Errors importing geometry from Alias AutoStudio

[a_bastidas]

Hello, I am new to using CFD, and I have already ran into a couple of errors while I attempt to load geometry into CFD.

I am currently modeling a car for my senior thesis project, using Autodesk Alias AutoStudio 2018, also with a student license. I export my surface data as a .stp file, so I can load it into CFD.

Every time I try to import geometry though, it seems as if a couple of the surfaces import corrupted. They randomly pull in towards the 0,0,0 coordinate, and the message window throws in a couple errors including "Invalid Model Detected" and "The 2D model is either non-planar or it is not on the Z = 0 plane". I have attached screenshots that show the issue, as well as the Alias file I am trying to bring into CFD.

[marwan_azzam]

Hello,

We can only see the three image files.

Can you share the step file with us?

Marwan

[a_bastidas]

Hey Marwan,

I thought I had attached the files but it seems like I didn't. I have attached a .stp file to this reply. It contains the geometry I want to test, as well as the outer box that will be used as the wind tunnel boundary.

Thank you very much for your time and help!

[marwan_azzam]

Hello,

Thank you for sending the step file.

The problem with the model is that it's all made up of surfaces and not solid bodies.  That is why it comes in as so many surfaces but no bodies.

I opened the step file in SimStudio Tools (not sure if you have that app) and combined the surfaces to make solid bodies.  That did the trick, almost.  The surfaces that make up the center of the tires (the hub if you will) were not converted to solids.  This is probably because they have no thickness.  As such, those hubs did not come into CFD.

You will need to give them a thickness then they will show up in CFD.

Please see attached images and new step file.

Good luck.

Marwan

[a_bastidas]

Hey Marwan,

Once again, thank you so much for helping me look into the issue, I really appreciate it.

In regards to your answer, does this mean that I will not be able to make a rough calculation of airflow over CAD data that is comprised of surfaces instead of enclosed volumes or solids? I am at the initial stage of designing a race car, and for now I would like to compare how air flows around lets say a teardrop-shaped canopy in comparison to an oval shaped one.

I am not currently looking for concise numbers, but rather an idea of what the air is doing, which I was hoping will help me make decisions on what parts work better than others. So, will I not be able to use CFD during the initial process because of the fact that I am just working on surfaces with no thickness right now instead of solids?

Thanks,

Andres