Asymmetric Cavitation Bubble Collapse

1973 ◽  
Vol 95 (1) ◽  
pp. 29-37 ◽  
Author(s):  
T. M. Mitchell ◽  
F. G. Hammitt
Keyword(s):  
Rigid Wall ◽  
The Body ◽  
Bubble Collapse ◽  
Fluid Viscosity ◽  
Uniform Pressure ◽  
Vapor Bubbles ◽  
Bubble Wall ◽  
Spherical Bubble ◽  
Spherical Bubbles ◽  
Wall Proximity

Numerical results describing the asymmetric collapse of vapor bubbles in an incompressible liquid for various cases of axial symmetry involving boundary conditions which prevent the maintenance of spherical symmetry are presented using a modified Marker-and-Cell (MAC) technique. The effects of fluid viscosity within the body of the liquid are considered, and upon the wall in the wall-proximity problem, but its effects at the bubble wall boundary are neglected. The cases studied include originally stationary spherical bubbles in a pressure gradient, an originally spherical bubble moving through an otherwise stationary liquid at uniform pressure, and an initially spherical bubble in a liquid at uniform pressure close to a rigid wall. This latter case applies approximately also to two identical bubbles collapsing in an infinite fluid in proximity to each other as shown by photographs here included. In all those cases which involve originally spherical bubbles, the bubble collapses in such a way as to form a jet.

Dynamics of expansion and collapse of explosive two-dimensional bubbles

2018 ◽  
Vol 859 ◽  
pp. 677-690
Author(s):  
Jérôme Duplat
Keyword(s):  
Water Vapour ◽  
Liquid Water ◽  
Indirect Measurement ◽  
Hot Water ◽  
Bubble Collapse ◽  
Gas Mixture ◽  
Two Dimensional ◽  
Initial Radius ◽  
Spherical Bubble ◽  
Spherical Bubbles

An explosive gas mixture of hydrogen and oxygen is introduced in liquid water between two horizontal walls, forming a flat cylindrical bubble. Ignition and explosion of the bubble lead to a large depressurized cavity that finally implodes. We investigate the dynamics of the bubble collapse, which is qualitatively similar to the collapse of a spherical bubble. It exhibits a slightly weaker singularity than for spherical bubbles. We also analyse the explosion process. Starting with an initial radius $R_{0}$, the bubble reaches a maximal radius $R_{max}$ that depends on the gap thickness $h$ between the two walls: for a thinner gap, the condensation of water vapour is more efficient, the overpressure consecutive to the combustion is weaker, and its duration is shorter. This leads to a smaller maximal radius $R_{max}$. An indirect measurement of the transport coefficient of hot water vapour can be inferred from this observation.

Jetting of viscous droplets from cavitation-induced Rayleigh–Taylor instability

2018 ◽  
Vol 846 ◽  
pp. 916-943 ◽  
Author(s):  
Qingyun Zeng ◽  
Silvestre Roberto Gonzalez-Avila ◽  
Sophie Ten Voorde ◽  
Claus-Dieter Ohl
Keyword(s):  
Bubble Dynamics ◽  
Stokes Equations ◽  
Droplet Surface ◽  
Taylor Instability ◽  
Bubble Collapse ◽  
Fluid Viscosity ◽  
Analytic Model ◽  
Radial Acceleration ◽  
Rayleigh Taylor Instability ◽  
Good Agreement

Liquid jetting and fragmentation are important in many industrial and medical applications. Here, we study the jetting from the surface of single liquid droplets undergoing internal volume oscillations. This is accomplished by an explosively expanding and collapsing vapour bubble within the droplet. We observe jets emerging from the droplet surface, which pinch off into finer secondary droplets. The jetting is excited by the spherical Rayleigh–Taylor instability where the radial acceleration is due to the oscillation of an internal bubble. We study this jetting and the effect of fluid viscosity experimentally and numerically. Experiments are carried out by levitating the droplet in an acoustic trap and generating a laser-induced cavitation bubble near the centre of the droplet. On the simulation side, the volume of fluid method (OpenFOAM) solves the compressible Navier–Stokes equations while accounting for surface tension and viscosity. Both two-dimensional (2-D) axisymmetric and 3-D simulations are performed and show good agreement with each other and the experimental observation. While the axisymmetric simulation reveals how the bubble dynamics results destabilizes the interface, only the 3-D simulation computes the geometrically correct slender jets. Overall, experiments and simulations show good agreement for the bubble dynamics, the onset of disturbances and the rapid ejection of filaments after bubble collapse. Additionally, an analytic model for the droplet surface perturbation growth is developed based on the spherical Rayleigh–Taylor instability analysis, which allows us to evaluate the surface stability over a large parameter space. The analytic model predicts correctly the onset of jetting as a function of Reynolds number and normalized internal bubble energy.

