Experimental Investigation of the Interaction of Fluid Transients with an In-Line Air Pocket
Publication: Journal of Hydraulic Engineering
Volume 146, Issue 3
Abstract
Entrapped air blocking the flow in pipeline systems is a common cause of increased pumping costs. At present, air is generally removed via valves or pipeline excavation and drilling. This becomes inefficient in large networks where the precise location of the air is unknown. Fluid transients are a potential tool for detecting and locating air in pipelines. The effect of a stationary air pocket part of the way along the pipe, which occupies the main flow path and acts as a blockage without causing a hydraulic jump or column separation, has not previously been studied experimentally. This paper presents experimental results for a transient pulse interacting with an in-line air pocket for a range of pocket sizes and system pressures. In accordance with the impedance theory, the reflective power of the air increases with pocket size. Other notable characteristics of the interaction include frequency-dependent transmissivity, an out-of-phase reflection, and a substantial reflection under zero base flow. These effects set air pockets apart from solid blockages, allowing a transient detection methodology to differentiate between the two cases, although they have similar effects at steady-state.
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Data Availability Statement
Some or all data, models, or code generated or used during the study are available from the corresponding author by request.
Acknowledgments
We would like to thank the Hong Kong Research Grants Council for the theme-based research scheme (TRS) Grant No. T21-602/15R for supporting this research.
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Published In
Journal of Hydraulic Engineering
Volume 146 • Issue 3 • March 2020
Copyright
©2019 American Society of Civil Engineers.
History
Received: Aug 22, 2018
Accepted: Jul 16, 2019
Published online: Dec 19, 2019
Published in print: Mar 1, 2020
Discussion open until: May 19, 2020
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