Energy Loss in Two Stage Meandering and Straight Compound Channels

Abstract

Suggested values for Manning's n are found tabulated in Chow (1959), Henderson (1966), and Streeter (1971). Roughness characteristics of natural channels are given by Barnes (1967). During uniform flow in open channels the resistance to the flow is dependant on a number of flow and channel parameters. The usual practice in one dimensional analysis is to select a value of n depending on the channel surface roughness and take it as uniform for the entire surface for all depths of flow. The influences of all the parameters are assumed to be lumped into a single value of n. Patra (1999), Patra and Kar (2000), and Pang (1998) have shown that Manning’s coefficient n not only denotes the roughness characteristics of a channel but also the energy loss in the flow. The larger the value of n, the higher is the loss of energy within the flow. Although much research has been done on Manning's n, for straight channels, very little has been done concerning the roughness values for simple meandering channels and also for meandering channels with floodplains. An investigation concerning the loss of energy of flows with depths ranging from in bank to the over bank flow, spreading the water to floodplains for meandering and straight compound channels are presented. The loss of energy in terms of Manning’s n, Chezy’s C, and Darcy-Weisbatch coefficient f are evaluated.