Wind-turbine wakes responding to stably stratified flow over complex terrain

Abstract

The wake characteristics of a hill-top wind turbine are investigated by means of large-eddy simulations (LESs) of stably stratified atmospheric boundary-layer (ABL) flows. All simulations are conducted with synchronized turbulent inflow data retrieved from an LES of diurnal cycle-driven boundary-layer flow over homogeneous surface. An investigation of different (weak, moderate, strong) stably stratified flow regimes passing over various 3 D hill configurations with heights up to 50 m reveals that the occurrence of flow separation not only depends on hill properties but also on the atmospheric stratification. The hill-top wake characteristics of all flow regimes are compared with wakes resulting from the same flow fields passing through the same wind turbine, however, sited on a homogeneous surface. For the same atmospheric stratification the flow over the hill impacts only the near-wake region. In contrast, the stratification impact on the hill-top wind-turbine wake is much more distinct, especially, in the far wake.