids Select connector QT 16 Select connector TM L5 Done Apply New Dims Cons Merge Auto x 90 c QN QA d ow o 0 1 10 Doms You may have already noticed that the grid on domain UTML looks a little strange Figure 21 7 shows a view of this domain from the bottom looking up Gridgen recognized that all the connectors for this domain lie on the same database entity so it created the grid using the parametric transfinite interpolation method Section 10 1 5 of the User Manual This is usually a nice property because it ensures that the grid points are on the database surface In fact it worked well on all the other surfaces of the nacelle Occasionally you will get a database surface that has an odd parametrization That is the case here an
101. eating extruded blocks using Extrude From Doms 13 3 Background Familiarity with basic Gridgen usage would be advantageous so it is recommended you work at least the second tutorial in Section 2 Also familiarity with Gridgen s GUI is recommended Section 2 of the User Manual Finally a complete volume the Glyph Reference Manual is devoted to the Glyph language and will be a valuable resource for this tutorial and all scripting work Section 1 of the Glyph Reference Man ual 13 4 Geometry The geometry to be gridded is a 3D 3 block structured grid for 1 4 symmetry of an axi symmetric converg ing diverging nozzle The grid will be generated by sweeping the symmetry plane surface grids Figure 28 1 through 90 degrees of rotation about the centerline axis 13 1 Converging Diverging Nozzle Using Glyph Scripting G H C E ru L A B Figure 28 1 Nozzle Geometry 13 5 Getting Started Because the focus of this tutorial is scripting and not building the grid a script is provided as your starting point This script nozzle g1f was generated by journaling creation of the symmetry plane s connectors and domains to a file You will use this file to get started and then append your work to it Begin by starting Gridgen either by typing the string gridgen on Unix workstations or simply double clicking the Gridgen shortcut on your PC s desktop We will select the analysis software package to be used at the end of the tuto rial The
102. ector The line connector is used twice in the domain either as edges 1 and 3 or as edges 2 and 4 The pole domain is used as one of the faces in the block that contains the pole The connectors in the pole domain must be shared with the neighboring faces in the block If you run into trouble when creating pole grids it is usually caused by having duplicate connectors i e two connectors that lie on top of one another You can search for and eliminate these types of coincident connec tor occurrences using Gridgen s Merge utilities Section 14 10 Although the grid is not complete there is one more block to build this is the end of the tutorial The con struction of the second block uses skills you have learned in this and previous Gridgen tutorials If you would like to complete this grid for practice please do 5 16 6 Intersecting Pipes Pole Grid Con struction Top Down 6 1 Introduction This tutorial will introduce you to several special Gridgen capabilities while you build a grid for two pipes intersecting in a Y junction using a top down approach The original tutorial was provided by Mr John Stone CFD Technologies Sheffield UK 6 2 Topics Covered Gridgen skills you will learn during this tutorial session are using Glyph commands to execute an existing script matching block topology to geometry using Block Modify and Connector Modify Using Domain Modify to project domains onto database geometry 6 3 Ba
103. ectors that are shared between domains that are currently being elliptically refined For this case the only connectors that we wanted to float were also the only con nectors between the two domains we were refining Now would be another good opportunity to save your grid Figure 21 6 Centerbody Domain After Elliptic Refinement Now back to creating connectors and domains The next domains we will create are the ones on the interior wall of the nacelle We will use another way of creating connectors and domains constrained to databases On DB Entities which lets you pick a set of database surface entities on which to create domains For any database surface that you pick Gridgen will create a connector for each edge of the surface using the default connector dimension and spacing constraints and will then attempt to put these connectors together in the definition of a domain This command will only be successful in completing structured domains from these connectors when the database surfaces have exactly four edges If you are setting the connector dimensions based on average spacing the opposite edges may not have the same number of grid points and Gridgen will not be able to put a structured domain on that surface Try it now 1 Doms Create Toggle on Auto Merge Set Toler 0 1 On DB Entities Select the 5 surfaces on the nacelle wall corresponding to OPUS SULK PQTU UTML and QRNM COs SN Bes G ub Done 7 12 Cr
104. ed Grid 2 Select the block 3 Done 4 Initialize 5 Done Save In rare cases the solver may have trouble creating an interior in a fashion that preserves the surface grid ele ments on the boundary of the block When this happens Gridgen will highlight the problem cell edges or entire cells while displaying an error message in the Message window These issues typically can be resolved by changing the resolution and or smoothness of the domain in the problem area There is now a complete tetrahedral volume for the block although there has been no visible change in how the model is shown in the Display window Examine Section 16 of the User Manual the block now to see some sample crinkle surfaces on the interior of the volume mesh Proceed as follows Examine 2 Select the block 3 Done 4 PhyX At this point Gridgen calculates a Cartesian extent box around the block and displays an x constant scan plane You may specify an exact location for the scan plane if you wish 1 Xkbrd 2 50 3 Ref Surf Crinkle Pressing the Crinkle button instructs Gridgen to generate a crinkle sheet made up of the faces of tetrahedra that are intersected by the scan plane Your Display window should now show the model with the extent box scan plane and crinkle surface as shown in Figure 22 10 9 14 Saving Your Model and Export to Solver Figure 22 10 A Crinkle Surface Helps to Visualize the Volume Grid You could also have selected Ref
105. ed rt kedeue ee duue read 5 8 5 8 Creating DOMAINS oo ra e Pate eiie b ed 5 13 5 9 Creating BOOKS viso oie n Wn Rs 5 15 6 Intersecting Pipes Pole Grid Construction Top Down 6 1 6 1 TE OCCT OTN shoot se sence aso rtl ette e ea paradise dnd os tee 6 1 6 2 TOPICS COVEled iO IG Ha Ee RN ME EO 6 1 6 3 Background o v n aeiveaey amas es ive wats een eee Ebor eiiD i 6 1 6 4 Geometry o oo ooo Dio iue quio oer nea hearse 6 1 5 5 GOING Started uie roo aree Rau SES 6 2 6 6 Importing the Database ssssisissssssee seen 6 2 6 7 Building Polar Block for Main Pipe sssssssssssseseneeennne 6 3 6 8 Building H Block for Branch Pipe ssssssssseeneeeennnee 6 9 6 9 Connector and Domain Projection sss 6 16 7 B 747 Nacelle Working With An IGES Database 7 1 FEV IIE OGUGUONN MERO 7 1 72 TOPICS CoVer d enciso rot DEF boston e Fog o sane asad Mrd E Eria 7 1 7 3 Background aoo eee tret avito oti eae aaa eio 7 1 rEZ GSOmelty tup DD Leu uu Oe dass ce Mun DICE 7 1 7 5 Getting Started ue eoo tu eer drat ba mvanbieds afe dai iiu 7 3 7 6 Importing the Database sss enne nennen 7 3 7 7 Creating The First Block au oie ee bees dn ae eles 7 6 7 8 Creating Block Two eii ceti ipM ptr uterine 7 8 8 LDI Combustor Advanced Structured Grid 8 1 8 T IDIFOdHUCHOD
106. ed to the left side of the Display window You probably noticed that the cursor changed to an image of four arrows while the left mouse button was pressed This is to remind you that you are panning the image Begin drawing the new connector by 1 Add Segment 2 3D Space Line Notice the 3D cursor small white cross appears at the last control point we placed during connector shape definition Point B in Figure 19 3 Fortunately this also happens to be one of the control points on the con nector we are drawing Proceed with the segment shape definition using 1 Add CP O by Picking 2 Add CP O via Keyboard di cde 4 Done Save Segment In case this new connector is not completely visible in the Display window use the panning and zooming controls to reposition the image so that it is This connector needs to have 17 points Do the following to assign the dimension and then begin point distribution 1 ReDimension From keybrd 17 Done ReDimension ReDistribute podes pid Gridgen provides a tool for ensuring the clustering on either side of a break point is the same since smooth variation of spacing along an edge is usually required by analysis software Specify the clustering toward the ramp using the following 1 Begin A Take note of the Message window text Enter the AS value at the beginning of the subconnector Use 1 to copy from the adjacent subconnector 0 to unconstrain the end Default 0 10000E 01
107. egments interpolate user specified control points There are three steps in creating a connector 1 Define its shape 2 Assign it a dimension number of grid points 3 Distribute the grid points The first connector you will create is the circular arc section from point C to point D The center of the arc is at point A From Gridgen s MAIN MENU 1 Select Connectors This will take you to the CONNECTOR COMMANDS menu 2 Select Create or type n to go to the CREATE CONNECTOR menu There are three main techniques for creating connectors Add Segment is for general connector creation 2 Point Connectors is for rapid creation of connectors composed of lines or database constrained lines On DB Entities is for turning database curves and edges of database surfaces into connectors in one step For this example 1 Select Add Segment 2 Select Rational Circle to begin creating arc CD You are now ready to begin creating a circular arc using commands on the CIRCULAR ARC menu Refer to Figure 18 3 for the following discussion On Gridgen s screen immediately above the menu is a rectangu lar area called the Blackboard window Gridgen reports topical information in this window During connec tor creation you will see information about the number of segments in the connector how many grid points have been assigned to it dimension and control point locations The blackboard also shows the x y and z coordinates of Gridgen s 3
108. ends and symmetry plane of the cylinder core forming a water tight enclosed shell A tetrahedral volume grid can then be initialized from the faces For convenience we have assigned a naming convention to important points in the grid shown in Figure 24 11 A B Figure 24 11 Labeled Coordinates on Cylinder Core Symmetry Plane 10 13 1 Close Cylinder Ends You are now going to create two unstructured domains that will cap the ends of the cylinder core From the MAIN MENU 1 Connectors 2 Create 3 2 Point Connectors Connector AB 1 Place the 3D cursor over Point A 2 Add CP O by Picking 3 Place the 3D cursor over Point B 4 Add CP O by Picking Connector CD 10 16 Volume Grid in the Core of Cylinder Close Cylinder Ends 1 Place the 3D cursor over Point C Add CP O by Picking Place the 3D cursor over Point D Add CP O by Picking Done Done Creating Conns Di Gv Uwe d c 9 Done The Display window should now look like Figure 24 12 Figure 24 12 Connectors on the Ends of Cylinder Core You will now create an unstructured domain for each of the end caps From the MAIN MENU 1 Domains Create Cell Type unstructured Assemble Edges Turn on the Auto Save toggle Pick connector AB then the half circle connector BA Pick connector CD then the half circle connector DC oo Sw QN GUN ES aa Done The unstructured domains are shown in Figure 24 13 10 17 D
109. enu and l Create 2 Cell Type structured 3 Assemble Faces 4 Add 1st Face 5 AutoSave Face 6 Position the cursor over the pole domain along line AC and when it highlights press the right mouse button 7 Leave the cursor over the pole domain and hit the x key until domain AEFGHC highlights then press the right mouse button 8 Leave the cursor over the pole domain and hit the x key until domain AMNC highlights then press the right mouse button 9 Position the cursor over connector EI and when domain AEIM highlights press the right mouse button 10 Position the cursor over connector HL and when domain CHLN highlights press the right mouse but ton 11 Pick Multiple Doms 12 Using the cursor and right mouse button pick the four domains on the outer surface of the main pipe 13 Done 14 Atthis point you will receive two messages regarding possible topologies and whether or not the block is right handed This is normal simply hit the space bar for each and continue 15 Done Save Blocks The key points to remember when creating grids with poles are A pole connector is a zero length connector with grid points on it You create it as a line connector with both end points at the same location Pole connectors are shown in the Display window as dots with circles around them 5 15 Intersecting Pipes Pole Grid Construction Bottom Up pole domain contains two pole connectors and one other conn
110. er references to this database and database file will be included in the Gridgen restart file Note that it is important to always save your database The database must be saved using Gridgen s native Composite database file format Any database entity from any source can be stored in a composite file You can also mix entities from different sources IGES PATRAN Gridgen in the same composite file In case you did not save your database model earlier do the following while still in the INPUT OUTPUT COMMANDS menu 1 Database Export 2 Composite 9 15 Pierced Elbow Basic Unstructured Grid 3 Done 4 Type In Name 5 elbow Note that Gridgen will automatically append the default file extension dba 6 Done Now to save your Gridgen restart file proceed as follows 1 Input Output 2 Gridgen Export 3 Type In Name 4 elbow Note that Gridgen will automatically append the default file extension gg Your restart file is saved immediately If you had typed in the name of an existing file you would have been prompted on whether to overwrite that file or not Now before you export your flow solver files for Fluent you will need to set some boundary conditions Proceed as follows 1 Analysis S W 2 Set BCs Your Blackboard window should now look like the one shown below The list contains an entry for each domain The first column which contains only the number 1 for this problem is the block number The
111. es for the Intersecting Pipes You should be at the DB CREATION menu and the Display window should look like Figure 20 4 You are now ready to create the surfaces of the two pipes You will construct the surfaces of the two pipes as surfaces of revolution Surfaces of revolution are created by specifying two curves a generatrix and an axis The generatrix is revolved around the axis to produce the surface By default Gridgen revolves the generatrix a full 360 degrees around the axis For this tutorial you will only use 180 degrees of rotation CREATE SURF OF REVOLUTION Reselect Axis Curve del Reselect Both Curves 0 Re Set Fit Tolerance 2 Re Set the Angle a Done Save Surf of Revol ent Abort Don t Save Surfaceesc Help Starting from the DB CREATION menu 1 Surface Revolution 2 Position the cursor over the edge curve of the main pipe the curve you offset from AC and press and release the right mouse button Re Set the Angle 180 Done Save Surf of Revol Surface Revolution 9e c OON CA ud ow release the right mouse button Position the cursor over line AC and press and release the right mouse button Position the cursor over the edge curve of the branch pipe the curve you offset from BD and press and 9 Position the cursor over line BD and press and release the right mouse button 10 Re Set the Angle 11 180 5 6 12 Done Save Surf of Revol 13 Done Creating a Database The fin
112. es later From the CONNECTOR COMMANDS menu 1 Modify Select connectors IJ KL JQ and KS from the Display window or from the Browser Done Project Closest Pt Done Project Done Replace Connectors 9e cb Ow o 9 Maintain Linkages Only one more connector to create The final connector is on the plane of symmetry of the smaller pipe between points O and P You could create it using 2 Point Connectors but Gridgen will try to put it on any adjacent database entities in that case and all we want is a straight line Actually Gridgen will create the straight line connector we want if all the available on database paths between the selected points are already filled It is easier in this case to create it explicitly as a straight line From the CONNECTOR COMMANDS menu 1 Create 2 Add Segment 3 3D Space Line 4 Position the 3D cursor over point O 5 Add CP O by Picking 6 Position the 3D cursor over point P 7 Add CP O by Picking 8 Done Save Segment 9 Done Save Connectors 10 Done Creating Conns 5 8 Creating Domains Go to the DOMAIN COMMANDS menu to begin creating domains The first domain you create will be a pole domain A pole domain is a domain that is collapsed into a line It consists of two pole connectors and a straight line connector The straight line connector is used twice in the definition of the pole domain In 5 13 Intersecting Pipes Pole Grid Construction Bottom Up this c
113. escription IV Move the source layer status Cancel OK 3 Enter 5 in the Target Layer field 4 OK You were not instructed to alter the toggles for either Move the source layer description or Move the source layer status The source layer has no description so that option is irrelevant The source layer sta tus on should be preserved Further Filtering Now finish the job with a new description for layer 5 5 Select layer 5 6 Description The Description dialog box pops up Description Cancel OK 7 Enter Sphere Smallin the Description field 8 OK Now all the major objects in the model should be layered and described consistently Your layer Browser should now show the updated layer list as shown below Note that layer 5 is now included in the list and layer 831 even though empty is still included in the list since it is the current working layer the current working layer is always listed in the layer Browser and set to on Traje pema o Construction All 10 Sphere Medium 15 Sphere Large 20 Cube Small 25 Cube Medium 30 Cube Large 831 1 10 Further Filtering Now try experimenting with the other filter tools First try the Description text string filter This filter will try to match the string you enter to the text in each layer description By default the field contains only an asterisk the wildcard character matching all layer descriptions and therefore all layers a
