Tutorial: 3D Pipe Junction Using Hexa Meshing
Contents
1. Apply Dismiss a Left click on max size The MAX SIZE dialog box will open mas ize fo Accept Cancel b Enter 10 for max size Click Accept Decrease max size for CYL2 to 5 Enter 1 for height for CYL1 and CYL2 Enter 1 2 for height ratio for CYL1 and CYL2 Click Apply and Dismiss in the Part Mesh Setup dialog box C or Ner Nea Ne Ne Ne Noe O 2 Select Hexa Sizes see Figure 10 OQ eR Geometry rms gt Surfaces ims gt Hexa Sizes The quad along the surface represents the max size the thickness represents the height while the number is the height ratio 16 ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing Figure 10 Hexa Mesh Sizes 3 Update the mesh The heza blocking file blk is different from the ICEM CFD geometry file tin You can set the entity mesh parameters at any point before or after blocking The Update Sizes command is a quick and easy way to translate the entity parameters from the geometry to the blocking Mesh counts are propagated through a mapped mesh Hence the smallest size across any index is used gt Pre Mesh Params gt Update Sizes a Enable Update All ANSYS Inc February 11 2010 17 3D Pipe Junction Using Hexa Meshing Pre Mesh Params ral Meshing Parameters A PTS Xie F 6 Sizes Method f Update All C Keep Distributions f Keep Counts im Curyve gt E dge2. Create Part by Selection Entities surface GEOMA0 Ve Adjust Geometry Hames E Apply Lox Dismiss a Enter CYL1 for Part in the Create Part DEZ b Retain the selection of Nw Create Part by Selection and click S Select entities The Select geometry selection toolbar will appear ANSYS Inc February 11 2010 3 3D Pipe Junction Using Hexa Meshing c Disable Toggle selection of points x Toggle selection of curves and Toggle selection of bodies 5 material region definition to avoid the selection of entities other than surfaces d Ensure to enable Toggle selection of surfaces e select geometry x DE EEE EN a surface selection enabled Note Entity types can also be deactivated by disabling them in the Model display control tree e Select the largest semi cylinder f Click the middle mouse button to accept the selection g Click Apply in the Create Part DEZ The new part CYL1 will be added to the Model display control tree see Fig ure 2 Figure 2 CYL1 in Model Display Control Tree 4 Similarly create new parts for the smaller semi cylinder CYL2 cylinder ends INL and OUT and symmetry planes SYM See Figure 3 When in continuation mode after pressing the middle mouse button or Apply you can type in a new Part name and continue to select the surface s without re invoking the function 4 ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Mesh
3. gt Move Vertex gt Move Vertex a Click S Select vert s and select one of the vertices in green on the smaller cylinder b Move the vertex along the associated curve such that the edges along the smaller cylinder are nearly equidistant Select the Vertex Pressing the left mouse button drag the vertex along the Curve c Similarly move the other vertices to appropriate locations on the geometry Figure 9 Note To optimize mesh quality the vertices should be spaced to minimize the average deviation of the edges from the curve To achieve the most even distribution with this half cylinder case place the vertices approximately 60 degrees apart 180 half circle 3 edges 60 per edge 14 ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing Figure 9 Moved Vertices 3 Save the blocking File gt Blocking gt Save Blocking As 4 Provide a filename 3D pipe geometry b1k so that the file can be reloaded at a later time using File gt Blocking gt Open Blocking ANSYS Inc February 11 2010 15 3D Pipe Junction Using Hexa Meshing Step 6 Generating the Mesh For this model you will set the sizes on the parts rather than on individual surfaces or Curves 1 Set the sizes on the parts to generate the mesh gt Part Mesh Setup a Part Mesh Setup iV Show size params using scale factor Apply inflation parameters to curves Remove inflation parameters from curves
