We present scaling laws for the jet velocity resulting from bubble collapse at a liquid surface which bring out the effects of gravity and viscosity. The present experiments conducted in the range of Bond numbers < 0.004<Bo and Ohnesorge numbers <0.001<Oh were motivated by the discrepancy between previous experimental results and numerical simulations. We show here that the actual dependence of on is determined by the gravity dependency of the bubble immersion (cavity) depth which has no power-law variation. The power-law variation of the jet Weber number, , suggested by Ghabache et al. (Phys. Fluids, vol. 26 (12), 2014, 121701) is only a good approximation in a limited range of values ( <0.1<Bo). Viscosity enters the jet velocity scaling in two ways: (i) through damping of precursor capillary waves which merge at the bubble base and weaken the pressure impulse, and (ii) through direct viscous damping of the jet formation and dynamics. These damping processes are expressed by a dependence of the jet velocity on Ohnesorge number from which critical values of are obtained for capillary wave damping, the onset of jet weakening, the absence of jetting and the absence of jet breakup into droplets. © 2017 Cambridge University Press.

Baburaj A. Puthenveettil

Department of Applied Mechanics

Sangeeth Krishnan

BUBBLE FORMATION

Damping

Drop breakup

Jets

Viscosity

breakup/coalescence

BUBBLE COLLAPSE

drops and bubbles

Jet velocities

LIQUID SURFACE

POWER LAW VARIATION

PRESSURE IMPULSE

Viscous damping

Fighter aircraft

Bubble

Droplet

experimental study

jet flow

Power law

Fulltext

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IIT Madras

Journal of Fluid Mechanics

Parametrically forced gravity waves can give rise to high-velocity surface jets via the wave-depression cavity implosion. The present results have been obtained in circular cylindrical containers of 10 and 15 cm in diameter (Bond number of order 103) in the large fluid depth limit. First, the phase diagrams of instability threshold and wave breaking conditions are determined for the working fluid used, here water with 1% detergent added. The collapse of the wave-depression cavity is found to be self-similar. The exponent α of the variation of the cavity radius rm with time τ, in the form rm=R/α τ α, is close to 0.5, indicative of inertial collapse, followed by a viscous cut-off of α ∼ 1. This supports a Froude number scaling of the surface jet velocity caused by cavity collapse. The dimensionless jet velocity scales with the cavity depth that is shown to be proportional to the last stable wave amplitude. It can be expressed by a power law or in terms of finite time singularity related to a singular wave amplitude that sets the transition from a non-pinching to pinch-off cavity collapse scenario. In terms of forcing amplitude, cavity collapse and jetting are found to occur in bands of events of non-pinching and pinching of a bubble at the cavity base. At large forcing amplitudes, incomplete cavity collapse and splashing can occur and, at even larger forcing amplitudes, wave growth is again stable up to the singular wave amplitude. When the cavity is formed, an impulse model shows the importance of the singular cavity diameter that determines the strength of the impulse. © 2019 Cambridge University Press.

On standing gravity wave-depression cavity collapse and jetting

On the scaling of jetting from bubble collapse at a liquid surface

We experimentally study the collapse of cavities formedby bubbles of different radius R at the free surface of five different fluids. The tangential and normal velocities of the disturbance front on the bubble surface were measured andshown that the tangential velocities scale as the capillary velocity (σ/ρR)1/2. The total time for the completion of cavity collapse was measured and shown to scale as capillary time scale R3/2/(σ/ρ)1/2. We hence infer thatthe cavity collapse is dominated by surface tension and inertia with viscosity not playing a role in the regime of our investigation. Such a behavior of cavity dynamics is different from the behavior of jet velocity discussed by Sangeeth et.al.[9] wherein the jet velocity showed a clear viscous cut off. The rate of change of cavity volume was found to be constant with time, the implications of which needs to be investigated further. © 2015 The Authors. Published by Elsevier B.V.

Procedia IUTAM

Dynamics of Collapse of Free Surface Bubbles

Partial coalescence from bubbles to drops

Physical Review E

Jet drops from bursting bubbles: How gravity and viscosity couple to inhibit droplet production

Nature Communications

Aerosol generation by raindrop impact on soil

Journal	Data powered by TypesetJournal of Fluid Mechanics
Publisher	Data powered by TypesetCambridge University Press
ISSN	00221120
Open Access	No