摘要:

A small, oscillating bubble in a liquid can be trapped in the antinode of an acoustic standing wave field. Bubble stability is required for the study of single bubble sonoluminescence (SBSL). The properties of the acoustic resonator are essential for the stable trapping of sonoluminescing bubbles. Resonators can be chosen according to the intended application: size and geometry can be varied in a wide range. In this work, the acoustic responses of different resonators were measured by means of holographic interferometry, hydrophones and a laser vibrometer. Also, high-speed photography was used to observe the bubble dynamics. Several single, stable sonoluminescent bubbles were trapped simultaneously within an acoustic resonator in the pressure antinodes of a higher harmonic mode (few bubble sonoluminescence, FBSL). ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1309254

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

A bubble is levitated in water in a cylindrical resonator which is driven by ultrasound. It has been shown that in a certain region of parameter space the bubble is emitting light pulses (sonoluminescence). One of the properties observed is the enormous spatial stability leaving the bubble “pinned” in space allowing it to emit light with a timing of picosecond accuracy. We argue that the observed stability is due to interactions of the bubble with the resonator. A shock wave emitted at collapse time together with a self generated complex sound field, which is experimentally mapped with high resolution, is responsible for the observed effects. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1309255

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Experiments with small quantities of simple organic impurities (short chain aliphatic alcohols) that can have dramatic effects on the light intensity of single-bubble sonoluminescence have been conducted. We will discuss measurements of the dynamical motion of the bubble with, and without, impurity doping. We have found that the bubble size increases with impurity concentration. A build-up of alcohol molecules within the bubble is likely to occur. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1309256

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The numerical calculations for the converging shock or compression wave model of sonoluminescence have been based primarily on continuum methods. Here an alternative approach by molecular dynamics simulation is shown to be successful and promising for spherically and aspherically collapsing bubbles. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1309257

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The spherically-symmetric problem of the oscillations of a single gas bubble in the center of a spherical flask filled with a compressible liquid that is excited by pressure oscillations on the flask wall is considered. The initial conditions of the problem correspond to the sonoluminescence experimental data. A semi-analytic model with “liquid drop” is given which allows to reduce the computational region by assuming that the liquid is quite incompressible far from the bubble surface. Using the numerical results an analysis of the heat transfer effects in the gas during the collapse time has been carried out. The calculations show that accounting for heat conductivity leads to disappearance of the shock waves which occur in the adiabatic model. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1309258

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The mechanism of the light emission of single-bubble sonoluminescence (SBSL) is studied theoretically for an argon bubble based on a quasi-adiabatic compression model. It is clarified that radiative recombination of electrons and ions and electron-atom bremsstrahlung are the dominant microscopic processes of the light emission and the intensity is mainly determined by the degree of ionization of the gas inside the bubble. It is also clarified that the pulse width of the light is nearly independent on wavelength. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1309259

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

It is shown that between the cavitation strength of a real liquid, the effective nonlinearity parameter and the concentration of gas bubbles (or function of bubble distribution on size) there exists a clear interrelation, expressed by the formulas (7), (8). ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1309260

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Multibubble sonoluminescence has been studied in conditions of low frequency field (LF), high-frequency field (HF) and combined(HF+LF)sonification. It is shown that combined action of the two fields can exceed the sum of the effects of each of them acting separately, i.e. there is considerably nonadditive summation of the effects. The highest effect has been reached in the case when the HF field was pulse modulated and the LF field was switched on for a short time (0.1–60 sec.) After deenergizing the LF field, the intensity of sonoluminescence (SL) generated by the HF field increases at first in a stepwise manner. After this jump the SL intensity slowly decreases tending to some limiting value, which usually is higher than the SL intensity before impact by the LF field. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1309261

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

We consider the major cases of local electrification of bubbles in a cavitation field: the fragmentation of cavitation bubbles and also their deformation only. We consider the splitting of cavitation bubbles taking into account the force of surface tension, the force of bubble perturbation, the Stokes force and electrostatic forces of repulsion between like charges on the wall of the collapsing neck of the fragment bubble. The problem of the uncompensated charge on the surface of the deformed cavitation bubble is solved in general view. Radial deformations are approximated by a paraboloid of rotation. The maximum electric strength is calculated. In terms of the electrical theory of the local electrification of cavitation bubbles an explanation of some physical and physico-chemical effects in cavitation fields is proposed. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1309262

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

A mathematical model which describes the behavior of a gas bubble cluster in an external acoustic field is presented. According to this model the bubbles of different ambient radii are assumed to be submerged into a spherical liquid volume. The boundary of this volume is considered as a cluster’s boundary. This model includes a set of coupled Rayleigh-type equations for bubble radii and cluster radius. The dynamics of a single bubble cluster excited by external periodic pressure is considered. The problem has been solved numerically under the assumption of spherically-symmetric oscillations of bubbles and the cluster’s boundary. A synchronization phenomenon has been found; namely, the numerical results have shown that bubbles of different initial radii in a cluster collapse in phase. Moreover, it has been noted that at some parameter values such a synchronization may lead to the intensification of bubble collapse. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1309263

出版商:AIP    

年代:1900

数据来源: AIP