Numerical study of regenerative pump characteristics operating under different fluid viscosities and multistage arrangement

Regenerative (peripheral) pumps offer compact, high-head solutions for low-flow applications; however, reliable performance data for viscous fluids and multistage configurations remain limited. This study employs high-fidelity geometry reconstruction and mesh-refined Computational Fluid Dynamics (CFD) to examine how fluid viscosity and stage number jointly influence the hydraulic performance of a commercial Pedrollo PKm60 pump. A laser scan of the impeller and side channel eliminated CAD simplifications and, together with a grid-convergence study, reduced the root-mean-square error between predicted and catalog heads to 1.71 m (5.8%). Simulations were performed using steady Reynolds-averaged Navier–Stokes (RANS) equations with a moving reference frame (MRF) formulation and the Realizable k–ε turbulence model. A single transient unsteady RANS (URANS) verification case with the SST k–ω model at Q = 10 L min−1 underpredicted the head (29.28 m) compared to the steady result (31.70 m) and manufacturer data (33.356 m). Because the steady solution matched the reference solution more closely, steady RANS (MRF) was adopted for all performance maps and analyses. Increasing viscosity shifted the best-efficiency point (BEP) from 23 to 17 L min−1 and reduced peak hydraulic efficiency from 34 to 20%. In the multistage configuration, the normalized head rose by 18% from Stage 1 to Stage 3, while power input increased by less than 5%, indicating efficient head development with diminishing internal losses. Flow visualizations of streamlines, turbulent kinetic energy, and pressure gradients revealed vortex suppression and boundary-layer thickening as the dominant mechanisms governing these performance changes. The resulting dimensionless correlations and validated flow-field data provide practical guidance for selecting and scaling regenerative pumps for handling viscous liquids, supporting Sustainable Development Goal 9 through energy-efficient, resource-conscious industrial fluid-handling design.