A new two-phase shallow water hydro-sedi-morphodynamic model with the HLLC solver for inter-grid numerical flux estimation

Abstract

<p>Given that fluvial flows carrying relatively coarse sediments involve strong interactions between the water and the sediment phases, two-phase shallow water hydro-sedi-morphodynamic models have been developed (Li et al. 2019, <em>Advances in Water Resources</em>, <em>129</em>(JUL.), 338-353; Lyu et al. 2021: EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4258). Here we report improvements over the model by Lyu et al. (2021), which lead to considerably improved numerical accuracies. Specifically, using finite volume method (FVM) to solve the governing equations on unstructured grids, the Harten-Lax-van Leer-Contact (HLLC) Riemann solver is proposed to estimate the inter-cell numerical flux for the flow phase and the sediment phases separately, in contrast to previous two-phase flow models using centered schemes. The improved numerical accuracy is demonstrated by numerically revisiting a series of experimental scenarios including refilling of a dredged trench, and a full dam-break flow in an abruptly widening channel.</p>