Active flow control actuators on wind turbines; comprehensive review

Abstract

Active flow control (AFC) techniques are designed to add or subtract momentum into/from the flow field in order to modify (usually delay) the boundary layer separation. AFC strategies are being considered in many industrial applications, particularly in aeronautics/aerodynamics, where the early separation of the boundary layer drastically affects the forces acting on an airfoil. AFC devices are divided into three different types, including fluidic actuators, plasma ones, and moving surfaces. The present paper is a comprehensive review of the different AFC actuators employed in wind turbines, including Dielectric Barrier Discharge (DBD) plasma actuator (PA), synthetic jet actuator (SJA), and suction and blowing actuators. All AFC applications on Horizontal axis wind turbines (HAWT) and Vertical ones (VAWT), whether reporting numerical or experimental methods, are considered. The actuation when employing moving surfaces shall be presented in a different review. AFC implementation on wind turbines needs to employ a strategy consisting of setting/optimizing the AFC parameters, as well as considering an energy assessment. This review is highlighting the research that has already addressed these points. Eventually, a comparison of the main achievements gathered from previous publications is presented and discussed in detail to assist researchers and engineers and give them a tool to design future AFC applications on WTs.