The Pressure Generated by the Bubble Collapse near a Rigid Wall

2019 ◽  
Vol 2019 (0) ◽  
pp. OS2-13
Author(s):  
Kenta USHIRO ◽  
Shu NAKASYOJI ◽  
Toshiyuki OGASAWARA ◽  
Hiroyuki TAKAHIRA
Keyword(s):  
Rigid Wall ◽  
Bubble Collapse

scholarly journals Non-spherical bubble dynamics in a compressible liquid. Part 1. Travelling acoustic wave

2010 ◽  
Vol 659 ◽  
pp. 191-224 ◽  
Author(s):  
Q. X. WANG ◽  
J. R. BLAKE
Keyword(s):  
Wave Equation ◽  
Numerical Model ◽  
Acoustic Wave ◽  
Compressible Liquid ◽  
Wave Frequency ◽  
Liquid Jet ◽  
Approximate Theory ◽  
Spherical Bubble ◽  
Spherical Bubbles ◽  
Bubble Behaviour

Micro-cavitation bubbles generated by ultrasound have wide and important applications in medical ultrasonics and sonochemistry. An approximate theory is developed for nonlinear and non-spherical bubbles in a compressible liquid by using the method of matched asymptotic expansions. The perturbation is performed to the second order in terms of a small parameter, the bubble-wall Mach number. The inner flow near the bubble can be approximated as incompressible at the first and second orders, leading to the use of Laplace's equation, whereas the outer flow far away from the bubble can be described by the linear wave equation, also for the first and second orders. Matching between the two expansions provides the model for the non-spherical bubble behaviour in a compressible fluid. A numerical model using the mixed Eulerian–Lagrangian method and a modified boundary integral method is used to obtain the evolving bubble shapes. The primary advantage of this method is its computational efficiency over using the wave equation throughout the fluid domain. The numerical model is validated against the Keller–Herring equation for spherical bubbles in weakly compressible liquids with excellent agreement being obtained for the bubble radius evolution up to the fourth oscillation. Numerical analyses are further performed for non-spherical oscillating acoustic bubbles. Bubble evolution and jet formation are simulated. Outputs also include the bubble volume, bubble displacement, Kelvin impulse and liquid jet tip velocity. Bubble behaviour is studied in terms of the wave frequency and amplitude. Particular attention is paid to the conditions if/when the bubble jet is formed and when the bubble becomes multiply connected, often forming a toroidal bubble. When subjected to a weak acoustic wave, bubble jets may develop at the two poles of the bubble surface after several cycles of oscillations. A resonant phenomenon occurs when the wave frequency is equal to the natural oscillation frequency of the bubble. When subjected to a strong acoustic wave, a vigorous liquid jet develops along the direction of wave propagation in only a few cycles of the acoustic wave.

Heat Transfer Controlled Collapse of a Cylindrical Vapor Bubble in a Vertical Isothermal Tube

1977 ◽  
Vol 99 (3) ◽  
pp. 392-397 ◽  
Author(s):  
D. R. Pitts ◽  
H. C. Hewitt ◽  
B. R. McCullough
Keyword(s):  
Heat Transfer ◽  
Vapor Bubble ◽  
High Speed ◽  
Experimental Results ◽  
Heat Transfer Analysis ◽  
Experimental Program ◽  
Bubble Collapse ◽  
Electric Heater ◽  
Vapor Bubbles ◽  
Experimental Apparatus

An experimental program was conducted to determine the collapse rate of slug-type vapor bubbles rising due to buoyancy through subcooled parent liquid in a vertical isothermal tube. The experimental apparatus included a vertical glass tube with an outer glass container providing a constant temperature water bath for the inner tube. The inner tube contained distilled, deaerated water, and water vapor bubbles were generated at the bottom of this tube with a pulsed electric heater. The parent liquid was uniformly subcooled with respect to the vapor bubble resulting in heat transfer controlled bubble collapse. Collapse rates and rise velocities were recorded by high-speed motion picture photography. Over a limited range of subcooling, the bubble collapse was well behaved, and a simple, quasi-steady boundary layer heat transfer analysis adapted from slug flow over a flat plate correlated the experimental results with a high degree of accuracy. Experimental results were obtained with tubes having inside diameters of 0.0127, 0.0218, and 0.0381 m and for a range of subcooling from 0.5 to 9.0 K.

Bubble Growth and Collapse in Liquid Nitrogen

1968 ◽  
Vol 90 (1) ◽  
pp. 22-26 ◽  
Author(s):  
H. C. Hewitt ◽  
J. D. Parker
Keyword(s):  
Experimental Data ◽  
Liquid Nitrogen ◽  
Bubble Growth ◽  
Theoretical Work ◽  
Nitrogen Pressure ◽  
Superheated Liquid ◽  
Bubble Collapse ◽  
Vapor Bubbles ◽  
Subcooled Liquid ◽  
Nitrogen Bubble

Experimental data on bubble growth in superheated liquid nitrogen, bubble collapse in subcooled liquid nitrogen, and bubble growth with decreasing liquid nitrogen pressure are compared to the theoretical solutions obtained for noncryogens. Vapor bubbles in liquid nitrogen were found to behave quite similarly to vapor bubbles in noncryogens. This paper provides experimental data in two areas where additional theoretical work is needed: Bubble collapse in subcooled liquid, and bubble growth with decreasing pressure.

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