Experimental validation and improvement of actuator line model in the large-eddy simulation of wind-turbine wakes

Abstract

Wind-turbine wakes significantly affect the power output of downstream wind turbines. In order to improve the calculation accuracy of wind-turbine wakes in the atmospheric boundary layer, a new improved actuator line - large-eddy simulation (AL-LES) method is proposed and verified by experiments. The traditional AL-LES method is improved in three aspects. Firstly, the atmospheric turbulence is generated by a dynamic k-equation LES with a wall shear stress model and a buoyancy effect model. Secondly, the nacelle and tower are modelled based on the static actuator line method. Finally, the distribution of blade body force is improved by using an anisotropic 3D Gaussian function. Based on the results of three wind tunnel experiments conducted by Norwegian University of Science and Technology (NTNU), China Aerodynamics Research and Development Centre (CARDC) and Von Karman Institute for Fluid Dynamics (VKI), the improved AL-LES method is validated from the aspects of wind-turbine power performance, the generation of tip vortex, and the distribution of wake velocity under typical offshore and onshore conditions. In addition, a full-scale wind turbine installed in Gansu is used for the experimental and numerical research. The main conclusion is that compared with the traditional method, the new AL-LES method improves the numerical accuracy by nearly 22%, and can more accurately simulate the interaction between atmospheric turbulence and wind-turbine wakes. The results can help the research of wind-turbine wakes and the micro-location selection of wind farm.