Problems in surface repair/mesh for an car model in star CCM+

supervisor 101 · February 25, 2020, 23:13

Dear Forum users,
Some of my students are working on a final project (i.e aerodynamic analysis of a vehicle using CFD). They had prepared a 3d CAD model using SolidWorks particularly using surface modelling through splines.
The next thing was to import that CAD model into star CCM+ (iges, step, Parasolid) formats and perform a CFD analysis on it. while creating the mesh (using auto mesh) they were facing problems related to surface mesh and this can also be seen while using the surface repair option. Kindly provide any suggestions to solve this problem. I personally tried to sort the problem and doubt that it is because of the spline methodology that was used in Solidworks. I think that it might have been no /fewer problems if they used CAD packages (e.g blender) that create polygon-based surfaces.
Kindly provide me valuable suggestions or solutions to solve this problem. Your help shall be highly appreciated.

fluid23 · February 26, 2020, 09:04

It is normal to have issues with model quality after import, however, automatic surface repair usually fixes a lot of them. I am not sure that I would pin it totally on Solidworks and I highly doubt you would get a better quality model out of polygon based modeler. That being said, a few thoughts/questions/suggestions:

1. Is the geometry a surface or solid body in SolidWorks before exporting? Trying to sew up the surfaces into a solid will help you track down surface quality issues.

2. Are they importing just the car and creating the domain or importing the domain? If not already doing so, try subtracting the solid car from the domain / air volume in solidworks and importing that domain. Again, this will help to highlight issues with model quality.

3. Make sure the automated mesh operation has automatic surface repair turned selected.

4. Import the native model if you can, there is a module for this but not everyone has it.

5. When importing, select 'Check Parts Validity' and 'Repair Invalid Bodies'.

6. If all else fails, try the surface repair options or the Surface Wrapper. The wrapper would be a good candidate for this model, I think. There are tutorials available for these as well as thorough documentation in the help files and the Steve Portal.

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February 26, 2020, 09:04		#2
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	It is normal to have issues with model quality after import, however, automatic surface repair usually fixes a lot of them. I am not sure that I would pin it totally on Solidworks and I highly doubt you would get a better quality model out of polygon based modeler. That being said, a few thoughts/questions/suggestions: 1. Is the geometry a surface or solid body in SolidWorks before exporting? Trying to sew up the surfaces into a solid will help you track down surface quality issues. 2. Are they importing just the car and creating the domain or importing the domain? If not already doing so, try subtracting the solid car from the domain / air volume in solidworks and importing that domain. Again, this will help to highlight issues with model quality. 3. Make sure the automated mesh operation has automatic surface repair turned selected. 4. Import the native model if you can, there is a module for this but not everyone has it. 5. When importing, select 'Check Parts Validity' and 'Repair Invalid Bodies'. 6. If all else fails, try the surface repair options or the Surface Wrapper. The wrapper would be a good candidate for this model, I think. There are tutorials available for these as well as thorough documentation in the help files and the Steve Portal.