Experimental investigations of airfoil surface flow of a horizontal axis wind turbine with LDV measurements

In order to study the performance characteristics and the near wake of a model wind turbine, the three-dimensional effect in the spanwise direction on the airfoil surface flow of the Horizontal Axis Wind Turbine (HAWT) was investigated in wind tunnel experiments. The HAWT model was a three-bladed upwind wind turbine with a rotor radius of R = 1.2 m. In this experiment, the pressure distribution was measured by a multiport pressure measurement device and the velocity characteristics of a HAWT rotor surface were measured by using an LDV system. Experiments were carried out at the optimal tip speed ratio of 5.2 in the three spanwise sections of r/R = 0.3, 0.5 and 0.7, respectively. It is discovered that the laminar separation bubble locates at the chord position of 0.3 < x/c < 0.4 for r/R = 0.5 and 0.4 < x/c < 0.5 for r/R = 0, with a nearly constant pressure coefficient on the suction surface. Furthermore, the flow over the blade surface accelerated around the leading edge and decelerated towards the trailing edge. Meanwhile, for the blade section at r/R = 0.7, the region with the strong velocity standard deviation near the blade leading edge was larger than that of r/R = 0.3 and 0.5. This study will provide rich information for the understanding of airfoil dynamics under the effect of blade rotation which are suitable for the effective design for wind turbine airfoil. (C) 2019 Elsevier Ltd. All rights reserved.