Dynamics of an initially spherical bubble rising in quiescent liquid

Tripathi, Manoj Kumar; Sahu, Kirti Chandra; Govindarajan, Rama

doi:10.1038/ncomms7268

Cited by 361 publications

(204 citation statements)

References 47 publications

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“…[21,25], where it was found to be made of a pair of intertwined counterrotating vortices resulting in a frozen structure in the reference frame rotating with the bubble. Some more recent DNS studies examined the wake evolution during the rise of a freely deforming bubble, mostly in the zigzagging regime under conditions where time-dependent deformations remain modest [27,28] or in the wobbling regime where the shape exhibits large capillary-driven oscillations [29]. However, none of these studies focused on conditions close to the path instability threshold.…”

Section: Introductionmentioning

confidence: 99%

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Paths and wakes of deformable nearly spheroidal rising bubbles close to the transition to path instability

et al. 2016

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 16174 (2016)] in which the neutral curve associated with this transition was obtained by considering realistic but frozen bubble shapes. Depending on the dimensionless parameters that characterize the system, various paths geometries are observed by letting an initially spherical bubble starting from rest rise under the effect of buoyancy and adjust its shape to the surrounding flow. These include the well-documented rectilinear axisymmetric, planar zigzagging, and spiraling (or helical) regimes. A flattened spiraling regime that most often eventually turns into either a planar zigzagging or a helical regime is also frequently observed. Finally, a chaotic regime in which the bubble experiences small horizontal displacements (typically one order of magnitude smaller than in the other regimes) is found to take place in a region of the parameter space where no standing eddy exists at the back of the bubble. The discovery of this regime provides evidence that path instability does not always result from a wake instability as previously believed. In each regime, we examine the characteristics of the path, bubble shape, and vortical structure in the wake, as well as their couplings. In particular, we observe that, depending on the fluctuations of the rise velocity, two different vortex shedding modes exist in the zigzagging regime, confirming earlier findings with falling spheres. The simulations also reveal that significant bubble deformations may take place along zigzagging or spiraling paths and that, under certain circumstances, they dramatically alter the wake structure. The instability thresholds that can be inferred from the computations compare favorably with experimental data provided by various sets of recent experiments guaranteeing that the bubble surface is free of surfactants.

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Section: Introductionmentioning

confidence: 99%

“…21 were extracted from a recent computational study [29], also performed with the GERRIS code. Although the critical conditions that can be inferred from these data are in good qualitative agreement with the present ones for Bo 2, they result in significantly lower values of Ga c for Bo 1.…”

Section: B Toward a Well-defined Critical Curve: Current Consensus Amentioning

confidence: 99%

Paths and wakes of deformable nearly spheroidal rising bubbles close to the transition to path instability

et al. 2016

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“…(2.9) and (2.10), respectively. The results obtained from this solver are validated against another finite-volume open source code, Gerris (Popinet 2003;Tripathi et al 2015) with dynamic adaptive grid refinement feature based on the vorticity magnitude and species concentration. We found that the finest grid size of 0.015 (approximately) in the diffusive region of the slower and faster diffusing species and grids of size 0.06 (approximately) in the vortical region are sufficient to yield grid independent results to capture the onset of instability and other flow features for the parameters considered in the present study.…”

Section: Direct Numerical Simulationsmentioning

confidence: 99%

“…We found that the finest grid size of 0.015 (approximately) in the diffusive region of the slower and faster diffusing species and grids of size 0.06 (approximately) in the vortical region are sufficient to yield grid independent results to capture the onset of instability and other flow features for the parameters considered in the present study. The readers are referred to Tripathi et al (2015) for detailed description of the numerical method used in this study.…”

Section: Direct Numerical Simulationsmentioning

confidence: 99%

“…A periodic boundary condition is implemented in the axial direction. A bespoke finite-volume flow solver (Sahu et al 2009;Tripathi et al 2015) is used to solve the governing equations on a staggered grid. The scalar variables (the pressure and the volume fraction of the outer fluid) are defined at the cell-centres and the velocity components are defined at the cell faces, respectively.…”

Section: Direct Numerical Simulationsmentioning

confidence: 99%

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Double-diffusive instability in core–annular pipe flow

Sahu

2016

J. Fluid Mech.

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The instability in a pressure-driven core-annular flow of two miscible fluids having the same densities, but different viscosities in the presence of two scalars diffusing at different rates (double-diffusive effect) is investigated via linear stability analysis and axisymmetric direct numerical simulation. It is found that the double-diffusive flow in a cylindrical pipe exhibits strikingly different stability characteristics compared to the double-diffusive flow in a planar channel and the equivalent single-component flow (wherein viscosity stratification is achieved due to the variation of one scalar) in a cylindrical pipe. The flow which is stable in the context of single-component systems, now becomes unstable in the presence of two scalars diffusing at different rates. It is shown that increasing the diffusivity ratio enhances the instability. In contrast to the single fluid flow through a pipe (the Hagen-Poiseuille flow), the faster growing axisymmetric eigenmode is found to be more unstable than the corresponding corkscrew mode for the parameter values considered, for which the equivalent single-component flow is stable to both the axisymmtric and corkscrew modes. Unlike single-component flows of two miscible fluids in a cylindrical pipe, it is shown that the diffusivity and the radial location of the mixed layer have non-monotonic influences on the instability characteristics. An attempt is made to understand the underlying mechanism of this instability by conducting the energy budget and inviscid stability analyses. The investigation of linear instability due to the double-diffusive phenomenon is extended to the nonlinear regime via axisymmetric direct numerical simulations. It is found that in the nonlinear regime the flow becomes unstable in the presence of double-diffusive effect, which is consistent with the predictions of linear stability theory. A new type of instability pattern of an elliptical shape is observed in the nonlinear simulations in the presence of double-diffusive effect.

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Bouncing of a bubble at a liquid–liquid interface

Singh¹,

Gebauer

Bart

2017

AIChE Journal

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Significant industrial relevance of gas–liquid–liquid flows calls for understanding of their various aspects. This study focusing on one of the aspects, i.e., interaction of a single bubble with a liquid–liquid interface, is aimed at providing the experimental evidence of a hitherto unreported phenomenon of conditional bouncing of a bubble at the interface between two immiscible, initially quiescent liquids. Bouncing of the bubble is observed for two of the six pairs of the immiscible liquids used in the experiments. The data, obtained by conducting experiments with different pairs of the lighter and heavier liquid bubble diameters and rise heights, suggest that a bubble crossing a liquid–liquid interface is expected to bounce when its average velocity is less than a threshold value that depends on the interfacial tension between the two liquids and the viscosity of the heavier liquid. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3150–3157, 2017

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Dynamics of an initially spherical bubble rising in quiescent liquid

Cited by 361 publications

References 47 publications

Paths and wakes of deformable nearly spheroidal rising bubbles close to the transition to path instability

Paths and wakes of deformable nearly spheroidal rising bubbles close to the transition to path instability

Double-diffusive instability in core–annular pipe flow

Bouncing of a bubble at a liquid–liquid interface

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