  We develop a numerical method for simulating coupled interactions of complex
floating structures with large-scale ocean waves and atmospheric turbulence. We
employ an efficient large-scale model to develop offshore wind and wave
environmental conditions, which are then incorporated into a high resolution
two-phase flow solver with fluid-structure interaction (FSI). The large-scale
wind-wave interaction model is based on the two-fluid dynamically-coupled
approach of Yang and Shen (2011), which employs a high-order spectral method
for simulating the water motion and a viscous solver with undulatory boundaries
for the air motion. The two-phase flow FSI solver, developed by Calderer, Kang,
and Sotiropoulos (2014), is based on the level set method and is capable of
simulating the coupled dynamic interaction of arbitrarily complex bodies with
airflow and waves. The large-scale wave field solver is coupled with the
near-field FSI solver by feeding into the latter waves via the pressure-forcing
method of Guo and Shen (2009), which has been extended herein for the level set
method. We validate the model for both simple wave trains and three-dimensional
directional waves and compare the results with experimental and theoretical
solutions. Finally, we demonstrate the capabilities of the new computational
framework by carrying out large-eddy simulation of a floating offshore wind
turbine interacting with realistic ocean wind and waves.
