FORMULA ON ENERGY LOSSES AT FOUR-WAY CIRCULAR MANHOLE UNDER SURCHARGE FLOW

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 Energy loss in a manhole as a junction of storm sewers or combined sewers is an important factor for more accurate calculation of inundation. The authors formulated energy loss coefficients in two-way and three-way circular drop manholes where one or two inflow pipes are connected to an outflow pipe. Since there are few studies on the four-way manhole where three inflow pipes are connected to an outflow pipe like one at an intersection, we conducted experiments on energy loss in a four-way circular manhole to which three inflow pipes and an outflow pipe with several types of inner diameter of the pipes and flow rate. We successfully obtained energy loss characteristics in the manhole through the experiments. Furthermore, we developed formulas for the energy loss coefficients on the manhole, considering structural elements and hydraulic factors on pipe and manhole. The results calculated with the formulae were in fair agreement with the measured values.