Investigating Turbulent Dynamics in the Nocturnal Boundary Layer: A Large Eddy Simulation Study of the South Fork Wind Farm

Abstract In this study, Large Eddy Simulations (LES) with realistic inflow conditions are conducted to investigate the dynamics of the nocturnal marine atmospheric boundary layer (MABL) (with approximately 8 m/s mean inflow speeds) around the South Fork Wind Farm, completed in March 2024 and located 35 miles offshore and east of Montauk Point, NY. The LES framework incorporates 12 turbines represented by actuator disk models. We analyze the turbulence and circulation dynamics in the wake regions, focusing on the effects of tilting and stretching on vorticity as they represent the biggest budget terms. Our findings reveal that these processes intensify circulation and induce convergent (upward) motions in the near wake, while acting as sinks of vorticity in the far wake, thereby weakening circulation and facilitating flow recovery mechanisms. Additionally, we identify shear production as the primary source of turbulent kinetic energy (TKE) downstream of the actuator discs, peaking above the hub height, particularly at the top tip. The summer nocturnal boundary layer typically has consistent upward buoyancy flux. Heating at the surface induces convection and produces TKE. Overall, TKE is primarily removed through dissipation and transport.