114. f the grid genera tion process As you can see from Figure 19 3 the face opposite the one you just made hi jkl1mnh max is the same except for the location of the ramp We will copy the existing domain translate it in z to the cor rect location and then move the ramp point j Domains Copy Position the cursor over one of the edges of the domain you have already created Press and release the right mouse button Done Position the cursor over Point A Press and release the right mouse button Set Handle via Keybrd 0 0 1 Ma Spec ee SOY ON cu ip lS 4 17 Swept Ramp Basic Multi Block Structured Grid 10 Done Translate 11 Save Domains You just made a copy of the original domain and translated it by moving one of its control points from 0 0 0 to 0 0 1 You can confirm that everything is OK by examining the Status window which should look like 0 Blocks 2 Domains 10 Connectors 10 Nodes 0 DBs STAR CD 3D To verify the scene graphically first change from an orthonormal default to perspective viewing transfor mation 1 Disp 2 Wndw Ortnrml This is a toggle button that switches between orthonormal and perspective viewing modes each time you press it To further graphically illustrate the two domains rotate the image 1 Press and hold the PAD key 2 Release the PAD key after about 45 of rotation 3 Press and hold the PAD key 4 Release the PAD key after about 45 of rotation Reca
115. g the domain of the structured grid for the swirler pas sage From the CONNECTOR COMMANDS menu 1 Modify 2 Select either connector 3 Done 4 Split 5 Oto Prev Grid Pt e 6 Splitat Cursor O 7 Oto Next Grid Pt e 8 Split at Cursor O 9 Press Enter on the keyboard acknowledging the warning message 10 Repeat steps 1 9 for the other connector of passage entity 9 Zoom into the area around the passage entity 9 and the Display window should look like Figure 22 7 on the next page t Figure 22 7 Passage Entity 9 Connectors You now need to join the connectors AE EB to define the edge AB and segment connectors CF FD to define the edge CD From the CONNECTOR COMMANDS menu 1 Modify 2 Pick connector AE 3 Done 4 Join 5 Pick connector EB 8 5 LDI Combustor Advanced Structured Grid 6 Abort 7 Done Replace Connectors 8 Repeatsteps 1 7 to join segment connectors CF with FD to form the connector CD This completes the connector creation for the passage entity 9 The Display window is shown in Figure 22 8 Figure 22 8 Joined Connectors on Passage Entity 9 You now need to redimension the connectors From the CONNECTOR COMMANDS menu Modify Pick All Done ReDimension From keybrd 5 Done ReDimension Done Replace Connectors O 0 Nay OF o A m Maintain Linkages Since the connectors for the other seven passages are identical to those of passage entity 9 you will use the copy and rotate command
116. ge of this fact by moving Gridgen s 3D cursor over point C hold down the right mouse button and move the mouse Select Add CP O by Picking Press Done Save Segment to complete the definition of the shape of this connector and return to the CREATE CONNECTOR menu Select ReDimension to assign a number of grid points to this connector Click on From keybrd Enter 7 for the number of grid points Done ReDimension The default equal spacing is fine for this connector Select Done Save Connectors to complete the connector definition and return to the CREATE CONNECTOR menu We will create the next connector the line segment DE in a slightly different fashion You should now be at the CREATE CONNECTOR menu QW du 2 COE Select Done Creating Conns to return to the CONNECTOR COMMANDS menu Now select Copy to go to the COPYING CONNECTORS menu Move the cursor over connector BC it will change to a pink color when the cursor is over it While connector BC is highlighted press and release the right mouse button Select Done to tell Gridgen you do not want to pick any more connectors The Message window will display l 2 TRANSLATE Pick a handle point to control translation or select from the options below Position the pointing finger cursor over the control point at the left end of the connector Press and release the right mouse button You have selected this node as the translation control point the handle
117. ght mouse button 5 Connector EF forms one entire edge of the domain so tell Gridgen you are ready to start defining the next edge by selecting Next Edge 6 Position the cursor over connector GF 7 Press and release the right mouse button This connector is also an entire edge of the domain so select Next Edge 2 10 Refine the Structured Domain Grid As soon as you tell Gridgen the second edge is complete it will recognize that connector BG must be the third edge since it is the only other connector sharing node G It has the right number of points to complete the third edge Continuing the process Gridgen recognizes connector BC must be the beginning of the fourth edge since it is the only connector sharing node B However it does not have enough grid points to complete the edge so Gridgen continues by adding connectors CD and DE to the edge until it is finished Gridgen then completes the domain and initializes the surface grid using transfinite interpolation TFI Your Display window should look like Figure 18 7 Figure 18 7 The Bump Domain is Initialized by Transfinite Interpolation 1 Select Done to return to the DOMAIN COMMANDS menu 2 8 Refine the Structured Domain Grid The surface grid created aut
118. gridded They might in unusual cases be pointing out of the block as shown in the side view of the model in Figure 22 9 SA MVP ae To pica rc rae Figure 22 9 Block Face Normals May Point Outward You want to have the normals pointing into the interior of this block since that represents the volume we intend to discretize with tetrahedra If your normals look like those in Figure 22 9 reorient the block face normals using Reorient Faces while still within the CREATE AN UNSTRUCTRD BLOCK menu Now you may save your block 8 Done Save Blocks You have now successfully created and saved your block with surface normals pointing into the interior Note that the color of the block edge connectors is now dark blue giving a color cue that the connectors are used in a block The block is now ready to be initialized in the unstructured solver 9 10 Initializing and Examining the Tetrahedra Now that the block has been created you can initialize the interior tetrahedral volume In order to minimize memory usage Gridgen does not compute interior volume grids by default Once a tetrahedral volume has been generated it will be maintained in memory by Gridgen until you release it intentionally or you take some action that requires re initialization such as changing the number of grid points on one of the blocks edge connectors Initialize the tetrahedral volume now by 1 Run Solver Unstrctrd 9 13 Pierced Elbow Basic Unstructur
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120. he Intersecting Pipes Now that a topology for the blocking system has been chosen you can begin creating the grid For conve nience we have assigned a naming convention to important points in the grid The points labels and coordi nate values are shown in the following table Table of Intersecting Pipes Tutorial Coordinates Label X Y Z A 10 0 0 B 0 0 0 C 10 0 0 D 5 10 0 5 5 Getting Started Begin by starting Gridgen either by typing the string gridgen on Unix workstations or simply double clicking the Gridgen shortcut on your PC s desktop Usually the first step in running Gridgen is to select the software Section 17 1 to be used in the analysis This will ensure that the grid generated by Gridgen is consistent with the capabilities of the analysis software Since setting the analysis software is not the focus of this tutorial you can use the default generic analysis software setting No action on your part is necessary 5 6 Creating a Database You will begin creating the pipes by entering the points that define important locations on the geometry Then you will build curves followed by surfaces The final step in geometry creation will be to find the intersection curve between the two pipes 5 2 Creating a Database From the Gridgen MAIN MENU 1 Database 2 Create 3 Points You should now be in the CREATE POINTS menu shown below CREATE POINTS at padEnt by Picking p
121. he U S and other countries licensed exclusively 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 1l 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
122. hey intersect Any duplicates are deleted and the remaining con nectors are split at the intersection locations For example connector EH is automatically split into connectors EF FG and GH The connectors on the end of the branch pipe that is inside the main pipe will not be part of the final grid so we can delete them 5 9 Intersecting Pipes Pole Grid Construction Bottom Up Starting from the CONNECTOR COMMANDS menu 1 Delete 2 Select the connectors on the end of the branch pipe inside the main pipe using the cursor and right mouse button 3 Done 4 Done We also need to redimension connectors EF EG and GH because they need a different number of points than the default setting 1 ReDimension Grids 2 Select connector EF using the right mouse button 3 TI 4 Select connector EG using the right mouse button 3e FLT 6 7 8 Select connector GH using the right mouse button 11 Done Apply New Dims To fit the topology we chose for this grid we also need to split the connectors at the ends of the pipes and on the intersection curve 1 Modify 2 Select connector EM 3 Done 4 Split 5 Oto GP e via Keybd 6 21 7 Split at Cursor O 8 Abort Don t Split 9 Done Replace Connectors 10 Modify 11 Select connector HN 12 Done 13 Split 14 Oto GP e via Keybd 15 2t 16 Split at Cursor O 17 Abort Don t Split 5 10 18 Done Replace Connectors The ends of the branch p
123. hould be available in your Gridgen installation directory under gridgen home path examples tutorial mixer You may wish to copy the file to some other working directory before proceeding From the MAIN MENU 1 Input Output 2 Database Import 12 2 Setting Defaults 3 Use the Browser to navigate to the directory containing the copy of mixer dba and select it 4 Open To clean up the display of the model go to the DISPLAY COMMANDS menu 1 Disp 2 Toggle off Show EnbIdDB 3 Toggle off RotAxs 4 Done You will see the model essentially disappear while in the DISPLAY COMMANDS menu However once this menu is exited the entities return in an outline demoted mode After some image manipulations Sec tion 2 7 of the User Manual your model should appear as shown in Figure 27 2 Figure 27 2 After Display Clean Up 12 6 Setting Defaults You will need to set one default value to facilitate the use of the On DB Entities command for domain cre ation For On DB Entities to be available at all you must set either a default dimension Con Dim dimen or average spacing Con Dim avg As In the SET DEFAULT VALUES menu 1 Con Dim avg As 2 X45 12 3 Mixer Using Baffles 3 Done This setting instructs Gridgen to calculate the number of grid points necessary on each newly created con nector in order to achieve an approximate spacing of 1 5 between equally spaced grid points 12 7 Creating Unstructured Domains We will
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125. ighlights press the right mouse button 6 Position the cursor over connector CA and when it highlights press the right mouse button 7 Position the cursor over connector AE and when it highlights press the right mouse button 8 Position the cursor over connector EF and when it highlights press the right mouse button Gridgen will then recognize that connectors FG and GH are needed to complete this domain and will add them Note that we left Auto Next Edge turned on while creating these domains even though each has an edge with three connectors on it You can do this as long as the first two domain edges you pick each have only one connector on them After that Gridgen knows enough about the domain to keep you out of trouble The next most interesting domains are the end caps of the main pipe They each have a pole connector on one edge While still in CREATE A DOMAIN 1 Position the cursor over connector AM and when it highlights press the right mouse button 2 Position the cursor over point A and hit the x key until the pole connector AA highlights 3 Press the right mouse button 4 Position the cursor over connector AE and when it highlights press the right mouse button Gridgen will then recognize that connectors EI and IM are needed to complete this domain and will add them H Position the cursor over connector CN and when it highlights press the right mouse button 6 Position the cursor over point C and hit the x
126. iiic eau eem en AGE iU IE M 8 1 8 2 Topics Covered BENNETT HU 8 1 8 3 Background e oo pU vrbi dq nete ape du eene 8 1 8 4 Geomelry e oet NN ML IMEEM E 8 1 6 5 Gelling Slarted iio e ovo Rd oto ee tutes d atit 8 2 8 6 Importing a Database o innate ease ee 8 2 8 7 Selling Detaulls c i e ot ld ue bx eed o qe eerta dein ds 8 3 8 8 Displaying Swirler Passages sssssssssssss esee 8 3 8 9 Connectors at the Inlet Plane of the Passages sssssss 8 4 8 10 Domain Topology Between Passages enne 8 8 8 11 Creating Boundary Topology sese 8 10 8 12 Structured Domains on Inlet Plane ssssssssssssseseee 8 13 8 13 Running the Elliptic PDE Solver sssssssssssse 8 16 8 14 Creating Domains for the Passages sss 8 17 8 15 Extruding Inlet Block oie eO rei ie dia dose 8 19 8 16 Creating Blocks for the Passages 1 sse 8 20 8 17 Tutorial Wrap up iei P ue tete te aes 8 22 9 Pierced Elbow Basic Unstructured Grid sssss 9 1 9T Introduclioh o ie od e eet et nde i eee n eius 9 1 9 2 TODICS COVBIOU i reni aei pn ME 9 1 9 3 Background ooi oro ipsae cbe t ERR iud SOR Sopas pu tee Es TSE 9 1 9 4 Geomelry i s odo od ane ada di a Pe M 9 1 9 5 GBlling Started o RERO ono nutem miM 9 3 9 6 Creating Database Entities ssss
127. in JRNI Toggle off Auto Next Edge Pick connector DO Next Edge Pick connector OS Pick connector SK Next Edge Pick connector KA Pick connector AB Gridgen will complete the domain Pick connector DO Next Edge Pick connector OP Pick connector PQ Pick connector QR Next Edge Pick connector RJ Gridgen will complete the upper symmetry domain Pick connector AK Next Edge Pick connector KL Pick connector LM Pick connector MN Next Edge Pick connector NI Gridgen will complete the lower symmetry domain 35 Done The grid spacing changes abruptly between some of the domains Reduce the abruptness using Set As Vals Je XP H9 Cons Set As Vals Select the end of connector PQ at P Select the end of connector LM at L 7 15 B 747 Nacelle Working With An IGES Database Select the end of connector HJ at H Select the end of connector EI at E 045 5 6 7 Done 8 9 Abort This will give you a smoother variation in grid spacing as shown in Figure 21 9 This also affects the two domains on the centerbody since they include connectors HJ and EI Use the structured solver to reinitialize them using Initialize via TFI and then use the elliptic solver for about 20 iterations with the attributes still set the way they were previously Figure 21 9 Use Set As Vals Command to Change Grid Cluste
128. in Projection Please reference Figure 20 16 to identify which connectors to select Connectors Selected for Redimensioning Old New Dimension Dimension Connector 11 From the MAIN MENU Connectors Redimension Grids Select connector EM Li Select connector TI 11 Select connector MT 7 N OOSA D Bo I0 Select connector IE 10 7 11 Select connector SQ 12 11 13 Select connector TU 14 102 15 Select connector FO 16 44 17 Done Apply New Dims 18 Done You are now ready to project your connectors onto the database From the MAIN MENU 1 Connectors 6 17 Intersecting Pipes Pole Grid Construction Top Down Modify Select connector MT TI IE NU UL LH OQ OS SP TU IJ KL JQ KS Done Project Closest Pt Select Nodes Too Done Project Welpen IX CON OG deo ts SES Done Replace Connectors o Maintain Linkages 11 Done Once you have finished projecting your connectors you will need to project your domains in the same fash ion From the MAIN MENU A Domains Modify Select domains MTUN ITUL EJF GKLH FJQO QJKS GKSP Done Project Closest Pt Select Cons Too Done Project 9000 Sell ION cU Subs db Sb Replace Domains jak Maintain Linkage 11 Done To improve the corner cells of domains OQSP and FJKG you may want to smooth those domains using the Structured Domain Solver From the M
129. ipe will be split into 3 pieces 1 Sn IY CA E 5 d Abort Don t Split Done Replace Connectors Modify Select connector OQSP using the right Modify Select connector GKJF using the right mouse button Done Split O to GP e via Keybd 11 Split at Cursor O O to GP e via Keybd 11 Split at Cursor O mouse button Done Split O to GP e via Keybd 11 Split at Cursor O O to GP e via Keybd wi Split at Cursor O Abort Don t Split Done Replace Connectors Now it is time to create a few more connectors Oy Uv sbe c SES Create 2 Point Connectors Hold down the right mouse button and move the 3D cursor over point J Add CP O by Picking Hold down the right mouse button and move the 3D cursor over point Q Add CP O by Picking Drawing Connectors 5 11 Intersecting Pipes Pole Grid Construction Bottom Up 7 Hold down the right mouse button and move the 3D cursor over point S 8 Add CP O by Picking 9 Hold down the right mouse button and move the 3D cursor over point K 10 Add CP O by Picking The next two connectors you create will be pole connectors A pole connector is a connector that is col lapsed to a point There are two pole connectors in this grid at points A and C You create them as a con nector with two control points at the same location You should still be in the 2 POINT LINE menu 1 Hold down the right mouse button and move the 3D cursor over p
130. ircular arc section defining the half circumference of the droplet The radius of the arc is at point 7 5 0 0 From Gridgen s MAIN MENU 1 Database 2 Create 3 Curve Circle 4 Add CP O via Keybrd 9s 005 14 55 10 6 Add CP O via Keybrd Jo y hee Sipe 0 8 Store CP O via Keybrd 9 Ju5 Oss 0 10 Done Save DB curve That completes the definition of the circular arc shape Next create the line that defines the center line of the cylinder and the radius of the cylinder You should still be at the DB CREATION menu 1 Curve Line 2 Add CP O via Keybrd 3 0 100 0 4 Add CP O via Keybrd 5 0 100 0 6 Save DB curve Next you will need to create an edge curve defining the radius of the cylinder by offsetting the center line curve by 64 0mm From the DB CREATION menu 10 4 Creating Database Entities 1 Curve Offset 2 Pick the center line curve 3 Enter Offset Distance 4 64 0 5 Save Press the keyboard hot key r to reset the view The Display window should look like Figure 24 3 Figure 24 3 Database Curve for Droplet and Cylinder You will create the surface of the droplet as a surface of revolution From the DB CREATION menu 1 Surface Revolution Pick the circular arc the generatrix of the droplet Pick the center line curve the axis curve Re Set the Angle 180 Done Save Surf of Revol a y xs Ex als Done You can change the surface rendering 1 Disp 2 Edit Dspla DB 3 Select
