A novel, state of-art, numerical model accounting for the main physical processes governing oil dispersion at sea is here formulated and discussed. The underground hydrodynamics is resolved using LES-COAST, a high definition numerical model suited for coastal or harbour areas. Oil dispersion is modelled considering the main physical features of the process. After spilling, the oil may form the so-called tars or it may spread over the sea surface as thin film, depending on the oil pour point with respect to the ambient temperature. We adopt two different approaches for the two different conditions respectively. In the former, oil tars are modelled as Lagrangian particles of characteristic diameter and density. In the latter the Nihoul's model (Nihoul, 1984) is considered, which accounts for the main forces acting on the oil film, namely gravity, sea current and wind stresses. In practical short-term studies (simulation of oil dispersion over few hours) forces as surface tension and the inertia can be neglected. Also, the relevant short-term weathering processes (mainly emulsification and evaporation) occurring in coastal and harbour regions, are taken into account through established literature models. We validate the model on standard test cases and we apply it to a real case scenario in the Barcelona Bay.
