Bio-inspired pressure side stepped NACA 23012 C as wind turbine airfoils in low Reynolds number

The current study focuses on obtaining a new form of stepped airfoil inspired by the shape of a bird's wing in nature, which consists of three steps of feathers. A stepped wing can be used for passive flow control to improve the aerodynamic characteristics and delay stall in wind turbine blades. This study focused on a one-stepped NACA 23012 C section and later a three-stepped airfoil section, which was numerically analyzed at various step lengths, depths, and angles of attack. The numerical results were experimentally verified using physical models, and the findings demonstrated a maximum lift coefficient (CL,max) of 11.3 % increment for the three-stepped airfoil. Furthermore, the three-stepped airfoil retained more CL values for the angle of attack (AOA) less than 14 degrees and increased lift-to-drag ratio CL/CD for AOA less than 6 degrees. For the one-stepped airfoil, CL,max was increased by 12.5 %, and stall AOA was delayed by 2 degrees while maintaining higher CL values after AOA 14 degrees.