Triple-lidar measurements of wind across a virtual rotor plane over a sea surface

Abstract

An improved understanding of the spatiotemporal characteristics of the wind velocity field above the sea surface will benefit the design of modern offshore wind turbines. This study examines wind velocity data recorded on a bow-tie-like measurement pattern, approximately covering a rotor area diameter of about 70 m. The measurement data are obtained by triple continuous-wave Doppler lidars (short-range WindScanners). Two of the instruments are installed on a stable platform in the form of a suspension bridge deck, whereas the third is stationed on the ground nearby. Data from sonic anemometers installed above the bridge deck are used to validate the wind characteristics observed by the lidars. The lidar measurement data are explored in terms of wind flow mapping, mean flow characteristics and co-coherences. The results demonstrate the difference between the co-coherence at lateral and vertical separations and also differences from the coherence model in the IEC standard. The results further show the potential of lidar measurements to provide new insight into mean wind flow and turbulence characteristics applicable for offshore wind turbine design.