A Wind Tunnel Experimental Study on the Wake Characteristics of a Horizontal Axis Wind Turbine

The characteristics of wind turbine wakes are influenced by multiple factors,including the atmospheric boundary layer(ABL) wind and wind turbine operating conditions(e.g.,tip speed ratio and yaw angle).In this study,two types of ABL winds with different velocity gradients and turbulence intensities are generated in a wind tunnel through configurations of spires,baffles,and various numbers of roughness elements.A wind turbine with a rotor diameter of 0.8 m and a hub height of 0.6 m is tested under varying tip speed ratios,yaw angles,and ABL wind conditions.The results indicate that the streamwise velocity deficit in the near-wake region becomes more pronounced with an increase in the tip speed ratio,while the far-wake velocity deficit remains largely unaffected by changes in the tip speed ratio.As the yaw angle increases,the wake deflection becomes more prominent and the wake narrows;the offset of the wake center at various downstream positions grows linearly,reaching a maximum value of approximately half the rotor diameter.Furthermore,the turbulence level and influence range in the wake region are reduced when the turbine is yawed.Under ABL wind conditions,high turbulence intensity in the incoming flow accelerates wake recovery,and the Reynolds stress at different lateral positions tends to become consistent with increasing longitudinal distance.Additionally,turbulence has a significant impact on the meandering characteristics of the wind turbine wake,with greater fluctuations in the wake center observed under higher turbulence intensities.Overall,this study provides insights that could inform the optimal operation of wind farms.