Prediction of the three-dimensional separation on a rotating blade

Blade rotation routinely and significantly augments aerodynam c forces during zero yaw horizontal axis wind turbine operation. To understand better the flow physics underlying this phenomenon, three-dimensional and rotational viscous effects on wind turbine blades are investigated by means of a 3-D boundary-Iayer model. The governing equations of the model are derived from 3-D primitive variable boundary-Iayer equations written in cylindrical coordinates in the rotating fratne of reference. The latter are integrated along the peripheral direction with the radial distance as parameter for a particular external flow. The skin friction coefficient is used to identify boundary layer separation and shear layer reattachment locations. Separation and reattachment kinematics shows at inboard locations that while the separation point location is not realIy atTected and remains near the leading edge, the reattachment point advances forward rapidly on the blade chord from the trailing edge as radial distance decreases. It is concluded that the rotational augmentation is linked to specific separation and reattachment state strictly determined by the Coriolis forces.