Vortex and energy characteristics in the hump region of pump-turbines based on the rigid vorticity and local hydraulic loss method.

This article focuses on investigating the hydraulic losses and vortex dynamics of pump-turbines operating in the hump region, a critical unstable zone affecting the safety and efficiency of pumped-storage hydropower units in power grids. Using three-dimensional numerical simulations based on computational fluid dynamics (CFD), the local hydraulic loss rate method, the Rortex vortex identification technique, and Particle Image Velocimetry (PIV) experiments, the study identifies that energy losses predominantly occur in the guide vane (GV) passage and draft tube (DT), with shear vorticity dominating losses in the vaneless space (VS) and both shear and rigid vorticity influencing the GV and DT. The research further reveals that rotating stall phenomena vary with flow rate and that the pseudo-Lamb term in the enstrophy transport equation plays a key role in vortex evolution and dissipation. These findings contribute to understanding flow instabilities in pump-turbines, which is essential for improving their structural durability and operational stability during energy transition efforts.