Abstract
Wind energy development increasingly targets complex mountainous and hilly terrains characterized by intricate flow separation, localized speed-ups, and elevated turbulence. In these environments, wind turbine wake interactions substantially deviate from canonical flat-terrain behaviors, introducing severe power deficits and amplified dynamic structural loads. This study employs high-fidelity Large Eddy Simulations (LES) coupled with an advanced Actuator Line Model (ALM) and a dynamic aeroelastic structural solver to investigate wake development, farm-level power production, and mechanical fatigue across a multi-megawatt wind farm sited over realistic undulating topography. A neutral atmospheric boundary layer with fully developed inflow turbulence is simulated over a double-ridge terrain configuration supporting an array of nine NREL 5-MW reference wind turbines. The results demonstrate that adverse pressure gradients and terrain-induced wake deflection reduce farm-level power output by up to 28.4% compared to an isolated un-waked baseline, which represents an additional 9.2% deficit relative to flat-terrain wake interactions. Furthermore, the combination of terrain-generated shear layers and persistent turbulent wake meandering increases the blade root flapwise bending moment damage equivalent loads (DELs) by up to 41.7% and tower-base fore-aft bending DELs by 36.3% on downstream units. These findings underscore the critical necessity of incorporating coupled aeroelastic-topographic wake physics into micro-siting optimization algorithms to balance power capture against turbine structural fatigue life.
