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Absence of a hydraulic threshold in small-diameter surcharged manholes
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Stovin, Virginia, Bennett, Paul and Guymer, I. (2013) Absence of a hydraulic threshold in small-diameter surcharged manholes. Journal of Hydraulic Engineering (Reston), Volume 139 (Number 9). pp. 984-994. doi:10.1061/(ASCE)HY.1943-7900.0000758 ISSN 0733-9429.
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Official URL: http://dx.doi.org/10.1061/(ASCE)HY.1943-7900.00007...
Abstract
Previous research into surcharged manholes has highlighted the existence of a threshold surcharge level that separates two distinctly-different hydraulic regimes. Sharp changes in manhole energy loss and solute transport characteristics occur when the surcharge depth passes through the threshold level. With respect to solute transport, two scale-independent cumulative residence time distributions (CRTDs) have been identified, corresponding to the below-threshold and above-threshold hydraulic regimes. However, previous studies focused on large diameter manholes, in which the manhole diameter () was at least 4.4times greater than the pipe diameter (). This paper utilizes a validated computational fluid dynamics (CFD) modeling approach to explore the hydraulic behavior and mixing processes in small-diameter surcharged manholes (). It is shown that the hydraulic threshold does not exist in the small diameter manholes; instead, the flow field is characterized by short-circuiting throughout the full range of surcharge depths. Data generated at low surcharge levels suggest that the mixing effects in the below-threshold region are not independent of surcharge level, as had previously been suggested. The absence of the threshold in small-diameter manholes is explained with reference to jet theory. Several previous studies that have characterized mixing and/or energy losses in surcharged manholes are revisited, allowing findings to be generalized across a broader range of manhole configurations, including effects attributable to benching and change in outlet angle.
Item Type: | Journal Article | ||||||||
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Divisions: | Faculty of Science, Engineering and Medicine > Engineering > Engineering | ||||||||
Journal or Publication Title: | Journal of Hydraulic Engineering (Reston) | ||||||||
Publisher: | American Society of Civil Engineers | ||||||||
ISSN: | 0733-9429 | ||||||||
Official Date: | 20 March 2013 | ||||||||
Dates: |
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Volume: | Volume 139 | ||||||||
Number: | Number 9 | ||||||||
Page Range: | pp. 984-994 | ||||||||
DOI: | 10.1061/(ASCE)HY.1943-7900.0000758 | ||||||||
Status: | Peer Reviewed | ||||||||
Publication Status: | Published | ||||||||
Access rights to Published version: | Restricted or Subscription Access |
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