Reading STL geometry without envelope

Hello,

I prepared geometry in STL that fits perfectly the domain in Palabos simulation. I would like to obtain inside flow that reaches cells from, e.g., 0 to nz-1, since I want to use periodic boundaries in one dimension.

I set such voxelFlags to fluid nodes:

setToConstant(flagMatrix, voxelizedDomain.getVoxelMatrix(), voxelFlag::inside, flagMatrix.getBoundingBox(), 1);
setToConstant(flagMatrix, voxelizedDomain.getVoxelMatrix(), voxelFlag::innerBorder, flagMatrix.getBoundingBox(), 1);
setToConstant(flagMatrix, voxelizedDomain.getVoxelMatrix(), voxelFlag::outerBorder, flagMatrix.getBoundingBox(), 1);

Also, I tried many different combination with setting margin, borderWidth and envelopeWidth to 0 or 1.
Each time, the best that I can obtain is one-cell envelope of bounce-back nodes around flow domain.

How can I remove this envelope?

Best regards
Mateusz Bancewicz