Statistics of Wind Farm Wakes for Different Layouts and Ground Roughness

Abstract

In this work, the effects of streamwise turbine spacings on the wake characteristics of wind farms are investigated using large-eddy simulation with an actuator disk model for the wind turbine. The simulated farm consists of 10 × 10 wind turbines located in an aligned way. Three different streamwise turbine spacings, i.e., S x /D = 6, 8 and 10 (where D is the rotor diameter), are considered. The simulation results showed that the effects of S x are mainly located in the near wake (x/D < 10), where the turbulence intensity is higher for smaller values of S x . In the far wake, the streamwise velocity deficit as well as the Reynolds stresses from cases with different streamwise turbine spacings are close to each other. Terms in the budget equation for the mean kinetic energy (MKE) are examined. The analysis showed that the vertical MKE transport via mean convection and turbulence convection plays a dominant role in the velocity recovery in wind farm wakes, which are different from that in the wind farm region where the streamwise MKE flux due to mean convection also plays an important role and the role of the vertical MKE transport is different. Lastly, an existing analytical model for the wind farm wake is tested using the simulation results. A modification to the analytical model is proposed to include the effect of vertical mean convection on the velocity recovery.

Upward Shift of Wind Turbine Wakes in Large Wind Farms

“…A schematic diagram showing the case setup with contours of the instantaneous streamwise velocity u is presented in Figure 1. The wind farm wakes of the simulated cases were systematically investigated in our recent paper [36]. In this work, we focus on wind turbine wakes on the farm.…”