Large-Eddy Simulation of Wind-Turbine Wakes: Evaluation of Turbine Parametrisations

Abstract

Large-eddy simulation (LES), coupled with a wind-turbine model, is used to investigate the characteristics of a wind-turbine wake in a neutral turbulent boundary-layer flow. The tuning-free Lagrangian scale-dependent dynamic subgrid-scale (SGS) model is used for the parametrisation of the SGS stresses. The turbine-induced forces (e.g., thrust, lift and drag) are parametrised using two models: (a) the 'standard' actuator-disk model (ADM-NR), which calculates only the thrust force and distributes it uniformly over the rotor area; and (b) the actuator-disk model with rotation (ADM-R), which uses the blade-element theory to calculate the lift and drag forces (that produce both thrust and rotation), and distribute them over the rotor disk based on the local blade and flow characteristics. Simulation results are compared to high-resolution measurements collected with hot-wire anemometry in the wake of a miniature wind turbine at the St. Anthony Falls Laboratory atmospheric boundarylayer wind tunnel. In general, the characteristics of the wakes simulated with the proposed LES framework are in good agreement with the measurements in the far-wake region. The ADM-R yields improved predictions compared with the ADM-NR in the near-wake region, where including turbine-induced flow rotation and accounting for the non-uniformity of the turbine-induced forces appear to be important. Our results also show that the Lagrangian scale-dependent dynamic SGS model is able to account, without any tuning, for the effects of local shear and flow anisotropy on the distribution of the SGS model coefficient.

Boundary-layer development and gravity waves in conventionally neutral wind farms

“…This method represents the wind turbines as porous disks exerting a thrust force perpendicular to the rotor plane. The performance of ADM has been investigated by Wu & Porté-Agel (2011) and later by Meyers & Meneveau (2013), and it is generally accepted that ADM provides an accurate representation of the turbine far wake and the wake mixing.…”

“…In recent years, LES has also been applied to study turbulent flow in and around wind turbines and wind farms (see, e.g. Jimenez et al 2007Jimenez et al , 2008Calaf et al 2010;Wu & Porté-Agel 2011). In the current study, we use large-eddy simulations to study wind farms in conventionally neutral boundary layers (CNBLs), which are often encountered in offshore conditions.…”

Thek-ε-fPmodel applied to double wind turbine wakes using different actuator disk force methods

“…One could consider to estimate the free-stream velocity UH,∞ by the axial induction factor ax from 1D momentum theory, as performed in the work of Prospathopoulos [9] et al, Calaf et al [16] and used by Wu and Porté-Agel [17] for an actuator disk model that does not include rotation (ADM-NR):…”

“…This method is based on blade element momentum theory and it is introduced by Sørensen and Shen [20] for the actuator line technique. In later work, the method is used for AD simulations by El Kasmi and Masson [8], Réthoré et al [13], Wu and Porté-Agel [17] and others. In the present work, the implementation of Réthoré et al [13] is used, which can be summarized as:…”

The impact of the diurnal cycle of the atmospheric boundary layer on physical variables relevant for wind energy applications

“…In most of the numerical simulations of an individual wind turbine, however, an NBL is assumed (e.g. Wu and Porté-Agel (2011), Porté-Agel 80 et al (Chapel Hill, 2010), Naughton et al (2011), Englberger and Dörnbrack (2015)). There are approaches considering the SBL ) or the CBL ) in a one-way nested Weather Research and Forecasting (WRF)-LES simulation.…”