Proceedings of the ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering OMAE2010 June 6-11, 2010, Shanghai, China OMAE2010-20882 MULTI-SCALE MODELING OF WIND-WAVE INTERACTION IN THE PRESENCE OF OFFSHORE STRUCTURES FOR RENEWABLE ENERGY APPLICATIONS Yi Liu, Di Yang, Xin Guo, and Lian Shen ∗ Department of Civil Engineering The Johns Hopkins University Baltimore, Maryland 21218 Email: lianshen@jhu.edu ABSTRACT We develop a multi-scale modeling capability for the simu- lation of wind and wave coupling dynamics, with a focus on pro- viding environmental input for wind and wave loads on offshore structures. For the large-scale wind–wave environment, large- eddy simulation for the wind turbulence and high-order spec- tral simulation for the nonlinear ocean waves are dynamically coupled. For the local-scale air and water flows past the struc- ture, we use a hybrid interface capturing and immersed boundary method. Coupled level-set/volume-of-fluid/ghost-fluid method is used to capture the wave surface. Immersed boundary method is used to represent the structure. The large-scale wind–wave sim- ulation provides inflow boundary conditions for the local-scale air–water–structure simulation. Our simulation captures the dy- namic evolution of ocean nonlinear wavefield under the wind action. The wind field is found to be strongly coupled with the surface waves and the wind load on a surface-piercing object is largely wave-phase dependent. INTRODUCTION To address the increasing demand of energy and the issue of global warming associated with the use of fossil fuel, clean and renewable energy is being actively seeked. The oceans pro- vide enormous resources for renewable energy. In addition to the wave energy, the offshore wind power possesses many advan- tages over the traditional wind power on land and has become a ∗ Address all correspondence to this author. new frontier in wind energy. According to a report of US Depart- ment of Energy [1], wind energy will provide 20% electricity of US demand by 2030 and 18% of them will be the offshore wind energy. Compared to the wind energy on land, the offshore wind energy is stronger and more stable, and the convenience is sea transportation makes the installation of very large wind turbine feasible. For the development of wind and wave energy tech- nologies, there is a critical need for the understanding and mod- eling of ocean wind-waves, the lower part of marine atmospheric boundary layer at various sea states, and wind load and wave load on offshore structures. A lot of efforts have been devoted to explore the physics in the marine atmospheric boundary layer and ocean bound- ary layer [2–4], but the complex air–sea interaction problem is still far from being solved. Complex sea condition makes the field measurement challenging and expensive. Most of the exist- ing numerical simulations focus either on large-scale flow or on local-scale flow–structure interaction with simple boundary con- ditions to approximate wind and wave environment. Simulation of the interaction among wind, wave, and structure with realistic environment input is challenging because of the scale difference. In this paper, we introduce a multi-scale modeling approach developed for the simulation of wind and wave coupling dy- namics and the simulation of wind and wave past a surface- piercing object. Preliminary results of large-scale wind over broadband waves and local-scale wind–wave–structure interac- tion are given, which show the wave effect on the atmospheric boundary layer and the wind load on the structure. 1 Copyright c  2010 by ASME