Simulation using MPS method in Particleworks for an industrial positive displacement lobe pump. Pump characteristics: rotor diameter 110 mm, rotor depth 36 mm, speed 600 rpm. Pumped fluid: water. Operating pressures (static): inlet 1 bar, outlet 2 bar. The model is 3D and uses aprox. 600k particles with a resolution of 1 mm. The animation covers one complete rotation (0.1 s of operation). The theoretical flow rate (not accounting for any losses) at 600 rpm is 2.8 l/s, while the numerically calculated flow rate is 2.4 l/s. The results show very complex flow patterns, particularly on the inlet side, and strongly pulsating flow. Extreme shear rates are observed within the temporary cavities created by the rotors relative motion, which explains why this lobe pump rotor shape — while having good specific flow rate performance — is not recommended for shear-sensitive fluids. The calculation runs very efficiently on GPU; at this resolution, one complete rotation takes approx. 1 h on a Quadro P5000 (time-step size, 1e-05s).