Characterization of slug initiation for horizontal air-water two-phase flow

Conte, Marco Germano; Hegde, Govind A.; Silva, Marco J. da; Sum, Amadeu K.; Morales, Rigoberto E. M.

doi:10.1016/j.expthermflusci.2017.04.023

Cited by 29 publications

(5 citation statements)

References 33 publications

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“…Figures 7E,F). In addition, the staircase shaped tail of a plug proposed by Conte et al (2017) can be seen both in Figures 7E,F. However, the mesh used in these two simulations is still not fine enough to track the interfaces of small bubbles, which might lead to the large discrepancy for the two-phase pressure drop.…”

Section: Plug Flowmentioning

confidence: 95%

CFD Simulation of Two-Phase Flows in Helical Coils

et al. 2020

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The behavior of two-phase flow and corresponding flow regimes in helical tubes significantly differ when compared to two-phase flows in straight tubes due to centrifugal and torsion effects. In order to gain physical insight and gather data for validating computational models, a large number of experiments were performed on a helical coil experimental setup operated with a mixture of water and air. The experimental data were used to assess the predictive capabilities of current two-phase Computational Fluid Dynamics (CFD) models based on the Volume of Fluid (VOF) approach. In the present paper, a comparison of the CFD simulation results with the high-resolution experimental data is discussed, with special emphasis on two-phase pressure drops and void fraction distributions. It is shown that the CFD VOF model is able to correctly capture the occurrence of five flow regimes observed in the experiments, namely bubbly flow, plug flow, slug flow, slug-annular flow, and annular flow. However, a good quantitative agreement for pressure drops and void fraction distributions is found in slug flow and slug-annular flow regimes only. The good agreement found only in a limited range of flow regimes demonstrates that there is not a single set of best-practice guidelines for CFD VOF models that can be applied across a wide range of two-phase flow regimes. Also, there is not a single mesh that can be used to simulate all of the flow regimes and a case-specific mesh and time-step convergence study is needed for each individual flow regime. In the current study, optimal mesh size and time step were obtained for a slug flow test case. Hence, good agreement was obtained only for similar flow regimes, leading to significant disagreement with experimental data for test cases with substantially different flow patterns.

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Section: Plug Flowmentioning

confidence: 95%

CFD Simulation of Two-Phase Flows in Helical Coils

et al. 2020

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“…The concepts, although different, are related by a harmonic mean, as reported by Conte et al (2017). While unit cell frequency may sound inconsistent at first glance, it is an important tool to evaluate flow frequency.…”

Section: Unit Cell Frequencymentioning

confidence: 99%

Horizontal Air-Water Two Phase Slug Flow: Eulerian and Lagrangian Data Analysis

Chiarello¹,

Barros²,

Neto³

et al. 2020

Procceedings of the 18th Brazilian Congress of Thermal Sciences and Engineering

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Multiphase flows are recurrent phenomena both in natural environments-such as volcanic eruptions and blood flow through veins-and industrial environments-such as the nuclear and petroleum industries. Knowledge about the hydrodynamics of the flow as well as its evolution across the pipeline is essential to correctly design pipelines, equipments (such as pumps and slug catchers) and to formulate strategies to optimize the crude oil exploitation from reservoirs. A frequently reported flow pattern in oil pipelines is slug flow, reason why the present study focuses in its investigation. In order to analyze the flow, a novel methodology is proposed and applied to data retrieved in Multiphase Flow Center (NUEM) experimental facilities. The experimental loop has a length of 35.6 m and 26 mm internal diameter and was operated under 18 different slug flow conditionsvarying gas superficial velocity from 0.3 to 2.5 m/s and liquid superficial velocity from 0.3 to 3.0 m/s-across 5 different measuring stations composed by a pair of two-wire resistive sensors distributed along the pipe. Data was analyzed using Eulerian reference frame (ERF), which provides distributions for each hydrodynamic parameter in each measuring station for every experimental point, and Lagrangian reference frame (LaRF), which follows unit cells across the pipeline in order to evaluate the change in hydrodynamic parameters of single structures. Correlations were proposed based on retrieved results for hydrodynamic parameters average values and standard deviation. Moreover, a comparison against previous works was made in order to test the presented correlations as well as to propose corrections to the existing ones. Furthermore, details of the flow were investigated using the developed methodology, which was able to provide additional and insightful information about the flow behavior-such as the intrinsically unsteady nature of slug flow, as slug lengths were found to oscillate at all times, even though average values did not report significant changes, which would indicate developed flow conditions. Moreover, it was shown that gas expansion is a driver phenomenon in heavily aerated points, but becomes lees pronounced in low aeration flows-such as plug flows.

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“…The liquid slug contains the liquid column and some bubbles, and the holdup for liquid slug ( H ls ) is the fraction of liquid in the slug head. The gas core is composed of the liquid film and gas core . Because of some bubble also existing in the liquid film, the holdup for liquid film ( H lf ) represents the fraction of liquid in the liquid film.…”

Section: Theoretical Modellingmentioning

confidence: 99%

Modelling and analysis of impact forces acting on elbow in gas–liquid slug flow

Xiao

Jing

Han³

et al. 2018

Asia-Pacific J Chem Eng

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The impact forces caused by gas-liquid slug flow can lead to the vibration of process system or fatigue failure of pipe fittings. In this study, a piston-flowmodel coupling with slug model is developed to calculate the impact forces, which can contribute to the structure design and flow assurance. An experiment installation is installed to study the characteristics of slug flow and validate the reliability of the model. The accuracy of this model is above 90% for the superficial velocity of gas below 2 m/s, whereas the average deviation is 29.2% for the cases of superficial velocity of gas above 2 m/s. The modified model addressing the liquid holdup agrees well with the experimental data, of which the average deviation is 6.25%.

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Characterization of slug initiation for horizontal air-water two-phase flow

Cited by 29 publications

References 33 publications

CFD Simulation of Two-Phase Flows in Helical Coils

CFD Simulation of Two-Phase Flows in Helical Coils

Horizontal Air-Water Two Phase Slug Flow: Eulerian and Lagrangian Data Analysis

Modelling and analysis of impact forces acting on elbow in gas–liquid slug flow

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