Influence of Wake Effects and Inflow Turbulence on Wind Turbine Loads

Wind turbines are emerging as an exciting and rapidly expanding form of renewable energy. However, there are numerous technological challenges that must be overcome before wind energy provides a significant amount of power in the United States. One of the primary challenges in wind turbine design and analysis is accurately accounting for the wake. This study represents an initial step towards including wake effects in wind turbine design and analysis codes. A free wake model is developed using a time marching vortex line method, and subsequently verified and validated against existing results. The model is then used to examine time step requirements in the presence of inflow turbulence. Finally, comparisons are made between the developed free wake model and typical aerodynamic modeling approaches such as Blade Element Momentum Theory and Dynamic Inflow. For the configurations considered, blade time step sizes of 10° in azimuthal angle are adequate for capturing the effect of inflow turbulence on the wake. Finally, the inability of Blade Element Moment Theory and Dynamic Inflow to predict blade loads with combined inflow turbulence and wake effects is demonstrated.