Flow Structure in an Asymmetric Compound Channel Flow

Abstract

During flood, movement of water occurs from main river stream to its both adjacent flood plains and vice versa. If the river has only one flood plain either side of it, then it is called as asymmetric compound channel. The difference in hydraulic resistances between the main channel and flood plain subsections causes the exchange of momentum between them. In recent centuries, a great deal of experimental investigations has been carried out in order to understand the complex turbulent flow structure in compound channel flow. The article reports the turbulence measurements undertaken in an asymmetric compound channel flow in the hydraulics laboratory, NIT, Rourkela. This experimental facility is designed in such a way that it characterizes a model of a river system with roughened floodplains. The principal focus in this study is on the nonlinear nature of flow structures in the shear layer region between the main channel and flood plain. The variation of secondary flow in lateral direction and influence of relative flow depths on flow structure were also investigated. The interaction phenomenon at junction between two subsections has been explored with respect to relative depth. The distribution of Reynolds stresses and friction factor across the cross channel distance of the compound channel have been studied and discussed widely. Different models for precise quantification of friction factors in subsections have been evaluated. The work will be of interest to hydraulics engineers associated with compound open channel flow in particular.