SHORT SEWER SIDEWEIR

Sideweirs for combined sewers in converging U-shaped channels are anal yzed. The results are applicable for storm sewers, Based on extended m odel observations and a hydraulic approach, the characteristics of sid eweir flow are determined. These include the surface profile, the disc harge distribution, the end depth ratio, and the energy losses due to lateral outflow. All results are presented in terms of approach condit ions, and it is demonstrated that the approach Froude number is the si gnificant flow parameter. For sideweirs with a relatively small weir h eight, the flow may become unstable and set up a surging phenomenon in the approach pipe. After careful experimentation, the instability was effectively removed with a so-called end plate. This device is positi oned at the end wall of the sideweir and is able to stabilize the vort icity interface between the bottom and the surface vortices. The end p late can simply be added to existing designs.