Unsteady numerical simulation of an air-operated piston pump for lubricating greases using dynamic meshes

► Modeling of air-operated piston grease pump is performed for the first time. ► Experimental testing and theoretical estimations are used to validate the model. ► Evidences on low fluidity and aspirating limitations are confirmed numerically. ► Unsteady viscosity maps reveal in detail the grease rheological behavior over time. ► The single-phase approach advices for the need of a two-phase scheme in future work.