131. irst two connectors will be the upper and lower airfoil connectors the third connector will be the wake connec tor Again from the MAIN MENU 1 Connectors Create 2 Point Connectors deo UNS 8S Move the 3D Cursor white cross to the leading edge LE of the airfoil 3 2 Connector Creation 5 Add CP O by Picking 6 Mowve the 3D cursor to the trailing edge TE of the airfoil 7 Add CP O by Picking Since two database points on the same database entity were picked Gridgen converts this connector to a database constrained line segment type If you pick the same two points again Gridgen will check for an alternative path on a different database entity Once no alternatives are available Gridgen will create a straight 3D line segment type Pick the same points again now 8 Move the 3D Cursor to the LE of the airfoil 9 Add CP O by Picking 10 Move the 3D Cursor to the TE of the airfoil 11 Add CP O by Picking You were instructed to place the 3D Cursor at the nose of the airfoil in each case since that is where you want your default clustering value to be applied Picking these same points again would result in a straight 3D line segment connector since there are only two database curves for Gridgen to use for database constrained seg ments Now create the wake connector continuing with the 2 Point Connector command The 3D Cursor should still be at the TE of the airfoil 12 Add CP O by Picking 13 Add CP O via Keybrd
132. is to generate the volume grid within the core of the cylinder From the MAIN MENU 1 Blocks Create Cell Type unstructured Assemble Faces Add 1st Face Pick Multiple Doms Pick the domains forming the face of the cylinder core Entities 6 14 15 16 amp 17 from the Browser SO Cue dee que C2 8 Done 9 Savethe Face 10 Done Save Blocks 11 Run Solver Unstrctrd 12 Pick core block of the cylinder 13 Done 14 Initialize 15 Done Save 10 19 Droplet in a Cylinder Hybrid Grid The unstructured solver has created a tetrahedral volume grid Pyramid elements are automatically created between the structured hexahedral block and the tetrahedral cells in the bulk of the volume These pyramid cells are the transition cells that allow an unstructured volume grid to be formed from a structured grid You can examine the entire volume grid using the Examine command in the BLOCK COMMANDS menu Figure 24 15 shows a cross section through the grid notice the different types of cells that form the hybrid grid Figure 24 15 Examining the Hybrid Grid 10 14 Saving Your Model and Export to Solver Now would be a good time to make sure you save a good copy of your database and grid models We rec ommend always exporting your database models first as your Gridgen restart file includes information per taining to your database file and itsFrom the MAIN MENU 1 Input Output 2 Database Export 3 Type composite 4 Do
133. ity types will not be available for picking 2 Others Off 3 Curves line This last command toggles the line entity back to active or unmasked while all other entity types are masked off 4 Done 5 Pick All 6 Done 7 Selectlayer 2 from the ASSIGN DB ENTITY LAYER Browser list Now the line entities disappear from the Display window Since no other entity types other than circular arcs remain in this layer restore the mask settings back to default before assignment Cubes and Spheres Layer Manager 1 DB Pick Mask Active Surfaces On Curves On Others On Done Pick All Done Select layer 3 from the ASSIGN DB ENTITY LAYER Browser list 9e ub Oy coh spe as SES Now the Display window is again empty Use Shift m to pop the Layer Manager panel back to the top Then use Status All On to turn all layers back on All entities should now be visible including the points lines and arcs as shown below Ta F H oD Wk 1 12 More Descriptions Now provide some descriptions for the three new layers in use for the construction entities Continuing with the Layer Manager panel 1 Select layer 1 using the mouse cursor and left mouse button Description Construction Points OK Select layer 2 Description Construction Lines OK Oo Oy bo Ex ES 1 10 Saved Sets 9 Select layer 3 10 Description ll Construction Arcs 12 OK Your layer Browser lis
134. l form the cross sectional shape of the elbow the 180 circular arc EGF 1 Curve Circle 9 4 Creating Database Entities Add CP O via Keybrd 20 0 0 Add CP O via Keybrd 80 0 0 Store CP O via Keybrd 50 0 30 9e c OON GUN Be es Done Save DB Curve The second entity to be revolved will be a line which you will create using the Curve Offset command Again from within the DB CREATION menu 1 Curve Offset After pressing this button you will now see in the Message window the following prompt PICK GENERATRIX Pick the curve to b offset For this particular operation the generatrix refers to the entity from which the new curve will be offset 2 Selectline CD The Message window should now display OFFSET CURVE Define how the generatrix is to be offset You should keep in mind when doing offsets that the operation is performed in a constant z plane in screen coordinates Section 5 3 6 of the User Manual or more simply stated in the plane of the screen If neces sary you can now revert to a view perpendicular to z 0 in body coordinates by simply using the r hot key Section 2 7 4 Now you are ready to continue the offset operation 3 Enter Offset Distance 4 5 5 Save Next we will create the two surfaces of revolution The first surface we will create will be the elbow itself This will be done by rotating the arc EGF about the axis AB You may wish to rotate the model to a
135. ll we need to somehow change the shape of the new domain to reflect the fact Point I in Figure 19 3 is at a different x value than Point B to account for the sweep of the ramp We do this by editing the shape of one of the connectors sharing that node Edit the connector corresponding to connector HI 1 Done Done Connectors Modify 2 3 4 5 Position the cursor over the connector corresponding to connector HI in Figure 19 3 6 Press and release the right mouse button 7 Done 8 Segment Edit 9 Position the cursor over the control point corresponding to Point I in Figure 19 3 10 Press and release the right mouse button 11 Store CP O via Keyboard 12 1 257 07 T 13 Done Editing 14 Done Replace Connectors The process to this point has been rather straightforward You modified a connector by changing the shape 4 18 More Connectors and Domains of its segment by moving a control point to a new location Now when you save the new connector shape you have to tell Gridgen how to treat the new shape Specifically the connectors corresponding to connec tors HI and IJ in Figure 19 3 share a common point we have just moved the common point We need to tell Gridgen whether to unlink the two connectors or to keep them attached by changing the shape of IJ to reflect the change in position of point I Since these connectors are part of a domain and since the domain must be bounded by a closed loop of connectors we choose to kee
136. lt we can use baffles to simply provide interior cluster control and not necessarily use them as physical boundaries For this tutorial however we will set the baffles to solid boundaries Select all of the domains including the baffles except the inlet and exit domains Done Wall Select the two inlet patches at the conical end Done Pressure Inlet Select the two remaining outlet patches at the other end SOE E 200 cdm Ox OS eB A NS Done Outflow E ie Bm 0 Done 12 7 Mixer Using Baffles 1 1 1 1 1 1 2 21 rage tn Boxlon box erred Eo oa oa CEE SortBy le nun2 o Be sji reva Done ent Help Abort esc Figure 27 5 Boundary Condition Browser This concludes our tutorial You are free to use the Export Analysis Data command to export a Fluent case cas file 12 8 13 Converging Diverging Nozzle Using Glyph Scripting 13 1 Introduction This section includes a brief tutorial to help you become familiar with Gridgen s scripting language Glyph and the tools available to work with it 13 2 Topics Covered Gridgen skills you will learn during this tutorial session are executing and appending to an existing script using Append to Journal journaling your interactive commands to a script file for later editing and playback using Add Variable to create variables for easier interaction and easier script playback editing and executing a journaled script to generate a new grid cr
137. lues are shown in Figure 22 3 and the following table respectively Note that the layout of this geometry has not been selected for any other reason than to produce the desired pierced elbow shapes of our eventual grid system 9 2 Getting Started Figure 22 3 Labeled Points For the Elbow Elbow Coordinates 9 5 Getting Started Begin by starting Gridgen either by typing the string gridgen on Unix workstations or simply double clicking the Gridgen shortcut on your PC s desktop The first step in running Gridgen is to select the soft ware Section 17 1 of the User Manual to be used in the analysis This will ensure that the grid generated by Gridgen is consistent with the capabilities of the analysis software For this analysis we will be using the Fluent flow solver by default Gridgen selects the generic solver To select Fluent do the following starting from the MAIN MENU 1 Analysis S W 2 Select Analysis S W 3 3D 9 3 Pierced Elbow Basic Unstructured Grid 4 Fluent 5 Next Page 6 Done 7 Done Use of the 3D button above tells Gridgen that you will be creating a 3D grid Verify that you have selected the 3D Fluent flow solver by checking the display in the Status window 9 6 Creating Database Entities You are now ready to begin creating the database geometry elements that will comprise the foundation of the grid The process begins with the creation of simple database lines Then you will
138. main topology using Run Solver Unstrctrd for domain decimation building an unstructured block quickly and initializing it with tetrahedra 14 3 Background The procedures followed in this tutorial use some of Gridgen s most automated commands Therefore this tutorial can be approached by the newest of users However as with all of the tutorials in this manual famil iarity with Gridgen s GUI is recommended Section 2 of the User Manual 14 4 Geometry The geometry to be meshed is a 3D mechanical part in IGES file format as shown in Figure 26 1 This grid will be unstructured so the topology will essentially match the topology of the geometry with the exception that tools will be used to slightly reduce the number of total domains 14 1 Mechanical Part Basic FEA Mesh Figure 26 1 Mechanical Part Geometry 14 5 Getting Started Begin by starting Gridgen either by typing the string gridgen on Unix workstations or simply double clicking the Gridgen shortcut on your PC s desktop The first step in running Gridgen is to select the soft ware Section 17 1 of the User Manual to be used in the analysis This will ensure the grid generated by Gridgen is consistent with the capabilities of the analysis software For this analysis we will simply leave the analysis software at the default setting of generic 3D which should be visible in the status window at the upper left hand corner of the Gridgen interface To begin the tutorial imp
139. mination you realize you likely saved the domain too quickly The final boundary connector saved from the extrusion does not really look like it is an adequate distance from the airfoil You set the outflow boundary downstream to 10 units from the airfoil TE The C boundary should be a similar distance Rather than do all of the extrusion settings over again you can use the Re Extrude command to simply re enter the extrusion where you left off prior to saving the domain While still in the DOMAIN COMMANDS menu 1 Modify 2 Select the domain 3 Done 4 Re Extrude You are now back exactly where you were prior to saving the extrusion earlier Let Gridgen s stop criteria figure out for you how many steps to run 5 Set Stop Criteria 6 Toggle on Total Height 7 Total Height Set 8 10 9 Done 10 Run The Total Height stop criteria instructs Gridgen to stop automatically when the first grid point on the marching front reaches that distance from its original location Using the Run command tells Gridgen to continue the extrusion indefinitely or until a stop criteria has been reached This extrusion stops automati cally at marching step 49 as shown in the Blackboard window in the figure below 3 6 Re Extrude Extrusion RUN gt Marching bby 49 Input ArCk 15 9 702E 001 Max ArCk 1 5 1 409E 000 Layer Stop Criterion Total Height 1 057E 001 Min Jacobian 2 414E 001 SELECT OPTIONS Pause delete step e
140. n are for convenience only and shall not 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 AAA s Dallas Texas office get the Pit Volume 3 Tutorial Workbook Version 15 TABLE OF CONTENTS 1 Cubes and Spheres Layer Manager ssssss 1 1 NE UB E 1 1 1 2 Topics COV CIC mmt renias E E EEEE EDEA EE EARO RELEET ERRER 1 1 1 3 Backgr d HMM EE 1 1 Ld GOON eoo o ede aaah o pepe ods asia nadie aig aA hain lat oc bed aane 1 1 1 5 Start Gridgen ccs 1 2 1 6 Database Model Import o DERE UAE Re ERR EEUU exp ESE RAPERE 1 2 1 7 Display Full Database Model ssss essere 1 3 1 8 Find and Enable Small Sphere 222 sse 1 4 1 9 Move and Description ueeeeesssisssseeeeee seen 1 6 1 10 SI iq 1 7 1 11 More Database Organization sss 1 8 1
141. n shortcut key on your PC s desktop The first step in running Gridgen is to select the software Section 17 1 of the User Manual to be used in the analysis This will ensure the grid generated by Gridgen is consistent with the capabilities of the analysis software For this tutorial you will be using the latest version of the FLUENT flow solver by default Grid gen selects the Generic flow solver To select the current FLUENT flow solver start in the MAIN MENU 1 Analysis S W 2 Select Analysis S W 3 Turn on the 3D and FLUENT toggles 4 Next Page 5 Done 6 Done Use of the 3D button above tells Gridgen that you will create a 3D grid containing volume cells as opposed 10 3 Droplet in a Cylinder Hybrid Grid to a 2D grid with only surface elements Verify that you have selected the 3D FLUENT flow solver by checking the Status window You also need to set up the default average grid spacing parameter for the unstructured surface mesh From the MAIN MENU 1 Defaults 2 Con Dim avg As 3 2 4 Done You have set up the grid attributes that will allow you to create the hybrid grid for this tutorial 10 6 Creating Database Entities You are now ready to begin creating the database geometry elements that will form the foundation of the grid The process begins with the creation of simple arcs and lines Then you will create surfaces of revolu tion to form the droplet surface The first entity you will create is the c
142. nager 1 4 Geometry For this introduction to Gridgen s Layer Manager we will work with a geometry model consisting of three nested spheres next to three nested cubes The model is shown in Figure 1 1 below Cubes and Spheres Layer Manager Figure 1 1 Database Geometry Model This is purely a contrived problem for demonstration purposes however the operations to be demonstrated will be common to any models you work with in Gridgen 1 5 Start Gridgen Start Gridgen by typing the string gridgen on Unix workstations or by simply double clicking the Gridgen shortcut on your PC s desktop After a few seconds Gridgen will start and you will see the Gridgen logo in the Display window The logo will disappear after a few seconds or as soon as you select your first menu button 1 6 Database Model Import To begin the tutorial import the composite geometry file 1yrmgr dba This file should be available in your Gridgen installation directory under gridgen_home_path examples tutorial lyrmgr You may wish to copy the file to some other working directory before proceeding From the MAIN MENU 1 Input Output Database Import Use the file Browser to navigate to the directory containing the copy of lyrmgr dba and select it PB qe os Done In your Display window you should now see nothing That is right the model has been imported but noth ing appears You can verify model import by looking
143. ndary condition on all domains as shown in Figure 22 20 on the following page Figure 22 20 Boundary Conditions for Elliptical PDE Solver You should still be in the SET STRUCTURED SOLVER ATTS menu 1 Solver Bound Conds Creating Domains for the Passages 2 Floating 3 Done Setting Attributes You now will run the elliptic solver 1 Elliptic Slvr Run N Iters 2 50 This runs the elliptic solver with the attributes that you have previously set As the elliptic solver iterates the grid display will be updated and you can monitor the progress of the surface grid You may stop the solver by pressing the following button 1 Done Save 2 Done This is a small grid so it will not take long to reach a state of equilibrium When done the grid looks something like the one in Figure 22 21 Figure 22 21 Inlet Plane after Running the Elliptic PDE Solver 8 14 Creating Domains for the Passages You can now proceed with the construction of the domains forming the inlet topology of the passages The labeling con vention used is shown in Figure 22 22 Figure 22 22 Labeling of Inlet Domains to Swirler Passages From the DOMAIN COMMANDS menu 1 Domains 2 Create 8 17 LDI Combustor Advanced Structured Grid 3 Assemble Edges 4 Turnon the Auto Next Edge toggle Domain on passage entity 9 1 Pick connector AB 2 Pick connector BC 3 Done The Display windo
144. ne 5 Type In Name 6 hybrid 7 Gridgen Export 8 Type In Name 9 hybrid 10 Done 10 20 Saving Your Model and Export to Solver Volume Grid within Core of Cylinder You can now export to your flow solver files for Fluent For the purposes of this tutorial you will not be set ting any boundary conditions but you may do so if you wish From the MAIN MENU 1 Analysis S W 2 Export Analysis Data 3 Type in Name 4 hybrid 5 Done 6 Done You have successfully exported all of your necessary files and you may now exit from Gridgen This tuto rial is now complete 10 21 Droplet in a Cylinder Hybrid Grid 10 22 11 Tension Bar Feature Extraction 11 1 Introduction This tutorial will give you a guided tour of the Gridgen process for using the Feature Extraction FE tool Feature Extraction is used automatically during shell import or interactively to find geometric features for example slope discontinuities in the shells Shells represent the faceted equivalent of a continuous B Spline surface in Gridgen s database The user sets a split angle that will be the maximum angle allowed between two adjacent triangles in a shell Feature lines identified by the FE algorithm will then be used to either split a shell into two shells along a feature line or to create a database curve a line segment Shells will also be split automatically during import based on point to point connectivity 11 2 Topics Covered
