Evaluating energy loss and internal flow structures using entropy production theory: A case study of the lateral inlet/outlet of pumped storage power stations

This study investigates the flow characteristics and energy-loss mechanisms of lateral inlet/outlet structures in pumped-storage power stations (PSPS) from the perspective of entropy production theory. The Delayed Detached Eddy Simulation (DDES) approach is employed to elucidate the relationship between entropy production and the distribution of flow structures, and to further clarify the origin of energy loss within the lateral inlet/outlet. The results show that the total entropy production decreases by approximately 8.8% as the vertical diffusion angle is reduced. The mean-flow entropy production (MEP) is negligible, whereas wall entropy production (WEP) dominates, accounting for approximately 55–60% of the total entropy production. This dominance arises from the strong wall shear stress generated by the interaction between the flow and the pier nose. Turbulent entropy production (TEP) represents the second-largest component and is strongly influenced by enhanced flow separation and vortex evolution. Based on the cross-sectionally integrated TEP along the streamwise direction, three characteristic regions can be identified: a sharp-entropy-growth region, a high-entropy-production region, and a reduced-entropy-production region. These findings provide insights into energy dissipation mechanisms and guidance for optimizing inlet/outlet design in PSPS.