Numerical Investigation of Tip Speed Ratio Effects on the Performance of a Jet-Driven Four-Bladed Waterwheel for Low-Head Hydropower Applications

Abstract

This study numerically investigates the influence of Tip Speed Ratio (TSR) on the performance of a jet-driven four-bladed waterwheel for low-head hydropower applications using transient Computational Fluid Dynamics (CFD). A two-dimensional transient model was developed in ANSYS Fluent, employing the Shear Stress Transport (SST) k–ω turbulence model to simulate the unsteady interaction between the water jet and the rotating runner. Simulations were conducted for eight operating conditions corresponding to runner speeds of 10–45 rpm at a constant inlet jet velocity of 3.0 m/s. The transient torque histories were analysed to determine the average torque, mechanical power, hydraulic efficiency, power coefficient, and corresponding TSR. The results show that waterwheel performance is strongly influenced by TSR. The highest average torque of 169.48 Nm was obtained at 10 rpm (TSR = 0.244), while the maximum mechanical power of 489.72 W, hydraulic efficiency of 60.57%, and power coefficient of 0.606 occurred at 35 rpm, corresponding to an optimum TSR of 0.855. The transient torque profiles exhibited periodic oscillations due to successive blade–jet interactions. The findings demonstrate that operation near the optimum TSR maximizes energy extraction and provides useful guidance for the design and optimization of jet-driven waterwheels for decentralized low-head hydropower generation.