Week 4 Challenge : CFD Meshing for BMW car

Aim: To perform CFD Meshing for a BMW car

Procedure:

1. First check if model is having single cons, select entire model and apply TOPO from FACES option on it to convert single cons to double/ triple cons, as and where possible.
2. Check the cons resolution of the model.
3. First option is FINE from auxiliaries and double click everywhere to smoothen the surface to get accurate shape. It will take so much time, second option is to set length of perimeter and macros as 1 mm in mesh mode by selecting entire model then it will give smooth surface
4. All these need to be resolved as part of topo cleanup. We will use symmetry option so delete half part of the model and keep only components which are not symmetric like car logo
5. We need to make the model topology clean to ensure only one volume is remaining that is the volume between wind tunnel and car exterior features. Remove all triple cons on the car inside part by part
6. Try to project single cons on required surfaces and try to delete unwanted surfaces
7. Topology cleanup in progress. Fin area- try to delete existing surface because it is incomplete, try to make new surface using coons option- grill area
8. Use EXTEND option from FACES to convert single con to triple con in order to find out hidden extra surface, then delete extra surfaces
9. Use INTERSECT tool to get triple con as more than three surfaces are present
10. Similarly rectify single. Triple cons from each tyre and ensure common volume with car
11. Use CURVE TO CONS option to get footprint of earlier area in order to create new surface later
12. Apply geometry check. All errors are resolved, now create PIDs as per challenge
13. Assign PIDs to each component
14. Now check the distance between cons and hot points in line with quality criteria, it is not passing, delete those cons wisely ensuring the importance of each con
15. Measure distances in all PIDs for checking any distance less than minimum length and store the values
16. Now start surface meshing. Select LOGO PID, define quality criteria- min length as 0.3, max length as 2 and target length as 1. Now set same values in mesh parameters. Now select PERMITER and MACROS length as 1 in MESH MODE and then do spot mesh for visible area
17. Go to HIDDEN drawing style in ENT mode to check for success of quality criteria
18. Use RECONSTRUCT option from SHELL MESH on visible area to try to reduce number of off elements. So after that, off elements are reduced from 48 to 12
19. Topo clean up to be done for off elements I TOPO mode and then again do spot mesh and reconstruct option and check for number of off elements. If it turns out to be zero, mesh is complete
20. Similarly do it for all PIDs. Finally it should like this after full surface meshing
21. Now go to TRANFORM – COPY option in TOP VIEW Mode, shift and left drag mouse click to select entire model and right click on LOGO PID to deselect it. Now do middle click and choose SYMMETRY option with MIRROR 3 POINTS PLANE
22. We got the entire model, now use PASTE option to get rid of single cons present at the line of symmetry
23. For creating wind tunnel select RLEATIVE option from POINTS in TOPO mode and set top part distance as 3X from top surface, 4X from front surface, 6 X from back side surface and X mm each on either side and some roughly close distance to bottom surface where X is the approx. length of model. Now create CURVE. Use NEW option to create a surface and assign new PID. For creating top surface, now add 375 mm to 3900 to create top surface
24. Set offset to 4275 and sign based on arrow direction
25. Now delete the points. Now close the wind tunnel by using NEW COONS option
26. Assign additional PIDs
27. Set perimeter and macros as 100 for top surface and 20 for bottom surface
28. Now for side surfaces, mesh element length has to vary gradually from 20 to 100 for that use SPACING option. Complete surface mesh on wind tunnel
29. Go to volumetric mesh, select AUTO DETECT in DEFINE WHOLE DB option
30. Delete other volumes other than the one between car and wind tunnel.

(MODEL ATTACHED)