145. ne Save Blocks Save the current grid to a Gridgen file 1 Done Input Output Gridgen Export Pick file name ramp gg Open Yes overwrite file pig opa Ria oN Done Just as was the case for domains Gridgen automatically initializes the volume grids using an algebraic method To view the volume grids do the following 1 Blocks 2 Examine 3 Pick All 4 Done 5 Topo Now use the left arrow and right arrow keys to increment and decrement the index of the plane being dis played respectively To view the r constant planes do 1 Topon A similar command is available for G constant planes Now create the second block in this system In order to keep the display as uncluttered as possible turn off the display of the domain grid points 1 Abort 2 Disp 3 Edit Dspla Dom 4 Pick all domains that currently use a wireframe display style 5 Done 4 28 Creating the Second Block 6 Off 7 Done Apply Atts 8 Abort 9 Done 10 Done 4 11 Creating the Second Block It is hoped at this point in the tutorial you can see several ways to continue with the construction of the sec ond block The technique you will use is to copy the downstream domain JMFCJ and translate it in the x direction to the position of KLEDK One x directed connector will be drawn between Points C amp D and copied to positions FE ML and JK Four new domains will be created and the downstream block con structed Since these s
146. nnectors so you are ready to begin creating the unstructured domain immediately 1 Create 2 Cell Type unstructured 3 Assemble Edges 4 Check Auto Save Selecting Auto Save will tell Gridgen to create a triangular surface grid as soon as it detects that you have chosen a closed loop of connectors 5 Check Auto Complete Selecting Auto Complete tells Gridgen that with each subsequent connec tor selected it should try to figure out a possible closed loop of connectors on which to create a domain 6 Position the cursor over connector BC 7 Press and release the right mouse button 8 The Auto Complete function figures out that a closed loop of connectors is present and creates an unstructured domain which is initialized and saved immediately by the Auto Save function 9 Done When you pick the last connector Gridgen will initialize the triangular surface grid Your grid should look something like the one in Figure 18 9 2 12 Tutorial Wrap up Figure 18 9 An Unstructured Domain for the Bump 2 10 Tutorial Wrap up This completes the Gridgen tutorial If you want to save this grid 1 F oO m Select I O from the Quick Keys Gridgen Export Type In Name Enter the file name for the grid Done When you are done use Quit Gridgen from the MAIN MENU to exit the program 2D Bump Basic Skills 2 14 3 2D Airfoil Re Extrude 3 1 Introduction This section includes a brief tutorial to help you
147. nnectors IF and LM Then return to the CONNECTOR COMMANDS menu 7 Done 8 Done Creating Conns You have successfully created all of the connectors necessary for this tutorial Now you can go into the DISPLAY COMMANDS menu Section 2 9 of the User Manual using Disp and toggle on Show Con GPs so all of your connector grid points will be displayed Press Done to exit from the DISPLAY COM MANDS menu Your model in the Display window should now look like the one shown in Figure 22 5 The remainder of your grid construction will be even easier than what you have done so far Next you will create your six domains before moving on to creating the block At this point you might use Gridgen s Quick Save command to save your grid to a file Simply press the Quick Key Section 2 3 6 marked Save it is one of the twelve small buttons in the three rows at the bottom of the menu This command exports a Gridgen restart file called quicksave gg in the directory in which Gridgen was started by default 9 8 Creating Domains Figure 22 5 All of the Connectors With Grid Points Displayed 9 8 Creating Domains An important point about domains in Gridgen is that each domain will represent a single boundary condition for your flow solver which we chose to be Fluent This is important to keep in mind for preparing your grid later to export to your flow solver For this tutorial we will be creating triangular mesh domains since our goal is to build an entirely
148. no longer be selected for other operations such as modification or deletion While still in the DISPLAY COMMANDS menu disable your database entities as follows 1 En Disable DB 2 Pick None 3 Done 4 Done Your model should now only have the edges of the domains rendered in the Display window as shown in Figure 22 8 Note that the domain edge connectors are now rendered in a light blue color to give you a visual cue as to how those connectors are being used Connectors that are a part of a domain are always dis played in this color You are now ready to move on to creating your block in the next section Figure 22 8 Turning Off the Domains Interiors Reduces Visual Clutter 9 9 Creating the Block For an unstructured topology you only need a single face to define a block but it will have to form a water tight enclosed shell Building a simple unstructured block with a single face proceeds very quickly Create your block now 1 Blocks 2 Create 9 12 Initializing and Examining the Tetrahedra Cell Type unstructured Assemble Faces Add 1st Face Pick All Domains Sl os Ue spe d Save the Face At this point you have already made a complete block which you could save and then move on But take note of the orange arrows emanating from the surfaces of the block These represent the face normal vectors Gridgen will always attempt to orient these properly but you should make sure that they are pointing into the volume to be
149. nsion 2 From keybrd 3 21 4 Done ReDimension The third and final step of connector creation is distributing the grid points along the connector Section 9 3 Since this grid is to be used for a simulation of the viscous flow over the ramp surface it is reasonable to clus ter grid points toward the ramp surface The requirements of your analysis software and the particular prob lem you are analyzing determine where and how much to cluster By default Gridgen will equally space the grid points along the connector To specify the distance of the first grid point above Point A is 0 01 do the following 1 ReDistribute Begin A 0 01 Done ReDistributing Done Save Connectors 9v De d ow pm Done Creating Conns In case you are curious as to how the grid points on this connector appear you can use a display command to turn this on From the button menu 1 Disp 2 Show Con GPs 3 Done This completes the connector creation process Each of the green dots on the screen is a grid point There should be 21 grid points and they should be clustered toward the ramp surface as shown in Figure 19 4 4 5 Swept Ramp Basic Multi Block Structured Grid Figure 19 4 Grid Points are Clustered Towards the Ramp Surface for First Connector Notice the connector is rendered in a light green color signifying that a number of grid points has been assigned as opposed to a bright green color signifying that no grid points have been assigned
150. nt Pause save step esc Cont inue y Help ie You can see also that the first point on the marching front to hit the Total Height criteria is actually at 10 57 While the entire boundary is obviously not this distance from the airfoil this grid is much more in line with your requirements and is likely sufficient Your choices now are to Pause delete step which will pause the extrusion and remove marching step 49 Pause save step which will pause the extrusion and keep marching step 49 or to Continue the extrusion which will only pause again at marching step 50 as more points meet the Total Height criteria Keep the extrusion as it is 11 Pause save step 12 Done You now have an opportunity to abort this modification and return to your original extrusion or replace the original with your newly extruded domain You will choose to replace the original domain 13 Replace Domains At this point Gridgen replaces the original domain updating all the connectors as necessary Your new extruded domain should appear as in the figure below 3 7 2D Airfoil Re Extrude 3 11 2D Block Creation and AS W Settings To make this a complete grid suitable for analysis in the Fluent 2D analysis software AS W select the AS W create the 2D block set boundary conditions BC s and export your analysis data Keep in mind that Gridgen requires that blocks exist before you can set BC s or export analysis data Therefore even for 2D grids you
151. nter in the List Filters Description field 1 11 More Database Organization Layer 0 contains all of the entities used to create the spheres and cubes All of the entities are currently dis abled Reorganize these now into layers 1 2 and 3 with layer 1 containing all point entities layer 2 contain ing all line entities and layer 3 containing all circular arc entities To make reassignment of the entities easier isolate layer 0 and use the DB Pick Mask command More Database Organization 1l Select layer 0 from the layer Browser 2 Isolate The Gridgen GUI should still be at the DATABASE COMMANDS menu continue there 3 En Disable 4 Pick All 5 Done All construction entities are now enabled and therefore visible in the Display window Continue now with the assignments 1 Assign Layer 2 DB Pick Mask 3 Surfaces Off 4 Curves Off 5 Others Off 6 Others point This last command toggles the point entity back to active or unmasked while all other entity types are masked off 7 Done 8 Pick All 9 Done 10 Select layer 1 from the ASSIGN DB ENTITY LAYER Browser list Since layer 0 was isolated all other layers are off including layer 1 Therefore since the database points were assigned to layer 1 they are no longer visible in the Display window Continue on to line and arc assignments 1 DB Pick Mask Active The Active addition to the button text indicates that a mask is in effect so that some ent
152. o improve volume grid quality use Examine to visually examining the volume grid setting boundary conditions for analysis software using the Analysis S W commands 43 Background You do not need to run any other tutorials before running this one However please read Section 2 to famil iarize yourself with the operation of the Gridgen user interface before attempting to run this tutorial 44 Geometry The swept ramp configuration you will use for this tutorial is shown in Figure 19 1 Presumably someone will use this grid with a computational fluid dynamics code to compute the flow field over this shape The CFD solver is not part of Gridgen 4 1 Swept Ramp Basic Multi Block Structured Grid top y to te Figure 19 1 The Swept Ramp Geometry Flow will be in the Positive X Direction The grid you will generate consists of two blocks arranged end to end as shown in Figure 19 2 Within each block one family of grid lines will run in the flow direction one family of grid lines will run from the ramp to the far field boundary and one family of grid lines will run in the z direction across the ramp The choices of blocking system and grid topology are up to you this particular blocking system is only one of many that could be used for this swept ramp The requirements of the particular analysis software you are using should be considered when planning the grid 31 21 11 points 15 21 11 points
153. o keep our database model 3 Turn off the Reset Defaults toggle since we wish to use the same default settings 14 5 Mechanical Part Basic FEA Mesh 4 Restart Now the grid should be cleared Proceed back to the DOMAIN COMMANDS menu 1 Create 2 Turnon the Auto Join toggle to automatically join adjacent domains whose turning angle at their com mon edge is less than the Set Angle 3 Set Angle 4 40 0 Note that we do not want to use the default Any for our join angle which is shown in the SET DEFAULT VALUES menu since this will instruct Gridgen to join domains regardless of turning angle between them and will result in almost all domains in this model being joined 5 Turnon the Auto Merge toggle to have coincident connectors merged automatically 6 Set Toler 7 0 01 8 OnDBEntities 9 Pick AII 10 Done Use the DISPLAY COMMANDS menu again to set attributes for the new domains 1 Disp Edit Dspla Dom Pick All Done 2 3 4 5 display style Shaded Wireframe 6 wireframe color red 7 solid shade color purple 8 Done Apply Atts 9 Abort 10 Done Now the grid should look like the one shown in Figure 26 4 Note there are now 54 domains There are no coincident connectors and the 360 degree domains are not just simply joined but also smoothed and deci mated The original database seams are no longer evident 14 6 Domain Decimation Figure 26 4 All Domains With Additional Clean up
154. ock system to a file 1 Input Output Gridgen Export Pick file name ramp gg Open Yes overwrite file Qv pA sun uA p Done 4 12 Running the Elliptic PDE Solver on Volume Grids At this point you have created two blocks with the volume grids initialized using an algebraic method As was the case with the surface grids we will apply an elliptic PDE method to the volume grids to improve the grid s smoothness clustering and orthogonality 1 Blocks Run Solver Structured Pick All Done Elliptic Slvr Run Let the elliptic solver run about 25 iterations Pause qos EAD GON ON ER eS Done Save The Examine function in the solver allows you to view a topological grid surface while the elliptical solver is running 4 13 Volume Grid Inspection Inspect the results of Gridgen 3D s elliptic PDE refinement of the two block volume grid 4 32 Customizing the Grid for the Analysis Software Examine 2 Pick All 3 Done 4 Topo 5 Use the left arrow and right arrow keys to scroll through the grid planes Figure 19 13 shows the 9 grid surface after elliptic smoothing The volume grid appears to be clustered and orthogonal where we wanted it There is additional diagnostic information printed in the Browser win dow Atthe top it shows global information about the grid function we are currently examining The bottom section of information shows the location and grid spacing at the point currently highlighted No
155. of the geome try that we are using consists of a central hub and a nacelle For simplicity we are not modeling the engine or the mounting hardware for the nacelle Since the geometry is symmetric about a vertical plane only half the geometry is included We can do the same thing for the grid If both sides of the grid are needed say for a yawed case it is easy to copy and mirror the grid about the symmetry plane after it is completed 7 1 B 747 Nacelle Working With An IGES Database Figure 21 1 The 747 Inlet Configuration To Be Gridded The grid you will generate consists of two blocks arranged as shown in Figure 21 2 One block will be essentially rectangular and will be attached to the nose of the central hub This block will run forward to the inlet inflow plane For this first block i direction grid lines will run in the positive x direction j direction grid lines will run in the positive y direction and k direction grid lines will run in the positive z direction The second block will be generated in a C Grid style and will wrap around the central hub and the internal hub nose block For the second block i direction grid lines will run in the positive x direction j direction grid lines will run around the hub from bottom to top and k direction grid lines will run from the hub out to the inner surface of the inlet The choices of blocking system and grid topology are up to you this particular blocking system is only one of many tha
156. oint A Add CP O by Picking Add CP O by Picking Hold down the right mouse button and move the 3D cursor over point C Add CP O by Picking Add CP O by Picking Done eos cw Ix cce Be tac ob Done Creating Conns Now you should have created all the connectors shown in Figure 20 8 Notice the special symbology Grid gen uses for a pole connector a dot with a circle around it Figure 20 8 Pole Connectors for the Two Pipes Are Located at A and C All the connectors we have created so far have had 31 grid points assigned to them initially We still have a few more connectors to make but the remainder will have 11 grid points on them Go to the SET DEFAULT VALUES menu and set that up 1 Done 2 Defaults 3 Con Dim dimen 4 11 5 Done 5 12 Creating Domains 6 Connectors You are ready to put the remaining connectors on the main pipe They will all be 2 Point Connectors Rather than tell you step by step how to create them we are going to assume you got the hang of it while creating the previous 2 Point Connectors and can try it on your own So here goes Create 2 Point Connectors for the point pairs AE AM CN CH IJ and KL Since connectors IJ KL JO and KS do not exactly traverse parallel to their respective pipes it will be pru dent to project them all to the underlying database surfaces to ensure they match the database shape This will also allow Gridgen to automatically surface constrain the domains on both pip
157. omatically by TFI can often be improved by applying an elliptic PDE based smoothing to the grid Gridgen offers a variety of elliptic PDE methods with various controls for boundary spacing orthogonality and smoothness 1 Select Run Solver Structured 2 Pick All 3 Done 4 Elliptic Slvr Run This runs the elliptic solver with the default settings As the elliptic solver iterates the grid display will be updated so you can monitor the progress of the surface grid This is a small grid so it will not take long to reach a state of equilibrium When the grid looks something like the one in Figure 18 8 you may stop the solver and save the grid by pressing the following button 1 Done Save 2 11 2D Bump Basic Skills Figure 18 8 The Bump Domain After Running the Elliptic PDE Solver 2 9 Create an Unstructured Domain It is also easy to create a triangular surface grid for the bump geometry You can even use the connectors you have already created Before beginning delete the structured domain you just created Starting from the DOMAIN COMMANDS menu 1 Delete 2 Pick All 3 Done 4 Delete Domains Only You just deleted the domain but kept the co
