Discharge Coefficient of Rectangular Side Weirs

The characteristics of flow over side weirs are taken into account to determine the discharge coefficient for subcritical flow conditions under the assumption of constant‐specific energy. The main‐channel discharge, length of the weir crest, and sill height of the weir are treated as the controlled variables. The discharge coefficient Cd is found to depend on the upstream Froude number F1 and, contrary to earlier findings, also on the ratio of sill height to upstream flow depth s/y1. Multiple regression analysis is conducted to establish the relationship of Cd with both F1 and s/y1 taken together. The relationship is of linear form and provides an easy means of estimating Cd.