Influence of Wake Effects and Inflow Turbulence on Wind Turbine Loads

Wind turbines are currently a 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 toward including wake effects in wind turbine design and analysis codes. A free wake model is developed using a time-marching vortex line method, and it is subsequently verified and validated against existing results. Subsequently, comparisons are made between the developed free wake model and typical wind turbine aerodynamic modeling approaches, such as blade element momentum theory and dynamic inflow. Time-step requirements for the model, in the presence of inflow turbulence, are also examined. For the configurations considered, blade time-step sizes of 10 degrees in azimuthal angle are adequate for capturing the effect of inflow turbulence on the wake. In addition, a maximum difference of 44% in the cycle average of predicted lift is found between the free wake model and blade element momentum theory.