Surfactant Effects on Bubble Motion and Bubbly Flows

Takagi, Shu; Matsumoto, Yoichiro

doi:10.1146/annurev-fluid-122109-160756

Cited by 230 publications

(139 citation statements)

References 42 publications

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“…Moreover, according to our visualization in the x−y and x−z planes, both the bubble-wall attachment as seen for smaller bubbles (Fig. 1) and the bubble cluster as seen in a vertical channel bubbly flow [39] do not occur at any φ, even though rising bubbles are located close to the wall, especially at φ=40˚. We speculate that the former relates to the buoyancy/surface tension ratio of injected bubbles, while the latter relates mainly to their interface shape and local bubble number density.…”

Section: Bubble Concentration and Wall-parallel Mean Velocity Of Bubblessupporting

confidence: 56%

Effect of heated wall inclination on natural convection heat transfer in water with near-wall injection of millimeter-sized bubbles

Kitagawa

Denissenko

Murai

2017

International Journal of Heat and Mass Transfer

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A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. ABSTRACT Natural convection heat transfer from a heated wall in water with near-wall injection of millimeter-sized bubbles is studied experimentally. Velocity and temperature measurements are conducted in the near-wall region. In the range of the heated wall angles from 0 to 40˚ from the vertical, the heat transfer coefficient increases by up to an order of magnitude with bubble injection. The ratio of the heat transfer coefficient with bubble injection to that without injection increases with the wall inclination angle. Based upon measured liquid temperature distributions and liquid flow velocity profiles, enhancement of heat transfer by bubble injection is explained by two mechanisms. First, wall-parallel transport of cold liquid into the thermal boundary layer is enhanced by the bubbledriven flow. Second, wall-normal mixing of warm liquid and cold liquid occurs, as a result of wall-normal velocity fluctuations of the liquid phase activated by a combination of bubble rising motion, vortex shedding from the bubbles, and unsteady vortices formed within the boundary layer. The unsteady vortices travel along the wall together with the bubbles, primarily contributing to the enhancement of heat transfer at higher wall inclination angles.

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Section: Bubble Concentration and Wall-parallel Mean Velocity Of Bubblessupporting

confidence: 56%

Effect of heated wall inclination on natural convection heat transfer in water with near-wall injection of millimeter-sized bubbles

Kitagawa

Denissenko

Murai

2017

International Journal of Heat and Mass Transfer

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“…The approach developed in this paper may be coupled with a realistic model of surfactant transport 12,44 to assess the changes induced in the wake dynamics by the adsorption/desorption and surface transport mechanisms that drive the contamination of bubbles in many real fluids, especially water. Nevertheless the next step of this stream of research performed in our group will still consider clean bubbles.…”

Section: Discussionmentioning

confidence: 99%

“…This features suggest that a disturbance applied on the rear part of the bubble surface, especially close to its symmetry axis, should significantly modify the stability of the wake. It may also be related to the well-known sensitivity of bubble paths to the presence of minute amounts of surfactants which are swept to the rear of the bubble by the base flow and modify the boundary condition, from shear-free to no-slip, in that region 12,34 .…”

Section: B Receptivity To a Localized Feedbackmentioning

confidence: 99%

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Linear stability and sensitivity of the flow past a fixed oblate spheroidal bubble

2013

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The stability properties of the wake past an oblate spheroidal bubble held fixed in a uniform stream are studied in the framework of a global linear analysis. In line with previous studies, provided the geometric aspect ratio of the bubble, χ, is large enough, the wake is found to be unstable only within a finite range of Reynolds number, Re. The neutral curves corresponding to the occurrence of the first two unstable modes are determined over a wide range of the (χ, Re) domain and the structure of the modes encountered along the two branches of each neutral curve is discussed. Then, using an adjoint-based approach, a series of sensitivity analyses of the flow past the bubble is carried out in the spirit of recent studies devoted to twodimensional and axisymmetric rigid bodies. The regions of the flow most sensitive to an external forcing are found to be concentrated in the core or at the periphery of the standing eddy, as already observed with bluff bodies at the surface of which the flow obeys a no-slip condition. However, since the shear-free condition allows the fluid to slip along the bubble surface, the rear half of this surface turns out to be also significantly sensitive to disturbances originating in the normal and shear stresses, a finding which may be related to the well-known influence of surfactants on the structure and stability properties of the flow past bubbles rising in water.

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“…気泡流には様々なスケールがあり、気泡が生成する乱れは多くの研究者の注目を集めている。その乱れは、流れ場と相互作用し、単相流とは異なる複雑な流動構造を示す [1][2][3][4][5][6]。特に気泡クラスターは、乱流の秩序渦構造よりも大きく、大規模な流動構造そのものを変化させる [7,8]。そのため気泡クラスター形成の有無について様々な報告が行われている [9][10][11]。気泡のクラスター形成は、まず理論的に予測された。ポテンシャル流れを仮定し、複数の気泡が上昇する際、気泡間相互作用によって水平面に気泡がクラスターを形成することが報告された [12,13]。一方で、実際の気泡流では、気泡同士の合体によって気泡径差が生まれ、通常気泡のクラスター構造は観察されない。さらに前述のポテンシャル流れを用いた理論でも、気泡径差を考慮するとクラスターは形成されない [14]。しかし、実験的研究において、界面活性剤や電解質を混入させることで気泡クラスターの形成が報告されている [15,16]。界面活性剤や電解質の混入は、気泡表面の境界条件を大きく変化させる。界面活性剤では気泡の抗力の増加や合体を防ぎ、電解質ではやクリーンな気泡を保ちながら気泡合体を防ぐ [17][18][19][20] /01 02 0/%/ü ! 1 ö 3 4 5 6 7 8 9 6 % !ú ÷ ù ' ü ü ö !…”

Section: 緒言unclassified

Influence of Surfactants on the Motion of a Pair of Bubbles in Quiescent Liquids

Kusuno¹,

Sanada²

2016

JAPANESE JOURNAL OF MULTIPHASE FLOW

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We experimentally investigated the motion of a pair of bubbles initially positioned inline configuration in ultrapure water or an aqueous surfactant solution. The bubble motion was observed by two high speed video cameras. The Reynolds number of bubbles were ranged from 50 to 200, and the bubbles hold a spherical shape in this range. In ultrapure water or small concentration of surfactant solution, initially the trailing bubble deviated from the vertical line on the leading bubble owing to the wake of the leading bubble. And then, the slight difference of the bubble radius changed the relative motion. When the trailing bubble slightly larger than the leading bubble, the trailing bubble approached to the leading bubble due to it's buoyancy difference. The bubbles attracted and collided only when the bubbles rising approximately side by side configuration. On the other hand, the trailing bubble was drafted to the wake region of leading bubble when the bubbles were rising in high concentration of surfactant solution. In this case, the bubbles always collided in line configuration. We consider that these phenomena are caused by the changes of lift force direction in the wake region owing to the surface contamination. In addition, bubble coalescence was inhibited in surfactant solution, even the relative motion was similar to the clean bubble case.

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Surfactant Effects on Bubble Motion and Bubbly Flows

Cited by 230 publications

References 42 publications

Effect of heated wall inclination on natural convection heat transfer in water with near-wall injection of millimeter-sized bubbles

Effect of heated wall inclination on natural convection heat transfer in water with near-wall injection of millimeter-sized bubbles

Linear stability and sensitivity of the flow past a fixed oblate spheroidal bubble

Influence of Surfactants on the Motion of a Pair of Bubbles in Quiescent Liquids

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