4. 2 Split the initial block into sub blocks Blocking gt Split Block gt Split Block a Enable Curves and Surfaces Ww Geometry rms gt Curves Geometry rms gt Surfaces b Display the left view for better visualization The L shaped topology is best seen in a side view View gt Left You can also select the X axis in the display triad in the lower right hand corner to re orient the model as it appears in Figure 5 ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing c Split the initial block vertically i Click rts Select edge s and select one of the horizontal edges ii Position the new edge near the front end of the small cylinder iii Click the middle mouse button to accept the new position d Split the initial block horizontally i Click rts Select edge s and select one of the vertical edges ii Position the new edge near the top of the large cylinder iii Click the middle mouse button to accept the new position Figure 5 shows the split block Figure 5 Geometry Showing Split Block Locations 3 Delete unnecessary upper block gt Delete Block Fd Select block s select the block to be deleted as shown in Figure 6 ANSYS Inc February 11 2010 9 3D Pipe Junction Using Hexa Meshing block to be deleted Figure 6 Block to be Deleted b Click middle mouse button and Apply in the Delete Block DEZ Ste
5. bunching El Apply ae Dismiss i Select Update All ii Click Apply 7N oO Ner UN OD O ct U lt a l N gt Blocking rms gt Pre Mesh The Mesh dialog box will appear asking if you want to recompute the mesh Click Yes E Mesh i curently out of date recompute es Mo Re mesh out of date parts Re mesh specific parts c Disable Surfaces Geometry tms Surfaces d Disable Edges Blocking zms Edges e Select Solid amp Wire Blocking rkms gt Pre Mesh ims gt Solid amp Wire The initial mesh is shown in Figure 11 18 ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing Figure 11 Initial Mesh Display Step 7 Checking the Mesh Quality The major quality criteria for a hexa mesh are angle determinant and warpage Refer to the User s Guide for details on the available quality measures gt Pre Mesh Quality Histograms Pre Mesh Quality ay Criterion Angle Histogram ptions Mines value 0 Maxes value 90 Mastr height 20 Nh Hum of bars 20 Only visible index range Active parts only ok Dismiss 19 ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing 1 Select Angle in the Criterion drop down list 2 Retain the default settings for Histogram Options and click Apply 3 Select the worst two bars from the histogram The selected bars will be
6. edge s and select one of the radial edges 24 ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing c Increase Nodes to 7 d Enter 0 2 for Spacing 1 e Enable Copy Parameters and select To All Parallel Edges in the Method drop down list Pre Mesh Params a Meshing Parameters A Edge R Length a Hodes r B Meshlaw BiGeometic Spacing1 faz J Spl Linked Select Reverse Ratiot f Spacing2 f J Sp2Linked Select Reverse Ratio2 f Max Space Spacing Relative Nodes Locked Parameters Locked W Copy Parameters Copy Method To AllParallelEdges gt W Copy absolute gl tony 0K Dimis f Enable Copy absolute and click Apply in the Meshing Parameters DEZ g Select Pre Mesh Blocking rms gt Pre Mesh h Click Yes in the Mesh dialog box i Disable Curves and Surfaces under Geometry and Edges under Blocking in the Model display control tree The final mesh is shown in Figure 17 ANSYS Inc February 11 2010 25 3D Pipe Junction Using Hexa Meshing Figure 17 The Final Mesh Step 9 Verifying and Saving the Mesh 1 Check the mesh quality gt Pre Mesh Quality Histograms a Select Angle in the Criterion drop down list and click Apply You can see the improved mesh quality in the histogram b Select Determinant 2 x 2 x 2 in the Criterion drop down list and click Apply 2 Save the mesh in unstructured format Pre Mes
7. Tutorial 3D Pipe Junction Using Hexa Meshing Introduction In this tutorial you will generate a mesh for a three dimensional pipe junction After checking the quality of the first mesh you will create an O Grid in the blocking to improve mesh quality Figure 1 shows the 3D pipe geometry lt sk A oe j Figure 1 3D Pipe Geometry This tutorial demonstrates how to do the following e Creating parts for geometry e Creating the material point e Blocking the geometry e Projecting edges to the curves e Moving the vertices e Generating the mesh e Checking the mesh quality e Creating an O Grid in the blocking e Verifying and saving the mesh ANSYS Inc February 11 2010 1 3D Pipe Junction Using Hexa Meshing Prerequisites This tutorial assumes that you are familiar with the menu structure in ANSYS ICEM CFD and that you have read about this functionality Some of the steps in setup and the procedure will not be shown explicitly For details about hexa mesh generation refer to the Chapter Hexa in ANSYS ICEM CFD user manual Conventions Some of the basic conventions used in this tutorial are e The icon to the left of the text here Blocking suggests that you have to select the option from the display tree Blocking e The arrow mark with the text LMB in the box the suggests that you have to click the left mouse button to enable or disable an option here Vertices ims
