Positivity-preserving Well-balanced PAMPA Schemes with Global Flux quadrature for One-dimensional Shallow Water Models

TL;DR

This paper introduces a positivity-preserving, well-balanced PAMPA scheme with global flux quadrature for one-dimensional shallow water models, effectively preserving equilibria, ensuring positivity, and reducing oscillations near shocks.

Contribution

The paper develops a novel high-order PAMPA method with global flux quadrature that preserves equilibria and positivity in shallow water simulations, improving robustness and accuracy.

Findings

Successfully preserves a wide range of smooth equilibria.

Exactly maintains still water states through quadrature strategy.

Effectively eliminates spurious oscillations near shocks.

Abstract

We present a novel hydrostatic and non-hydrostatic equilibria preserving Point-Average-Moment PolynomiAl-interpreted (PAMPA) method for solving the one-dimensional hyperbolic balance laws, with applications to the shallow water models including the Saint--Venant system with the Manning friction term and rotating shallow water equations. The idea is based on a global flux quadrature formulation, in which the discretization of the source terms is obtained from the derivative of and additional flux function computed via high order quadrature of the source term. The reformulated system is quasi-conservative with global integral terms computed using Gauss--Lobatto quadrature nodes. The resulting method is capable of preserving a large family of smooth moving equilibria: supercritical and subcritical flows, in a super-convergent manner. We also show that, by an appropriate quadrature strategy for the source, we can exactly preserve the still water states. Moreover, to guarantee the positivity of water depth and eliminate the spurious oscillations near shocks, we blend the high-order PAMPA schemes with the first order local Lax--Friedrichs schemes using the method developed in [R. Abgrall, M. Jiao, Y. Liu, and K. Wu, arXiv preprint arXiv:2410.14292, 2024]. The first-order schemes are designed to preserve the still water equilibria and positivity of water height, as well as to deal with wet-dry fronts. Extensive numerical experiments are tested to validate the advantages and robustness of the proposed scheme.