Numerical simulation and experimental study on cavitation and pressure fluctuation characteristics of low head pumped storage system under pump operating conditions

Low-head pumped storage systems are essential components of renewable energy infrastructure due to their cost-effectiveness and operational flexibility. However, cavitation during the pump mode poses challenges to system stability and energy efficiency. This study combines experimental measurements with Computational Fluid Dynamics (CFD) simulations to investigate cavitation dynamics and associated pressure fluctuations characteristics in a 1:5.25 scaled model of a low-head pumped storage system. The results reveal that cavitation-induced pressure fluctuations are most pronounced at the impeller inlet and chamber, and the pressure fluctuations caused by cavitation result in changes in the number of pressure pulsation peaks and valleys at the impeller during a single rotation cycle. The guide vane exhibit intricate spectrum behaviors dominated by blade-passing frequencies as well as rotor-stator interactions. Meanwhile, high-frequency fluctuations observed at the guide vane outlet indicated significant vortex activity. The outlet bend is characterized by turbulent flow accompanied by energy losses, whereas the outlet passage sustained low-frequency fluctuations. Vortex structures show strong correlations with vapor formation, predominantly accumulating on blade pressure surfaces under low head conditions while extending toward suction surfaces at higher heads. Both experimental and numerical results demonstrate high consistency, featuring simulation errors below 4 %. This work underscores the necessity for real-time monitoring of critical components alongside adaptive operational protocols aimed at mitigating cavitation phenomena. The findings provide actionable strategies for optimizing system design and enhancing energy efficiency within renewable-integrated power grids.