Single film hot-film measurements in the near
wake of a horizontal axis wind turbine are
performed in the Delft University of Technology
Open Jet Facility in order to capture the blade
azimuth dependent velocity vectors. A novel
approach to determine the average, blade
azimuth dependent, velocity vector is
proposed. It makes use of the asymmetric
response of hot-films that have the film parallel
to its probe. Contrary to the traditional
approach in which the direction of velocity
components cannot be determined and which
poorly predicts relatively small velocity
components, the proposed method yields
velocity direction as part of the solution and
consistently predicts relatively small velocity
components. An uncertainty analysis is
performed on the velocity magnitude and flow
angle, quantifying the data quality.
Furthermore, comparisons with previously
published data on the same rotor, in the same
wind tunnel are made. The comparisons
increase confidence in the data and reveal the
advantages of the proposed velocity
determination method. Qualitatively, the
velocity signals derived with the proposed
approach are in agreement with expectations
from a general vortex wake model, also the
relatively small tangential and radial velocity
components.peer-reviewe
