Influence of cavitation on energy loss in a side channel pump at different flow rates

Abstract

Side channel pumps are extremely prone to cavitation, and the internal exchange flow between the impeller and the side channel induces numerous vortical structures that causes significant energy loss. Therefore, it is important to investigate the cavitation characteristics and flow loss in side channel pumps under cavitating conditions. This paper investigates the cavitating flow in a side channel pump using the scale-adaptive simulation turbulence model coupled with the Zwart cavitation model. The development of cavitation in the side channel pump is divided into three stages according to the critical net positive suction head and turning net positive suction head. Stages I, II, and III correspond to the inception of cavitation, development of cavitation, and severe cavitation, respectively. The vortex energy is adopted to analyze the variations in vortices with respect to the available net positive suction head. Entropy production considering viscous dissipation, turbulent dissipation, and the wall effect is used to calculate the irreversible energy loss. However, the energy loss caused by the rotation of vortices cannot be calculated by this method, resulting in large discrepancies between the entropy production and the hydraulic loss calculated by the pressure drop method. The entropy production generated by turbulent dissipation (S2) is found to be dominant in the side channel pump and increases with decreasing flow rate. S2 exhibits different variation trends with respect to the available net positive suction head at different flow rates under severe cavitation. S2 also dominates in the impeller, but the entropy production terms exhibit slight discrepancies in the side channel. The distribution of local entropy production rate further reveals the complicated interaction mechanism between cavitation and entropy production.