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

Abstract

Energy loss at manholes under surcharge conditions is an important as friction loss in pipes in the design of storm sewer networks and in flood analysis. Some researchers have already proposed the formula to calculate energy loss at three way manhole under surcharged conditions. However, in most of these proposed formulas, all variables of structural elements for the pipes and the manholes have not been considered enough yet. Therefore, development of the formula to exactly calculate the energy loss at three way manhole is needed. In this paper, the effect of diameter ratios between inflow pipes and outflow pipe, the ratios of flow rates between inflow pipes, connected angles among those pipes and drop gaps between inflow pipe and outflow pipe on energy loss at three way circular drop manholes were investigated. Based on the experimental results, a new formula that consider all structural elements and the ratio of flow rates between inflow pipes was proposed for the energy loss coefficients at the manholes. In the proposed formula, calculated energy loss coefficients reproduced measured values more exactly than existing formulas do.