REDUCTION OF HORIZONTAL WIND-SPEED IN A BOUNDARY-LAYER WITH OBSTACLES

The reduction of horizontal wind speed at hub height in an infinite cl uster of wind turbines is computed from a balance between a loss of ho rizontal momentum due to the drag and replenishment from above by turb ulent fluxes. This reduction is derived without assumptions concerning the vertical wind profile above or below hub height, only some basic assumptions on turbulent exchange have been made. Two applications of the result are presented, one considering wind turbines and one pressu re drag on orographic obstacles in the atmospheric boundary layer. Bot h applications are basically governed by the same kind of momentum bal ance.