Abstract

We consider the Saint-Venant system for shallow water flows with nonflat bottom. In past years, efficient well-balanced methods have been proposed in order to well resolve solutions close to steady states at rest. Here we describe a strategy based on a local subsonic steady state reconstruction that allows one to derive a subsonic-well-balanced scheme, preserving exactly all the subsonic steady states. It generalizes the now well-known hydrostatic solver, and like the latter it preserves the nonnegativity of the water height and satisfies a semidiscrete entropy inequality. An application to the Euler-Poisson system is proposed.

Highlights

  • We consider the classical Saint-Venant system for shallow water flows with topography

  • It is a hyperbolic system of conservation laws that approximately describes various geophysical flows, such as rivers, coastal areas, oceans when completed with a Coriolis term, and granular flows when completed with friction

  • The Saint Venant system describes the evolution of the water height ρ(t, x) and the velocity u(t, x) in the horizontal direction, of a thin layer of water flowing over a slowly varying topography

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Summary

Introduction

We consider the classical Saint-Venant system for shallow water flows with topography. One has to use the so called well-balanced schemes, that properly balance the fluxes and the source at the level of each interface. To the well-balanced property, the difficulty is to haves schemes that satisfy very natural properties such as conservativity of the water height ρ, nonnegativity of ρ, the ability to compute dry states ρ = 0 and transcritical flows when the Jacobian matrix F of the flux function becomes singular, and eventually to satisfy a discrete entropy inequality. Shallow water, subsonic reconstruction, subsonic steady states, well-balanced scheme, semi-discrete entropy inequality. Note that a solver proposed in [9] is able to maintain all the steady states, but it is not satisfying a discrete entropy inequality

Saint Venant system and well-balanced schemes
Well-balanced scheme with subsonic reconstruction
Application to the Euler-Poisson system
Numerical results
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