8. Vertices e The arrow mark with the text RMB in the box the suggests that you have to click the right mouse button to enable or disable an option here Numbers Rms gt Numbers For detailed information about GUI and text conventions refer to the document Getting Started with ANSYS ICEM CFD Preparation 1 Download the ICEM_hexa_3dpipe_FILES zip file from the ANSYS Customer Por tal It contains the necessary input geometry file hexa_3dpipe tin 2 Start ANSYS ICEM CFD and open the geometry hexa_3dpipe tin File gt Geometry gt Open Geometry Step 1 Creating Parts In the first two tutorials the parts were already defined For this and the remaining tutorials the initial geometry is contained in a single part You will put the geometry into different parts to define different boundary regions 2 ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing 1 Enable Surfaces under Geometry in the Model display control tree 2 Select Create Part option in the display tree Rms gt Parts ims gt Create Part Subsets Points Cues wf Surfaces Parts at GE Create Fart Create Assembly Show All Hide All Reverse Blank All Expand All Collapse All Blank Selected Restrict Selected Delete Empty Parts Edit Attributes Part Mesh Setup Good Colors Color By Material 3 Create a new part for the largest semi cylinder Create Part ral Part CYL ils Create Part
9. ces The radial blocks are adjacent to the cylinder surfaces 22 ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing Figure 15 Blocking with the O Grid Structure 4 Modify the O Grid gt Edit Block gt Modify Ogrid al Edit Block a Edit Block Sei yy Ja N Modify OGrid Method Rescale Ogrid Rescale Ogrid Block Select f AlVisible C Selected Ede 12330 X Absolute distance Offset os a Retain the selection of Rescale Ogrid in the Method drop down list b Retain the selection of All Visible for Block Select ANSYS Inc February 11 2010 23 3D Pipe Junction Using Hexa Meshing c Click rts Select edge s d Select the radial edge shown in Figure 16 edge selected Figure 16 Edge Selected for Modifying the O Grid e Ensure that Absolute distance is disabled f Enter 0 5 for the Offset g Click Apply in the Modify Ogrid DEZ 5 Update the surface mesh sizes on the blocking Blocking gt Pre Mesh Params gt Update Sizes 9 Retain the selection of Update All Click Apply in the Recalculate Sizes DEZ Select Pre Mesh a b c Nee W Ne Blocking rms gt Pre Mesh d Click Yes in the Mesh dialog box 6 Refine the mesh using edge parameters Blocking gt Pre Mesh Params gt Edge Params in a J D V e ct U OD lt OD Ww gt Blocking rms Pre Mesh b Click A Select
10. ces rms gt Hexa Sizes Create an O Grid Blocking gt Split Block gt Ogrid Block a Click i Select block s ie b Select Select all appropriate visible objects oe from the selection tool bar Enter v for all visible blocks or drag a box to select all blocks Note The option a indicating all is not available for blocking to avoid selec tion of VORFN blocks which are not visible but are still in the model Split Block a Split Block m Ogrid Block SelectBock QR GR SelectFace s AS AQ Select Edges A A Select Vertis Ny NS Clear Selected E Apply Lok _ Dismiss c Click S Select face s and select the faces representing the planar geom etry INL SYM OUT See Figure 14 You can also select the faces using any of the following ANSYS Inc February 11 2010 21 3D Pipe Junction Using Hexa Meshing o Select in the selection toolbar that appears or type Shft D on the keyboard This will allow you to select two diagonally opposite corners that make up the face BB e sles o Select 4 amp 8 in the selection toolbar that appears or type Shft P on the keyboard This will open the Select Blocking parts dialog box and will allow you to select the faces Figure 14 Selected Blocks and Faces d Click the middle mouse button to accept the selection e Retain the default settings and click Apply in the Ogrid Block DEZ In Figure 15 the O Grid passes through the selected fa
