An Experimental Study for Estimation of Head Loss Coefficients at Surcharged Circular Manhole

Abstract

Urban sewer systems are designed to operate in open-channel flow regime and energy loss at circular manholes are usually not significant. However, the energy loss at manholes, often exceeding the friction loss of pipes under surcharge flow, is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze the head loss associated with manholes, especially in surcharge flow. Hydraulic experimental apparatus which can be changed the invert type(CASE A, B, C) and step height(CASEⅠ,Ⅱ,Ⅲ) was installed for this study. The range of the experimental discharges were from 1.0ℓ/sec to 5.6ℓ/sec. As the manhole diameter ratio(Dm/Din) increases, head loss coefficient increases due to strong horizontal swirl motion. Head loss coefficient was maximum because of strong oscillation of water surface when the range of manhole depth ratios(hm/Din) were from 1.0 to 1.5. The average head loss coefficients for CASE A, B, and C were 0.45, 0.37, and 0.30, respectively. Accordingly, U-invert is most effective for energy loss reduction at circular manhole.This head loss coefficients could be available to design the urban sewer system with surcharge flow.

An experimental study for estimation of head loss coefficients at surcharged four-way combining manholes

“…측면에서의 유량이 유입되지 않는 중간맨홀에서의 손실계 수 값을 검증하기 위하여Kim et al (2008a)의 중간맨홀 손실 계수 값과 본 연구의 측면유량비가 0.0인 실험조건의 손실계 수 값을 Fig. 14에 나타내었다.…”