A fully Eulerian two-layer model for the simulation of oil spills spreading over coastal flows.

This article presents the development and numerical validation of a fully Eulerian two-dimensional (2D) two-layer shallow water model designed to simulate coastal oil spills, treating the oil as a thin upper layer flowing over a thicker water layer. The model incorporates key physical processes including inter-layer friction, wind stress, temperature transport, and evaporation, with the latter modeled locally based on oil temperature and age to capture mass loss accurately. Numerical schemes employing a finite volume upwind method with an augmented Roe solver address challenges such as wet-dry boundaries and friction source term discretization, comparing explicit and semi-implicit approaches for interface friction; the semi-implicit method shows greater robustness in scenarios with strong friction and wet-dry fronts. Validation against steady-state reference solutions and test cases involving evaporation and wind effects demonstrate the model's stability and capacity to simulate oil spreading over water and land, highlighting its potential for improved prediction of oil spill dynamics in coastal environments.