A Comparison of Wake Model Performances

1
A Comparison of Wake Model Performances in an
Offshore Environment
Konstantinos Rados, The Robert Gordon University,
School of Mechanical and Offshore Engineering,
Aberdeen AB10 1FR, SCOTLAND, k.rados-gatsias_at_rgu
.ac.uk Gunner Larsen and Rebecca Barthelmie, Wind
Energy Department, Risø National Laboratory, 4000
Roskilde, DENMARK Wolfgang Schlez and Unsal
Hassan, Garrad Hassan and Partners Ltd, Bristol
BS2 0QD, UK Bernhard Lange and Igor Waldl, Dept.
of Energy and Semiconductor Research EHF,
University of Oldenburg, D-26111 Oldenburg,
GERMANY Gerard Schepers and Terry Hegberg,
Netherlands Energy Research Foundation ECN, Solar
and Wind Energy, 1755 ZG Petten, THE
NETHERLANDS Mikael Magnusson, c/o Dept. of Earth
Sciences, Meteorology, Uppsala University, 752
36 Uppsala, SWEDEN
The Wake Models
Vindeby Wind Farm
Case StudySingle Wake of Turbine 6E
Conclusions
? Considerable variability in the predictions of
the models is shown the largest discrepancy
appearing in the near wake region. In this region
predictions of the models differ by almost
40.Almost all models overestimate the wake
effects at 8.6D in terms of the velocity deficit
and the turbulence intensity levels. Large
deviations appear in the low turbulence intensity
case (6) where all models predict an expected
slower wake recovery compared to the higher
turbulence intensity (8) while the measurements
show similar recovery rates.? All models show
higher rates of wake recovery as the ambient
turbulence intensity increases and thrust
coefficient decreases.? GH model predicts
turbulence intensity levels in the wake very
close to the observed values whereas ECN, RGU and
RISOE significantly overestimate the turbulence
added by the rotor.? ECN and RGU
three-dimensional models agree quite well in both
the velocity and turbulence intensity profiles in
the wake. The differences observed in the near
wake can be attributed to the different near wake
approximations used by these models.? ECN and
RGU both predict a downward shift of the maximum
velocity deficit most so for the ECN model.
ResultsVelocity and Turbulence Intensity
Profiles in the wake of 6E
Wind Speed, Uo15 m/sTurbulence Intensity, Io8
Future Work
? Evaluation of the models against the single
wake data available from the Bockstigen offshore
wind farm? Improvements in the near wake
modelling? Comparative investigation of the
model performance against the double and multiple
wake situations at Vindeby
Acknowledgements
Financial support for this research was given in
part by the European Commission's Fifth Framework
Programme under the Energy, Environment and
Sustainable Development Programme. Project
Reference ERK6-1999-00001 ENDOW(EfficieNt
Development of Offshore Windfarms).