Wall-modeled LES of wind-wave-wake dynamics affecting an offshore wind turbine

Offshore wind has the potential to supply a significant proportion of the global electricity use. However, complex flow interactions between the atmospheric boundary layer, the wind turbine array and the ocean can affect the power output and the loading on individual turbines. In order to gain an understanding of the wind-wave-wake dynamics, we perform Large Eddy Simulations of an offshore wind turbine with a moving wave boundary condition to model a monochromatic wave. Drag generated from the interaction of wind with moving waves is modeled using a novel equilibrium moving surface gradient (EMSG) wall model. This EMSG model includes both an equilibrium wall stress that follows the local law-of-the-wall and a moving surface gradient stress. The equilibrium wall stress accounts for momentum loss due to small scale interactions and the latter for momentum loss of a flow that impinges onto an arbitrary surface. The robustness and accuracy of the EMSG wall model is validated against several benchmark cases (flow over moving waves). Comparisons of results from our wall-modeled LES and experiments of a fixed bottom turbine conducted by the PSU Wind Energy and Turbulence lab are discussed.