Fouling is the main hurdle of the widespread of MBR systems. One way to decrease and/or control fouling is by hydrodynamics, increasing the liquid cross-flow velocity. In rotational cross-flow MBR systems, this is attained by the spinning of the impellers. Validation of the CFD model was made against LDA tangential velocity measurements (error less than 8 %) using water as a fluid. The shear stress over the membrane surface was inferred from the CFD simulations for water. Shear stress and area-weighted average shear stress relationships were made based on the CFD results. These relationships can be link to the energy consumption of this type of system.