Numerical Simulations of Oil Spills and Wind Turbine Flows for Applications in Offshore Environmental Sustainability

Environmental sustainability has currently become one of the biggest issues faced by the mankind. The high demand of fossil fuel has resulted in considerable offshore oil drilling activities, significantly increasing the possibility of offshore oil spill accident. Specifically, the 2010 Deepwater Horizon accident has shocked the world with its severe adverse impact on the ocean ecosystem and the human society around the Gulf of Mexico. On the other hand, the technological advancement of floating turbines has made offshore wind a feasible resource to help supply the high energy demand. This doctoral dissertation covers three research topics related to offshore environmental sustainability, including the dynamics of multiphase buoyant plumes related to subsea hydrocarbon blowout, the effects of surface oil plume on upper-ocean radiative transfer related to the adverse impact of offshore oil spill on the ocean ecosystem, and the fluid dynamics of offshore floating wind farm for energy harvesting. A number of high-fidelity numerical simulation models are developed and applied to tackle these challenging problems, including the large-eddy simulation model for the oceanic and atmospheric turbulent flows, the Eulerian large-eddy simulation model for particle plume dispersion in ocean environment, the high-order spectral method for ocean waves, the Monte Carlo photon transport model for ocean radiative transfer, and the actuator disk model for wind turbines. The results show that the inherent properties of oil droplets including their size and rising velocity, under the background of cross flow, will significantly affect their temporal-spatial distribution and the resulting photosynthesis within the ocean mixed layer. Besides, pitch motions will be induced on offshore wind turbines via their interaction with ocean surface wave, leading to modified wake flow statistics and power extraction rate compared with that on shore. Therefore, these findings can give guidance for fast-response strategy when oil spills happen and design of offshore wind turbines.