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Water 2017, 9(10), 752; doi:10.3390/w9100752

Energy Dissipation in Circular Drop Manholes under Different Outflow Conditions

Nanjing Hydraulic Research Institute, Nanjing 210029, China
College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China
State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing 210029, China
Author to whom correspondence should be addressed.
Received: 3 September 2017 / Revised: 21 September 2017 / Accepted: 26 September 2017 / Published: 30 September 2017
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Circular drop manholes have been an important device for energy dissipation and reduction of flow velocities in urban drainage networks. The energy dissipation in a drop manhole depends on the manhole flow patterns, the outflow regimes in the exit pipe and the downstream operation conditions, and is closely related to the hydraulic and geometric parameters of the manhole. In the present work, the energy dissipation of a drop manhole with three drop heights was experimentally investigated under free outflow conditions and constrained outflow conditions. The results demonstrate that the local head loss coefficient is solely related to the dimensionless drop parameter for free surface outflow without a downstream backwater effect, whereas it depends on the dimensionless submerge parameter for constrained outflow. Moreover, it is concluded that the energy dissipation is largely promoted when outlet choking occurs. View Full-Text
Keywords: drop manhole; energy dissipation; free outflow conditions; constrained outflow conditions; outlet choking drop manhole; energy dissipation; free outflow conditions; constrained outflow conditions; outlet choking

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Zheng, F.; Li, Y.; Zhao, J.; An, J. Energy Dissipation in Circular Drop Manholes under Different Outflow Conditions. Water 2017, 9, 752.

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