Offshore marine boundary-layer winds predicted by a large eddy simulation model with resolved surface waves

Offshore winds offer a significant energy source for generating electricity through optimal placement of coastal wind parks. To develop an improved understanding of the characteristics of offshore winds in which these wind turbines operate, a large-eddy simulation (LES) model is developed that couples the marine atmospheric atmospheric boundary layer to a 3D time-dependent surface gravity wave field. A coordinate transform from physical to computational space is used that accounts for vertical movement of the mesh in physical space. The algorithm is used to carry out a series of simulations over a broadband moving wave field that conforms to a well established Pierson-Moskowitz wave spectrum. The wave age C_p/U₁₀ = [1.5, 4.8] varies from near wind-wave equilibrium to a low-wind swell dominated regime. In the low wind cases we find features similar to previous observational and modeling investigations: the surface layer winds show clear departures from rough wall law-of-the-wall scaling. The coherence and magnitude of the velocity and pressure fields depend critically on the motion of the underlying wave field and the turbulence level. Future siting and deployment strategies of offshore wind parks need to account for the local climatology of winds and waves to accurately predict boundary-layer winds and turbulence.