Phenomenon of White Mist in Pipelines Rapidly Filling with Water with Entrapped Air Pockets
Publication: Journal of Hydraulic Engineering
Volume 139, Issue 10
Abstract
The phenomenon of white mist in a rapidly filling pipeline containing an entrapped air pocket is numerically and experimentally investigated. The air-water flow patterns, pressure, and temperature histories are synchronously recorded to illustrate their interrelations. The white mist phenomenon is particularly observed during fast transients, especially during the first compression of the air pocket. Comparisons between calculations and experiments indicate that the white mist primarily reflects a condensation process. More specifically, the air temperature increases because of rapid compression of an entrapped air pocket, and the high temperature could cause water to adhere to vapor at the pipe surface. For fast transients, the first compression causes a near-adiabatic air compression, but heat exchange effects become more significant in the subsequent compression and expansion cycles. As the initial air length decreases, the maximum pressure first increases and then declines, with the most dangerous air length occurring when about 3.4% is initially occupied by air. The ratio of the maximum pressure to the driving pressure increases approximately linearly with respect to the upstream pressure. A local-interpolation elastic-water model is developed by considering air-temperature change and its validity is confirmed by comparing the model and experimental results.
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Acknowledgments
The writers gratefully acknowledge financial support from the National Natural Science Foundation of China (Grant No. 51209073 and No. 50979029), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120094120002), and the China Scholar Council (CSC), File No. 2009671024.
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Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 139 • Issue 10 • October 2013
Pages: 1041 - 1051
Copyright
© 2013 American Society of Civil Engineers.
History
Received: Mar 12, 2012
Accepted: Apr 11, 2013
Published online: Apr 13, 2013
Discussion open until: Sep 13, 2013
Published in print: Oct 1, 2013
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