Study of Energy and Momentum Coefficients for Compound Transitions in an Open Channels

Abstract

A series of laboratory experiments was performed in order to investigate momentum and kinetic energy correction coefficients in compound transitions of rectangular channel. Also, In this study, the influence of several independent factors on the kinetic energy and momentum correction coefficients that are connected to the characteristics of the channels transitions is investigated. The Reynolds number varied between 2145.8 and 14388.14. Kinetic energy and momentum correction coefficients, α and β, were computed for different models by using two methods. The first one was based on the calculation of ε and the second method was based on dividing the cross section into slides and using the corresponding velocity for each slides. The results of the present study show that the second one was found to be more accurate than the first method. This method of slides can be used to derive the relationship between both energy and momentum coefficients versus ε values. The values of α and β averaged 1.237 and 1.10, respectively. The energy and momentum coefficients exhibit higher values in the transition zone than the corresponding ones in the upstream section. This is mainly due to turbulence effect. The values of (α-1β-1) ranges from 2.71 to 2.81, this range don't exceed 4% for different Reynolds number. The error of (α-1β-1) for different discharges is less than 5% which could be accepted.