Effects of Overlap Ratio on the Power and Aerodynamic Coefficients of a Newly Developed Parabolic-Bladed Savonius Rotor

The Savonius-style wind turbine is a vertical-axis turbine known for its simple design, low cost, and ability to generate electricity off-grid. Diverse blade configurations have been devised in past studies to enhance wind energy efficiency beyond the traditional semicircular profiles, and there is a scope for generating novel blade designs. The overlap ratio (OR) is a crucial geometric parameter that affects the performance of a turbine. A novel parabolic blade profile is designed in this work, and the impact of the OR on power and aerodynamic coefficients is examined using the SST k-ω turbulence model at a Reynolds number (Re) of 0.86 × 105. Quantitative two-dimensional simulations demonstrate that at OR = 0.0, the newly developed parabolic rotor outperforms traditional semicircular profiles across all tested tip speed ratios (TSR). This is evidenced by a 12.26% increase in the maximum power coefficient (Cpmax). The effect of the OR is then examined in greater detail by varying the ratio within the range of 0.0 to 0.30 for the newly developed rotor at different TSRs. Numerical results show that the optimal OR is 0.15, improving Cpmax by 2.64% compared to an OR of 0.0. This optimal OR enhances aerodynamic interactions between the blades, boosting energy capture and efficiency. Furthermore, the results are substantiated by analyzing the lift and drag coefficient along with the velocity and total pressure contours.