NREL Phase VI Wind Turbine Modeling Using an Unsteady Panel Method

Wind energy production has been increasing steadily in the past decade. The majority of wind power is generated by horizontal axis wind turbines (HAWT). We investigate the modeling of the HAWT using the vortex panel method, which is an inviscid, steady, computationally inexpensive method. Pressure coefficient profiles, calculated by the vortex panel method, were compared to NREL phase VI wind turbine experiments under two different flow conditions. We show that if the flow is not separated over the blade, the vortex panel method can capture the pressure profile on the blade. Furthermore, the panel method has been extended to handle unsteady inviscid flows to investigate the effect of blade oscillations on the power generation, which is not known. The unsteady behavior is modeled by accounting for the time rate of change of circulation. Unsteady effects due to heaving and pitching motion were quantified for different blade oscillation frequencies. It is estimated that the mean thrust coefficient with heaving and pitching motion can be higher than the thrust generated without blade motion in some cases assuming that the flow does not separate.