Measurements of Flow Distortion within the CSAT3 Sonic Anemometer

Friday, 19 December 2014: 8:15 AM
Thomas W Horst1, Ebba Dellwik2, Jakob Mann2 and Nikolas Angelou2, (1)National Center for Atmospheric Research, Boulder, CO, United States, (2)Technical University of Denmark, Wind Energy, Roskilde, Denmark
We have measured flow distortion within the CSAT3 sonic anemometer using two quite different techniques. One method compares three adjacent, differently-aligned CSAT3 sonics to each other, using a data analysis technique similar to that of Kochendorfer et al.~(2012). The two 'outside' sonics are upright references while the central, test sonic is oriented with its v-axis vertical, so that fluctuations of wind direction are surrogates for variations in the vertical wind component. The second technique compares CSAT3 measurements to independent velocity measurements with a 3-component Doppler LIDAR. The LIDAR is focused at a distance of 0.8 m in front of the sonic and is thus a flow-distortion-free reference. Here we compare the results of the two techniques to each other, as well as to a transducer-shadowing model for CSAT3 flow distortion. On the basis of these measurements, recommendations are made for correction of CSAT3 flow distortion.