158. ook like Figure 18 4 2 5 2D Bump Basic Skills Figure 18 4 Creating the Bump from a Circular Arc That completes the definition of the circular arc shape l Select Done Save Segment from the EDIT CIRCULAR ARC menu to go back to the CREATE CONNECTOR menu 2 Select ReDimension to assign a number of grid points to the connector This takes you to the REDI MENSION CONNECTORS menu 3 You might want to note that the Apply dimen button is set so when you press the From keybrd the Message window should will prompt you for the number of grid points to be assigned to the connector 4 Enter 15 5 Finish dimensioning the connector by selecting Done ReDimension The final step in connector creation is to distribute the grid points to satisfy whatever clustering requirements you have For this problem we will use equal spacing the default so no further action is required 1 Select Done Save Connectors to complete this connector and return to the CREATE CONNEC TOR menu Next you will create the connector from point B to point C 1 Select Add Segment to go to the ADD SEGMENT menu 2 Connector BC is a straight line segment so select 3D Space Line to go to the LINE menu 3 Enter the control point at B by selecting Add CP O via Keybrd 2 B 8 9 10 11 12 Draw Connectors Enter the coordinates of point B 20 0 0 Point C was created earlier when you made the circular arc connector You can take advanta
159. or MJ This completes the outflow domain Pick connector JC Pick connector CB This completes the ramp surface domain 9o gy OCA d we PR Pick connector BI 4 24 Creating a Block 9 Pick connector IH This completes domain BIHA 10 Done 11 Done All of the domains necessary for defining the perimeter of the upstream block are now created Before pro ceeding save another Gridgen file 1 Input Output Gridgen Export Pick file name ramp gg Open Yes overwrite file ev cd ue T Done 4 10 Creating a Block You can now proceed with construction of the highest level element of the grid hierarchy the block Block creation proceeds along the same lines as domain creation albeit volume rather than surface You pick the domains comprising of each of the six faces of the block Begin by 1 Blocks 2 Create 3 Assemble Faces 4 Add 1st Face Gridgen is now waiting for you to pick all the domains that make up one face of this block You can have any number of domains on a face Some of the reasons you may have more than one domain on a face are To apply more than one boundary condition type on a face Each domain can have only a single boundary condition type By grouping multiple domains on a face you can have multiple boundary condition types on a face For proper block to block connectivity Each domain must be fully contained in the blocks on either side i e a domain cannot span multiple blo
160. ort the IGES geometry file The file should be available in your Gridgen installa tion directory under gridgen home path examples tutorial dbdom You may wish to copy the file to some other working directory before proceeding From the MAIN MENU 1 Input Output Database Import Use the Browser to navigate to the directory containing dbdom igs and select it e p R Open After some image manipulations Section 2 7 of the User Manual your model should appear as shown in Figure 26 2 14 2 Setting Defaults Figure 26 2 After Display Clean Up 14 6 Setting Defaults You will need to set three default values to facilitate the use of the On DB Entities command First in order for the command to be available at all you must set either a default dimension Con Dim dimen or average spacing Con Dim avg As Dfit 2 Con Dim avg As 3 0 05 This setting instructs Gridgen to calculate the number of grid points necessary on each newly created con nector in order to achieve an approximate spacing of 0 05 between grid points Gridgen can apply more grid points to high curvature areas of connectors to improve geometric resolution 4 Con Dim Max Ang 5 5 0 This setting tells Gridgen there can be a turn angle between three consecutive grid points of no more than 5 degrees If the angle is greater than 5 degrees after applying the above average spacing Gridgen will insert additional points until the maximum angle criteria is met Now
161. owed in this tutorial use some of Gridgen s most automated commands Therefore this tutorial can be approached by the newest of users However as with all of the tutorials in this manual famil iarity with Gridgen s GUI is recommended Section 2 of the User Manual 12 4 Geometry The geometry to be gridded is a 3D pipe with four mixing baffles and is shown in Figure 27 1 in shaded ren dering The straight pipe surfaces are outlined to make the internal baffles visible The surface representing the inlet is not shown This model has been saved in Gridgen s native database format composite format and is completely closed This grid will be unstructured so the topology of the grid will essentially match the topology of the geometry 12 1 Mixer Using Baffles Figure 27 1 Mixer Geometry 12 5 Getting Started Begin by starting Gridgen either by typing the string gridgen on Unix workstations or simply double clicking the Gridgen shortcut on your PC s desktop The first step in running Gridgen is to select the soft ware Section 17 1 of the User Manual to be used in the analysis This will ensure the grid generated by Gridgen is consistent with the capabilities of the analysis software For this analysis we will use Fluent To make this solver setting begin at the MAIN MENU Analysis S W Select Analysis S W 3D Fluent Next Page Done zb OUO d Ske 3 Done To begin the tutorial import the composite geometry file The file s
162. p the connectors linked 1 Maintain Linkages You have now changed the shape of the domain but as the Display window shows the grid within the domain needs to be updated Gridgen will attempt to regenerate a grid that has been run in the elliptic PDE solver by interpolating the existing grid distribution If the grid had been generated using only the algebraic methods then Gridgen would have algebraically regenerated it automatically The interpolated grid should be pretty close to what you would get from the elliptic solver but go ahead and run the elliptic PDE solver as was done on the first domain to make sure Note when you copied the domain Gridgen also copied all of the original domain s PDE solver attributes 1 Done Domains Run Solver Structured Pick domain 2 Done Elliptic Slvr Run Run solver until you think the grid looks OK Rael OY Seo deo 9X gp Done Save You should now have something that looks like Figure 19 9 4 19 SSS FeRAM EEE AIS ese uem V RR d SS Sees aad a AH HS SN SANANA SSS a ANN ee E NT SES wt NS i EN Lot oS COSS SS SE C CR VS we we a w n Swept Ramp Basic Multi Block Structured Grid Figure 19 9 Re apply the Elliptic Solver After Modifying the Ramp s Domain Shape Save this latest version of the grid to a file Done 1 Input Output 2 Gridgen Export 3 4 Pick filename ramp gg J Open 6 Yes overwri
163. r Manager panel has been pushed to the background on your desktop due to your use of Grid gen s primary GUI To restore it immediately use the keyboard hot key Shift m First some discussion of the layer Browser and its contents is warranted Refer to the next figure below for the following description The first column labeled Layer shows the layer number There are a total of 1024 layers starting with 0 and ending at 1023 An asterisk is shown in this column for layer 0 this means layer 0 is the current working layer This is also why layer 0 is highlighted in green The second col umn labeled Ents indicates the existence of entities with either a positive or negative sign or If neither are present there are no entities in that layer A positive sign 4 indicates the existence of enabled entities a negative sign indicates the existence of disabled entities Finally the third column labeled Description contains an alpha numeric description of that particular layer presumably of its contents raver ente oeseeiotim E Construction All g 2 3 4 5 6 3 8 9 10 Sphere Medium 11 12 13 14 Find and Enable Small Sphere Note that in our case we only see two layers that contain any entities Layer 0 contains construction entities all of which are disabled as indicated by the negative sign Layer 10 contains the medium sphere and all entities are enabled as indicated by the positive sign
164. radius of unit and a length of 20 units Since the block is 10 units long a scale factor of 2 in the x direction will be necessary to make the block fit the length of the main pipe The main pipe s radius of 1 unit requires that the polar block will need to be 2 units wide in the y direction and 1 unit tall in the z direction to fit the half cylinder of the main pipe The scaling factors of 0 1 and 0 2 will be used to fit the block in the y and z directions respectively From the MAIN MENU ees Blocks Modify Pick AII Done Scale Enter Anchor via Keybrd 0 0 5 Enter Scaling Factors Oe c Qv Ux Re ts R9 Zy Ol 04 2 Done Scale n 11 Done Replace Blocks 12 Maintain Linkage The polar block should be scaled down around the pointx 0 y 0 andz 5 and running parallel to 6 5 Intersecting Pipes Pole Grid Construction Top Down the main pipe We now need to translate it over to the main pipe then rotate it You will move the polar block by setting the handle you will move it by to the end of the pole that you scaled it about Once you have set this handle you will move the block to point A the end of the main pipe pole see Figure 20 4 The polar block will then be rotated about point A From the BLOCK COMMANDS menu Nw eccL Og Ux dO t 9 Modify Pick All Done Translate Select the end of the polar block pole corresponding to x 0 y 0 z 5 Drag the polar block to point A
165. re journaling you cannot simply use Elliptic Slvr Run you must enter a number of iterations 10 Elliptic Slvr Run N Iters 11 100 12 Done Save Finally you may end the journaling of your work by returning to the GLYPH COMMANDS menu and pressing End Journaling 13 8 Script Editing and Playback You can now edit some of the variables in the journaled script you just made nozzle glf and execute the script to get a different grid Edit nozzle g1f with your favorite text editor At the top you will see several initialization commands These are followed by variables defining various distances radii and 3D points throughout the grid Notice that everything has been non dimensionalized by the nozzle radius a variable named Rt h 13 5 Converging Diverging Nozzle Using Glyph Scripting Assume you want to make the nozzle s exit smaller Therefore you have to reduce the value of the nozzle exit radius variable re Find where this variable is set by searching for the string Gridgen Journal Variable re You will see as in Figure 28 5 that its value is set to 2 19 Change its value to 1 5 and save the file nozz1e glf gg updatePolicy DISPLAY ONLY Gridgen Journal Variable Rth set Rth 3 76 Gridgen Journal Variable 11 set 11 1 33 Gridgen Journal Variable 12 set 12 2 93 Gridgen Journal Variable 13 set 13 1 86 it Gridgen Journal Variable le set le expr 11 12 13 Gridgen Journal Variable 14 set 14 15
166. re shown in the list The Show Empty filter takes precedence over the Description filter which takes precedence over the Range filter Since layer 5 is currently selected make it the current working layer first so that layer 831 will drop from the list 1 Set Current 2 Enter Sphere in the List Filters Description field Now the layer Browser lists only the layers whose description begins with Sphere Cubes and Spheres Layer Manager 10 Sphere Medium i15 Sphere Large List Fitters Show Description Spheref mic Range 0 1023 3 Enter Cube in the List Filters Description field Now the layer Browser lists all of the layers whose description begins with Cube plus layer 5 the Sphere Small layer raver ents percre 20 Cube Small 25 Cube Medium 30 Cube Large El List Filters r Show Description Cube Empty Range Jo 023 This illustrates the fact that the current working layer will always be shown in the list The current working layer will also always be on If you wish to turn off the current working layer so that its entities are no longer displayed you must select a new current working layer This is done by simply selecting a single layer in the layer Browser list and using the Set Current command Feel free to experiment with these list filters more when the tutorial is complete For now return to the full list of all layers containing entities 4 E
167. reation example 4 3 block create structured example use 4 25 unstructured example use 9 7 9 12 10 10 elliptic PDE solver example use 4 32 boundary conditions setting example use 9 6 12 7 C computational coordinates respecifying example use 8 22 connector create 2 point connectors example use 9 6 example use 2 3 on database entities example use 5 9 9 7 segment 3D Space Curve example use 4 4 circular arc example use 2 3 DB cnstr Line example use 7 8 pole example use 5 2 distribution example use 4 6 merge example use 72 5 modify join example use 8 5 rotate example use 8 6 split example use 8 5 project example use 5 3 Converging Diverging Nozzle 3 Cubes and Spheres D database create curve example use 9 4 example use 9 4 10 4 line example use 9 4 offset curve example use 5 5 9 5 point example use 5 3 surface example use 9 5 surface of revolution example use 5 6 9 5 creating entities example use 9 4 intersection example use 5 7 9 6 modify split example use 7 4 database entity disable example use 8 3 shell example use 71 2 default angular deviation example use 4 3 average connector spacing example use 12 3 14 3 connector dimension example use 8 3 maximum angular deviation example use 4 3 Display Commands menu Show Con GPs example use 9 8 domain copy example use 4 17 create Auto Next Edge example use 5 4 On Database Entities example use 70 6 12 4
168. red Gridgen skills you will learn during this tutorial session are using the Points Curve and Surface database creation tools finding intersections between database entities using Intersect creating pole connectors pole domains and blocks containing poles 5 3 Background You should complete the tutorials in Section 2 and Section 4 before beginning this lesson since this tutorial assumes you already have the skills covered in those sections 5 4 Geometry The intersecting pipe configuration you will use for this tutorial is shown in Figure 20 1 Figure 20 1 Geometry for Intersecting Pipes Tutorial The grid you will generate consists of two blocks One block fills the main pipe The other block is in the branch section The block topology you will build is shown in Figure 20 2 Within each block one family of grid lines will run in the flow direction however the cross section grid topology will be different for the two blocks 5 1 Intersecting Pipes Pole Grid Construction Bottom Up In the main pipe an O topology is used with a pole running down the center of the pipe This topology makes efficient use of the cells allows you to cluster tightly in the pipe wall boundary layer and keeps grid lines normal to the walls In the branch section an H topology is used This is not as efficient as the O topology but it makes interfac ing with the main pipe grid easier Figure 20 2 Two Block Grid Topology for t
169. ring You can improve the grid distribution on the symmetry plane domains as well by elliptically refining them using the default solver attributes 1 Doms 2 Run Solver Structured 3 Select the two domains on the plane of symmetry 4 Done 5 Elliptic Slvr Run N Iters 6 30 7 Done Save You can see in Figure 21 10 and in your Display window that the default settings in the elliptic PDE solver try to make the grid lines orthogonal to the domain edges This is usually a desirable property 7 16 Figure 21 10 Symmetry Domain After Running the Elliptic PDE Solver Creating Block Two You can also improve the two inflow plane domains using elliptic refinement This time use the floating boundary condition to let the connectors between the domains move S es c4L Cgy Cue ses GA IBS ji e Run Solver Structured Select the two inflow plane domains Done Set Solver Attribs Apply to All Solver Bound Conds Floating Done Setting Attributes Elliptic Slvr Run Let the solver run for approximately 100 iterations 11 Done Save Now you are ready to build the second block Oe c OF eer ey Blks Create Assemble Faces Add 1st Face Pick domain OPQRJHD Save the Face Pick domain RNIJ Save the Face Pick domain AEINMLK 7 17 B 747 Nacelle Working With An IGES Database 10 Save the Face 11 Pick domain HJIEFG 12 Pick domain DHG
170. roplet in a Cylinder Hybrid Grid Figure 24 13 Domains on Ends of Cylinder Core 10 13 2 Close Symmetry Plane Next you need to create the domain that closes the core of the cylinder at the symmetry plane From the DOMAIN COMMANDS menu 1 Create 2 Assemble Edges 3 Turnoff the Auto Save toggle 4 Pickthe connectors AB BC CD and DA defining the outer loop connectors of the cylinder core sym metry plane Next Edge d 6 Pick connectors EF then pick the other connector FE on the outer edge of the exterior prism layer on the droplet This defines the inner loop connectors of the cylinder core symmetry plane When creating a domain that contains a hole such as this one the orientation of the inner loop of connec tors must be opposite to the orientation of the outer loop of connectors If the inner loop of connectors has the same orientation as the outer loop they must be reoriented through use of the Reorient Edge button Then you may go on to the next step of the domain creation process 7 Save Domain 8 Done 9 Done You have now created a completely enclosed shell of the cylinder s interior core The unstructured domain on the symmetry plane is shown in Figure 24 14 10 18 Volume Grid in the Core of Cylinder Volume Grid within Core of Cylinder Figure 24 14 Domain on Symmetry Plane 10 13 3 Volume Grid within Core of Cylinder The final step in the Gridgen process
171. rs you create after this point will automatically have 35 grid points assigned to them You will now create the connector defining the length of the cylinder at its radius From the MAIN MENU 1 Connectors 2 Create 3 On DB Entities 4 Pick the database curve defining the length of the cylinder at its radius Entity 3 from the Browser 5 Done 6 Done You now extrude from the new connector a structured grid around the center axis You will be using another type of extrusion command rotation to extrude the connector around a predefined axis of rotation From the MAIN MENU 1 Domains Create Cell Type structured Extrude From Cons Pick the connector defining the length of the cylinder at its radius Oy cgo eee ono LS Done You now need to select the rotation type of extrusion method Since you are only modeling half of the cylin der you only need to rotate the extrusion by 180 1 Type Rot Set Attributes Total Rotation Angle Enter via Keybd 180 Set Rotation Axis Use Y Axis Sly oy dom eb ee T9 10 13 Droplet in a Cylinder Hybrid Grid 8 Done Finally run the rotation extrusion command From the DOMAIN EXTRUSION menu 1 RunN 2 35 3 Done 4 Done Your topology should now look like Figure 24 9 Use the keyboard hot key r to reset the view and display the topology Figure 24 9 Structured Surface Grid on Cylinder 10 12 Hexahedral Cells from the C
