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

Abstract

Energy loss at manholes under surcharged conditions is as important as the friction loss in pipes in the design of storm sewer networks and in flood analysis. Some researchers have already proposed the formula to calculate the energy loss at three-way manholes 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 manholes is needed. In this paper, the effect of diameter ratios between inflow pipes and an outflow pipe, the ratios of flow rates between inflow pipes, connected angles among those pipes and drop gaps between inflow pipes and outflow pipe on the energy loss at three-way circular drop manholes were investigated. Based on the experimental results, a new formula that considers all structural elements and the ratios of flow rates between inflow pipes was proposed for the energy loss coefficients at the manholes. In the proposed formula, calculated energy loss coefficients reproduce measured values more exactly than existing formulas do.

Physical modelling of energy losses at surcharged three-way junction manholes in drainage system

“…Results in Figure 11 show that the tendencies of the total head loss coefficients were in a relatively good agreement for both empirical formulae. It was observed that the formula proposed by ARAO et al (2016) performs better than the formula of UDDM for K and K 2 . However, the formula of UDDM has better accuracy than ARAO et al (2016) in terms of calculating K 1 .…”

“…It was observed that the formula proposed by ARAO et al (2016) performs better than the formula of UDDM for K and K 2 . However, the formula of UDDM has better accuracy than ARAO et al (2016) in terms of calculating K 1 .…”

“…In previous works, several types of empirical formulae of head loss coefficients have been proposed to reproduce energy loss at junction manholes (Lindvall 1984;Marsalek 1984;FHWA 2009;Arao et al 2016). In this work, two empirical formulae were examined for the three-way junction manhole.…”

“…The expression of the head loss coefficients provides an important tool for the design of urban drainage system and flood modelling. To validate the existing empirical head loss coefficient formulae, the head loss coefficients of a surcharged three-way junction manhole obtained from experiments were used to examine two empirical formulae by FHWA (2009) and Arao et al (2016). Results in Figure 11 show that the tendencies of the total head loss coefficients were in a relatively good agreement for both empirical formulae.…”

“…One representative head loss coefficient formula guideline was proposed in the urban drainage design manual (UDDM) by the federal highway administration (FHWA 2009). Following this guideline, an alternative formula was proposed for three-way manholes under surcharged conditions by considering more variables of structural elements for the pipes and the manholes (Arao et al 2016). In the proposed formula, the effect of diameter ratios between inflow and outflow pipes, flow rate ratios between inflow pipes, connected angle between inflow pipes, and drop gaps between inflow pipes and outflow pipe were included.…”