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
Comparison of Flow Hydraulics in Different Manhole Types
Manhole is a very common and important element in an urban drainage system. The complex flow pattern in a manhole may include the effects of retardation, acceleration and rotation, creating energy losses in the network. Different types of manhole are seen in various countries due to different design criteria. Three different manhole types were modelled in this study to analyze the hydraulic properties of them. Type C has a guided channel at the bottom, while Type A and Type B do not. Type A also has a seal underneath the inflow-outflow pipe; but in Type B, the invert level of the inflow pipe is at the same level of the manhole floor. Analysis were done numerically using volume of fluid (VOF) model with open source CFD modelling tools OpenFOAM®. The numerical results were verified by mesh independency test using Richardson extrapolation method. Results showed that the flow structures and head loss coefficients vary in different manholes. All three manholes showed higher head loss coefficients at low surcharge conditions. Out of the three manhole types, Type A and B showed higher head loss coefficient than Type C. The threshold surcharge levels at Type A and B were found approximately 20% of the manhole diameter. However, for Type C, the surcharge threshold level was found higher. The study may provide essential information to calculate the head losses of these types of manhole in an urban drainage network model.
Energy Losses in a Surcharged Three Pipe Stormwater Pit
With increasing urban development the provision of efficient stormwater drainage systems is becoming increasingly important for social and economic reasons. The stomwater pit, or junction box, is often a major component of a typical stormwater drainage system and it is the understanding of the performance of this hydraulic structure which warrants attention. This paper details the results of an experimental physical model study which was completed to investigate the energy losses encountered at a typical junction box. These measured losses are compared with those predicted by a recently developed set of semi-empirical equations and suggest that, generally, comparisons are good. However, at certain important flow conditions there are differences between the experimental and predicted values. Details of tests are also presented which show that significant reductions in head losses are possible if small deflectors, or baffles, are incorporated in the junction box geometry.