Abstract: Classical fluvial models usually describe suspended sediment-laden flows by directly borrowing the Reynolds equations from the fluid dynamics that are limited to single-phase flows and adding an advection-diffusion equation to calculate suspended load transport. Such models lack the capability of modeling the complicated mechanisms of interphase interaction and particle collisions, thereby suffering from too large prediction errors in the case of large particle sizes or high concentration. A two-phase mixture model is adopted in this study to investigate sediment-laden flows, consider solid-liquid flows as an integrity, and simulate interphase interactions and particle collisions. This new model takes a form very similar to the classical fluvial model, and hence it is easy to insert it in an existing code and apply to practical cases. This paper first summarizes its basic equations, and then recasts them in the form of the SCHISM governing equations for 3D hydrodynamic modeling. Finally, we apply our two-phase mixture model to simulations of fully-developed steady uniform open channel flows, trench observations, and a 2012 real flood event in the Huayuankou-Aishan reach of the Yellow.

Key words: two-phase mixture model, suspended load, three-dimensional, numerical modeling of sediment-laden flows, Yellow River