Discharge coefficient for compound sharp crested side weirs in subcritical flow conditions

SummarySide weirs are one of the most common diversion structures used for flow control, irrigation, drainage networks, and waste-water channels. Side weirs are generally rectangular sharp crested in form and hence, have some limitations in precise flow measurement. For accurate flow measurement and management in wide range of discharges, use of compound side weirs are suggested in this study. Experiments have been carried out in a rectangular compound side weir with variable heights and widths. It was determined that discharge coefficient of a compound side weir is a function of upstream Froude number (Fr1), ratio of weighted crest height of weir to upstream water depth w¯/y1 and ratio of weir length to upstream water depth (L/y1). Based on the experimental data and regression modeling, a dimensionless equation has been developed for prediction of the discharge coefficient and an equation has been proposed for estimation of flow discharge in compound rectangular sharp crested side weirs. Through comparison of results of these equations and experimental data, good agreement was achieved. The mean and maximum relative errors of the discharge equation were −2.3% and 10.7%, respectively.

► Experiments have been carried out in a rectangular compound side weir.
► Based on the experimental data a dimensionless equation has been developed for cm.
► Good agreement achieved with our equation.
► The mean and max relative errors of these equations were −2.3% and 10.7%, respectively.