Large-eddy simulation study of wind-turbine wakes in the coastal stable atmospheric boundary layer

There are many wind farms built in coastal areas. When the wind blows from land to sea, surface roughness and temperature change abruptly. However, the evolution of wind-turbine wakes in this condition is still not well understood to date. To this end, we use large-eddy simulation to study the wind turbine wake in the coastal stable atmospheric boundary layer characterized by an abrupt rough-to-smooth surface roughness and high-to-low surface temperature transition. Results show that the wind speed near the ground gradually increases at locations closer to the abrupt location dominated the abrupt roughness reduction. As the distance increases, the effect of surface temperature reduction gradually becomes apparent, suppressing the vertical momentum transport and leading to the velocity reduction. The farther away from the abrupt location, the greater the difference between the local shear stress and inflow shear stress, and a three-layer structure is formed. When the distance between the wind turbine and the abrupt location decreases, the wake recovery becomes faster. This is mainly because, with the decrease in the distance, the spanwise and vertical Reynolds shear stresses increase in the wake region and the corresponding spanwise and vertical turbulent transport increase.