Study on the wind-farm wake under neutral atmospheric condition

Wake effect leads to the power loss and fatigue damage increase on wind turbines. Therefore, wind turbine wake is seriously considered as one of the key parameters in the micro-sitting and layout optimization. Interestingly, according to the recent research of observations and simulations, similar to individual wind turbine wake, the wake of large-scale wind farm also exists which has significant impact on surrounding wind farms and the local meteorology. However, few research focused on quantitative study of wind farm wake. As a result, in this research, firstly, the numerical simulation for the neutral atmospheric flow has been carried out and preliminarily verified. By using actuator disc model, the horizontal and vertical velocity profiles behind the wind farm are analyzed. Secondly, the effective wind-farm drag coefficient has been decomposed into two components, which represent the vertical and horizontal momentum flux, respectively. By analyzing the drag coefficient, the momentum transport of wind farm was studied. The average velocity behind wind farm was also calculated, from which it was found that, with the length scale increasing, the wind farm starts to absorb energy from upper atmosphere. Lastly, the velocity decay behind wind farm can also be modeled by the formulation of Jensen wake model.