Supercritical junction flow in sewer manholes

The hydraulics of supercritical junction flow in a 45° junction manhole as applied in sewer systems are explored. Based on an experimental approach and previously collected evidence on supercritical flow in wastewater hydraulics, the main hydraulic features of this standard structure, with the manhole extension added, are determined. First, the governing wave system including waves A through D is described. Then, the various flow types are presented in a diagram relating to seven regimes. Further, the heights of waves B and C, as also the swell at the manhole end are specified, and the discharge capacities for flows in either one branch, or both branches are given. Finally, it is outlined that under otherwise equal conditions, the capacity of junction manholes is at least 20% larger than in the bend manhole. The present indications allow a direct application