Measuring the local wind field at an escarpment using small remotely-piloted aircraft

A remotely-piloted aircraft (RPA) is used in this study to collect high resolution data of the flow in complex terrain at a potential site for a wind energy test field in Southern Germany. It is described how such a system was used to retrieve information about the flow field, turbulence intensity, vertical wind components and shear at an escarpment site that is known for its high wind potential. Measurements were done with the aircraft on several days with varying wind and weather conditions, while the focus of the study is on the characterisation of the flow field in main wind direction and neutral stratification. It is shown that flow inclination of up to 30° is found over the escarpment, but attenuates within a few hundred metres downstream. The formation of a reattached boundary layer could be measured, as well as an increased turbulence intensity in the reattachment zone. The results are highly valuable information for the planning of a wind energy test site at the location of the experiment and can also be used for the validation of numerical simulations and remote sensing instruments.