Measurement and modelling of tip vortex paths in the wake of a HAWT under yawed flow conditions

Abstract

Tip vortex locations have been measured in the wake of a model rotor in both axial flow and yaw using quantitative flow visualisation. For each setting, the axial force coefficient has been derived as well from measurements. The results seem to agree well with those previously published on the Delft University of technology model rotor. The main interest is to determine the tip vortex pitch, wake skew angle and wake expansion and to physically interpret the data. The results should also help to validate and construct models. The tip vortex locations data complement the existing skewed wake velocity data from hot-wire anemometry, making it a valuable experimental database.