Air-Pocket Entrapment Caused by Shear Flow Instabilities in Rapid-Filling Pipes
Publication: Journal of Hydraulic Engineering
Volume 146, Issue 4
Abstract
Understanding air-pocket formation in closed conduits is important in urban water systems subject to rapid-filling conditions, such as in the case of stormwater sewers and tunnels during intense rain events. Captured air pockets influence surging and, upon uncontrolled release, lead to issues such as manhole cover displacement and/or geysering. Different mechanisms for air-pocket formation have been identified, among which are shear flow instabilities that have the potential to capture large volumes of air. This paper presents experimental and numerical research on air-pocket entrapment based on shear flow instabilities. A fully filled horizontal water pipe was opened at the downstream end to create a cavity flow and air intrusion of varying thicknesses. After some time, a second valve was maneuvered near the upstream end, triggering flow pressurization through a pipe-filling bore. The bore pushed air in high velocity over the free surface, and in some cases air-pocket entrapment was observed. A computational fluid dynamics (CFD) model replicating experimental conditions was able to reproduce shear flow instabilities, as well as measured velocities and pressures obtained with experimental measurements. Other larger-scale CFD simulations with similar geometry quantified the air fraction initially in the conduit that became entrapped within pockets. It is hoped that this research can help practitioners in anticipating the risk of large air-pocket entrapment in existing and proposed stormwater systems that may undergo rapid filling.
Get full access to this article
View all available purchase options and get full access to this article.
Data Availability Statement
Some or all data, models, or code generated or used during the study are available from the corresponding author by request, including analytical, numerical, and experimental test data.
Acknowledgments
The first and second authors acknowledge the support of the General Directorate of State Hydraulic Works (DSI), under the Republic of Turkey Ministry of Forestry and Water Affairs, which has provided fellowships through Grants 33070922-772.02-736534 and 33070922-772.02-826712.
References
Arai, K., and K. Yamamoto. 2003. “Transient analysis of mixed free-surface-pressurized flows with modified slot model: Part 1—Computational model and experiment.” In Proc., ASME/JSME 2003 4th Joint Fluids Engineering Conf., 1–9. New York: ASME.
Baines, W. D. 1991. “Air cavities as gravity currents on slope.” J. Hydraul. Eng. 117 (12): 1600–1615. https://doi.org/10.1061/(ASCE)0733-9429(1991)117:12(1600).
Benjamin, T. B. 1968. “Gravity currents and related phenomena.” J. Fluid Mech. 31 (2): 209–248. https://doi.org/10.1017/S0022112068000133.
Chosie, C. D., T. M. Hatcher, and J. G. Vasconcelos. 2014. “Experimental and numerical investigation on the motion of discrete air pockets in pressurized water flows.” J. Hydraul. Eng. 140 (8): 04014038. https://doi.org/10.1061/(ASCE)HY.1943-7900.0000898.
Greenshields, C. J. 2015. OpenFOAM user guide. London: OpenFOAM Foundation.
Hamam, M. A., and J. A. McCorquodale. 1982. “Transient conditions in the transition from gravity to surcharged sewer flow.” Can. J. Civ. Eng. 9 (2): 189–196. https://doi.org/10.1139/l82-022.
Hirt, C. W., and B. D. Nichols. 1981. “Volume of fluid (VOF) method for the dynamics of free boundaries.” J. Comput. Phys. 39 (1): 201–225. https://doi.org/10.1016/0021-9991(81)90145-5.
Kordyban, E. 1990. “Horizontal slug flow: A comparison of existing theories.” J. Fluids Eng. 112 (Mar): 1–10. https://doi.org/10.1115/1.2909372.
Leon, A. S., I. S. Elayeb, and Y. Tang. 2018. “An experimental study on violent geysers in vertical pipes.” J. Hydraul. Res. 57 (3): 283–294. https://doi.org/10.1080/00221686.2018.1494052.
