Levitation of a drop over a film flow

Sreenivas, K. R.; De, Prithwiraj; Arakeri, Jaywant H.

doi:10.1017/s0022112098003486

Cited by 37 publications

(61 citation statements)

References 4 publications

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“…The probability of bouncing also increases with the film Reynolds number. This is consistent with the phenomenon of droplet levitation at the hydraulic jump point of a liquid film produced from a vertical jet impinging on a horizontal surface [61], which corresponds to a large Re and negligible We in Figure 9. …”

Section: Iii6 Regime Mapsupporting

confidence: 86%

Impact of droplets on inclined flowing liquid films

2015

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The impact of droplets on an inclined falling liquid film is studied experimentally using highspeed imaging. The falling film is created on a flat substrate with controllable thicknesses and flow rates. Droplets with different sizes and speeds are used to study the impact process under various Ohnesorge and Weber numbers, and film Reynolds numbers. A number of phenomena associated with droplet impact are identified and analysed, such as bouncing, partial coalescence, total coalescence, and splashing. The effects of droplet size, speed, as well the film flow rate are studied culminating in the generation of an impact regime map. The analysis of the lubrication force acted on the droplet via the gas layer shows that a higher flow rate in the liquid film produces a larger lubrication force, slows down the drainage process, and increases the probability of droplet bouncing. Our results demonstrate that the flowing film has a profound effect on the droplet impact process and associated phenomena, which are markedly more complex than those accompanying impact on initially quiescent films.

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Section: Iii6 Regime Mapsupporting

confidence: 86%

Impact of droplets on inclined flowing liquid films

2015

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“…This phenomenon was already observed in a slightly different situation in which a drop levitates over a hydraulic jump (Sreenivas et al 1999;Pirat et al 2010). Sreenivas et al (1999) suggested the levitation is due to the pressure built-up generated by the lubrication flow under the drop.…”

Section: Introductionmentioning

confidence: 73%

Levitation of a drop over a moving surface

et al. 2013

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We investigate the levitation of a drop gently deposited onto the inner wall of a rotating hollow cylinder. For a sufficient velocity of the wall, the drop steadily levitates over a thin air film and reaches a stable angular position in the cylinder, where the drag and lift balance the weight of the drop. Interferometric measurement yields the three-dimensional (3D) air film thickness under the drop and reveals the asymmetry of the profile along the direction of the wall motion. A two-dimensional (2D) model is presented which explains the levitation mechanism, captures the main characteristics of the air film shape and predicts two asymptotic regimes for the film thickness h 0 : For large drops h 0 ∼ Ca 2/3 κ −1 b , as in the Bretherton problem, where Ca is the capillary number based on the air viscosity and κ b is the curvature at the bottom of the drop. For small drops h 0 ∼ Ca 4/5 (aκ b ) 4/5 κ −1 b , where a is the capillary length.

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“…Tangential flow away from the point of contact then tends to drive air out of the gap between drop and reservoir, and reduce the time the drops spends above he interface before coalescence. 26 Obtaining reproducible initial conditions was thus proved challenging and limited the scope of our experimental observations. The drop and reservoir fluids were made of either pure water, pure ethanol, or one of five ethanol-water mixtures, as shown in Table I.…”

Section: Methodsmentioning

confidence: 99%

The influence of surface tension gradients on drop coalescence

2009

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We present the results of a combined experimental and numerical investigation of the coalescence of a drop with a liquid reservoir of a miscible but distinct fluid. Particular attention is given to elucidating the influence on the coalescence process of a surface tension difference between drop and reservoir. Drops are gently deposited on the surface of the reservoir, and so coalesce with negligible initial vertical velocity. Depending on the drop size and reservoir composition, partial or total coalescence may occur. Three distinct regimes, depending on the reservoir to drop surface tension ratio, Rσ, are identified and delineated through both experiments and numerics. If Rσ<0.42, droplets are ejected from the top of the drop, while satellite droplets are left in its wake. For 0.42≤Rσ<0.93, only total coalescence is observed. When Rσ≥0.93, partial coalescence is increasingly favored as the reservoir’s surface tension increases.

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Levitation of a drop over a film flow

Cited by 37 publications

References 4 publications

Impact of droplets on inclined flowing liquid films

Impact of droplets on inclined flowing liquid films

Levitation of a drop over a moving surface

The influence of surface tension gradients on drop coalescence

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