Investigation on the unsteady cavitation flow and energy loss mechanism of mixed-flow pumps based on bionic structures

This study investigates trapezoidal (scheme A) and triangular (scheme B) bionic structures, inspired by the leading edge pectoral fin of a humpback whale, arranged at the impeller blade leading edge of a guide vane mixed-flow pump. The effects of them on the cavitation performance and internal flow were compared through numerical simulation, and the accuracy of the numerical simulation was verified by experimental test. Entropy production analysis quantified and visualized flow losses induced by cavitation and bionic structures. Results show both schemes suppress cavitation development, with scheme B exhibiting slightly better hydraulic performance: 0.78% head increase at critical cavitation (NPSHa = 9.46 m) and 15.35% at severe cavitation (NPSHa = 8.27 m). Entropy production analysis indicates that after adding the bionic structures, at the severe cavitation stage turbulence dissipation is reduced by 21.9%–22.8% and wall entropy production is decreased by 10.6%–11.2% by suppressing large-scale vortexes and inducing secondary flows. The bionic structures optimize leading-edge pressure distribution, delay flow separation, and disperse cavitation bubble collapse, enhancing cavitation resistance and stability. The findings offer theoretical and engineering insights for bionic optimization in hydraulic machinery.