Investigation on critical equilibrium of trapped air pocket in water supply pipeline system

A trapped air pocket can cause a partial air lock in the top of a hump pipe zone. It increases the resistance and decreases the hydraulic cross section, as well as the capacity of the water supply pipeline. A hydraulic model experiment is conducted to observe the deflection and movement of the trapp...

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Bibliographic Details
Published in:Journal of Zhejiang University. A. Science 2017-03, Vol.18 (3), p.167-178
Main Authors: Wan, Wu-yi, Li, Chen-yu, Yu, Yun-qi
Format: Article
Language:English
Subjects:
Air pockets
Civil Engineering
Classical and Continuum Physics
Dimensional analysis
Drag coefficients
Empirical analysis
Engineering
Flow velocity
Hydraulic models
Industrial Chemistry/Chemical Engineering
Mechanical Engineering
Pipe flow
Risk reduction
Water pipelines
Water supply
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Summary:A trapped air pocket can cause a partial air lock in the top of a hump pipe zone. It increases the resistance and decreases the hydraulic cross section, as well as the capacity of the water supply pipeline. A hydraulic model experiment is conducted to observe the deflection and movement of the trapped air pocket in the hump pipe zone. For various pipe flow velocities and air volumes, the head losses and the equilibrium slope angles are measured. The extra head losses are also obtained by reference to the original flow without the trapped air pocket. Accordingly, the equivalent sphere model is proposed to simplify the drag coefficients and estimate the critical slope angles. To predict the possibility and reduce the risk of a hump air lock, an empirical criterion is established using dimensional analysis and experimental fitting. Results show that the extra head losses increase with the increase of the flow velocity and air volume. Meanwhile, the central angle changes significantly with the flow velocity but only slightly with the air volume. An air lock in a hump zone can be prevented and removed by increasing the pipe flow velocity or decreasing the maximum slope of the pipe.
ISSN:1673-565X
1862-1775
DOI:10.1631/jzus.A1600325