Modeling Wind Turbine Tower and Nacelle Effects within an Actuator Line Model

It is common practice in computing wind plant aerodynamics with computational fluid dynamics to represent the turbine rotors using actuator lines or disks in which body forces are applied to the flow field. It is less common in such work to include the effect of the tower and nacelle. Here we examine ways to include the effect of the tower and nacelle in a body-force setting without having to explicitly resolve them using complex geometry- conforming meshes. We feel that including their effect is certainly important in better predicting the near wake, and may be of importance in the far wake. Recent research by others suggests that the nacelle wake causes interactions with the rotor wake that affect the meandering behavior of the rotor wake far downstream, and properly capturing meandering is important to computing both unsteady power and mechanical loads in a wind plant. We present different body force tower and nacelle representations of incremental complexity. We then apply these methods to two different wind turbine cases, one with emphasis on the wake, and the other with emphasis on blade loads. We show that these methods are relatively easy to implement and are capable of capturing the gross effects of towers and nacelles.