Numerical study of the performance of twin Savonius hydrokinetic turbines with adjacent advancing blades in a side-by-side configuration placed in a narrow channel

This study investigates the effects of twin Savonius vertical-axis turbines arranged side-by-side in a narrow water channel on turbine performance. The turbines, rotating in opposite directions, were analyzed using ANSYS FLUENT 2023, with a grid refined through independence testing and simulations employing the k-epsilon turbulence model. Dynamic torque data were collected at 1° increments over 10 revolutions to evaluate the power and moment coefficients. The experimental setup included a 500 mm wide water channel, turbines with a 60 mm blade diameter, and a 10 mm shaft diameter. Shaft spacing ratios (S/D) of 2, 2.333, 2.667, 3, 3.333, and 5 were examined at a water speed of 0.25 m/s (Re = 3.1 × 104). Results indicate that an S/D ratio of 2.667 yields optimal performance, achieving a maximum power coefficient of 0.34 for both turbines at a tip speed ratio (λ) of 1.2. The twin Savonius turbine configuration achieved a maximum coefficient of power with an 82% increase in CoP at S/D = 2.667 compared to single turbine. Furthermore, the operating range of the dual turbine system (λ = 0–2) surpasses that of a single turbine (λ = 0–1.5). These findings demonstrate the potential of strategic turbine spacing to enhance power output and operational efficiency.