[JayM]

Hi,

I am attempting to simulate a car to find lift and drag etc. At the bottom of my wheel I have a small tab to avoid tight corners with the floor when meshing. However additional surfaces (highlighted purple in the images) are formed in both front and rear wheels after meshing.

The problem occurs both with a trimmer and polyhedral meshes however with the polyhedral mesh, the simulation actually runs and I get Cl and Cd values. Whereas with the trimmer mesh I get the following error:

"A floating point error has occurred. The following error has been logged:
A non-finite residual (Tke) was added by star.keturb.KeTurbSolver. Typical causes are overflow, underflow, or a division by zero.
Please check your usage and inputs."

Does anyone have any idea how I can prevent the additional surfaces from forming? Thanks in advance for your time and help!

Image 1.png

Image 2.png

Image 3.png

[fluid23]

It's a little hard to tell what's going on here. Most likely, you either have a problem with surface quality of your CAD file that is corrupting your mesh or you are running into proximity issues. You can try changing your auto-repair minimum proximity setting in your mesher controls and see if that helps.

[cwl]

On the screenshot those addisional surfacel look just like part or the tab.

Maybe try wrapping - there is a good example: https://www.youtube.com/watch?v=OGIYYLziZWI

The video is a bit out of date: no more Region-based meshing and Surface Wrapper is now a separate Part Operation, but the method is still actual.

[Paulh]

If you're wrapping your geometry, car to tunnel, then I'd say that contact prevention would fix your additional surfaces. If you're not wrapping, then adding in a local refinement at the base of the tire would probably help. Perhaps both.

Your software crash problem looks similar to what I've run into. I locate, using a threshold of max velocity, where the solution is beginning to blow up. An example would be identifying cells with velocities over 1000m/s. They are typically flat pancake cells. I then remove them out of the domain, usually just one or two cells, and continue running the simulation. I've convinced myself that I really don't care about a small bump on the surface of my vehicle. It's happened enough that I've automated the process.

[JayM]

Contact prevention fixed it, thank you very much!!

[cwl]

Option of Surface Wrapper called "Wrapper Defeature" might also help in those areas as an addition to Contact Prevention.