Decoupling vortex-induced hydraulic loss and noise sources in a centrifugal pump via liutex-shear decomposition

Abstract

Centrifugal pumps in waste heat recovery systems frequently operate under off-design conditions, where complex turbulent structures induce significant irreversible energy dissipation and flow-borne noise. However, distinguishing the specific contributions of rigid vortex rotation from boundary layer shear remains a challenge for classical identification methods. This study elucidates the mechanisms coupling vortex dynamics, entropy production, and acoustic radiation in a low-specific-speed pump using the Liutex-shear decomposition method. A hybrid Detached Eddy Simulation (DES), rigorously validated against experimental hydraulic performance and pressure pulsation data, is employed to resolve transient turbulent structures. Results demonstrate that high-magnitude Liutex vectors, rather than general shear layers, exhibit the strongest spatiotemporal correlation with local entropy production rates. Quantitatively, vortex-induced dissipation accounts for approximately 35% of the total hydraulic loss under overload conditions, directly impacting the system’s parasitic power consumption. Furthermore, acoustic analogy analysis shows that coherent Liutex structures organize the wake–tongue interaction and localize the blade-passing-frequency-related dipole source region. Crucially, the results indicate that while shear deformation dominates viscous dissipation and directly amplifies the acoustic source intensity, rigid rotation primarily modulates the coherent source topology and phase relationship. These findings establish a direct physical link between specific vortex topologies and performance degradation, providing a theoretical basis for targeted flow control in energy conservation equipment.