Reply To: Wall Shear Stress on Bouzidi Wall
Taking a quick look at the implementation in src/functors/lattice/latticePhysWallShearStress3D.hh the normals are computed w.r.t. the given IndicatorF3D. This means that you can provide the same STLreader indicator you used to set up the interpolated bounce back boundaries as an argument here and it will be used to compute the normals.
However the lattice functors are by design evaluated lattice-cell-wise and exported to VTK at discrete cell locations and not mapped to any surface. One could add such capabilities to OpenLB e.g. as an analytical functor that is evaluatable at the STL surface but this is not currently being worked on.