The role of turbulence in the impeller-volute interaction in a centrifugal pump

Abstract

Centrifugal pumps operating at off-design conditions suffer flow separation at the blade leading edge, with the resulting turbulent wakes subsequently developing along the blade passage. Turbulent eddies finally interact with the volute tongue, affecting jet-wake patterns and producing highly anisotropic flow structures. In such scenario, the ability of URANS models to correctly capture pump dynamics is penalized by their inherently isotropic approach. The present work compares DES and URANS calculations of the flow fields in a centrifugal pump with PIV data to assess the influence of turbulence in impeller-volute interactions. Three working points at 40%, 100% and 150% of the nominal flow rate are analysed, with special emphasis on tongue-induced excitations. The Reynolds stress anisotropy field is computed along the impeller periphery, proving that the dominant turbulence regime in the impeller-volute interface is mainly one or two-dimensional. While the URANS solution fails to reproduce the PIV velocity field, DES succeeds by accurately quantifying flow anisotropy. The identified turbulent interaction mechanism thus deserves an analysis of its own and should not be neglected in the design of centrifugal pumps.