Trimmed surfaces export for CFD recommendations

[Valentin Le Bailly]

Hello,

I am currently working on a project where I'm doing some aerodynamic analysis of blended wing body configurations at different levels of fidelity. After having automatized the generation of BWB's according to my parametrization within your Python API and having ran VLM analyses, I now want to use the trimmed surfaces capability to export CAD files for future RANS simulations within starccm+. I originally wanted to use the trimmed surfaces export option because my BWB configurations feature two vertical stabilizers that are modelled in OpenVSP as subsurfaces of the main wing and are physically embedded within that main wing. However, a simple .stl export of this configuration to the CFD software resulted in the mesh to be created inside the main wing as the vertical stabilizers are untrimmed.

To tackle this issue, I switched to trimmed surfaces but this caused lots of open surfaces which the CFD software doesn't like. I've already tried decreasing the STEP tolerance and increasing the number of chordwise and spanwise panels but this seems to have no effect. The CFD software reacts very randomly, accepting some models and rejecting others. The most problematic areas appear to be the trailing edge of the vertical stabilizers and the wingtips.

Finally, there comes my question... Has anybody tried automating the export of CAD files before for CFD purposes and if so, what are your recommendations? Or more generally, what would you recommend to obtain a smooth, closed surface with trimmed surfaces exports?

You can find an example of the .vsp3 and .step file attached

Thanks in advance

[Rob McDonald]

If you want to use the STL file, I suggest you run CompGeom before exporting the STL file.  That will produce a trimmed STL file.

Otherwise, instead of using the trimmed surfaces (which some CAD and Pre-processing tools can have trouble with) if you want to use STEP files, I suggest you go to File... Export... Untrimmed STEP... and export that way.

Rob