Exploration by Shake-the-Box technique of the 3D perturbation induced by a bubble rising in a thin-gap cell

The rise of a single bubble confined between two vertical plates is investigated over a wide range of Reynolds numbers. In particular, we focus on the evolution of the bubble speed, aspect ratio and drag coefficient during the transition from the viscous to the inertial regime. For sufficiently large bubbles, a simple model based on power balance captures the transition for the bubble velocity and matches all the experimental data despite strong time variations of bubble aspect ratio at large Reynolds numbers. Surprisingly, bubbles in the viscous regime systematically exhibit an ellipse elongated along its direction of motion while bubbles in the inertia-dominated regime are always flattened perpendicularly to it.

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“…This is due to secondary flows around the bubble as becomes large (Bush & Eames 1998; Pavlov et al. 2021 a ).…”

Section: Resultsmentioning

confidence: 99%

“…Nonetheless, as Re 2h increases, inertia becomes important and the bubble speed deviates from the viscous limit, v M . This is due to secondary flows around the bubble as Re = (d 2 /h) 2 Re 2h = ρv b d 2 /η becomes large (Bush & Eames 1998;Pavlov et al 2021a).…”

Section: Bubble Rising Speedmentioning

confidence: 99%

Bubble rise in a Hele-Shaw cell: bridging the gap between viscous and inertial regimes

et al. 2022

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“…Therefore, ξ is a parameter that quantifies, in the studied regimes, how much slower a bubble of diameter d rises in a cell of width W with respect to the velocity that the same bubble would have in the absence of lateral confinement. In the limit of no lateral confinement, ξ =⇒ 1, and thus U rel ≃ V b,∞ , which can be used to generalize equation ( 1) in order to account for the lateral confinement [13].…”

Section: Resultsmentioning

confidence: 99%

Oscillating Bubbles Rising in a Doubly Confined Cell

Pavlov¹,

D’Angelo²,

Cachile³

et al. 2022

AnAFA

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The motion of bubbles rising in confined geometries has gained interest due to its applications in mixing and mass transfer processes, ranging from bubble column reactors in the chemical industry to solar photobioreactors for algae cultivation. In this work we performed an experimental investigation of the behavior of air bubbles freely rising at high Reynolds numbers in a planar thin-gap cell of thicknessh=2.8 mm filled with distilled water. The in-plane width of the cell W is varied from 2.4 cm to 21 cm. We focus on the influence of lateral confinement on the motion of bubbles in the regimes with regular path and shape oscillations of large amplitude, that occur for the size range 0.6 cm<d<1.2cm. In addition, a rise regime that consists of a vertical rise path with regular shape oscillations, that does not appear in the laterally unconfined case, is uncovered. In the presence of lateral walls, the mean rise velocity of the bubble Vb becomes lower than the velocity of a laterally unconfined bubble of the same size beyond a critical bubble diameterdcVthat decreases as the confinement increases(i.e. as W decreases). The influence of the lateral confinement on the bubble mean shape can be determined from the change in the mean aspect ratio χ of the ellipse that best fits the bubble contour at each instant. It is observed that bubbles become closer to circular (χ closer to 1) as the confinement increases. The departure from the values ofχof the laterally unconfined case occur at a critical diameterdcχthat is lower for greater confinement and also greaterthandcVfor each confinement, thus indicating that the effect of the lateral confinement is seen earlier (i.e. on smaller bubbles) on the velocity than on the aspect ratio. Assuming that the wall effect is related to the strength of the downward flow generated by the bubble, we introduce the mean flow velocity in the space let free for the liquid between the walls and the bubble, Uf, that can be estimated by mass conservation asUf=dVb/(W−d). We further introduce the relative velocity between the bubble and the downward fluid in its vicinityUrel=Vb+Uf=Vb/ξ, whereξ=1−d/Wis the confinement ratio of the bubble. We found that, for a given bubble size in the oscillatory regime, Urel is approximately constant for all the studied values of W, and matches closely the value in the absence of lateral confinement. This provides an estimation, at leading order, of the bubble velocity that generalizes the expression proposed by Filella et al. (JFM, 2015) and accounts for the additional drag experienced by the bubble due to the lateral walls. We then show that, for givendandξ, the frequency and amplitudes of the oscillatory motion can be predicted using the characteristic length and velocity scales d and Urel.

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“…Xu et al [23] found that the fully developed turbulent gas–liquid slug flow and slug translation velocity depended on the local maximum velocity adjacent to the trailing edge of the Taylor bubbles in a long horizontal pipe with an inner diameter of 51 mm. Many methods have been employed to investigate the bubble velocity during flow boiling in minichannels [24] , [25] , [26] , [27] , [28] . Pavlov et al [24] used a high-speed camera to trace the motion of a single bubble in a rectangular minichannel.…”

Section: Introductionmentioning

confidence: 99%

“…Many methods have been employed to investigate the bubble velocity during flow boiling in minichannels [24] , [25] , [26] , [27] , [28] . Pavlov et al [24] used a high-speed camera to trace the motion of a single bubble in a rectangular minichannel. They found that the velocity of the bubble in the rising direction did not follow the Poiseuille parabolic distribution and observed that wall restriction markedly disturbs the bubble wake.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on flow boiling bubble motion under ultrasonic field in vertical minichannel by using bubble tracking algorithm

Xiao

Zhang

2023

Ultrasonics Sonochemistry

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Exploration by Shake-the-Box technique of the 3D perturbation induced by a bubble rising in a thin-gap cell

Abstract: Exploration by Shake-the-Box technique of the 3D perturbation induced by a bubble rising in a thin-gap cell. (2021) Experiments in Fluids, 62 (22).

Cited by 10 publications

References 29 publications

Bubble rise in a Hele-Shaw cell: bridging the gap between viscous and inertial regimes

Bubble rise in a Hele-Shaw cell: bridging the gap between viscous and inertial regimes

Oscillating Bubbles Rising in a Doubly Confined Cell

Experimental investigation on flow boiling bubble motion under ultrasonic field in vertical minichannel by using bubble tracking algorithm

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