11. h Convert to Unstruct Mesh 26 ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing This saves the uns file as the mesh in the working directory and automatically loads tt 3 Save the project file 3D pipe geometry final prj File gt Save Project As 4 Exit the current session File gt Exit 27 ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing 28 ANSYS Inc February 11 2010
12. highlighted in pink Figure 12 24 18 Angle 12 Min 2 061 E Maz 58 56 E ea ee ae ee ee ee ee 0 9 18 27 36 45 34 63 72 01 30 Figure 12 Histogram of Angle 4 Right click in the histogram window and ensure that Show is enabled 5 Deselect Pre Mesh Blocking rms gt Pre Mesh The highlighted elements are shown in Figure 13 Most of the bad elements with the worst angles are on the block corners This is due to the H grid nature of the mesh within a curved geometry Figure 13 Worst Quality Elements Highlighted 6 Right click in the histogram window and select Done 20 ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing Step 8 Creating an O Grid in the Blocking In this step you will create an internal O Grid to improve the angles in the block corners This 1s the best method for fixing bad angles in block corners within cylindrical geometry The ANSYS ICEM CFD has a specific O Grid tool to make it easy to accomplish on even complicated geometry Before proceeding to this step make sure that your surface vertices are aligned as you want them and internal edges are straight The O Grid tool offsets the boundary faces orthogonally and you may end up with twice as many vertices It is convenient to adjust your surface blocking to ideal locations before O Grid than after l Enable Surfaces Geometry ims Surfaces Disable Hexa Sizes Geometry rms gt Surfa
13. ing CYL2 Figure 3 3D Pipe Geometry and its Surface Parts 5 Create a new part comprising all the curves in the geometry a Enter CURVES for Part in the Create Part DEZ b Retain the selection of Ne Create Part by Selection and click S Select entities c Enable Toggle selection of curves R in the Select geometry selection toolbar d Disable Toggle selection of surfaces L in the Select geometry selection tool bar oelect geometry x Select geomety O O OOOO O DAANA ox OS agg Aa A AM wR 8 ag curve selection enabled e Click x Select all appropriate objects or type a to select all the curves You need not click the middle mouse button when using Select all appropriate objects or Select all appropriate visible objects option f Click Apply in the Create Part DEZ 6 Create a new part comprising all the points in the geometry a Enter POINTS for Part in the Create Part DEZ b Retain the selection of Ne Create Part by Selection and click S Select entities c Enable Toggle selection of points se in the Select geometry selection toolbar ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing d Disable Toggle selection of curves in the Select geometry selection toolbar select geometry x EF EELEE haserkit sis point selection enabled e Click x Select all appropriate objects or type a to select all the points You need not c
14. lick the middle mouse button when using the Select all appropri ate objects or the Select all appropriate visible objects option f Click Apply in the Create Part DEZ Note The selection logic is flexible and there are many ways to select the entities This step illustrates an example of selection logic Step 2 Creating a Material Point 1 Select Create Body in the Geometry tab gt Create Body a Enter FLUID for Part b Retain the selection of yer Material Point c Click S Select location s Create Body a Part FLUID yah BE Haterial Point Location Centroid of 2 points O At specified point 2 screen locations 49 9961 Ta aay J Ok Dismiss 6 ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing d Select two locations such that the midpoint lies within the volume These can be two points as shown in Figure 4 e Click middle mouse button to accept the selection of points To see the selected points enable Points under the Model display control tree A a Points selected ban for creating the NI material point Figure 4 Selection of Points for Material Point Creation f Click Apply so that FLUID appears in Parts in Model display control tree Tip Rotate the model to confirm that the new material point is within the volume and does not just appear so from one perspective Note Parts such as GEOM will be deleted when they no longer con
