Simulation of channel confluence and bifurcation using the CCHE2D model

Abstract

The CCHE2D model, a depth-averaged, two-dimensional, unsteady-flow model, developed at the National Center for Computational Hydroscience and Engineering, has been verified for channel confluence and bifurcation applications. The computational efficiency for natural-river applications was the governing factor in the selection of the mixing-length model for turbulence closure. In the absence of field data, flume data for channel bifurcation and confluence collected in the laboratory were used to verify the simulated results. The simulated depth-averaged velocity and water surface profiles in the main and branch channels of a bifurcating channel compare well with the experimental data. In addition, the ratio of the discharge in the branch channel to the upstream discharge in the main channel, which is the most commonly sought value in the case of bifurcation, is in good agreement with the experimental data. The width and length of the recirculation zone in the branch channel are satisfactorily predicted by the model. The simulation results for the water surface profile near a channel confluence agree well with the measured data.