Three-Dimensional Numerical Modeling of Dam-Break Flows with Sediment Transport over Movable Beds

Abstract

A three-dimensional (3D) numerical model has been developed to simulate dam-break flows with sediment transport over movable beds. The hydrodynamic model solves the 3D Reynolds-averaged Navier-Stokes equations using a finite-volume method on collocated hexahedral meshes. The volume-of-fluid (VOF) technique with the compressive interface capturing scheme for arbitrary meshes is used to track the water surface boundary. The sediment transport model solves the nonequilibrium transport equations of suspended load and bed load separately, and in turn calculates the resulting bed change. A moving mesh technique is adopted to track the time evolution of bed topography. The grid moving velocity and computational cell volume change due to the moving mesh are taken into consideration when the hydrodynamic and sediment transport equations are discretized. The developed model has been tested using several experimental dam-break flows over movable beds. The calculated temporal and spatial variations of water and bed surfaces are in generally good agreement with the measured data. The effects of 3D features of the flow on morphological changes are discussed by comparing the results of the present model with results calculated by one-dimensional (1D) and two-dimensional (2D) models documented in the literature. The comparisons reveal that the present 3D model improves the accuracy of calculated morphological changes at the initial stages of dam-break flow, near the wave front, and around in-stream structures.