Highly turbulent Couette–Taylor bubbly flow patterns

Atkhen, Kresna; Fontaine, Jean-Pierre; Wesfreid, José Eduardo

doi:10.1017/s0022112000001592

Cited by 33 publications

(34 citation statements)

References 18 publications

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“…In the present experiment, the breakup or coalescence of the bubbles does not occur. Also, trapping phenomena observed in the literatures (Climent et al, 2007, andAtkhen et al, 2000) was not observed in the present experiment. The effects of the accumulation are possibly smaller with respect to the buoyancy effects because the diameter of the bubbles of D = 4.7 mm is larger than those of the literatures, where the mean floating velocity ≈ 0.25 m/s is higher than the rotating speed of about 0.14 m/s.…”

Section: Relationship Between Position Of Aeration and Time For Floatcontrasting

confidence: 52%

Effective mixing and aeration in a bioreactor with Taylor vortex flow

Yokoyama

Hirose

Iida

2016

Mechanical Engineering Letters

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Section: Relationship Between Position Of Aeration and Time For Floatcontrasting

confidence: 52%

Effective mixing and aeration in a bioreactor with Taylor vortex flow

Yokoyama

Hirose

Iida

2016

Mechanical Engineering Letters

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“…However, the wall bubbles are found only in the outflow regions along the inner cylinder (shown by P4 in Figure 2), while positions denoted by P1, P2 and P3 are not favored. This may be attributed to the fact that pressure dominates among the various forces on the bubble [1], and P4 corresponds to the lowest pressure according to the pressure distribution calculated by Atkhen et al [4] 3.1 Core bubbles When bubbles of the same size are injected into a certain vortex core, a bubble ring forms at the center of the vortex such that bubbles are azimuthally uniformly distributed. Figure 3 shows a picture of a ring consisting of 61 bubbles.…”

Section: Resultsmentioning

confidence: 99%

“…Djeridi et al reported bubble capture and migration in a Couette-Taylor flow [3]. Atkhen et al presented an experimental study on the highly turbulent Couette-Taylor bubbly flow patterns [4]. Djeridi et al studied the mutual interactions between dispersed and continuous phases in the CouetteTaylor flow [5].…”

Section: Introductionmentioning

confidence: 99%

Bubble behavior in a Taylor vortex

2006

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-We present an experimental study on the behavior of bubbles captured in a Taylor vortex. The gap between a rotating inner cylinder and a stationary outer cylinder is filled with a Newtonian mineral oil. Beyond a critical rotation speed (ω c ), Taylor vortices appear in this system. Small air bubbles are introduced into the gap through a needle connected to a syringe pump. These are then captured in the cores of the vortices (core bubble) and in the outflow regions along the inner cylinder (wall bubble). The flow field is measured with a twodimensional particle imaging velocimetry (PIV) system. The motion of the bubbles is monitored by using a high speed video camera. It has been found that, if the core bubbles are all of the same size, a bubble ring forms at the center of the vortex such that bubbles are azimuthally uniformly distributed. There is a saturation number (N s ) of bubbles in the ring, such that the addition of one more bubble leads eventually to a coalescence and a subsequent complicated evolution. N s increases with increasing rotation speed and decreasing bubble size. For bubbles of non-uniform size, small bubbles and large bubbles in nearly the same orbit can be observed to cross due to their different circulating speeds. The wall bubbles, however, do not become uniformly distributed, but instead form short bubble-chains which might eventually evolve into large bubbles. The motion of droplets and particles in a Taylor vortex was also investigated. As with bubbles, droplets and particles align into a ring structure at low rotation speeds, but the saturation number is much smaller. Moreover, at high rotation speeds, droplets and particles exhibit a characteristic periodic oscillation in the axial, radial and tangential directions due to their inertia. In addition, experiments with non-spherical particles show that they behave rather similarly. This study provides a better understanding of particulate behavior in vortex flow structures.Index Terms -bubble, droplet, particle, Taylor vortex I. INTRODUCTIONBubbles can be found in Taylor vortices during various processes. For example, a careless operation can introduce air bubbles into a liquid system; or small bubbles may be employed for the purpose of visualization of a Taylor vortex [1]. Thus, a study of bubble behavior is of great interest to experimental work. In addition, the mutual bubble-fluid interaction can be an interesting topic in fundamental research.Shiomi et al. investigated the gas-liquid twophase flow in a concentric annulus with axial flow. . However, a detailed study of the bubble behavior is still unavailable, due partially to the narrow operating range of the traditional Taylor cells.In the present study, a viscous liquid layer within a wide gap between two concentric cylinders is adopted to generate the Taylor vortices necessary to trap air bubbles. As a result,

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“…Unlike what was seen for a lighter liquid dispersed in a heavier continuous phase where droplets tended to go toward the vortex cores, it has been shown that bubbles migrate toward the inner cylinder and are most stably located in rings along the regions of outflow between toroidal TC vortices [154][155][156][157]. Numerical studies have also been able to predict this behavior [154,158,159]. Batten et al [160] developed a method of using the average bubble distribution to identify the location of Taylor cells.…”

Section: Gas-liquid Dispersion Due To the Annular Region Beingmentioning

confidence: 99%

“…Atkhen et al [154] have observed the fluid mechanics of an annular contactor apparatus with radial vanes beneath the rotor directing the flow toward a downward axial exit (see also [149,162]). The device used in this work had a very long aspect ratio (total height relative to annular gap)-hydrodynamic observations were made with a liquid height of ∼50 cm and annular gaps of 5 mm and 10 mm.…”

Section: Gas-liquid Dispersion Due To the Annular Region Beingmentioning

confidence: 99%

CFD Simulation of Annular Centrifugal Extractors

Vedantam

Wardle

Tamhane

et al. 2012

International Journal of Chemical Engineering

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Annular centrifugal extractors (ACE), also called annular centrifugal contactors offer several advantages over the other conventional process equipment such as low hold-up, high process throughput, low residence time, low solvent inventory and high turn down ratio. The equipment provides a very high value of mass transfer coefficient and interfacial area in the annular zone because of the high level of power consumption per unit volume and separation inside the rotor due to the high g of centrifugal field. For the development of rational and reliable design procedures, it is important to understand the flow patterns in the mixer and settler zones. Computational Fluid Dynamics (CFD) has played a major role in the constant evolution and improvements of this device. During the past thirty years, a large number of investigators have undertaken CFD simulations. All these publications have been carefully and critically analyzed and a coherent picture of the present status has been presented in this review paper. Initially, review of the single phase studies in the annular region has been presented, followed by the separator region. In continuation, the two-phase CFD simulations involving liquid-liquid and gas-liquid flow in the annular as well as separator regions have been reviewed. Suggestions have been made for the future work for bridging the existing knowledge gaps. In particular, emphasis has been given to the application of CFD simulations for the design of this equipment.

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Highly turbulent Couette–Taylor bubbly flow patterns

Cited by 33 publications

References 18 publications

Effective mixing and aeration in a bioreactor with Taylor vortex flow

Effective mixing and aeration in a bioreactor with Taylor vortex flow

Bubble behavior in a Taylor vortex

CFD Simulation of Annular Centrifugal Extractors

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