Pressure Transients due to Compression of Trapped Air in Rapidly Filling Sewer Storage Tunnels

Wright, Steve; Determan, Kelly V.; Vargas, Silvana M.

doi:10.14796/jwmm.r245-01

Cited by 3 publications

(6 citation statements)

References 10 publications

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“…The sequence of events in a dry lake tap can suddenly compress the air in the associated tunnel and thus produce extreme overpressures (Chaudhry and Reddy 2011). Under wet-weather flow conditions, a hydraulic bore moving along a sewer pipe may compress an air pocket at a drop shaft and induce extreme pressures; subsequent reflection of the induced overpressures may then result in negative pressures (Wright et al 2012;Vasconcelos and Leite 2012).…”

Section: Introductionmentioning

confidence: 99%

Physical Understanding of Sudden Pressurization of Pipe Systems with Entrapped Air: Energy Auditing Approach

2016

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A global energy-auditing approach is used to describe the complex transient flow associated with sudden pressurization of a confined pipe system containing entrapped air pockets. The key concept is that the greatest pressures following pressurization are directly related to the amount of energy absorbed by the air pockets. The energy approach leads to an insightful understanding of the transient pressurization event, one that clarifies the underlying physics and that better explains several previously published observations. Moreover, the energy formulation leads to analytical algebraic expressions that can be numerically confirmed. individual papers. This paper is part of the Journal of Hydraulic Engineering, © ASCE, ISSN 0733-9429/04015044 (11)/$25.00. © ASCE 04015044-1 J. Hydraul. Eng. J. Hydraul. Eng. Downloaded from ascelibrary.org by UNIVERSITY OF TORONTO on 08/14/15. Copyright ASCE. For personal use only; all rights reserved. © ASCE 04015044-4 J. Hydraul. Eng. J. Hydraul. Eng. Downloaded from ascelibrary.org by UNIVERSITY OF TORONTO on 08/14/15. Copyright ASCE. For personal use only; all rights reserved. © ASCE 04015044-8 J. Hydraul. Eng. J. Hydraul. Eng. Downloaded from ascelibrary.org by UNIVERSITY OF TORONTO on 08/14/15.

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Section: Introductionmentioning

confidence: 99%

Physical Understanding of Sudden Pressurization of Pipe Systems with Entrapped Air: Energy Auditing Approach

2016

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“…Notice in this situation, there is no bore inertia to arrest by compression of the air and therefore no significant pressure rise is to be expected even though the trapped air volume may be quite small. Given the two scenarios for air entrapment predicted by SHAFT-Air for the proposed Thames Tideway Tunnel system, it appears that the experimental investigation previously performed by Wright et al (2012) represents more severe conditions than would be expected in this application, especially for small air pocket volumes where the strong bore inertia would not generally be encountered. That experimental study was limited by constraints of performing tests in small scale systems where it would be difficult to reproduce the conditions described above; the experiments were conducted to produce what was considered to be an extreme transient.…”

Section: Nature Of the Air Entrapment Processmentioning

confidence: 98%

“…One such effort is reported by Wright et al (2012) and was conducted in the apparatus indicated schematically in Figure 2. The general concept is somewhat similar to the process modeled by Martin (1976) except that the conduit is laid on an almost horizontal slope so that the initial water is spread over the length of the conduit with the air distributed above the free surface.…”

Section: Laboratory Studiesmentioning

confidence: 99%

“…Transient pressures along the crown of the pipe were measured and exhibited an oscillatory nature that gradually damped with time. Both the maximum and minimum transient pressures were recorded and the results are discussed in Wright et al (2012). Figure 3 indicates the maximum and minimum pressures recorded as a function of the trapped air volume.…”

Section: Laboratory Studiesmentioning

confidence: 99%

“…The first one has been discussed previously by Wright et al (2006Wright et al ( , 2012 and involves a free surface bore that reflects off a tunnel transition, closing the cross section and entrapping air. The second involves a tunnel filling bore that encounters a vertical shaft or a spur tunnel.…”

Section: Nature Of the Air Entrapment Processmentioning

confidence: 99%

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Assessment of Pressure Transients Due to Trapped Air Compression in Rapidly Filling Combined Sewer Overflow Tunnels

Wright

Klaver²,

Vasconcelos

2016

JWMM

Self Cite

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Numerical modeling indicates that high pressures can be expected when trapped air at the end of a pipeline is compressed as it stops a moving water column. In particular, the model results show that larger pressures are to be expected when compressed air volumes are small. Laboratory experiments where a trapped air pocket is compressed by an advancing filling front also confirm that small air volumes lead to the highest pressure rises. However, the model formulation essentially treats the moving water column as a vertical front with a trapped volume of air in front of it, an assumption that cannot be expected to hold for large diameter stormwater tunnels. The authors have been involved in the numerical modeling of rapidly filling flows in CSO storage tunnel systems. The Two-component Pressure Approach can predict the location where air can become entrapped and the associated volume, but the model framework is a single phase flow simulation and the air is not explicitly modeled. This leads to conceptual errors in the modeling of flow processes once the air becomes entrapped. The numerical model was reformulated to allowed the inclusion of the trapped air volume in the simulation in a simplified fashion. Simulations with the modified model for a specific application suggest that there are two types of flow conditions that can lead to trapped air pockets that are subsequently compressed although future investigations may define additional conditions. The simulation results suggest that only modest pressure rises should be expected in the particular application investigated and the physical explanations for this outcome are described.

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Experiments and numerical analysis of the dynamic flow characteristics of a pump−pipeline system with entrapped air during start-up

Li,

Bai,

Wang

2023

Engineering Applications of Computational Fluid Mechanics

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Pressure Transients due to Compression of Trapped Air in Rapidly Filling Sewer Storage Tunnels

Cited by 3 publications

References 10 publications

Physical Understanding of Sudden Pressurization of Pipe Systems with Entrapped Air: Energy Auditing Approach

Physical Understanding of Sudden Pressurization of Pipe Systems with Entrapped Air: Energy Auditing Approach

Assessment of Pressure Transients Due to Trapped Air Compression in Rapidly Filling Combined Sewer Overflow Tunnels

Experiments and numerical analysis of the dynamic flow characteristics of a pump−pipeline system with entrapped air during start-up

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