Reported by @yue: calculateVelocity seems to be missing the extrusion area. ``` void calculateVelocity(...) const { ... if constexpr (isBox && dim == 1) { ... for (auto&& scvf : scvfs(fvGeometry)) { if (scvf.boundary()) continue; // insantiate the flux variables FluxVariables fluxVars; fluxVars.init(problem_, element, fvGeometry, elemVolVars, scvf, elemFluxVarsCache); // get the volume flux divided by the area of the // subcontrolvolume face in the reference element Scalar localArea = scvfReferenceArea_(geomType, scvf.index()); Scalar flux = fluxVars.advectiveFlux(phaseIdx, upwindTerm) / localArea; const auto& insideVolVars = elemVolVars[scvf.insideScvIdx()]; flux /= insideVolVars.extrusionFactor(); tmpVelocity *= flux; const int eIdxGlobal = gridGeometry_.elementMapper().index(element); velocity[eIdxGlobal] = tmpVelocity; } return; } ``` **Proposed strategy for resolution** Add velocity output to rotational symmetric test and make sure it's correct. **Possible fix** *There might be a factor `Extrusion::area(scvf)/scvf.area()` missing. Care has to be taken in case there is a mapping from local to global coordinates.*