Abstract
Head loss in surcharged four-way junction manholes is a factor that increases damage due to urban inundation; thus, the flow characteristics of such manholes must be analyzed to reduce the head loss. In this study, a physical model was constructed; this model included a manhole and a connection pipe, fabricated on a 1/5 scale by applying sewer facility standards to perform a physical model investigation. Numerical simulations were performed using the Fluent model to derive efficient benching designs that can reduce head loss. Physical model investigations were performed by varying the ratio of the lateral influent flow rate to the effluent flow rate as well as by varying the effluent flow rate and benching designs. The result of physical model investigations showed that the installation of half rectangular benching reduced the head loss coefficients by 7% and 10% on average compared with square and circular manholes, respectively. The installation of full rectangular benching reduced the head loss coefficients by 28% and 17% on average compared with square and circular manholes, respectively. Thus, the benching proposed herein can be installed and used to improve the drainage capacity of urban stormwater conduit facilities.
Highlights
Localized heavy rainfall in urban areas commonly leads to damage due to inundation in lowlands, where the drainage rate sharply increases [1], as well as in areas with poor sewage systems or insufficient drainage capacity [2,3]
Depending on the joint shapes in the inflow pipe, outflow pipe, and manhole, manholes are divided into middle manhole and junction manholes
A physical model investigation was performed under the same conditions listed in Tables 1 and 2 to compare and analyze the head loss coefficient in four-way junction manholes without benching (Figure 4)
Summary
Localized heavy rainfall in urban areas commonly leads to damage due to inundation in lowlands, where the drainage rate sharply increases [1], as well as in areas with poor sewage systems or insufficient drainage capacity [2,3]. Rainwater in urban areas drains through stormwater conduit facilities in the drainage system; it is essential to increase the rainwater drainage capacity of drainage systems for preventing urban flooding [4,5,6]. Manholes, storm overflow diverging tanks, gutters (including sewage, stormwater, and catchment gutters), and connection pipes. Drop manholes are widely implemented in drainage networks for steep urban catchments, where the topography induces excessively high flow velocities [8]. Of particular relevance are 45◦ and 90◦ deflections [9]
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