Li, J., and A. McCorquodale. 1999. “Modeling mixed flow in storm sewers.” J. Hydraul. Eng. 125 (11): 1170–1180. https://doi.org/10.1061/(ASCE)0733-9429(1999)125:11(1170).
Milne-Thomson, L. M. 1938. Theoretical hydrodynamics. London: Macmillan.
Muller, K. Z., J. Wang, and J. G. Vasconcelos. 2017. “Water displacement in shafts and geysering created by uncontrolled air pocket releases.” J. Hydraul. Eng. 143 (10): 04017043. https://doi.org/10.1061/(ASCE)HY.1943-7900.0001362.
Politano, M., A. J. Odgaard, and W. Klecan. 2007. “Case study: Numerical evaluation of hydraulic transients in a combined sewer overflow tunnel system.” J. Hydraul. Eng. 133 (10): 1103–1110. https://doi.org/10.1061/(ASCE)0733-9429(2007)133:10(1103).
Rusche, H. 2003. “Computational fluid dynamics of dispersed two-phase flows at high phase fractions.” Ph.D. thesis, Dept. of Mechanical Engineering, Imperial College of Science, Technology and Medicine.
Townson, D. 1991. Free-surface hydraulics. London: CRC Press.
Vasconcelos, J. G., P. K. Klaver, and D. J. Lautenbach. 2015. “Flow regime transition simulation incorporating entrapped air pocket effects.” Urban Water J. 12 (6): 488–501. https://doi.org/10.1080/1573062X.2014.881892.
Vasconcelos, J. G., and S. J. Wright. 2006. “Mechanisms for air pocket entrapment in stormwater storage tunnels.” In Proc., World Environmental and Water Resources Congress. Reston, VA: ASCE.
Vasconcelos, J. G., and S. J. Wright. 2008. “Rapid flow startup in filled horizontal pipelines.” J. Hydraul. Eng. 134 (7): 984–992. https://doi.org/10.1061/(ASCE)0733-9429(2008)134:7(984).
Vasconcelos, J. G., and S. J. Wright. 2017. “Anticipating transient problems during the rapid filling of deep stormwater storage tunnel systems.” J. Hydraul. Eng. 143 (3): 06016025. https://doi.org/10.1061/(ASCE)HY.1943-7900.0001250.
Wang, J., and J. G. Vasconcelos. 2017. “Manhole cover displacement caused by the release of entrapped air pockets.” J. Water Manage. Model. 26: C444. https://doi.org/10.14796/JWMM.C444.
Wilkinson, D. L. 1982. “Motion of air cavities in long horizontal ducts.” J. Fluid Mech. 118: 109. https://doi.org/10.1017/S0022112082000986.
Wright, S. J., J. G. Vasconcelos, and J. L. Lewis. 2017. “Air–water interactions in urban drainage systems.” Proc. Inst. Civ. Eng. Eng. Comput. Mech. 170 (3): 91–106. https://doi.org/10.1680/jencm.16.00024.
Wylie, E. B., V. L. Streeter, and L. Suo. 1993. Fluid transients in systems. Englewood Cliffs, NJ: Prentice Hall.
Zhou, F., F. E. Hicks, and P. M. Steffler. 2002. “Transient flow in a rapidly filling horizontal pipe containing trapped air.” J. Hydraul. Eng. 128 (6): 625–634. https://doi.org/10.1061/(ASCE)0733-9429(2002)128:6(625).
Zukoski, E. E. 1966. “Influence of viscosity, surface tension, and inclination angle on motion of long bubbles in closed tubes.” J. Fluid Mech. 25 (4): 821–837. https://doi.org/10.1017/S0022112066000442.
Information & Authors
Information
Published In
Copyright
©2020 American Society of Civil Engineers.
History
Received: Dec 21, 2018
Accepted: Aug 23, 2019
Published online: Jan 29, 2020
Published in print: Apr 1, 2020
Discussion open until: Jun 29, 2020
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.