Aerodynamic optimization of Magnus wind turbine blades using a stator-integrated design behind rotating cylinders

Abstract

To improve the efficiency and viability of Magnus wind turbines (MWTs) as a competitive alternative to conventional wind turbines, it is essential to address their aerodynamic limitations. Despite the high lift generated by the rotary cylinders in Magnus wind turbines (MWTs), they lag in overall performance compared with blade-type wind turbines because of their rotary cylinders’ high drag coefficient and frictional torque. In this paper, an aerodynamic body positioned behind a rotary cylinder is designed to control flow, prevent flow separation, and minimize drag effectively. This new and innovative design is proposed for the cross-section of MWT blades. Initially, a segment of the Risø-B1–18 airfoil was chosen as the baseline aerodynamic body behind the rotary cylinder, and its impact on aerodynamic performance was numerically analyzed. Reynolds-averaged Navier–Stokes equations were solved using the k‒ω shear stress transport turbulence model within the Fluent 2022 R2 solver at a Reynolds number of 800,000 and cylinder speed ratios of 1.5 to 4.5. Subsequently, the baseline body was optimized through a parametric study and adjoint-based optimization. The optimal size of the gap between the cylinder and the body and the optimal positions of the gap inlet and outlet were determined through the parametric study. Then, the profile of the entire body was optimized by solving adjoint equations in Fluent 2022 R2. The outcomes revealed that incorporating the optimized aerodynamic body behind the rotary cylinder significantly enhanced the lift-to-drag ratio across all speed ratios. Specifically, the lift-to-drag ratio increased by 400% and 450% at the speed ratios of 1.5 and 4.5, respectively, compared to the rotary cylinder without the aerodynamic body. Moreover, the rotary cylinder with the optimized aerodynamic body yielded a 70% reduction in frictional torque compared with the rotary cylinder without the aerodynamic body. These findings demonstrate the potential of aerodynamic shaping in unlocking higher efficiency for MWTs. Future research will focus on experimental validation and full-scale rotor integration, paving the way for practical implementation in the wind energy sector.