Wake impacts on aeroelastic characteristics of horizontal axis wind turbine blades

Abstract

Wake effects of a horizontal axis wind turbine blade on aeroelastic characteristics were investigated for the uniform inflow condition. A structural analysis was performed employing a nonlinear beam model based on the large deflection beam theory. For inflow analysis on rotor blades, a free-vortex wake method was employed. An advantage of the present approach is its ability to calculate directly the induced velocities from the wake. Also, for the predictions of aerodynamic loads, a fully turbulent flow solution is invoked in FLUENT, where the k-ω SST turbulent model of two-dimensional airfoils is adopted for transient analysis. To verify and validate the aerodynamic model for wind turbines, the wake geometry and the aerodynamic coefficients from the present simulation are compared with measurements and numerical results of previous studies. Finally, an analysis of the tightly coupled fluid-structure interaction phenomena of a wind turbine blade has been carried out to investigate aeroelastic characteristics, such as steady-state blade deflections and dynamic stability. The present results are compared with the numerical results obtained using a uniform inflow model, which clearly confirms the importance of wake effects on the blade aeroelastic characteristics. In addition, the horizontal axis wind turbines operate under yawed conditions for a considerable period of time due to the power control mechanism or sudden changes in the wind direction. This in turn can alter the dynamic characteristics of a turbine blade because the flow over the rotor plane may trigger complicated induced velocity patterns. Thus, an aeroelastic analysis under yawed flow conditions is carried out to investigate the effects of yaw error on the blade behaviors and dynamic stability. The aerodynamic approach for a horizontal axis wind turbine blade under yawed flow conditions is verified through comparison with measurements. The dynamic instabilities of a National Renewable Energy Labora...