Case Study: Numerical Evaluation of Hydraulic Transients in a Combined Sewer Overflow Tunnel System

Politano, Marcela; Odgaard, A. Jacob; Klecan, W.

doi:10.1061/(asce)0733-9429(2007)133:10(1103)

Cited by 63 publications

(33 citation statements)

References 15 publications

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“…A range of experimental investigations have been performed to elucidate phenomena that may originate in sewer systems that are filling rapidly and several of of these have shown multiple ways in which large pockets of air can become entrapped in such systems during the filling process Observations have informed the required capability of numerical models to reproduce relevant phenomena and such models have been validated (e.g. Vasconcelos et al 2007b) by comparison to experimental data, but have also been used to assist in the design of actual storage tunnel pro-jects (Lautenbach et al 2008;Politano et al 2007 ). Application of the numerical models to these storage tunnel projects has in turn indicated important phenomena that cannot be readily reproduced in small scale experimental systems, and the resulting feedback between experimental and numerical observations has led to an enhanced understanding of the dynamics of rapidly filling sewer systems.…”

Section: Introductionmentioning

confidence: 99%

“…If the bore encounters a tunnel transition (reduction in upstream diameter, for example, or a vertical offset in the tunnel alignment), the bore can partially re-flect off this transition and create a strong surge which can result in increased pressures in the tunnel. Numerical models (Cardle and Song 1988;Leon et al 2006;Politano et al 2007) have been developed to model this process. Bousso and Fuamba (2012) provide a review of modeling approaches.…”

Section: Introductionmentioning

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

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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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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Wright

Klaver²,

Vasconcelos

2016

JWMM

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“…However, no model integrates the effect of both air-entrainment and air-entrapment in transient mixed flows. In addition, all shock-capturing models are known to develop posttransition oscillations (Politano et al 2007, Leon et al 2010). This problem is linked to the rapid variation of the pressure wave celerity at the transition ).…”

Section: Introductionmentioning

confidence: 99%

Three-phase bi-layer model for simulating mixed flows

Kerger

Archambeau

Dewals

et al. 2012

Journal of Hydraulic Research

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“…The most widespread of these methods is the Preissmann slot [8,12] because it only uses the classical Saint-Venant equations [13]. Such a model is however unable to simulate sub-atmospheric pressurized flows [14]. Recently, research focuses to integrate the effect of the air phase on the behavior of mixed flows.…”

Section: Introductionmentioning

confidence: 99%

1D unified mathematical model for environmental flow applied to steady aerated mixed flows

Kerger

Erpicum

Dewals

et al. 2011

Advances in Engineering Software

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a b s t r a c tHydraulic models available in literature are unsuccessful in simulating accurately and efficiently environmental flows characterized by the presence of both air-water interactions and free-surface/pressurized transitions (aka mixed flows). The purpose of this paper is thus to fill this knowledge gap by developing a unified one-dimensional mathematical model describing free-surface, pressurized and mixed flows with air-water interactions. This work is part of a general research project which aims at establishing a unified mathematical model suitable to describe the vast majority of flows likely to appear in civil and environmental engineering (pure water flows, sediment transport, pollutant transport, aerated flows. . .). In order to tackle this problem, our original methodology consists in both time-and spaceaveraging the Local Instant Formulation, which includes field equations for each phase taken separately and jump conditions, over a flow cross-section involving a free-surface. Subsequently, applicability of the model is extended to pressurized flows as well. The first key result is an original 1D Homogeneous Equilibrium Model which describes two-phase free-surface flows. It is proven to be fundamentally multiphase, to take into account scale heterogeneities of environmental flow and to be very easy to solve. Next, applicability of this free-surface model is extended to pressurized flows by using the classical Preissmann slot concept. A second key result here is the introduction of an original negative Preissmann slot to simulate sub-atmospheric pressurized flows. The model is then closed by using constitutive equations suitable for air-water flows. Finally, this mathematical model is discretised by means of a finite volume scheme and validated by comparison with experimental results from a physical model in the case of a steady flow in a large scale gallery.

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Case Study: Numerical Evaluation of Hydraulic Transients in a Combined Sewer Overflow Tunnel System

Cited by 63 publications

References 15 publications

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

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

Three-phase bi-layer model for simulating mixed flows

1D unified mathematical model for environmental flow applied to steady aerated mixed flows

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