Large-eddy simulation of the diurnal variation of wake flows in a finite-size wind farm

Wake Conference 2015

Abkar, Mahdi^1 ; Sharifi, Ahmad^1 ; Porté-Agel, Fernando^1

École Polytechnique Fédérale de Lausanne (EPFL), Wind Engineering and Renewable Energy Laboratory (WiRE), EPFL-ENAC-IIE-WIRE, Lausanne

CH-1015, Switzerland^1

关键词: Atmospheric stability;    Diurnal variation;    Dynamic actuators;    Scale-dependent dynamics;    Subgrid scale stress;    Turbulence intensity;    Turbulence productions;    Wind turbine wakes;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/625/1/012031/pdf
DOI  :  10.1088/1742-6596/625/1/012031

来源: IOP

【 摘 要 】

In this study, large-eddy simulation (LES) is used to study the evolution of the wind-turbine wakes and their effects on power losses inside an idealized finite-size wind farm in the course of a full diurnal cycle. In the LES, turbulent subgrid-scale stresses are modeled using tuning-free Lagrangian scale-dependent dynamic models, while the turbine-induced forces are parameterized using a dynamic actuator disk model with rotation. The simulation results show a strong effect of atmospheric stability on the wind farm wakes and associated power losses. During the night, the relatively low turbulence intensity of the ambient ABL flow results in a relatively slow rate of entrainment of momentum into the wake and, consequently, a slow wake recovery. In contrast, during the day the positive buoyancy flux and associated turbulence production lead to a relatively high turbulence level in the background ABL flow, which enhances turbulent mixing and wake recovery. As a result, the averaged power deficit in the wind farm is found to increase with increasing thermal stability. In particular for that day, the averaged power deficit increased from 28% under the most convective condition to about 57% under the most stable condition.