Proceedings of ASME Turbo Expo 2015, June 15 - 19, 2015, Montréal, Canada
Authors: Stefan Vey, Henning M. Lang, Christian N. Nayeri, Christian O. Paschereit, Georgios Pechlivanoglou, Guido Weinzierl

Results from a quantitative tuft flow visualization of a utility scale wind turbine undergoing a yaw movement are presented. Based on the turbine’s SCADA data suitable pre- and post-yaw timeframes were defined and the surface flowfields were anal- ysed. A distinct asymmetry between the surface flow patterns of the 90 ◦ and 270 ◦ azimutal blade positions was observed in the pre-yaw timeframe. After the turbine yawed back into the wind the symmetry was restored. Yaw-misalignment is a source of dy- namic loads which limit a turbine’s life time. The characteriza- tion of the involved flow structures and their dynamics is an es- sential step towards possible future load alleviation techniques. The quantitative tuft flow visualization technique is a measure- ment tool that can be used to assess the surface flow field.