CFD investigation of aerodynamic performance enhancement in a savonius vertical-axis wind turbine

The Savonius Wind Turbine (SWT) is widely adopted for converting low wind into electricity, primarily due to the simplicity of the SWT’s design, the relatively low manufacturing cost, and its ability to self-start at lower wind speeds than other designs. However, Savonius wind turbines (SWTs) exhibit limited aerodynamic performance because they generate a small pressure difference across the advancing blade and experience reverse (negative) torque from the returning blade, which constrains their efficiency. In this study, the effect of modifying the concave side of the advancing blades of an SWT is examined to assess its influence on aerodynamic performance while the primary geometric dimensions remain unchanged. Two-dimensional, time-accurate computational fluid dynamics (CFD) simulations using the SST k–ω turbulence model were performed over a range of tip-speed ratios. The simulation results indicate that the controlled curvature modification produces a higher-pressure difference along the advancing blade and enhances positive torque generation, while the negative torque exhibits angular variations throughout the rotation cycle, resulting in a higher net torque and improved rotational stability. At a tip-speed ratio (TSR) of 0.5, the maximum power coefficient (Cp) for the curvature-modified design reached 0.185, representing a 16.6% improvement compared with the unmodified SWT.