Experimental Study of Plunging-Flow Dropshafts with an Internal Divider for Air Circulation
Publication: Journal of Hydraulic Engineering
Volume 144, Issue 9
Abstract
Plunging-flow dropshafts can entrain a large amount of air into sewer systems, pressurize downstream airspace, and cause potential sewer odor issues. In this study, a new design for a plunging-flow dropshaft is investigated by installing an internal divider to form a wet shaft and an air shaft. The air shaft allows the air entrained by the falling water to partially circulate back to the wet shaft, thus significantly reducing the air demand from the outside. Laboratory experiments were conducted using a 7.72-m-tall dropshaft with a divider with different sizes of opening for air circulation. External air demand and air pressure variation in the dropshaft were examined. The effects of inflow impingement and breakup of inflow into small water drops were found to be the main cause of the air pressure gradient along the dropshaft. Air flow circulation was modeled and compared well with the experimental measurements. The divider was found to effectively reduce the external air demand and the air pressurization of the dropshaft.
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Acknowledgments
The authors are thankful for the financial support from the China Scholarship Council, the City of Edmonton, the Natural Sciences, Engineering Research Council of Canada (NSERC), the National Key Research and Development Program of China (Grant No. 2016YFC0401810) and the Fundamental Research Funds for the Central Universities (Grant No. 2016B10814). The authors would like to thank Perry Fedun for building the model.
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Published In
Journal of Hydraulic Engineering
Volume 144 • Issue 9 • September 2018
Copyright
©2018 American Society of Civil Engineers.
History
Received: Oct 31, 2017
Accepted: Mar 30, 2018
Published online: Jul 2, 2018
Published in print: Sep 1, 2018
Discussion open until: Dec 2, 2018
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