Lateral flow through the sharp crested side rectangular weirs in open channels

Abstract

A side rectangular weir is a flow diversion structure provided in the side wall of a channel to divert water from main channel to a branch channel. They are widely used in hydraulics, environmental and irrigation engineering for controlling and directing flow of water in irrigation–drainage systems, waste water channels, drainage canal systems, diverting excess water into relief channels for flood-protection works, and as storm overflows from urban sewage systems. The present study is aimed at to compile the past observations on coefficient of discharge for side rectangular sharp crested weir, supplement them with new experimental results and reanalysing resulting data bases with a view towards seeing if better prediction are possible. Therefore, a new model for determination of coefficient of discharge of side rectangular sharp crested weir is developed. It is observed that approach Froude number is an important parameter for coefficient of discharge. The ratio of the crest height of side weir to length of the side weir, ratio of width of the main cannel to length of side weir and ratio of the upstream depth in the channel to length of side weir also affect the coefficient of discharge. The performance of the present model is based on the coefficient of correlation of the linear regression line between predicted values from the present model and desired output (R), mean absolute percentage error (MAPE), average percentage error (APE), root means square error (RMSE) etc. The qualitative performance of the present predictor indicates that it has highest R (0.865) and lowest MAPE (4.8936), RMSE (0.0337), APE (−0.346) as compared to other existing predictors. Flow profile and flow pattern are also observed in the vicinity of side weir in the main channel.