snappyHexMesh with zero Thickness surface imported from a Geometry
 

Hello!

I have a Geometry of an Umbrella structure (in dwg format) [see the attached photo] and I need to do a wind simulation on it using OpenFOAM

As far as I know, I need to make an STL file.

The problem is that the membrane part of the Umbrella is surfaces (not a solid) so I could not make an STL file out of it.

One approch is to give the membrane a thickness (convert it to solid) I did that. but when asking autoCAD to export it as an STL the membrane is messed up!

My question is: Is there a way to make an STL file including zero Thickness surface?!
or
Is there a way to use snappyHexMesh without doing the STL step? if there is, how to deal with the internal faces in openFoam? Can I deal with them as patches and assign BC to them?

Thanks for your help!