172. s to create them From the CONNECTOR COMMANDS menu 1 Copy 2 Pick All 3 Done 4 Abort Don t Translate 5 Rotate 6 Enter Axis 1 via Keybrd 7 0 5 2 5 0 8 UseZ directed Axis 9 Enter Rotation Angle 10 45 11 Done Rotate 12 Done Save Connectors The Display window should look like Figure 22 9 on the following page 8 6 OS Connectors at the Inlet Plane of the Passages Figure 22 9 Passage 9 Connectors Copied and Rotated Use the same commands to create the other passage connectors From the CONNECTOR COMMANDS menu 1 Copy 2 Pick All 3 Done 4 Abort Don t Translate 5 Rotate 6 Enter Axis 1 via Keybrd 7 0 5 2 5 0 8 UseZ directed Axis 9 Enter Rotation Angle 10 90 11 Done Rotate 12 Done Save Connectors The Display window should look like Figure 22 10 on the following page OS O D Figure 22 10 Copied and Rotated Connectors at Passage Inlets Finally create the last four sets of connectors for the swirler passages From the CONNECTOR COMMANDS menu 1 2 3 Copy Pick AII Done 8 7 LDI Combustor Advanced Structured Grid 4 Abort Don t Translate 5 Rotate 6 Enter Axis 1 via Keybrd 7 0 5 2 5 0 8 UseZ directed Axis 9 Enter Rotation Angle 10 180 11 Done Rotate 12 Done Save Connectors This completes the connector creation for the inlets to the swirler passages The finished topology is shown in Figure 22 11 The labeling convention is al
173. se south and the 3D cursor will move in the negative y direction on the screen 3 Continue holding down the right mouse button and moving the mouse until the 3D cursor is over the 4 6 Drawing Connectors node at 0 0 0 4 Release the right mouse button 5 Add CP O by Picking If the point was picked correctly you will notice that the Browser window changes to Connector Segments 1 Connector Dimensions 0 Control Points Cross Position x 0 0000000E 00 y 0 0000000E 00 z 0 0000000E 00 Distance To Last Point D 0 0000000E 00 The important information to note is that the segment now has one control point If Gridgen s Message win dow displayed an error message saying that a point had not been picked you should repeat the above steps until the control point is added Note after the first control point is added a small open yellow square appears at the control point location Also a large open white circle will appear around the 3D cursor This is Gridgen s way of telling you the current segment consisting of the picked control point and the current 3D cursor position has zero length In order to complete the shape definition of this connector we need to add a second control point at Point B Figure 19 3 To add this control point we will do the following 1 Add CP O via Keybrd 2 Q 75 0j 0 After you do this confirm the Browser window shows Connector Segments 1 Connector Dimensions 0 Control
174. sic Gridgen skills you will learn are creating connectors the edge curves on which grid points are distributed using the Add Segment com mand copying and translating connectors using Copy creating structured domains which are quadrilateral surface grids using Assemble Edges Run Solver Structured to improve a domain s grid quality through application of an elliptic PDE method creating unstructured domains which are triangular surface grids 2 3 Background Work through this tutorial to familiarize yourself with the basic operations of Gridgen 2 4 Geometry For this brief introduction to Gridgen we will generate a 2D grid for a rectangular domain with a circular bump on one wall The table below gives the coordinates of important points in Figure 18 2 Bump Coordinates label E y Zz A 0 0 840 0 0 B 20 0 0 0 0 0 C 10 0 0 0 0 0 D 10 0 0 0 0 0 E 20 0 0 0 0 0 F 20 0 20 0 0 0 2 1 2D Bump Basic Skills Bump Coordinates label Es y Z G 20 0 20 0 0 0 A Figure 18 2 Schematic of the Bump Geometry This is purely a contrived problem for demonstration purposes however similar problems arise when study ing fairings on aircraft constricted channel flows wavy wall heat exchangers and many other practical engineering problems 2 Start Gridgen Start Gridgen by typing the string gridgen on Unix workstations or by simply double clicking the Gridgen shortc
175. smoother more clustered or more orthogonal according to your require ments Gridgen does not judge the quality of your grid It is up to you to decide whether or not elliptic PDE refinement is necessary You will apply the elliptic PDE method to the domain you just created 1 Domains 2 Run Solver Structured The first thing you must do is pick the domain or domains to be run in the solver You can do this by picking from either the Display window as we have done for connectors or by picking from the tabular list in the Browser Let s pick this domain from the Browser 1 Position the cursor over the entry for domain 1 in the Browser Note how the domain is highlighted in salmon indicating that it is pickable Press and release the right mouse button Note how the domain is highlighted in pink indicating that it is picked Done ON re OX cp Elliptic Slvr Run The elliptic PDE solver is now running using the default attributes After each iteration the grid is redrawn so that you can monitor the grid quality as the solution proceeds Notice the Browser window Ellip PDE Solver RUN Iteration N Total Residual nnn o Max Residual nnn It indicates how many iterations have been run the residual of the PDE solution for the entire grid and the maximum residual The location of the maximum residual symbol in the Display window indicates the grid point at which the PDE solution is changing most rapidly We recommend
176. sms into the interior of the droplet You should read Section 12 for explanations of the various attributes used in this section These attributes are shown in the menus below CREATE BLOCK Cell Type Ostructured unstructured Assemble Faces 1 Extrude From Doms 9 From A Face oj Abort Done Creating esc Display Commands a Help From the MAIN MENU 1 Blocks BLOCK EXTRUSION eNrm 9Rot OTran Path Run s Back al Run 1 1 Back 1 1 Run N n Back N n Restart q Set Attributes s Set Stop Criteria c Done ent Abort esc Help 10 7 Droplet in a Cylinder Hybrid Grid 2 Create 3 Extrude From Doms 4 Pick All 5 Done You are going to extrude the layer of prisms using the normal extrusion method The normal extrusion attributes menu is shown below NRML EXTRUSION ATTRIBS Focus Apply to O Focus Al11 s Smoothing Normal Count 1 Relax 1 Step Count 2 Relax 2 Grid Count 3 Angle A3 Edges O1D 2D o nt Corner Suppression Stretching Factor Set 4 Turning Angle Corner Flat Primry Sendry Aspect Ratio Factor 4 s Init 5 Min 6 Max 7 Growth Rate Geometric a Set 8 Subcon b Boundary Conditions i F1 ip d Done ent Help 1 Type Nrml 2 Set Attributes This should take you to the NRML EXTRUSION ATTRIBS menu 3 As Init 0 1 4 5 Boundary Conditions 6 Turnon th
177. so shown for the next step in the construction process X qiee e D c ah Figure 22 11 Connectors at the Inlet Plane of Swirler Passages 8 10 Domain Topology Between Passages You will now create the connectors CF and DE which define the topology between the swirler passages From the CON NECTOR COMMANDS menu Create 2 Point Connectors Position the 3D cursor over node C Add CP O by Picking Position the 3D cursor over node F Add CP O by Picking Position the 3D cursor over node D Add CP O by Picking Cm NAA RYN za Position the 3D cursor over node E 10 Add CP O by Picking 11 Done 12 Done Creating Conns Redimension connectors CF and DE You should still be in the CONNECTOR COMMANDS menu 1 ReDimension Grids 8 8 Domain Topology Between Passages 2 Select connector CF 3s 6 4 Select connector DE 5 6 6 Done Apply New Dims 7 Done The Display window with connectors CF and DE is shown in Figure 22 12 Figure 22 12 Connectors Between Swirler Passages You will create a domain bound by the connectors DC CE FE and ED From the MAIN MENU Domains Create Assemble Edges Turn on the Auto Next Edge toggle Pick connector DC followed by CF Oo OD Done The Display window should shown in Figure 22 13 on the following page Figure 22 13 Domain Topology Between Passages You now copy and rotate the domain you have just created in much the same way as Section 8 9 in the tutorial From the
178. ssssssssssssssee nenne 9 4 9 7 Creating Connectors ec eati eR pte eat tm pf Debs 9 7 9 8 Creating DOMAINS s oic fei ete ied Re Retos tn eee 9 9 9 9 Creating the Block roti ebenso Dien iat bid 9 12 9 10 Initializing and Examining the Tetrahedra ssusssssse 9 13 9 11 Saving Your Model and Export to Solver ssssssssss 9 15 10 Droplet in a Cylinder Hybrid Grid sess 10 1 10 1 Introduction eo b A ete oit aic OE er dis 10 1 TU 2 TODICS COVO E aio oe b atat bonn 10 1 10 3 BackgtOUhu orines rii oodd diri tie e deett Leu keds 10 1 10 4 Geomelty odo oo ttm m a eG eee el tees o iu en ue eod auge 10 1 0 5 Getling Started iod ea pH t eI Pre ea ees abs 10 3 10 6 Creating Database Entities sess 10 4 10 7 Unstructured Surface Grid on Droplet sssssssusss 10 6 10 8 Droplet Interior Prism Extrusion ssssssssssssseeneeenne 10 7 10 9 Droplet Core Volume HM REL e MEM ds 10 9 10 9 1 Close the Core of the Droplet ssssssssssseseneeeee 10 9 10 9 2 Droplet Core Volume Grid essssessesssseneie 10 10 10 9 3 Initializing the Tetrahedral Volume Grid sssesssssss 10 11 10 10 Droplet Exterior Prism Extrusion esee 10 11 10 11 Structured Surface Grid on Cylinder ssssss
179. ssusss 10 13 10 12 Hexahedral Cells from the Cylinder Surface Grid 10 14 10 13 Volume Grid in the Core of Cylinder ssssssssssusss 10 16 T0 13 1 Ulo56 Cylinder Ends ode etat beso eee eons i 10 16 10 13 2 Close Symmetry Plan eder o pep Hohen a 10 18 10 13 3 Volume Grid within Core of Cylinder 10 19 10 14 Saving Your Model and Export to Solver ssssssss 10 20 11 Tension Bar Feature Extraction sss 11 1 IT T IDtFOQdUCIHOID eiae Ned b diee ep ideni 11 1 11 2 TOPICS COV CIC 5 o oro HUC Edu esie Edict cec 11 1 11 3 BACK Ol OUI ont eid dern ote ea desde otio iare iia 11 1 IL GOoInelty 2 oet b ecelesie demas E 11 1 11 5 Gelting SIared oio EE s ba ai eed 11 2 11 6 Import Shell STL Model ssssssssssess eene 11 2 IH SOTO Delaults ise Dd ee Ei uade 11 3 11 8 Feature Extraction uei ae vedi ee dia reo o uot 11 4 11 9 Creating Structured Surface Grids sssssuusss 11 5 11 10 Grealing BIOCKS oo OE IECUR a niia 11 7 12 Mixer Using Balll6S deron etii ets tended asta 12 1 I2 T IBUOOUCHON oii de e buit ide au Sent ta iad 12 1 12 2 Topics COVOled 1 uio ee eredi eroe timete iocis ta cie Pise eps 12 1 12 3 Backgro hd o op RO talent a RUE DEREN anaes 12 1 12 4 GBOmeli oer ia Ub i aia uidet 12 1 12 5 Gelting Started ERR e UEM ib C 12 2 12 6 Setting Defa
180. stributing 4 Done Save Connectors Connector CF is to be created next Do the following 1 Add Segment 3D Space Line Add CP O by Picking Add CP O via Keyboard 2 1 5 0 Ov Oe ee Done Save Segment 4 10 Drawing Connectors Figure 19 2 indicates connector CF will be an edge of a surface grid opposite connector AG In a structured grid this means the two connectors will have the same number of points In our particular grid it is also rea sonable to apply the same type of grid point distribution to both connectors Therefore we can now do the following 1 ReDimension Using the mouse move the cursor over the connector corresponding to connector AG in Figure 19 3 When the connector is highlighted in salmon press and release the right mouse button Done ReDimension Copy Values Ov ww oui o Done Save Connectors You just told Gridgen to apply the number of grid points on connector AG to connector CF You also told the code to copy the distribution constraints specified clustering distribution function etc One more connector must be drawn before the tutorial may proceed to something other than connector cre ation This is a good time to point out that typically a large percentage of your work in Gridgen will be expended during connector creation things get a lot less laborious after this You can probably guess the next connector we will draw is connector FG in Figure 19 3 Let s finish this one quickly by 1
181. t J to J and point K to K From the MAIN MENU xe 90 l4 29v Ue dece GB Connectors Modify Select connector JK Done Segment Edit Move point J to point J by selecting point J with your right mouse button and dragging it to point J Store CP by Picking Edit Pick Select point K Move point K to point K by selecting point K with your right mouse button and dragging it to point K Store CP by Picking Done Editing Done Replace Connectors Maintain Linkages Done Domain FJKG should now following the intersection curve as seen in Figure 20 15 6 15 Intersecting Pipes Pole Grid Construction Top Down Figure 20 15 Domain FJKG Conformed to the Pipe Intersection The blocks are now ready for the final stage of grid construction projecting the block faces onto the data base surfaces 6 9 Connector and Domain Projection Projecting the block faces onto the database surfaces is the last step in the top down grid construction pro cess Before projecting the faces all connectors must be redimensioned via the Redimension Grids but ton Afterwhich the connectors then the domains are projected to the database Figure 20 16 Pipes Labeled Blocks For your grid you will only need to redimension seven connectors for the entire grid to be redimensioned appropriately The following table lists the connectors that need to be selected and their new dimensions 6 16 Connector and Doma
182. t automatically merged during the On DB Entities command since implementa tion of the merging tools during On DB Entities will stop considering connectors once they become part of a manifold edge effectively disallowing baffles Press the Abort Done Merging button to exit from the Merge Pick function set TopoFltr back to All and simply use Merge Auto to have Gridgen look for candidates automatically based on your input toler ance and topology filter settings 1 TopoFltr All This choice ensures Gridgen will consider all connectors for merging regardless of their use in existing domain connections 2 Merge Auto 3 0 5 4 Update Now there are no longer any overlapping connectors and we are ready to proceed to block construction 12 9 Creating Unstructured Block with Baffle Faces Completing the grid simply involves creation of a single unstructured block which will consist of one closed face and four baffle faces Create the block starting from the BLOCK COMMANDS menu 12 5 Mixer Using Baffles 1 Create 2 Cell Type unstructured 3 Assemble Faces 4 Add 1st Face 5 AutoSave Faces This instructs Gridgen to automatically save completely closed faces and baffle faces 6 Turn off the NonMnfld Cnnct toggle so that Gridgen will only allow manifold connections between domains and properly differentiate between the tube face and baffle faces 7 Pick All Domains Gridgen immediately beeps and indicates in the Message Win
183. t could be used for this inlet configuration The requirements of the particular flow solver or other analysis software you are using should be considered when planning the grid Now that a topology for the blocking system has been chosen we can begin creating the grid For conve nience we have assigned a naming convention to the connector node points which will be used to create the grid The node labels are shown in Figure 21 2 for clarity connectors and nodes are shown only the data base model is not visible in this image Note that in order to accurately model this internal flow field one would likely grid and solve the region external to the inlet as well To satisfy the goals of this tutorial how ever it is sufficient to grid only the internal region of the inlet For further practice you are free to develop an external grid for this database geometry 7 2 Getting Started Figure 21 2 Two Block Grid Topology for the Inlet 7 5 Getting Started Begin by starting Gridgen either by typing the string gridgen on Unix workstations or simply double clicking the Gridgen shortcut on your PC s desktop The first step in running Gridgen is to select the soft ware Section 17 1 of the User Manual to be used in the analysis This will ensure that the grid generated by Gridgen is consistent with the capabilities of the analysis software For this analysis we will be using the WIND flow solver by default Gridgen selects the generic solver To
184. t point O to O and point P to P should will now be used to connect point Q to Q and point S to S Since the points Q and S do not physically exist you will need to use an option to pick the closest database point instead of picking a pre existing point From the MAIN MENU 6 11 Intersecting Pipes Pole Grid Construction Top Down 1 Connectors Modify Select connector QS Done Segment Edit Qy coh se my SES Move point Q to Q by selecting point Q with your right mouse button and dragging it to just beyond the branch pipe in that area Store CP at Clsest DB Pt 8 Edit Pick 9 Select point S 10 Move point S to S by selecting point S with your right mouse button and dragging it to just beyond the branch pipe in that area 11 Store CP at Clsest DB Pt 12 Done Editing 13 Done Replace Connectors 14 Maintain Linkages Next you need to connect opposite face of the block opposite to domain FJKG using the same technique you used to connect points O and P to their corresponding branch pipe locations You will use the Segment Edit and the Store CP by Picking commands to move connector endpoints to their corresponding loca tions on the FJKG domain This is left as an exercise for you to complete since you have already used these steps once before When you have finished your block should appear as seen in the following figure Figure 20 12 H Block Connected to Branch Pipe and Polar Block Bo
185. t should now look like the one below Note that since we previously set layer 0 to the current working layer it is still shown in the list even though it is now empty But this is probably a good setup since any newly created entities will now be placed in this top layer in the list which is clean raver ente oescrivtsen Construction All T Construction Points 2 Construction Lines 5 10 15 20 25 3 Sphere Small Sphere Medium Sphere Large Cube Small Cube Medium Cube Large t 4 1 13 Saved Sets Finally to get a handle on quickly displaying certain groups of objects create saved layer sets for the con struction entities the spheres and the cubes 1 Select layers 5 through 30 click on 5 and drag the mouse down the list 2 Status Off 3 Saved Layer Sets Save The Saved Layer Set dialog box pops up Layer Set Name 4 Enter Construction in the Layer Set Name field 5 OK You now have a new saved layer set in the Saved Layer Sets Browser 1 11 Cubes and Spheres Layer Manager m Saved Layer Sets Construction Save Restore Delete So Continue on for the spheres and cubes Select layers 1 through 15 Status Toggle Saved Layer Sets Save Enter Spheres in the Layer Set Name field OK Select layers 5 through 30 Status Toggle Saved Layer Sets Save xe 0o O Uv R6 9 F9 Enter Cubes in the Layer Set Name field 10 OK
