Abstract

Oil spills are a serious environmental problem. To better support risk assessment and pollution control for oil spills, a good understanding of oil transport in the environment is required. This information is essential for managing response priorities and preparing contingency and mitigating measures. This study focused on the numerical simulation of the nearshore oil behaviors based on computational fluid dynamics. Based on the Reynolds-averaged Navier-Stokes momentum equations for an incompressible viscous fluid and volume of fluid (VOF) method, a 3D numerical model of three-phase transient flow was developed.
It was found that the wave number, averaged flow velocity, and oil properties would affect the oil spread extent and the oil volume fraction for open water. The higher the averaged flow velocity and wave number, the lower the oil concentration, and the faster the oil's horizontal movement. The spilled oil may move to contact the seafloor by increasing the averaged flow velocity at the inlet boundary. By increasing the wave number, the oil would stay near the water surface. In nearshore, where the wave is the main seawater motion, the oil containment boom should be set preferentially to the direction of wave transmission for oil cleaning. It was also shown that by doubling the wave number and increasing the averaged flow velocity (ten times) simultaneously, the maximum oil volume fraction would be reduced by around 32%. Finally, it was found that water temperature had no significant impact on oil migration, and the impact of evaporation can be further considered in the future simulation.
In addition, this study showed that the presence of ice would make the spreading of spilled oil slower in horizontal direction because the ice can build natural barriers to oil movement. The higher the ice concentration, the slower spilled oil migrates in all directions, and the maximum oil volume fraction will vary by increasing the ice coverage on the water surface area. The wave frequency, the averaged flow velocity, and oil properties would affect the oil spread extent and the oil volume fraction. The dumping effect of the wave due to the presence of ice also makes the impact of this factor less critical than those in the open water.