Passive flow control of a Francis turbine operating in sand-laden rivers for mitigating sediment erosion.

This article focuses on a bioinspired passive flow control method using biomimetic convex domes to mitigate severe sediment erosion caused by inter-blade vortices in Francis turbines, particularly under low flow rate conditions. Numerical simulations and experimental tests on a low-specific-speed Francis turbine model, based on the Jhimruk hydropower plant in Nepal, demonstrate that the convex domes reduce particle impact velocity and accretion rate at the runner blade outlet by inducing small-scale vortices that inhibit vortex formation and accelerate vortex dissipation. The method achieves at least a 50% reduction in sediment erosion with minimal impact on turbine performance, slightly improving efficiency under partial-load conditions. This approach offers a cost-effective alternative to design modifications or variable-speed technologies for erosion control in sediment-laden hydropower environments.