Numerical simulation study on wake characteristics of dual wind turbines coupled with Variable-Slope Hills

In the micro-siting of complex wind farms, one of the primary challenges in wind turbine arrangement is the overall power loss caused by terrain effects and wake interference between turbines. This study focuses on dual wind turbines arranged in a longitudinal tandem configuration under varying hill aspect ratios. A RANS is employed to model the flow characteristics within the wake region generated by the power output and aerodynamic behavior of the turbines across multiple terrain configurations. The underlying flow mechanisms within the wake region under different hill aspect ratios are systematically investigated. The results indicate that in hilly terrain with a Hill aspect ratio ranging from 0.14 to 0.25, when wind turbines are arranged with vertical elevation differences, the influence of the terrain on the flow field at the base of the windward slope is relatively minor. However, for turbines located near the hilltop, the inflow wind speed increases by 10%–30% compared to those situated at the leeward base, while turbulence intensity decreases by approximately 2%–6%, leading to a 1 to 2fold increase in power output. As the terrain aspect ratio increases, the recovery of wake interference within the coupled terrain – turbine wake system is enhanced, regardless of elevation differences. Specifically, the wake recovery distance shortens from 15D to 13D. In conjunction with spectral analysis of turbine power output, these findings suggest that wind farm micro-siting should prioritize low-aspect-ratio hilly terrains and adopt elevated arrangements (with height differences) to maximize wind energy utilization efficiency.