SimScale CAE Forum

Can't assign a geometry primitive as an entity for boundary conditions or material domain

I’ve been following the Applications of CFD in Formula Student & Formula SAE course and I’ve run into a few issues with selecting the primitive geometry.

I’m trying to assign a cartesian box to the fluid material I selected, but there seems to be no way to select the volume. I also tried to select a face of the box to assign to a boundary condition, but I can’t find any way to assign the primitive geometry to anything whatsoever.

Here’s the link to the project, I’m pretty new to SimScale so please do let me know if I’m missing something obvious.

Hey there @ichohan!

I recently created a tutorial for external aerodynamics here:

Hope that helps out! You can create the bounding box directly at the beginning and then choose it for your material assignment.

All the best,


Hi I think that should solve my problem, however all the operations under “Flow Volume Extraction” are grayed out and I can’t click on them. Is there something I’m missing or something I need to do to enable them?

I cannot access your project anymore, what file format is your geometry?



Oh sorry about that, I restarted the project, here’s the link:

The geometry’s an STL file I believe.

Hi Jousef,

I figured out that the project that I was duplicating was no longer supported by SimScale. I created my own geometry and everything seems to be working fine. The tutorial was also very useful. Thanks for all the help.

Sorry for not getting back to you! Glad you figured it out in the meantime, I am sure others who might have this issue will find your post useful, will mark it as the solution :slight_smile:

Cheers and let us know how things go!


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