Numerical Simulation of Confluence Flow in Open Channel with Dynamic Meshes Techniques

Abstract

Due to the interaction between branch flow and main stream at confluence zone in open channel, the water level of free surface often varies dramatically. In three dimensional simulations of confluence flow, multi-phase models are usually adopted in treating the free-surface boundary, for example, the Volume of Fluid model. The major dilemma for adopting multi-phase modes is that the method consumes more time and computation resources. In this study, the new mesh technique, the dynamic meshes, is adopted to track the position of free surface. The simulation results show that simulation adopting dynamic meshes converges rapidly and is in good agreement with the experimental data. In addition, simulations and comparisons of different turbulence models coupled with dynamic meshes, rigid lid, or the Volume of Fluid method are carried out to investigate the impact by tracing the free-surface boundary. The simulated position of free surface, velocity distribution, and vector field are all compared to the data collected in the flume test. The results of numerical simulations of confluence flow using the dynamic meshes present much better accuracy than those of Volume of Fluid or rigid-lid method, although they take the same turbulence model.