Determination of discharge coefficient of compound triangular- rectangular sharp-crested side weirs

Sharp crested side weirs are one of the most common hydraulic structures used for flow diversion and control in irrigation, drainage networks, and waste-water channels. Simple side weirs generally have some limitations in flow escape and measurement face with relatively heavy flows from the main channel. The use of combined side weir is one way to solve this problem. Few studies have conducted flow hydraulics in combined side weirs. For this reason, in this study, compound rectangular–triangular sharp crested side weirs were studied experimentally in subcritical flow conditions. Finally, using dimensional analysis, parameters affecting the discharge coefficient of a compound side weir are a function of the upstream Froude number, the ratio of weighted crest height of the weir to upstream water depth and the ratio of weir length to upstream water depth and a relationship for estimating the discharge coefficient was proposed. Comparison of results by using proposed equation with experimental results, shows high accuracy (RMSE=0.00131 and R^2=0.991) in estimation of diverted discharge through compound side weir.