Numerical study of underwater oil spill diffusion in complex hydrodynamic environments

Waves and currents are key dynamic factors that influence the diffusion of underwater oil spills. To study the behavior of such spills under complex hydrodynamic conditions, an oil spill diffusion numerical model was established and physically verified by model test data. The drift and diffusion of crude oil from seabed to surface under current, wave, and wave–current coupling conditions were analyzed. The results reveal that under the wave–current coupling condition, the oil spill diffusion exhibits the movement characteristics of oil particles influenced by both currents and waves. The oil particles oscillate with water particles while simultaneously diffusing in the direction of the water flow. The rising speed of oil droplets is fastest in still water but slows significantly under the influence of waves and currents. The shape of the oil slick at the leakage point is related to the hydrodynamic conditions. The oil slick diffuses vertically upwards in still water. While in current and wave conditions, it takes on “C” and “Z” shapes, respectively. Under the influence of the wave–current coupling, the slick spreads in an “S” shape. Moreover, the faster the oil spill, the more significant the entrainment effect, leading to an intensified lateral and vertical diffusion of the oil particles. These research findings offer valuable insights for tracking underwater oil spill trajectories during accidents.