Water Column Separation and Cavity Collapse for Pipelines Protected with Air Vacuum Valves: Understanding the Essential Wave Processes
Publication: Journal of Hydraulic Engineering
Volume 143, Issue 2
Abstract
Elevated high points along a pipeline profile are the most common places where air vacuum valves (AVVs) are installed. This paper uses basic water hammer theory to semianalytically explore the effects of such AVVs. A simple frictionless reservoir-pipe-reservoir system with an exaggerated intermediate high point is considered with a sudden flow curtailment assumed upstream. Key design parameters such as the maximum air pocket volume, the duration of air pocket growth and collapse, and the maximum magnitude of the pressure spike resulting from water column rejoinder are semianalytically developed for various high point locations. The magnitude of the reduced pressure wave created by the refraction at the high point, and both its vertical and horizontal position, are demonstrated to crucially determine system performance. Numerical examples are compared with the semianalytical expressions to highlight the accuracy of the derived expressions. The effect of friction is later introduced to help reveal friction’s influence on air valve performance.
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Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 143 • Issue 2 • February 2017
Copyright
© 2016 American Society of Civil Engineers.
History
Received: Nov 29, 2014
Accepted: Jun 27, 2016
Published online: Sep 30, 2016
Published in print: Feb 1, 2017
Discussion open until: Feb 28, 2017
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