Author(s): Raphael Paulus; Sebastien Erpicum; Benjamin J. Dewals; Michel Pirotton; Pierre Archambeau
Keywords: No Keywords
Abstract: In surface runoff modeling, the Richards equation (which depicts groundwater flows) is required for the determination of water transfers through the soil surface. Within our unit, researches are carried out in order to set up a model that would give reliable and physically-based information about these exchanges at a large time scale, with minimal computing resources. The subsoil domain is conceptualized into sub-layers of fixed depths, in order to restrict the calculation to what predetermines the surface runoff model for large scale events (a detailed 3-dimensional representation of the entire domain being out of the scope and costly). A first layer, characterized by essentially vertical unsaturated flow, is modeled with a coupled 1Dvertical/2Dhorizontal model based on the Richards equation. A second layer, characterized by mainly 3-dimensional saturated flow, is modeled by a 3D model solving the Darcy equation and enabling the presence of a free surface. This paper focuses on the development relative to the handling of the interface between these two layers, and more precisely the relative position of the free surface of the saturated media. The numerical resolution of the equations is not discussed, and the original aspect lies in the properties of the top-cells of the saturated layer, i. e. the interface cells. The proposed solution consists in a suitable manipulation of these cells so that they record the relative position of the free-surface and that the mass transfers between the subdomains are correctly computed. The numerical exploitation is for now limited to 1-dimensional test cases.