Exploring Two-Phase Flow Regime Transition Mechanisms Using High-Resolution Virtual Experiments

Zimmer, Matthew D.; Bolotnov, Igor A.

doi:10.1080/00295639.2020.1722543

Cited by 7 publications

(5 citation statements)

References 34 publications

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“…The study by Kashima et al [20] brings us the study from Svendsen [37]; with those models, if the TKE values in the range from 0.05 m 2 /s 2 to 0.15 m 2 /s 2 are used together with a certain turbulent length scale, one may obey the energy dissipation rate in the context of breaking surf zone wave analysis. It is interesting to note that these values coincide with the TKE values obtained in instability of a stable vapor flow study presented by Zimmer and Bolotnov [38]. In their study, the authors found a 0.15 m 2 /s 2 value of TKE as the threshold value in causing instability to the stable slug flow.…”

Section: The Applied Turbulent Kinetic Energy Valuesupporting

confidence: 83%

Film Boiling around a Finite Size Cylindrical Specimen—A Transient Conjugate Heat Transfer Approach

et al. 2023

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The DNS of film boiling requires strong computational resources that are difficult to obtain for daily CFD use by expert practitioners of industrial R&D. On the other hand, film boiling experiments are associated with the usage of expensive and highly sophisticated apparatus, and research to this end is relatively difficult due to high heat flow rates that are present in the process itself. When combined with transient heat conduction in a solid, the problem becomes significantly difficult. Therefore, a novel method in computation of conjugate heat transfer during film boiling in a quiescent liquid is proposed in this paper. The method relies on the solution of mass, momentum and energy conservation equations in a two-fluid framework, supplemented with the appropriate closures. Furthermore, turbulent flow was determined as an important parameter in obtaining an accurate solution to temperature field evolution in a solid specimen, via the proper modeling of the turbulent kinetic energy (TKE) value, that was imposed as a constant value, i.e., the frozen turbulence approach. It was found, in addition, that the appropriate TKE value can be obtained by use of Kelvin–Helmholtz instability theory in conjunction with boundary layer theory. The obtained results show excellent agreement with the experimental data within the first 15 s of the experiment, i.e., the first ca. 10% of the total duration of the film boiling mode of heat transfer. Furthermore, the heat transfer coefficient matched the error bands prescribed by the authors of this paper, which presented the correlations, whilst the averaged values are far beyond this band, i.e., are slightly more than 30% higher. Further inspection revealed a measure of similarity between the computational result of the volume fraction field distribution and the experiment, thus confirming the capability of the method to obtain realistic interface evolution in time. The method shows full capability for further pursuing industrial-scale film boiling problems that involve turbulent flow and the conjugate heat transfer approach.

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Section: The Applied Turbulent Kinetic Energy Valuesupporting

confidence: 83%

Film Boiling around a Finite Size Cylindrical Specimen—A Transient Conjugate Heat Transfer Approach

et al. 2023

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“…The largest loss of void is observed in mesh 9-10, although the difference is rather small with mesh 10-10 and 10-11. Quite interestingly, the average shape of the bubble tail varies from flat (9-10) to somewhat concave (10-10) and somewhat convex (10)(11). The streamlines indicate that the bubble itself consists of a large toroidal vortex with its rotational center relatively close to the tail.…”

Section: Simulation Strategy Meshing and Averagingmentioning

confidence: 98%

“…However, a deviation of the turbulent fluctuations in the wake of the Taylor bubble due to over-prediction of the loss of void of the Taylor bubble made the authors of [2] conclude that the LES mesh resolution is not sufficient to capture the break-up and bubble formation accurately. Meanwhile, other researchers have also performed high fidelity simulation of turbulent Taylor bubble flow, e.g., see [10] and [11].…”

Section: Introductionmentioning

confidence: 99%

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LES of Turbulent Co-current Taylor Bubble Flow

Frederix

Komen

Tiselj

et al. 2020

Flow Turbulence Combust

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The modeling and simulation of two-phase flows using CFD can contribute significantly to the topic of nuclear reactor safety, e.g., in the accurate prediction of the pressurized thermal shock phenomenon under two-phase conditions. However, there are still many challenges remaining in the development of a general two-phase model which is capable of capturing all two-phase flow regimes within the same setting, ranging from bubbly flow to large interface flow such as slug flow, Taylor bubble flow or stratified flow. One of those challenges is the appropriate representation of the behavior of turbulence at a large scale two-phase interface, and the subsequent break-up of such an interface into smaller structures. This requires the development and validation of more advanced two-phase turbulence models. The first step in this direction was made in [1], in which Egorov's idea of turbulence damping near a two-phase interface was generalized towards a more meshindependent formulation. For specific settings, the model could be calibrated to give good agreement with experimentally measured velocity and velocity fluctuation profiles of two-phase stratified flow. However, for real-world problems, a much more general interfacial turbulence damping model should be developed which adapts to local conditions automatically.

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“…Ultrasonic detection was applied for moving slug interfaces detection in gas-liquid two-phase flow [25]. Two-phase flow regime transition mechanisms were exploited with high-resolution virtual experiments [26]. It was shown that the transition out of the slug flow regime could take at least two pathways:…”

Section: Experimental Investigation Of Slug Regime Of Gas-liquid Flow...mentioning

confidence: 99%

Slug Regime Transitions in a Two-Phase Flow in Horizontal Round Pipe. CFD Simulations

et al. 2020

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The main objective of the study is to propose a technical solution integrated into the pipeline for the transition of the flow regime from slug to bubbly two-phase flow. The object of research is isothermal two-phase gas–Newtonian-liquid flow in a horizontal circular pipeline. There is local resistance in the pipe in the form of a streamlined transverse mesh partition. The mesh partition ensures the transition of the flow from the slug regime to the bubbly regime. The purpose of the study is to propose a technical solution integrated into the pipeline for changing the flow regime of a two-phase flow from slug to bubbly flow. The method of research is a simulation using computational fluid dynamics (CFD) numerical simulation. The Navier–Stokes equations averaged by Reynolds describes the fluid motion. The k-ε models were used to close the Reynolds-averaged Navier–Stokes (RANS) equations. The computing cluster «Polytechnic—RSK Tornado» was used to solve the tasks. The results of simulation show that pressure drop on the grid did not exceed 10% of the pressure drop along the length of the pipeline. The mesh partition transits the flow regime from slug to layered one, which will help to increase the service life and operational safety of a real pipeline at insignificant energy costs to overcome the additional resistance integrated into the pipeline.

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Exploring Two-Phase Flow Regime Transition Mechanisms Using High-Resolution Virtual Experiments

Cited by 7 publications

References 34 publications

Film Boiling around a Finite Size Cylindrical Specimen—A Transient Conjugate Heat Transfer Approach

Film Boiling around a Finite Size Cylindrical Specimen—A Transient Conjugate Heat Transfer Approach

LES of Turbulent Co-current Taylor Bubble Flow

Slug Regime Transitions in a Two-Phase Flow in Horizontal Round Pipe. CFD Simulations

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