Boundary Shear Stress Distribution in Compound Open Channel Flow

Abstract

Reliable prediction of boundary shear distribution in open channel flow is crucial in many critical engineering problems such as channel design, calculation of energy losses, and sedimentation. During floods, part of the discharge of a river is carried by the simple main channel and the rest are carried by the floodplains located to its sides. For such compound channels, the flow structure becomes complicated due to the transfer of momentum between the deep main channel and the adjoining floodplains which magnificently affects the shear stress distribution in floodplain and main channel sub sections. Knowledge of momentum transfer across the assumed interfaces starting from the junction between main channel and flood plain can be acquired from the distribution of boundary shear in the sub sections. An investigation concerning the distribution of shear stress in the main channel and floodplain of meandering and straight compound channels are presented. Based on the experimental results of boundary shear, this paper predicts the distribution of boundary shear carried by main channel and floodplain sub-sections of meandering and straight compound channels. Five dimensionless parameters are used to form equations representing the total shear force percentage carried by floodplains. A set of smooth and rough sections is studied with aspect ratio varying from 2 to 5. The model is also validated using the data of other investigators.