The effect of rotation on the boundary layer of a wind turbine blade

Design and analysis methods for wind turbines are presently based on relati vely simple models of rotor blade aerodynamics, such as 2-D blade element/m omentum theory (BEMT). Field investigations over the past few years have sh own discrepancies between predicted and measured performance, owing to the effect of rotation on the wind turbine blade boundary layer distribution. T he present paper is aimed at describing a fundamental phenomenon: the effec t of rotation on the blade boundary layer of a wind turbine. In this paper, 3-D incompressible steady momentum integral boundary layer equations are e mployed to study this complex problem. By solving the 3-D integral boundary layer equations with the assumed velocity profiles and a closure model (in cluding both laminar and turbulent boundary layer models), the effects of r otation on blade boundary layers are investigated. Several key parameters, such as separation position and momentum thickness, are calculated and comp ared for the rotation and non-rotation cases. It is concluded that the stal l is postponed due to rotation and the separation point is delayed as a res ult of increasing rotation speed or decreasing blade spanwise position. Pos sible modifications that should be considered to the existing 2-D BEMT meth od are suggested. (C) 1999 Elsevier Science Ltd. All rights reserved.