Abstract

This study numerically investigates kinematics of dynamic stall, which is a crucial matter in wind turbines. Distinct movements of the blade with the same angle of attack (AOA) profile may provoke the flow field due to their kinematic characteristics. This induction can significantly change aerodynamic loads and dynamic stall process in wind turbines. The simulation involves a 3D NACA 0012 airfoil with two distinct pure-heaving and pure-pitching motions. The flow field over this 3D airfoil was simulated using Delayed Detached Eddy Simulations (DDES). The airfoil begins to oscillate at a Reynolds number of Re = 1.35 × 105. The given attack angle profile remains unchanged for all cases. It is shown that the flow structures differ notably between pure-heaving and pure-pitching motions, such that the pure-pitching motions induce higher drag force on the airfoil than the pure-heaving motion. Remarkably, heaving motion causes excessive turbulence in the boundary layer, and then the coherent structures seem to be more stable. Hence, pure-heaving motion contains more energetic core vortices, yielding higher lift at post-stall. In contrast to conventional studies on the dynamic stall of wind turbines, current results show that airfoils’ kinematics significantly affect the load predictions during the dynamic stall phenomenon.