Aerodynamic Investigations On Tower-Shadow Impacts For HAWTs

This paper presents a numerical method for aerodynamic investigations on tower-shadow impacts for downwind horizontal-axis wind turbines. In this method, the flowfield is described by the incompressible three-dimensional Navier-Stokes equations. The rotor and tower are idealized respectively as actuator disk and flat plate permeable surfaces, on which external normal surficial forces are balanced by fluid pressure discontinuities. The external forces exerted by the rotor and tower on the flow are prescribed according to the blade-element theory. Dynamic behavior of the rotor aerodynamic characteristics is simulated using either Gormont or Beddoes-Leishman model. The resulting mathematical formulation is solved using a control-volume finite element method. The results presented in this paper include comparisons between predicted and measured data of azimuthal distribution of the angles of attack and the normal force coefficients related to the NREL's combined experiment phase III downwind rotor. In general, the proposed method has demonstrated its capability to represent adequately the measured data. It has been shown that the accuracy of the predicted results depend strongly on the dynamic-stall model as well as on the turbulence model employed.