25 research outputs found
Blind test comparison on the wake behind a yawed wind turbine
This article summarizes the results of the Blind test 5
workshop, which was held in
Visby, Sweden, in May 2017. This study compares the numerical predictions of
the wake flow behind a model wind turbine operated in yaw to experimental
wind tunnel results. Prior to the workshop, research groups were invited to
predict the turbine performance and wake flow properties using computational
fluid dynamics (CFD) methods. For this purpose, the power, thrust, and yaw
moments for a 30° yawed model turbine, as well as the wake's mean and
turbulent streamwise and vertical flow components, were measured in the wind
tunnel at the Norwegian University of Science and Technology (NTNU). In order
to increase the complexity, a non-yawed downstream turbine was added in a
second test case, while a third test case challenged the modelers with a new
rotor and turbine geometry.Four participants submitted predictions using different flow solvers, three
of which were based on large eddy simulations (LES) while another one used an
improved delayed detached eddy simulation (IDDES) model. The performance of a
single yawed turbine was fairly well predicted by all simulations, both in
the first and third test cases. The scatter in the downstream turbine
performance predictions in the second test case, however, was found to be
significantly larger. The complex asymmetric shape of the mean streamwise and
vertical velocities was generally well predicted by all the simulations for
all test cases. The largest improvement with respect to previous blind tests
is the good prediction of the levels of TKE in the wake, even for the complex
case of yaw misalignment. These very promising results confirm the mature
development stage of LES/DES simulations for wind turbine wake modeling,
while competitive advantages might be obtained by faster computational
methods.</p