15. on Using Hexa Meshing 12 Figure 7 Associating Edges to Curves Similarly associate the three edges in the front of the large cylinder e Associate B in Figure 7 with the three curves forming the large semi circle B Associate the three edges on the Y plane near the cylinder intersections e Associate C in Figure 7 with the semi circle curve forming the intersection C Associate the side rear edges of the large cylinder to the curves forming the rear ends e Associate D to D e Associate E to E Verify that the correct associations have been set Figure 8 In Figure 8 Surfaces display has also been enabled Blocking rms gt Edges ims Show association ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing Figure 8 Projection of Edges to the Associated Curves 7 Deselect Show association Blocking rms gt Edges ims Show association ANSYS Inc February 11 2010 13 3D Pipe Junction Using Hexa Meshing Step 5 Moving the Vertices 1 Move all the vertices onto the geometry wer gt Associate gs gt Snap Project Vertices x Blocking Associations al Edit Associations ee ITa KIX L POA e aeee Project Yertices Yertex Select AllVisible C Selected R Move D Grid nodes ees Apply Lo Dismiss a Retain the selection of All Visible for Vertex Select b Click Apply 2 Manually move the vertices
16. p 4 Projecting the Edges to the Curves 1 Disable Surfaces Geometry tms gt Surfaces When associating edges to curves you need to display only curves and edges Hence you can disable unwanted entities to avoid confusion gt Associate ig gt Associate Edge to Curve 10 ANSYS Inc February 11 2010 3D Pipe Junction Using Hexa Meshing Blocking Associations a Edit Associations DOE a Aa ae JED KORY S Associate Edge gt Curve Edgets 25730 AS Curve s GEOM 24 amp o Project vertices Project to surface intersection Project ends to curve Intersechon zl Apply lo Dismiss 2 Associate the three edges at the top A in Figure 7 with the three curves forming the small semi circle A in Figure 7 a Select the required edges i Click rts Select edge s li Select the edges denoted by A in Figure 7 iii Click the middle mouse button to accept the selection b Select the appropriate curves i Click R Select compcurve s ii Select the curves denoted by A in Figure 7 Tip When selecting multiple curves the first curve selected determines the curve color of the final grouped curve To avoid confusion with green edges experts try to avoid selecting the green curve segments first iii Click the middle mouse button to accept the selection c Click Apply in the Associate Edge gt Curve DEZ ANSYS Inc February 11 2010 11 3D Pipe Juncti
17. tain any entities 2 Save the geometry file 3d pipe geometry 1 tin File gt Geometry gt Save Geometry As Step 3 Blocking the Geometry The blocking strategy for the 3D pipe geometry as shown in Figure 3 involves creating two blocks from the initial block one each for each half cylinder forming an L shaped configuration You need to create an O Grid to improve the mesh quality The blocking functionality in ANSYS ICEM CFD provides a projection based mesh gener ation environment All block faces between different materials are projected to the closest CAD surfaces Block faces within the same material may also be associated to specific CAD surfaces to allow for definition of internal walls In general there is no need to ANSYS Inc February 11 2010 7 3D Pipe Junction Using Hexa Meshing perform any individual face associations to underlying CAD geometry which reduces the tame for mesh generation 1 Create an initial block Blocking gt Create Block W gt Initialize Blocks Create Block c Part FLUID g Create Block Initialize Blocks Type 3D Bounding Box Entities SA 2 Project vertices Orient with geometry A F I OK Dismiss a Ensure that Part is set to the correct material FLUID b Retain the selection of 3D Bounding Box in the Type drop down list You need not select Entities when creating a bounding box around the entire geometry c Click Apply
Download Pdf Manuals
Related Search