A numerical study of the complex flow structure in a compound meandering channel

In this study, we report large eddy simulations of turbulent flow in a periodic compound meandering channel for three different depth conditions: one in-bank and two overbank conditions. The flow configuration corresponds to the experiments of Shiono and Muto (1998). The predicted mean streamwise velocities, mean secondary motions, velocity fluctuations, turbulent kinetic energy as well as mean flood flow angle to meandering channel are in good agreement with the experimental measurements. We have analyzed the flow structure as a function of the inundation level, with particular emphasis on the development of the secondary motions due to the interaction between the main channel and the floodplain flow. Bed shear stresses have been also estimated in the simulations. Floodplain flow has a significant impact on the flow structure leading to significantly different bed shear stress patterns within the main meandering channel. The implications of these results for natural compound meandering channels are also discussed

Numerical Simulation of the Hydrodynamics and Turbulent Mixing Process in a Drinking Water Storage Tank

Jet-mixing and residence time in a rectangular water storage tank with a constant water level are investigated using the tools of Computational Fluid Dynamics (CFD). A set of Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations using a realisable k-ε model for different inlet configurations has been used. Numerical simulations were validated by means of experimental measurements. A saline inflow was simulated and the computed salinity in the outflow was compared with the measured values, with the aim of improving the tank performance based only on simple modifications of the inlet position and inflow rate. The results show that the URANS technique is able to adequately capture the experimental dilution curve measured at the outlet of the tank. The residence time is mainly influenced by advective transport. Modifications of the horizontal angle and Reynolds number of the inflow jet produce changes in the mixing characteristics when different performance indexes are compared