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Impact of Modified Inlets on Residence Times in Baffled Tanks
Author(s) -
Carlston Jeremy S.,
Venayagamoorthy Subhas Karan
Publication year - 2015
Publication title -
journal ‐ american water works association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.466
H-Index - 74
eISSN - 1551-8833
pISSN - 0003-150X
DOI - 10.5942/jawwa.2015.107.0078
Subject(s) - inlet , mechanics , scalar (mathematics) , mixing (physics) , residence time (fluid dynamics) , environmental science , residence time distribution , computational fluid dynamics , marine engineering , flow (mathematics) , engineering , mathematics , geotechnical engineering , mechanical engineering , physics , geometry , quantum mechanics
Sharp inlets, although prevalent, tend to reduce mixing efficiency in hydraulic contact tanks by affecting fluid and scalar transport throughout the entire system. Superior inlets are often not an option because of the prohibitive cost of upgrading preexisting tanks. To remedy this, seven inexpensive yet easily implemented attachments to a sharp inlet were tested on a full‐scale, baffled, prototypical contact tank. Cumulative residence time distributions of a conservative, passive scalar were obtained for each attachment to assess their performance. A study using computational fluid dynamics of the same tank with the various attachments was then performed to strengthen the empirical results by explaining them from a hydrodynamic perspective. Six modifications improved mixing efficiency as estimated by the baffling factor parameter. Five of these modifications produced gains of roughly 30% over the unmodified scenario, whereas the horizontal tee attachment resulted in an increase of over 70%.