186. te file 7 Done Five more domains have to be made before you can create the first block Before making the domains you will have to draw several z directed connectors Start by creating the connector corresponding to connector AH Connectors 1 Create 2 Add Segment 4 3D Space Line 3 5 Position the cursor over the node corresponding to Point A in Figure 19 3 4 20 More Connectors and Domains Add CP O by Picking Position the cursor over the node corresponding to Point H in Figure 19 3 Add CP O by Picking Done Save Segment ReDimension From keybrd 11 Done ReDimension Done Save Connectors Instead of redrawing the z directed connector GN as we did for this last connector copy connector AH and translate it to the new position This process is very similar to what you have already done in copying and translating a domain SE ou o OM oan cde Mes 9 o Add Segment Others Copy Pick the connector corresponding to connector AH in Figure 19 3 Pick the node corresponding to Point A in Figure 19 3 Press and hold the right mouse button Move the cursor over the node corresponding to Point G in Figure 19 3 Release the right mouse button Set Handle by Picking Done Copy Connector Copy Break Point Info 11 Done Save Connectors Now copy this last connector to positions FM and CJ xc OO wol CO UE sx M SPP E Uu o Add Segment Others Copy
187. te turning the Hiliter extend toggle on allows you to scroll through the grid planes for both blocks and thus view the grid surface across the chosen topological plane XV i V ray A AN AAS N at 27 AP L RT SEE LT L X LEE ar CP GP MV d j Figure 19 13 Block Examine Lets You Assess the Ramp s Volume Grid Quality The volume grid looks good Let s go to the final part of the tutorial generating the input files for a CFD flow solver 1 Abort 2 Done 4 14 Customizing the Grid for the Analysis Software The Gridgen process is nearly complete The volume grid is done and ready to be used The final task is to set up the grid and boundary condition information for the analysis software If you check the beginning of this tutorial we told Gridgen we would be using the STAR CD flow solver to compute the flow field on this grid The Status window should also show this We need to set a STAR CD flow solver boundary condition on each domain in the system and then export STAR CD s files To begin setting boundary conditions do the 4 33 Swept Ramp Basic Multi Block Structured Grid following 1 Analysis S W 2 Set BCs The Browser has an entry for each domain on the block is shown in Figure 19 13 1 6 i 5 i 2 Type 1 2 5 1 4 ls 3 i 7 2 6 9 2 0 113 2 2 Type 1 1 2 10 2 8 2 125 Figure 19 14 Domains in the Browser for BC Selection Each domain entry in
188. teps have all been covered in detail during construction of the first block the com mentary here will be kept to a minimum First copy the domain and move it downstream 1 Domains Copy Pick the downstream domain defined by JMFCJ Done Pick the node corresponding to Point C Set Handle via Keybrd ml OY GA cube Cw S 3 Notice when this last coordinate was entered only the x coordinate was actually typed and the default values for y and z were used The default values for all three of the components are the current cursor position shown in the Browser window Because of this it is only necessary to enter the value of the component s that change 8 Done Translate 9 Save Domains 10 Done Now create an x directed connector For practice we will create this connector in a different way than the previous connectors as a 2 Point Connector 2 Point Connectors are created by picking two end points If both end points lie on a common database entity a DB cnstr Line connector is created between the two points Otherwise a 3D Space Line connector is created between the two points In this example we do not have any database entities so we will use 2 Point Connectors to create a straight line segment Before creating the connector you will set a default number of grid points to place on any new connectors that are created 1 Defaults 2 Con Dim dimen 3 15 4 Done 5 Connectors 6 Create 4 29 Swept Ramp Basic
189. ter Modification Later you will create grid entities on the modified geometry It is important to save the modified geometry so that the association with the grid can be preserved in future sessions Save your database model now 1 Input Output Database Export type composite Done Navigate using the file Browser to a suitable directory where you have permission to save this new file Type In Name 747 mod 9e LOS Ue Es oo H9 Done We have completed all of the database tasks required You can now proceed to building the connectors for 7 5 B 747 Nacelle Working With An IGES Database this grid Finally to help speed grid construction we will set a default value for connector dimension and change the connector and node tolerances using the SET DEFAULT VALUES menu option To make these changes 1 Defaults Con Dim dimen 30 Tolerances Connector 0 02 Done BOS CON Es oh WES spa Done Any connectors you create after this point will automatically have 30 points assigned to them If you want a different number of grid points on any connector you will have to change the dimension manually or change the default value We changed the connector tolerance to a higher value than the usual default so that later in the tutorial Gridgen will automatically grid over gaps in the database by removing coincident connectors Note that this change automatically increased the node tolerance as well The node tolerance may not be less than
190. terior of the volume or solid you wish to analyze Grid gen should automatically orient these in most cases but verify their orientation in the Display window and use Reorient Faces to reverse the orientation if necessary 7 Done Save Blocks Also in the BLOCK COMMANDS menu 14 8 Completing the Grid 1 Run Solver Unstrctrd 2 Pick All 3 Done 4 Initialize 5 Done Save Now use the Examine command to have a look at the interior of your new unstructured block 1 Examine 2 Pick All 3 Done 4 PhyZ 5 Zkbrd 6 0 0 7 Ref Surf Crinkle You should now see a reference surface like the one shown in Figure 26 6 You may also wish to examine some particular quality measure using Function None to go to the DIAGNOSTIC menu and choosing a specific quality measure for Gridgen to calculate This concludes our tutorial Feel free to try other angles and tolerances for the On DB Entities command to see what other results you can obtain on this geometry 14 9 Mechanical Part Basic FEA Mesh Figure 26 6 Crinkle Reference Surface in Examine 14 10 15 Index ABCDEFGHIJKLMNOPQRSTUVWXYZ Numerics 2 Point Connectors example use 9 6 2D Airfoil 3 2D Bump 2 A Analysis Software selection example use 4 4 9 3 setting boundary conditions example use 4 34 axis surface of revolution 5 6 B B 747 Nacelle 7 baffle face example use 72 1 Blackboard block face creation example use 4 27 domain c
191. th the Polar Block and the H Block share the domain FJKG This domain now has to be modified to fol low the shape of the intersection curve First move points F and G to the end points of the intersection curve using the Segment Edit command in the CONNECTOR COMMANDS menu From the MAIN MENU 6 12 On Ye Cw dS 9 GPS Building H Block for Branch Pipe Connectors Modify Select connector FG Done Segment Edit Select point F Keep the right mouse button pressed and drag point F to the end of the intersection curve Store CP by Picking In Figure 20 13 in the close up view of the domain and the intersection curve you can see the arrows which point to the ends of the curve These point to the locations that you want to move points F and G to respec tively Figure 20 13 Main and Branch Pipe Intersection Curve Now that you have moved point F you will need to move point G to the other endpoint of the intersection curve Edit Pick Select point G Keep the right mouse button pressed and drag point G to the end of the intersection curve Store CP by Picking Done Editing Done Replace Connectors Maintain Linkages Points J and K now need to be moved to follow the intersection curve To make the connectors FJ JK and KG follow the intersection curve exactly you will need to split the intersection curve into three sections From the MAIN MENU 6 13 Intersecting Pipes Pole Grid Construction Top Down
192. the Browser lists the block coordinate that is constant on the domain the domain num ber in parentheses and the boundary condition set on that domain Notice only two domains have an entry for a boundary condition Let us examine it further 1 Position the cursor over the Browser entry containing the text Type 1 2 Notice in the Display window the domain corresponding to this entry is highlighted It is the domain shared between the two blocks Gridgen is telling you it has detected a point to point Type 1 inter block connec tion on this domain and has automatically set the boundary condition In general Gridgen will automati cally set all inter block connections All you have to do is specify the boundary conditions corresponding to flow boundaries Position the cursor over the Browser entry containing the text 1 Cmin Press and release the right mouse button Position the cursor over the Browser entry containing the text 2 Cmin Press and release the right mouse button Position the cursor over the Browser entry containing the text 1 Cmax Press and release the right mouse button Position the cursor over the Browser entry containing the text 2 Cmax Press and release the right mouse button NO eo co gv UM ghe t R9 Done You are now presented with a menu of boundary conditions used by the STAR CD flow solver These domains are xy planes of symmetry so choose 1 Symmetry Notic
193. the User Manual to be used in the analysis This will ensure that the grid gener ated by Gridgen is consistent with the capabilities of the analysis software Since setting the analysis soft ware is not the focus of this tutorial you can use the default generic analysis software setting No action on your part is needed 6 6 Importing the Database Now we need to import the intersecting pipes database into Gridgen There are two possible ways that you may import the database into Gridgen The first option is if you completed the tutorial in Section 6 you should already have the interesting pipes database available saved in a location on your computer as pipes dba You can read in the database in from the MAIN MENU 1 Input Output 2 Database Import 3 Navigate to the appropriate directory and select pipes dba from the Browser 4 Open 5 Done The second option for importing the database is to_load the Intersecting Pipes tutorial from the MAIN MENU and restart Gridgen keeping only the database From the Gridgen MAIN MENU 1 Tutorials 6 2 Building Polar Block for Main Pipe Intersecting Pipes Done Restart Gridgen Toggle off Clear DB Qu oA Es IUS SES Restart Before you go much further you may want to change the display attributes of the database Turning off the display of domains and placing the database entities in outline mode will make the database easier to see and work with 1 Disp Toggle off Doms Edit
194. to have Grid gen resize the view extents for the model and return to the original orientation Your model should now appear as in the figure below 3 9 Domain Extrusion Now you can create your extruded C style domain using the three connectors For this next step you may wish to zoom back up on the airfoil to make connector selection a little easier Use the z hot key to pop up the zoom box and size it around the airfoil to obtain a view similar to the one below If you make a mistake with the zoom box use Shift z to undo the previous zoom operation and try again CR o Now begin your extrusion work starting from where you left off in the CONNECTOR COMMANDS menu 1 Doms 2 Create 3 Cell Type structured 4 Extrude From An Edge Now Gridgen wants you to define a single beginning edge which will be extruded into a single domain 3 4 Domain Extrusion Using the From An Edge option allows the wake connector to be used twice in the original marching front and have the marching direction be maintained consistently along the entire front The alternative From Cons only allows the wake connector to be used once 5 Select the wake connector 6 Select the upper airfoil connector 7 Select the lower airfoil connector 8 Select the wake connector again 9 Save Edge You are now placed in the DOMAIN EXTRUSION menu Here you will choose the extrusion method set up attributes and set some criteria to have the extrusion stop au
195. tomatically if poor cells are detected 10 Type Hyp 11 Set Attributes Notice immediately that the marching direction vectors rendered around the edge appear to be pointing through the interior of the airfoil In other words vectors from the upper airfoil connector are point down and vectors from the lower airfoil connector are point up Since the same wake connector is used twice it is impossible to tell what those vectors are doing However you can assume that they are consistent with the ones on the airfoil Fix this problem first 12 March Flip Keep the default smoothing control settings and initial spacing of 0 01 You should set a boundary condi tion though that will keep the downstream end of the wake at a constant x coordinate value 13 Boundary Conditions 14 Edges All 15 Edges Set 16 Symmetry X 17 Done Now set up some automatic cell checking using Set Stop Criteria 18 Set Stop Criteria 19 Toggle on all four Jacobian checks 20 Done Now run the extrusion 21 Run N 22 40 23 Done Obviously no poor Jacobians were encountered during the extrusion so all 40 steps were completed You have saved a nice looking extruded domain that should look like the one below after using the r hot key to restore orientation 3 5 2D Airfoil Re Extrude 3 10 Re Extrude However after some exa
196. tor BC 2 Press and release the right mouse button 3 Move the cursor off the connector 4 13 Swept Ramp Basic Multi Block Structured Grid Note the change in the Browser window The two connectors we have picked make up one of the four edges of this domain It is time to define the second edge and you must tell Gridgen this by doing the following 1 Next Edge Note the Browser window now indicates you are Defining the Second Edge To continue our counterclockwise loop 1 Position the cursor over the connector corresponding to connector CF 2 Press and release the right mouse button 3 Move the cursor off the connector Notice how the connector is colored red and corresponds to the red edge in the Browser window This is the only connector in edge 2 To proceed with edge 3 do the following 1 Next Edge Gridgen knows in a structured grid the number of grid points on opposite edges of the same domain must be the same Since edge 3 is opposite edge 1 and since we have defined edge 1 to have 31 points the code can complete edge 3 automatically by recognizing connector FG has 31 points and it connects to the appropriate end of edge 2 Likewise Gridgen recognizes connector AG is the only possible choice for edge 4 so it com pletes the domain construction and generates the domain interior points using transfinite interpolation The resulting grid should look like Figure 19 7 TR Figure
197. tream block Sur face grids in Gridgen are known as domains Since the grid is to be structured we know each surface grid must map into a four sided region of I x J grid points That is why it was important for us to ensure the num ber of grid points on the two vertical connectors was the same Also Gridgen requires each edge of a domain be defined by at least one connector so there is a node in each of the corners This requirement is why we did not create the connector ABCFGA as one connector comprised of six control points there would not have been nodes in the corners The process of creating a domain is rather simple point to the connectors forming the perimeter of the domain Begin by doing the following 1 Domains 2 Create 3 Make sure the Cell Type structured radio button is selected 4 Assemble Edges Gridgen is now in the mode where it expects you to pick connectors You can tell this by looking at the Mes sage window Before proceeding note the Browser window shown Figure 19 6 4 12 Creating A Domain 0 Blocks 0 Domains 23 Connectors 14 Nodes 0 DBs generic 3D CREATE A DOMAIN Begin drawing the loop of connectors by picking a connector coincident to a domain corner Domain 1 0 Defining the First Edge CREATE A DOMAIN L Auto Next Edge aj MaAuto Complete c Merge Nodes n Conns c Nod Con 2 Auto t Pick k Update d TopoFltr 4411 3 oFree 4 ONonMnfld Free 5 Done ent Help Td Figur
198. two connectors Entities 3 amp 4 on the interior perimeter of the extruded prism layer Done Done An unstructured domain on the symmetry plane forming the core of the droplet is created by the above oper ation To display the symmetry plane core domain of the droplet 1 Ban GUN cBe Ye d Disp Edit Dspla Dom Select the domain Entity 5 from the Browser on the symmetry plane of the droplet Done display style Hidden Lines Removed Done Apply Atts Abort Done The Display window should now look like Figure 24 7 on the following page Figure 24 7 Closed Core of the Droplet 10 9 2 Droplet Core Volume Grid To finish the grid within the droplet you will now need to create a 3D volume grid enclosed by the core sur face grid The core block has one face defined by two domains the inner domain of the prism extrusion block and the symmetry plane domain just created From the MAIN MENU 1 Ie dnd Blocks Create Assemble Faces Add 1st Face 10 10 Droplet Exterior Prism Extrusion Initializing the Tetrahedral Volume Grid Pick Multiple Doms Pick the domain on the symmetry plane of the core Entity 5 from the Browser Pick the inner surface domain of the extruded prism layer Entity 2 from the Browser Done S o9 c nm Save the Face At this point you have made a complete unstructured block but take note of the orange arrows emanating from the surfaces of the block Make sure they are all pointing
199. u may want to try gridding the other geom etries found in the remaining tutorials in this workbook using the top down approach 6 20 T B 747 Nacelle Working With An IGES Database 7 1 Introduction This tutorial will give you a guided tour of the Gridgen process for creating a simple two block structured grid for the internal flow field of a 747 inlet geometry imported from an IGES formatted database file We encourage you to complete this tutorial before using IGES databases of your own to create more complex grids 7 2 Topics Covered This tutorial covers the basics of using an IGES database in Gridgen Gridgen skills you will cover during this tutorial session are creating database constrained connectors using On DB Entities creating connectors using DB cnstr Line segments creating database constrained connectors with branch segments modifying and redimensioning connectors using the SET DEFAULT VALUES menu and the Redimension Grids command creating database constrained domains using Project to put domains onto database entities elliptically smoothing database constrained domains using Run Solver Structured creating blocks 7 3 Background This tutorial covers advanced topics and assumes that you already understand the basics that are covered in previous tutorials particularly Section 2 and Section 4 74 Geometry The 747 inlet configuration you will use for this tutorial is shown in Figure 21 1 The portion
