Experimental Investigation of Trailing Edge Surface Roughness on the Aerodynamic Characteristics of the Wind Turbine Blades

Numerous research studies have been conducted on the effects of aerodynamic characteristics of airfoils with leading-edge modifications such as adding roughness, undulations, and so on, which have resulted in favourable changes in aerodynamic characteristics as a successful passive flow control method, thereby increasing the repository of scientific data for the corresponding research. This led to the present study, which deals with a new passive flow control technique that has a distributed roughness element in the form of an emery sheet, placed on the suction side of the airfoil with an area covering about 50% chord from the trailing edge of the airfoil. An experimental analysis of the modified NACA 0015 airfoil was performed in the low subsonic wind tunnel situated at SASTRA Deemed to Be University for the free stream Reynolds number of 2.04 × 105 at angles of attack ranging from 0° to 45°. A multichannel Ethernet-Based Simultaneous Pressure Scanner was used to measure the surface pressure of the airfoil, which was further processed for aerodynamic characteristics. The investigation has revealed exceptional aerodynamic characteristics in the pre-stall region with a decrease in the coefficient of drag, thereby increasing the aerodynamic efficiency. The stall behaviour has also been altered by the addition of a roughness element at the flow transition region on the airfoil surface. This in turn reduces the effects of the adverse pressure gradient at critical and post-critical angles of attack, inducing turbulence kinetic energy at the transitional boundary layer, enhancing an attached flow and a delay in the stall. The addition of the roughness element at the trailing surface of the airfoil has predominantly affected the aerodynamic characteristics, which may reduce the effects of dynamic stalls, thus paving the way for the design of an efficient wind turbine blade.