Abstract

Cleanup of oil spills, especially at the shoreline, is confronted with challenging problems of both technology and cost-effectiveness. Over the past decades, a new hypothesis has emerged, that the formation of Oil-Mineral Aggregates (OMAs) consisting of oil droplets and mineral fines, enhances the dispersion of oil in aquatic environments. Despite its documented role in cleaning oil spills along shorelines through reported experimental studies, the literature on the mathematical modeling of the formation and dispersion of OMAs has been limited. In the present study, the physical processes were investigated including oil slick breaking up under breaking wave, the formation of OMAs, and oil/OMAs vertical mixing. A modeling approach was developed for simulating the formation and vertical mixing of oil droplets and OMAs, namely Oil Droplet and OMAs Simulation (OMA-SIM). This method integrated modeling tools for addressing the oil vertical mixing model and density based OMAs formation model to examine the dispersion of oil droplets and OMAs. The OMA-SIM was validated using data obtained from mesoscale wave tank experiments. The concentration and size of oil droplets and OMAs generated under breaking wave condition were simulated and compared with experimental data. The main factors that affect oil droplets and OMAs formation and vertical mixing have been studied and concerned in the developed model. These factors include oil density and viscosity, oil/water interfacial tension, wave energy dispersion rate, dispersants, and environment temperature. The results of the case studies suggest that the OMA-SIM developed in this study provide effective methods for simulating and predicting the vertical dispersion of spilled oil. A computation system was then developed that couples the OMA-SIM with a user-friendly interface system, and the system was applied to real case studies based on field data. OMA-SIM results indicated that the energy dissipation rate of breaking waves is the predominant factor which affects the concentration and particle size of oil droplets and OMAs. The higher the breaking wave energy, the more oil was dispersed with time after the experimental oil spill. Oil viscosity has a significant influence on dispersed oil concentration. The mass of dispersed oil decreased with increasing oil viscosity. Increasing temperature to decrease oil viscosity and then to enhance the formation of OMAs resulted in a greater concentration of oil. The dispersants reduce oil/water interfacial tension and result in a decreased size of oil droplets and OMAs. The application of mineral fines facilitates the formation of OMAs.