200. ults conia DAG o Ee i eee des 12 3 12 7 Creating Unstructured Domains sss 12 4 12 8 Additional Connector Merging ssssssssseeeeee 12 5 12 9 Creating Unstructured Block with Baffle Faces susss 12 5 12 10 Setting Flow Solver Boundary Conditions susuussss 12 7 13 Converging Diverging Nozzle Using Glyph Scripting 13 1 13 1 InttOdUcllOn ed diay a a ctos ete eee ed 13 1 13 2 TOPICS COVBled e derer tero e a Rae a oe Sede 13 1 13 3 Background ouo REPRE aie ie M Ee 13 1 13 4 Geometry ono cis pesados do ee DAR ORO eee eae 13 1 13 5 Getting Started coo DD Rib o o a dtes 13 2 13 6 Setting Variables for Spacing Constraints sssssssussss 13 3 13 7 Using Variables eo ueteres tr tended eo cuted ee roo E RSA TUR Ry wate 13 4 13 8 Script Editing and Playback ssss eene 13 5 13 9 Completing the Grid Baca eee nel ieee 13 6 14 Mechanical Part Basic FEA Mesh 14 1 14 1 LE OGU CU OV ics hic oe tee oet e usi d pete dea deitas dide tue 14 1 14 2 Topics COVOlied ood rtp er enun Udine e bai edens 14 1 14 3 Background be o Reges ibas aao Foe aed t M T Ra Reged 14 1 14 4 Geometry eee a eaa a nta ipei utei ted tud 14 1 14 5 Getting Started ucc cated DP piace UD uM 14 2 14 6 Setting Defaults oorr UE bM petia
201. ured domain or block In cases where such a connector is chosen Redimension Grids is configured to automatically propagate that connector s dimension changes to all connectors within the domain or block that must maintain the same dimensions Section 9 2 of the User Manual This allows you to quickly change the dimensions of a grid by only select ing a few connectors for redimensioning instead of all connectors As such you will only have to select con nector TU to redimension all the lengthwise connectors From the MAIN MENU 1 Connectors Redimension Grids Select connector TU 101 une ES Done Apply New Dims Now you are ready to split domain EILH You will want to split the domain just slightly to either side of the intersection curve The end result is that the intersection curve will be entirely contained within one small domain From the MAIN MENU 1 Domains 2 Modify 3 Select domain EILH from the Display window or from the Browser list entity 8 4 Done 5 Split 6 7 Intersecting Pipes Pole Grid Construction Top Down 8 I Lines Move the Hilite in the Display window to a point just to the right of where the branch pipe intersects the main pipe Done Split at Hilite The domain EILH has now been split into two domains EIKG and GKLH respectively seen in Figure 20 8 Figure 20 8 Domains EIKG and GKLH Now you need to split domain EIKG at the other location that the branch pipe intersects th
202. urface grid should now look like Figure 25 6 on the next page Figure 25 6 Surface Grid on Tension Bar 11 10 Creating Blocks Finally you can create the blocks making up the volume of the tension bar From the MAIN MENU 1 Blocks 2 Create 3 Assemble Faces 11 7 Tension Bar Feature Extraction Add 1st Face Pick the domain defined by the connectors ABCDEFG as the first face of block 4 5 6 Savethe Face 7 Continue picking the appropriate domains and saving each face in turn to form the block 8 Done Save Blocks You have now successfully created the block and you may Examine it if you wish This completes the tutorial on Feature Extraction The grid including the nodes connectors domains blocks surface and volumes grids can now be saved 11 8 12 Mixer Using Baffles 12 1 Introduction This section includes a brief tutorial to help you become familiar with Gridgen s block face creation tools for topologies containing baffles 12 2 Topics Covered Gridgen skills you will learn during this tutorial session are setting defaults appropriate for unstructured grids using the Defaults command using the On DB Entities domains command to create unstructured domains using the Merge Auto command to clean up connector overlap building regular and baffle faces automatically using AutoSave Faces setting wall boundary conditions on the baffles using the Set BCs command 12 3 Background The procedures foll
203. ut on your PC s desktop After a few seconds Gridgen will start and you will see the Gridgen logo in the Display window The logo will disappear after a few seconds or as soon as you select your first menu button Navigating through Gridgen s menu system is covered in depth in Section 2 of the User Manual If you do not want to read Section 2 of the User Manual before running this sample session just remember to use the right mouse button to select menu and screen items assuming that the Left Pk has not been set in the DIS PLAY COMMANDS menu The first step in running Gridgen is to select the software Section 17 1 of the User Manual to be used in the analysis This will ensure that the grid generated by Gridgen is consistent with the capabilities of the analy sis software For this tutorial we will not be performing an analysis using this grid Therefore we will use the generic analysis software which is the default The geometry for the sample problem is simple enough we can create it directly without a database We are ready to begin generating a grid 2 6 Draw Connectors Connectors are 3D curves made up of one or more segments connected end to end In other words a con 2 2 Draw Connectors nector is a composite curve A segment is a particular type of curve such as a line or conic section Section 6 2 of the User Manual Therefore a single connector may consist of a line followed by a circle followed by another line The s
204. uto Next Edge toggle Domain CFVWXYZ Structured Domains on Inlet Plane Pick the connector CF followed by EV Next Edge Pick the connector VW followed by WX Next Edge Pick the connector XY followed by YZ Dur PY ND Done The Display window should look like Figure 22 18 Figure 22 18 Center Domain Topology Use the copy and rotate commands to create the opposite boundary domains on the inlet plane From the DOMAIN COMMANDS menu Copy Pick domains GHIJ ADEGJK ABMNLK NOPL and GHROSTU Done Abort Don t Translate Rotate Enter Axis_1 via Keybrd Q5 2 5 0 Use X directed Axis E e E B Enter Rotation Angle 10 180 11 Done Rotate 12 Save Domains Your Display window should look like Figure 22 19 8 15 LDI Combustor Advanced Structured Grid Figure 22 19 Domain Topology on Inlet Plane to Swirler Passages 8 13 Running the Elliptic PDE Solver The surface grid created automatically by TFI can often be improved by applying an elliptic PDE based smoothing to the grid Gridgen offers a variety of elliptic PDE methods with various controls for boundary spacing orthogonality and smoothness You will run the elliptic solver from the DOMAIN COMMANDS menu Run Solver Structured Pick All Done Set Solver Attributes Apply to All LaPlace Foreground Cont Funcs Form Off 2 3 4 5 6 Background Cont Funcs 7 8 9 10 Set Other Attributes You will finally set the floating bou
205. utton unless you have LeftPk selected in the Display menu in which case you would press and hold the left mouse button 2 Move the mouse east and west to move the 3D cursor forward and backward along the connector s length Note as the cursor moves the coordinates in the Browser window change accordingly For this connector we want to cluster at both ends so do the following 1 Begin A 2 0 01 3 Ending A 4 0 01 Notice every connector has a direction associated with it the direction in which it was drawn The connec tor we are currently working with was drawn in the positive x direction It is this direction the clustering commands refer to with the terms Begin A and Ending A As we will discuss later in this tutorial the direction of a connector is irrelevant to the Gridgen process We could have drawn this connector in the neg ative x direction without affecting our grid or the amount of work we will have to do Now save this con nector 1 Done Redistributing 2 Done Save Connectors The next connector to be drawn is connector BC in Figure 19 3 First we will reposition the image in the 4 8 Drawing Connectors Display window to the left side All of connector BC will be visible as we create it We will pan the image to the left 1 Press and hold the left mouse button 2 Move the mouse to the west on the mouse pad The image will pan to the left on the screen 3 Release the left mouse button when the image has mov
206. v De d ow Fm pipes Note that Gridgen will automatically append the correct file extension dba 5 7 Drawing Connectors The geometry you just created will be used to determine the shape of the grid you will create next Before starting to build the grid set a default number of grid points to put on each new connector we create Starting from the MAIN MENU 1 Defaults 2 Con Dim dimen 3 31 4 Done The connector topology you will create is shown in exaggerated scale in Figure 20 6 along with labels that will be used for reference in the discussion that follows This figure will be repeated every few pages for convenient reference 5 8 Drawing Connectors Figure 20 6 Connector Topology Begin by creating some connectors on the surfaces of the two pipes the center line of the main pipe and the intersection curve From the MAIN MENU 1 Connectors 2 Create 3 OnDB Entities 4 Select the two surfaces of revolution the axis of the main pipe and the intersection curve between the two pipes from the Browser or Display window 5 Done Figure 20 7 Connectors Created With On DB Entities Command The connectors you have just created are displayed in Figure 20 7 You can see that the On DB Entities command puts connectors along the length of the selected database curves and around the perimeter of the selected database surfaces It also checks to see if any of the connec tors are duplicates of other connectors or if t
207. ver To select STAR CD do the following starting from the MAIN MENU 1 Analysis S W 2 Select Analysis S W 3 Press the radio buttons for 3D and STAR CD you may have to go to the menu s second page with the Next Page button to do this 4 Done 5 Done Use of the 3D button above tells Gridgen you will be creating a 3D multiple block grid in other words the blocks will consists of I x J x K points where K 2 2 In order to create 2D multiple block grids I x J x 1 simply choose the 2D button instead of the 3D button Verify you have selected the 3D STAR CD flow solver by checking the display in the Diagnostic window 4 6 Drawing Connectors You are now ready to begin creating the geometric elements that will comprise the grid The process begins with the lowest level element in the grid element hierarchy the connector Section 6 Connectors are 3D curves made up of one or more segments connected end to end In other words a connector is a composite curve A segment is a particular type of curve such as a line or conic section Section 6 2 A connector may be composed of several segments such as a line followed by a circle followed by another line The segments interpolate a set of user specified control points There are three major steps in creating a connector 1 Define the shape 2 Specify the number of grid points 3 Distribute the grid points The first connector you will create is the connector AG From the tabl
208. w should now look like Figure 22 23 Figure 22 23 Inlet Domain on Passage Entity 9 You now copy and rotate the inlet passage domain to complete the structured mesh on the inlet plane on the Inlet section From the DOMAIN COMMANDS menu Copy Pick the passage entity 9 inlet domain Done Abort Don t Translate Rotate Enter Axis 1 via Keybrd 0 85 5254 0 Use Z directed Axis oc 9mgms onmcza zd Enter Rotation Angle 10 45 11 Done Rotate 12 Save Domains Repeat steps 1 13 for 90 and 180 angles of rotation each time selecting the newly copied domains It is hoped that your Display window should look like Figure 22 24 You want to run the elliptical solver for the passage domains to improve the quality of the surface grid Figure 22 24 Domains on the Inlets to the Swirler Passages 8 15 Extruding Inlet Block You can now proceed with the construction of the inlet block You will extrude the inlet plane domains to create a 3D structured block in the negative z direction From the MAIN MENU E 2 ON o m amp 0 M You may want to reorient the Display window as shown in Figure 22 25 0 11 12 132 14 15 16 17 Blocks Create Extrude From Doms Pick AII Done Type Tran Set Attributes Total Translation Dist Enter via Keybd 0 5 Set Translation Vector Enter Vector via Keybd 0 0 1 Done Run N 18 Done Extruding Inlet Block 8 19 LDI Combustor
209. wept Ramp Basic Multi Block Structured Grid 4 1 Introduction This tutorial will give you a guided tour of the Gridgen process for creating a simple two block structured grid for the flow field over a swept ramp Note that working through this tutorial will not make you a Gridgen expert It will also not make you a grid generation expert Grid generation is not a trivial task that can be mastered in a couple of hours Generating a good grid involves both skill and patience and Gridgen has been designed to minimize as much as possi ble the required levels of both You should complete this tutorial before attempting any of the other tutorials since they cover advanced top ics and assume you already understand the basics that are covered in this session 42 Topics Covered This tutorial covers the basics of using Gridgen Basic Gridgen skills you will learn during this tutorial ses sion are creating connectors the edge curves on which grid points are distributed using 3D Space Line in the Add Segment command copying and translating connectors using the Others Copy command redistribute grid points on connectors using ReDistribute creating domains which are surface grids using Assemble Edges elliptically smoothing domains to improve surface grid quality using the Run Solver Structured use Copy and Modify to speed grid generation creating blocks which are volume grids using AutoSave Face elliptically smoothing blocks t
210. will need to use scaling factors of 0 4 in the x direction and 0 2 in the z direction For the y direction we will use a scaling factor of 1 to leave the block s size in the y direction unchanged Please note that these scaling factors are not exact but merely approximations to make fitting the block to the pipe slightly easier From the MAIN MENU 1 Blocks Modify Select the H block from the Display window or the Browser list entity 2 Translate Move point O to point O by selecting point O with your right mouse button and dragging it to point O Set Handle by Picking Done Translate OO del VOV SUA bes ay 9 Scale 6 10 Building H Block for Branch Pipe Select point O Enter Scaling Factors VE Tu 0 2 Done Scale Done Replace Blocks Maintain Linkage Now you will need to attach point P of the domain OQSP to point P on the branch pipe using the Segment Edit command found within the CONNECTOR COMMANDS menu From the MAIN MENU jud eC o c OON UN Re ow dp Connectors Modify Select connector OP Done Segment Edit Move point P to point P by selecting point P with your right mouse button and dragging it to point P Store CP by Picking Done Editing Done Replace Connectors 10 Maintain Linkages Your branch pipe block should now appear linked to the branch pipe as seen in Figure 20 11 Figure 20 11 H Block Connected to the Branch Pipe The same procedure used to connec
211. y terminate this License upon thirty 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 i 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 herei
212. ylinder Surface Grid You will now extrude hexahedral cell layers from the surface grid into the interior of the cylinder The pro cess is similar to the extrusion of the prism layer in Section 10 8 of this tutorial You will be extruding cells inward normal to the cylinder surface but using the hyperbolic extrusion method From the MAIN MENU 1 Blocks 2 Create 3 Extrude From Doms 4 Pickthe surface domain of the cylinder 5 Done You will select the extrusion method and set the extrusion attributes From the BLOCK EXTRUSION menu 10 14 SOR c OON ee p o Type Hyp Set Attributes As Init L0 Boundary Conditions Edges All Edges Set Constant Auto March Flip 10 Done Run the hyperbolic extrusion 1 Pe OS Run N 10 Done Done Hexahedral Cells from the Cylinder Surface Grid Initializing the Tetrahedral Volume Grid The Display window should look like Figure 24 10 Again the faces have been displayed as Hidden Lines Removed from the DISPLAY COMMANDS menu Figure 24 10 Extruded Hexahedral Layer Inwards of the Cylinder Surface Notice the cells are clustered towards the cylinder surface and become coarser as they move inwards from the cylinder surface 10 15 Droplet in a Cylinder Hybrid Grid 10 13 Volume Grid in the Core of Cylinder You now have to close the core of the cylinder to form the 3D volume You will do this by creating unstruc tured domains that cap the
213. you do not get too hung up on the value or convergence rate of the residual Instead by simply watching the grid in the Display window you will know how the solution is proceeding It is also important to note Gridgen will not stop the solver It is up to you to tell the code when to stop the refinement process Running the elliptic smoother with the default settings should give you a grid that looks like the one in Figure 19 8 4 15 Swept Ramp Basic Multi Block Structured Grid 111 Jmm i uuu TU Iu Figure 19 8 Running the Elliptic PDE Solver on the Ramp s Domain Improves the Grid s Quality When you are ready to stop 1 Pause Earlier we mentioned that the solver was running with the default attributes Let us examine the PDE attributes in more detail 1 Set Solver Attribs The Browser window presents a summary of the PDE attributes for this domain Domain Num 1 31 x 21 TFI standard Shape Free Relaxation Optimal BG ConFun Thom amp Midd As Angle type decay type decay base interp 6 ortho 6 Hilg interp 6 ortho 6 Hilg interp 6 ortho 6 Hilg interp 6 ortho 6 Hilg Boundary Conditions Fixed Fixed Fixed Fixed The line containing BG ConFun is the background control function By default Gridgen uses the Tho mas Middlecoff method clustering points on the interior based on how they are clustered on the four edges The table with the headings As

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