Supercritical Flow in Circular‐Shaped Side Weir

Abstract

The flow features of a side weir in a prismatic circular‐shaped channel as used in sewage and irrigation systems are considered. The complex cross‐sectional channel geometry is simplified, and a generalized de Marchi equation is presented for the free‐surface profile. The general solution is further modified to obtain a similarity plot of normalized flow depth as a function of normalized location for arbitrary weir height. The solution for supercritical approach flow is compared to experimental data for one‐ and two‐sided lateral outflow. Although the agreement between theory and experiment is only fair, the normalized parameters yield all data on a single curve. Eq. (15) may be regarded as the generalized free‐surface profile, provided no hydraulic jump occurs. The hydraulic jump is studied with a modified momentum approach, and a simple relation comparable to that for rectangular channels is obtained. No indications on the length or the velocity distribution in jumps with spatially decreasing discharge can be made with the existing data, however.