HEAD LOSSES IN STORM-SEWER MANHOLES - SUBMERGED JET THEORY

The design of storm sewers especially suffers from lack of knowledge of the head losses in manholes. A submerged jet theory for the flow in manholes with straight throughflow has been outlined. The entrance head loss has been related to the kinetic energy transformation associated with the entrainment/detrainment in the jet. The exit head loss is calculated as a Carnot-loss in connection with the vena contracta in the exit pipe. The jet theory and the experiments have shown that the only governing parameter for a specific manhole shape is the ratio of manhole diameter to pipe diameter. The theory has been compared to laboratory experiments. The head loss in storm sewer manholes is shown to be considerably smaller than the values calculated by traditional formulas. © ASCE.