On the Validity of Energy and Momentum Approaches for Analysis of Gradually Varied Flow in Compound Channels

Document Type : Research Article



Energy and momentum approaches can lead to different results in analysis of flow through compound channels. This study is an attempt to shed more light on the validity of these approaches for analysis of gradually-varied flow in compound channels. At first the energy and momentum equations and a generalized form of steady gradually-varied governing equation are introduced. This G.E. provides a framework to highlight the differences between the two approaches using some numerical examples. Then, experimental data available in the literature and those collected in this study are used to compare different numerical water surface profiles with laboratory measurements. This study indicates that the momentum principle can perform better for water surface profile computation in compound channels, at least for the investigated experimental data. Error analysis also supports this conclusion. Two dimensional Shiono and Knight method for velocity distribution is employed to study more on the subject. In addition, two dimensional analyses introduces a procedure by which one can decide on the superiority of one approach over the other, based on geometrical and hydraulic characteristics of a compound channel, with no need for experimental work.