Fast wake measurements with LiDAR at Risø test field

Abstract

The vast majority of wind turbines are today erected in wind farms.As a consequence, wake generated loads are becoming more and moreimportant. We present a new and successful experimental technique,based on remote sensing, to measure instantaneously the flow in thewake of wind turbines. Downstream wind speed can be quantified spatiallyin one and two dimensions. Data analysis allows us to identify thewake transversal position, thus enabling us to quantify the wakemeandering as well as the instantaneous wake expansion expressedin a meandering frame of reference. The experimental results aresubsequently used in a preliminary verification of the basic conjectureof a wake meandering model that essentially considers the wake asa passive tracer.