Bubble-induced turbulence modeling for vertical bubbly flows

Vaidheeswaran, Avinash; Hibiki, Takashi

doi:10.1016/j.ijheatmasstransfer.2017.08.075

Cited by 52 publications

(24 citation statements)

References 116 publications

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“…Turbulence predictions are highly empirical because of the lack of knowledge about BIF. Many authors use single-phase modelling extended to two-phase flows by the addition of a specific source term for turbulent kinetic energy and/or dissipation, suggesting that BIF and SPT are statistically independent and that WIF and WIT have features similar to SPT itself (Hosokawa & Tomiyama 2013;Colombo & Fairweather 2015;Vaidheeswaran & Hibiki 2017). Besides, there is no consensus about the modelling of these additional terms.…”

Section: Analysis and Modelling Of The Reynolds Stress Transport Equamentioning

confidence: 99%

“…The classical way to model two-phase turbulence involves only the splitting of turbulence into SPT and BIF. In order to adapt single-phase turbulence models to two-phase flows, many authors have implicitly assumed that WIF and WIT may be modelled together (Hosokawa & Tomiyama 2013;Colombo & Fairweather 2015;Vaidheeswaran & Hibiki 2017). Although there have been several attempts to use other decompositions based on physical considerations (Risso 2018), to the best of our knowledge all turbulence models are still based on a coarse vision of two-phase flow (except for the work of Chahed, Roig & Masbernat (2003) who proposed distinguishing between the dissipative and the non-dissipative parts of BIF).…”

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confidence: 99%

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Analysis and modelling of Reynolds stresses in turbulent bubbly up-flows from direct numerical simulations

2019

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Two-phase bubbly flows are found in many industrial applications. These flows involve complex local phenomena that are still poorly understood. For instance, two-phase turbulence modelling is still commonly based on single-phase flow analyses. A direct numerical simulation (DNS) database is described here to improve the understanding of two-phase turbulent channel flow at a parietal Reynolds number of 127. Based on DNS results, a physical interpretation of the Reynolds stress and momentum budgets is proposed. First, surface tension is found to be the strongest force in the direction of migration so that budgets of the momentum equations suggest a significant impact of surface tension in the migration process, whereas most modelling used in industrial application does not include it. Besides, the suitability of the design of our cases to study the interaction between bubble-induced fluctuations (BIF) and single-phase turbulence (SPT) is shown. Budgets of the Reynolds stress transport equation computed from DNS reveal an interaction between SPT and BIF, revealing weaknesses in the classical way in which pseudoturbulence and perturbations to standard single-phase turbulence are modelled. An SPT reduction is shown due to changes in the diffusion because of the presence of bubbles. An increase of the redistribution leading to a more isotropic SPT has been observed as well. BIF is comprised of a turbulent (wake-induced turbulence, WIT) and a non-turbulent (wake-induced fluctuations, WIF) part which are statistically independent. WIF is related to averaged wake and potential flow, whereas WIT appears when wakes become unstable or interact with each other for high-velocity bubbles. In the present low gravity conditions, BIF is reduced to WIF only. A thorough analysis of the transport equations of the Reynolds stresses is performed in order to propose an algebraic closure for the WIF towards an innovative two-phase turbulence model.

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Section: Analysis and Modelling Of The Reynolds Stress Transport Equamentioning

confidence: 99%

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confidence: 99%

Analysis and modelling of Reynolds stresses in turbulent bubbly up-flows from direct numerical simulations

2019

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“…Several turbulence closure models have been analyzed and tested in the literature in the context of two‐phase flows. The large eddy simulation (LES) model and the Reynolds averaged models, such as the k ‐ ε and the Reynolds stress (RSM) models have been extensively used . It was shown that the LES and the k ‐ ε models predict comparable transient flow structures .…”

Section: Model Descriptionmentioning

confidence: 99%

On the prediction of gas hold‐up in two‐phase flow systems using an Euler–Euler model

et al. 2020

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We quantify the ability of the two-fluid Euler-Euler model to predict the overall gas hold-up during two-phase flow in vertical columns using a combination of experiments and simulations. Gas hold-up in a bubble column and gas hold-up in the less-frequently studied co-current flow are investigated. For homogeneous flow characterized by nearly uniform bubble size, Euler-Euler model predictions are within 10% of the experimental values for both modes of operation, if the bubble diameter supplied as input to the model is the average bubble diameter in the physical system. This also holds true for heterogeneous flow in bubble columns despite the presence of a broad distribution of bubble sizes, if turbulence and bubble swarm effects on momentum exchange between phases are properly accounted for. Swarm corrections adequate for bubble columns, are less successful for co-current heterogeneous flow, for which gas hold-up predictions are least accurate (average error of 22%). K E Y W O R D S churn-turbulent flow regime, dispersed flow regime, experimental validation, gas-liquid flow, two-fluid Euler-Euler model

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“…The velocity resulting from the RSM is discussed to verify the predictions in swirling flow. 29 With oxygen gas and water feeding, the volume fraction of gas phase was modeled through the RSM and two-fluid model. 29 With oxygen gas and water feeding, the volume fraction of gas phase was modeled through the RSM and two-fluid model.…”

Section: Verification Through Simulationmentioning

confidence: 99%

“…28 Step 2 employed an Euler-Euler approach. 29 With oxygen gas and water feeding, the volume fraction of gas phase was modeled through the RSM and two-fluid model. 30,31 The oxygen gas was treated as a dispersed fluid with a specific diameter equal to that in the corresponding experiment.…”

Section: Verification Through Simulationmentioning

confidence: 99%

Bubble‐separation dynamics in a planar cyclone: Experiments and CFD simulations

Qian

et al. 2018

AIChE Journal

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A planar cyclone is designed for visualizing bubbles in the cross‐section of a degassing hydrocyclone. The pressure distribution is studied through a series of experiments and Reynolds stress model simulations. The velocity distribution of the planar cyclone mostly exhibits the quasi‐forced vortex zone and boundary layer zone. The bubble dynamics are simulated using both Euler‐Euler and Euler‐Lagrange approaches, and the output is compared with the imaging results. The Euler‐Euler simulation provides more accurate predictions of the bubble trajectory. The histograms of residence time and traveling distance given by the Euler‐Lagrange approach exhibit a reasonably regular pattern. With higher values of the inlet Reynolds number, stronger forces acting on the bubbles lead to a decreased but more uniform residence time. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2689–2701, 2018

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Bubble-induced turbulence modeling for vertical bubbly flows

Cited by 52 publications

References 116 publications

Analysis and modelling of Reynolds stresses in turbulent bubbly up-flows from direct numerical simulations

Analysis and modelling of Reynolds stresses in turbulent bubbly up-flows from direct numerical simulations

On the prediction of gas hold‐up in two‐phase flow systems using an Euler–Euler model

Bubble‐separation dynamics in a planar cyclone: Experiments and CFD simulations

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