Energy losses at three-way circular drop manholes under surcharged conditions

Abstract

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.

Formula on Energy Losses at Three-Way Circular Drop Manhole Under Surcharge Flow

“…The equations described in UDDM assume the pipe shape and manhole shape to be circular and include all structural variables except the drop gap between the inflow and outflow pipes in the variables of Equation (1). In the authors' research 12) , 13) for Equations (14)−(19), however, it was confirmed that there was a difference between the calculated results and the experimental results according to the combination of the pipe diameter and the flow rate ratio, and a problem remains on the application of the equations in UDDM (refer to Figs. 7 and 8).…”

“…The authors 13) have developed the formula for energy loss at the manhole in which the drop gap was considered between the straight-through pipe or the lateral pipe and the outflow pipe. However, only the horizontal connecting angle of the lateral pipe is changeable in this calculation formula.…”

Quantification of energy losses at a surcharging manhole

“…The lack of reliable data sets during lood events means direct calibration of energy losses in surcharging lows is diicult (Hunter et al 2008) and appropriate energy losses coeicients associated with these hydraulic conditions have not been fully identiied. A lack of understanding of head losses in drainage systems can lead to inaccurate modelling and lood hazard maps (Arao et al 2012) and other drainage infrastructure problems such as the blowout of manhole covers (Guo and Song 1991;Zhou, Hicks, and Steler 2002).…”

Utilizing Modern Experimentation Method to Quantify Jet-Breaker Dimension Effects on Drop Manhole Pool Height

“…In this equation, the left-hand side term is the dimensionless pool free-surface height, the first right-hand side dimensionless variable is a variant of the impact number, the second variable is inlet pipe filling ratio, and the third one is dimensionless drop height. All dimensionless variables are well-known in the drop manhole field of study [4,6,13,15], apart from the jet-breaker related variables, fourth to eighth terms, which are firstly introduced in this research. Equations 1 and 3 show, pool height which depended on 16 variables becomes a function of 14 dimensionless variables.…”