FORMULA ON ENERGY LOSSES AT THREE-WAY CIRCULAR DROP MANHOLE UNDER SURCHARGE FLOW
1Member of JSCE, Professor, Dept. of Civil and Environmental Eng., National Institute of Technology, Matsue College (14-4 Nishi-ikuma, Matsue, Shimane 690-8518, Japan) E-mail: arao@matsue-ct.jp 2Member of JSCE, Electric Power Development Co., Ltd. (15-1 Ginza 6-chome, Chuo-ku, Tokyo 104-8165, Japan) E-mail: Shunsuke_Hiratsuka@jpower.co.jp 3Honorary Member of JSCE, Professor, Kyushu University (744 Motooka, Nish-ku, Fukuoka 819-0395, Japan) E-mail: kusuda@kyudai.jp
Energy losses at three-way circular drop manholes under surcharged conditions.
Energy loss at manholes is of importance in the design of storm sewer networks and in flood-analysis. Some researchers have already investigated the energy loss at three-way manholes under surcharged conditions. However, formulation to calculate the energy loss at manholes, including all variables of structural elements of the pipes and of the manhole has not yet been accomplished. Therefore, more study to formulate the energy loss at three-way drop manholes is needed. In this study, the ratio of the diameter between inflow pipes and an outflow pipe, the ratio of flow rates between those pipes, water depth in a manhole and the drop gaps between those pipes are considered and the energy loss at three-way circular drop manholes is examined. Finally, a modified formula, more accurate than that in the U.S. Federal Highway Administration's 2001 Urban Drainage Design Manual is proposed. The proposed formula takes the influence of the ratio of the diameter between inflow pipes and outflow pipe and drop gaps between those pipes into consideration. The calculated energy loss coefficients in both straight-through and lateral pipes successfully reproduce the measured values.
Head Losses at Sewer Junction Manholes
Head losses at sewer pipe junctions have been studied in a model. The junction geometry was varied by using manholes of different widths and cross-sections, and by using various arrangements inside the manholes. The pipe diameter and alinement upstream and downstream of the junction were identical. In all experiments, pipes were flowing under pressure, but a free water surface was maintained inside the junction manhole. Observed piezometric heads and flow velocities served to calculate the upstream and downstream energy grade lines and the junction head loss. The head loss was found to increase linearly with the increasing velocity head and the observed experimental relationship was therefore approximated by a regression line. The head loss coefficient was then determined as the slope of the regression line. Head loss coefficients are presented for nine cases studied.