Abstract
Offshore wind turbine near wakes can extend downstream up to 5D due to low atmospheric turbulence intensities. They are characterised by strong velocity deficits, a transitioning Gaussian shape, and strong added turbulence intensities. Classical analytical wake models are still used due to their low computational costs, but they mainly focus on far-wake characteristics. A super-Gaussian wake model valid in near-and far-wake regions has recently been developed at IFP Energies nouvelles. This wake model requires calibration and validation. To this end, large-eddy simulations of the large DTU-10MW reference wind turbine under different neutrally stratified atmospheric flows are carried out with the LES Meso-NH model. A database is generated based on these results and used to calibrate and validate the super-Gaussian model.
Highlights
Estimation of wake losses is a critical part in a wind farm design process
The workflow introduced in this work aims at providing an extensive dataset based on large-eddy simulations of a large wind turbine
This wind turbine modelled with the actuator line method is placed in a neutral atmospheric boundary layer simulated with Meso-NH, an open-source nonhydrostatic mesoscale atmospheric model [7]
Summary
Estimation of wake losses is a critical part in a wind farm design process. power losses due to wake effects are typically in the range of 10 to 20% and can rise up to 70% in the case of aligned turbines for wind velocities lower than the rated wind speed of the turbines [1]. The near wake, in the vicinity of the turbine, has features that are directly related to the rotor geometry, its aerodynamics, and the inflow conditions. It is characterised by strong velocity deficits, a transitioning top-hat/Gaussian shape, and strong added turbulence intensities. Geographical constraints (e.g. due to zoning regulation, water depth or soil conditions) can lead to wind farms with closely-spaced wind turbines (e.g. 3.3D and 4.2D minimal inter-distances respectively for Lillgrund and Ormonde offshore wind farms instead of 6 to 8D for most offshore wind farms in the last decades) Under these conditions, wind turbines can operate in the near wake of upstream turbines. It is necessary to accurately model near wake behaviour
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