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Reply To: STL porous media loading

#9018
jan
Participant

Dear araeli,

Do I understand that your question is about the layer of zeros around the actual geometry you imported?

– Is this behavior normal?
Yes, this is normal. Without periodic boundaries, OpenLB sets a layer of 0 on the outside. (Feel free to check some examples).

– Is the excess always just one cell?
Yes, in many examples an extra layer is added to the geometry using IndicatorLayer3D (e.g. cylinder3d, line 336 in cylinder3d.h).

– Shift:
I think this is caused by the discretization? In OpenLB you only have the information if a certain point is inside or outside, and this information seems to match your geometry, doesn’t it?

– Is there a way to force the boundary mesh to adhere to the vertices of the porous medium once they are given as voxels, thus theoretically already cubic and easily adaptable in structure?
Is this related to the shift above? As mentioned above, this seems to be caused by the discretization. Maybe you can make the simulation domain “better” match your geometry (does the STL start at the origin or is it shifted a bit?). However, this discretization error should get better with increasing resolution. If it is your intention to keep a structure made up of smaller cubes, you could also consider using many IndicatorCuboid3D to create in the OpenLB case, like this it might be easier to align them with the lattice.

Best regards,
Jan