Characteristics of Water Surface Profile over Rectangular Side Weir for Supercritical Flows

Abstract

The supercritical flow over a side weir is a type of spatially varied flow with decreasing discharge. Most studies of side weir flows are limited to the estimation of the discharge coefficients, and less attention has been paid to the characteristics of the water surface profile. This paper investigated the characteristics of the supercritical water surface profile along the side weir. Based on the characteristics of the general flow profile, a dimensionless quadratic function is proposed for the variations of the flow depth along the main channel which depends on the geometric and hydraulic parameters of the side weir. Using an experimental study, the equation of water surface profiles was derived. Following the determination of the flow depth and investigation of the velocity variations along the side weir, variations of the discharge along the main channel were investigated, and a new equation of the main-channel discharge along the side weir is proposed. Using the proposed equations, the flow depth and discharge in the main channel are estimated at any section of the side weir. Comparison of the predictions of the proposed equations with different sets of existing experimental data showed that these equations can predict the water surface profile and the flow discharge with good accuracy, and are of design relevance.