Temperature fields in a liquid due to the thermocapillary motion of bubbles and drops

Wozniak, G.; Balasubramaniam, R.; Hadland, P. H.; Subramanian, R. Shankar

doi:10.1007/s003480000262

Cited by 29 publications

(14 citation statements)

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“…Since the YGB theory was published, there have been many studies on this problem using theoretical, experimental and numerical tools (see Balasubramaniam & Chai 1987;Chen & Lee 1992;Treuner et al 1996;Haj-Hariri, Shi & Borhan 1997;Welch 1998;Wozniak et al 2001;Sun & Hu 2002Nas, Muradoglu & Tryggvason 2006;Borcia & Bestehorn 2007;Liu, Zhang & Valocchi 2012;Liu et al 2013). Most early findings have been summarized and discussed in the review book by ; see also Subramanian, Balasubramaniam & Wozniak (2002).…”

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confidence: 99%

Thermocapillary migration and interaction of drops: two non-merging drops in an aligned arrangement

Yin

2015

J. Fluid Mech.

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A numerical study on the interaction of two spherical drops in thermocapillary migration in microgravity is presented. Unequal drop sizes in the axisymmetric model lead to strong drop interaction if the leading drop is smaller. The effect of the ratio of the two drop radii, their initial distance apart, and non-dimensional numbers on the interaction is studied in the case of non-merging drops in detail. The Marangoni number adopted in this paper is fairly large (around 100) so as to reveal the phenomena of real flows. As a result, the heat wake behind the leading drop plays an important role in drop interaction, and obviously different final drop distances and transient migration processes are observed for various sets of non-dimensional numbers. The influence of drop deformation on drop interaction is also investigated for relatively large capillary number (up to 0.2). Finally, some simulations are performed to explain the phenomena of drop interaction in previous experiments, and some suggestions for future experiments are also provided.

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confidence: 99%

Thermocapillary migration and interaction of drops: two non-merging drops in an aligned arrangement

Yin

2015

J. Fluid Mech.

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“…The sub-droplet distribution is also affected by the internal circulation induced by a relative velocity between the droplet and the ambient air. [11][12][13] Second, droplet heating causes thermocapillary (Marangoni) migration of inner sub-droplets toward the hot side, 1,7,25,26 which may lead to sub-droplet coalescence. In experiments with a longer time scale (∼O(1 s) for heating) using larger droplets, complete phase separation of the oil and the water was observed before microexplosion.…”

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confidence: 99%

Physics of puffing and microexplosion of emulsion fuel droplets

et al. 2014

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The physics of water-in-oil emulsion droplet microexplosion/puffing has been investigated using high-fidelity interface-capturing simulation. Varying the dispersed-phase (water) sub-droplet size/location and the initiation location of explosive boiling (bubble formation), the droplet breakup processes have been well revealed. The bubble growth leads to local and partial breakup of the parent oil droplet, i.e., puffing. The water sub-droplet size and location determine the after-puffing dynamics. The boiling surface of the water sub-droplet is unstable and evolves further. Finally, the sub-droplet is wrapped by boiled water vapor and detaches itself from the parent oil droplet. When the water sub-droplet is small, the detachment is quick, and the oil droplet breakup is limited. When it is large and initially located toward the parent droplet center, the droplet breakup is more extensive. For microexplosion triggered by the simultaneous growth of multiple separate bubbles, each explosion is local and independent initially, but their mutual interactions occur at a later stage. The degree of breakup can be larger due to interactions among multiple explosions. These findings suggest that controlling microexplosion/puffing is possible in a fuel spray, if the emulsion-fuel blend and the ambient flow conditions such as heating are properly designed. The current study also gives us an insight into modeling the puffing and microexplosion of emulsion droplets and sprays.

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“…In this case, the bubble performs translational motion toward the light beam, which, in essence, is equivalent to classical thermocapillary bubble motion in a longitudinal temperature gradient [8,14]. Then, as soon as the distance between the bubble surface and the light beam decreases to approximately the beam diameter, the occurrence of localized vortices is observed again.…”

Section: Vortex Visualizationmentioning

confidence: 94%

Thermocapillary Vortices Induced by a Light Beam near a Bubble Surface in a Hele-Shaw Cell

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Bezuglyi

2005

J Appl Mech Tech Phys

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This paper studies thermocapillary vortices induced by local heating of a bubble surface in a HeleShaw cell by a light beam. It is found that the vortex rotation frequency and its depth depend on the distance from the light-beam projection onto the layer to the bubble boundary. The surface velocity of the thermocapillary flow is calculated using the balance of the near-surface and return flows of the thermocapillary vortex and the equality of capillary and dynamic pressures. It is shown that a decrease in the surface velocity and the vortex rotation frequency with increase in the distance from the light beam to the bubble surface is due to a decrease in the temperature gradient between the illuminated and cold poles of the bubble. Introduction. Bubble motion in a Hele-Shaw cell (h/D1, where D is the bubble diameter and h is the cell spacing) has been extensively studied both theoretically and experimentally [1][2][3][4]. Recently, interest in this problem has increased because of the need to develop methods for controlling liquids and bubbles in microscale bubble pumps, biochips, etc. [5,6]. However, for duct flows, the examined mechanisms of bubble motion due to mechanically produced pressure gradients [1][2][3] or the buoyancy forces arising from the cell inclination [4] are inefficient or do not operate altogether. For example, for ethanol drops (ρ = 800 kg/m 3 and σ = 22.8 · 10 −3 N/m [7]) moving at a velocity of 1 cm/sec inside a microchannel with a cross-sectional size of 100 µm, the Bond number and the capillary number have orders of magnitude Bo ≈ 10 −3 and Ca ≈ 10 −4 , respectively. That small values indicate that in the problems considered, capillary forces dominate over gravitational and viscous forces. The migration of bubbles under the action of thermocapillary forces was first demonstrated by Young et al. [8], who studied bubble motion under the action of a vertical temperature gradient ∇T opposite to the buoyancy force. Mazouchi and Homsy [9] and Lajeunesse and Homsy [10] performed experimental and theoretical studies of bubble motion in polygonal microchannels under the action of thermocapillary forces related to a longitudinal temperature gradient [9, 10].The possibility of controlling bubbles in a Hele-Shaw cell by means of a local temperature gradient induced by the thermal action of a light beam was first shown by Bezuglyi [11]. Later, Bezuglyi and Ivanova [12] reported results from studies of bubble motion behind a light beam and for the first time gave a qualitative explanation of the motion mechanism based on the action of localized thermocapillary liquid vortices induced by the light beam at the lateral surface of the bubble.In the present work, an attempt was undertaken to obtain quantitative information on the size of thermocapillary vortices induced by the thermal action of light, the frequency of their rotation and flow velocity on the bubble surface.

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Temperature fields in a liquid due to the thermocapillary motion of bubbles and drops

Cited by 29 publications

References 0 publications

Thermocapillary migration and interaction of drops: two non-merging drops in an aligned arrangement

Thermocapillary migration and interaction of drops: two non-merging drops in an aligned arrangement

Physics of puffing and microexplosion of emulsion fuel droplets

Thermocapillary Vortices Induced by a Light Beam near a Bubble Surface in a Hele-Shaw Cell

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