Synergistic mechanism of the energy dissipation and sediment erosion in pump turbine under sand-laden water based on entropy production theory

Sediment erosion of hydraulic machinery can cause a lot of energy loss, thereby affecting their operational stability. Herein, solid–liquid two-phase flow simulations are conducted on a pump turbine using the Euler–Lagrangian model to predict the sediment-laden flow and sediment erosion. The predicted results are verified through experiments. The correlation between the energy loss characteristics and sediment erosion in hydraulic turbines is analysed using the entropy production and vorticity theories. Results show that the total vorticity in the runner area increases with the guide vane opening. The entropy production corresponds to a high-vorticity region. Energy dissipation is positively correlated with the degree of turbulence in the flow regime. Certain phenomena, such as vortex flow, impact, and friction in the runner area, are important causes of energy loss. Vortices can also cause local sediment erosion on runner blade walls. Severe wall sediment erosion typically occurs at locations with high entropy production. The total entropy production along the particle flow path is consistent with the variation law of the wall sediment erosion rate.