3-D Modeling of unsteady free-surface flow in open channel

Abstract

We present the hydrodynamic part of a three-dimensional model for pollutant dispersion in turbulent free-surface flow in open channels. It does not require any strong assumption such as hydrostatic pressure and is able to simulate an unsteady free-surface flow as flood waves or discharge over a weir. Our main objective was to model the moving free-surface and the boundary conditions under two constraints. The first constraint was to keep a point of view as close as possible to that of the 1-D modeling generally used in river engineering, especially relative to the upstream and downstream boundary conditions. The second one was that our model had to be sufficiently flexible to be implemented in a general computational fluid dynamics package. After describing our model, we present some numerical tests and comparisons with 1-D simulations from a hydrodynamic point of view.