OpenLB – Open Source Lattice Boltzmann Code › Forums › on OpenLB › Bug Reports › External field omega problem using DynOmegaD2Q9Descriptor and MPI compiler › Reply To: External field omega problem using DynOmegaD2Q9Descriptor and MPI compiler August 26, 2019 at 8:16 pm #4528 mathiasKeymaster Dear Junwei, that is not a bug. A communication step is missing. Add SuperExternal3D sExternal( superGeometry, sLattice, sLattice.getOverlap() ); sExternal.communicate(); and it will work! Best Mathias