Vertical 2D Nonhydrostatic Model Using Mode Splitting for Dam-Break Flows

Abstract

A vertical two-dimensional (2D) nonhydrostatic numerical model for dam-break flows is proposed. This model combines a depth-averaged shallow-water equations (SWEs) model and a nonhydrostatic core using mode splitting. The nonhydrostatic core is solved under the free surface provided by the SWE model, in which tracking the complex and discontinuous free surface of dam-break flows in vertical spaces is avoided. In a test of an ideal dam-break flow, the new model was revealed able to capture the discontinuous free surface of dam-break flows and produce reasonable simulation results for velocity and nonhydrostatic pressure. The proposed model was further tested using an experiment of dam-break flow over dry bed with a trapezoidal step. The new model with the first-order Riemann solver produces a discontinuous reflected wavefront in the simulated free-surface profiles. The simulated free-surface profiles are improved by the new model with the second-order Riemann solver, and further improvements by using the volume-of-fluid (VOF) three-dimensional (3D) model are slight.