Stable multibubble sonoluminescence bubble patterns

Multibubble standing wave patterns can be generated from a flat piezoceramic transducer element radiating into water. By adding a second transducer positioned at 90 degrees from the transducer generating the standing wave, a 3-dimensional volume of stable single bubbles can be established. Further, the addition of the second transducer stabilizes the bubble pattern so that individual bubbles may be studied. The size of the bubbles and the separation of the standing waves depend on the frequency of operation. Two transducers, operating at frequencies above 500 kHz, provided the most graphic results for the configuration used in this study. At these frequencies stable bubbles exhibit a bright sonoluminescence pattern. Whereas stable SBSL is well-known, stable MBSL has not been previously reported. This paper includes discussions of the acoustic responses, standing wave patterns, and pictorial results of the separation of individual bubble sonoluminescence in a multibubble sonoluminescence environment.     

有机溶液中圆锥泡声致发光

在U形管声致发光装置的基础上建立了一套新型的声致发光装置——直管圆锥泡声致发光装置. 利用此装置以有机溶液为液体介质得到了超强的发光脉冲并测量得到了其发光光谱. 结果表明发光光谱为一从紫外光至可见光波长范围的连续谱,上面叠加有C₂的d³Π_g→d³Π_u跃迁形成的五个序列谱带,分别对应于Δv=-2,Δv=-1,Δv=0,Δv< 关键词： 声致发光 光谱 斯旺带 振动温度     

High bubble concentrations produced by ultrasounds in binary mixtures.

It was discovered that simultaneous insonification and air blowing of different aqueous binary solutions such as water/sodium-dodecyl-sulphate (SDS), water/methanol or water/potassium-sulphate yields a very concentrated bubble cloud invading the whole vessel in a few seconds. After the end of insonification, this cloudiness remained in the solution for about 1 min. The phenomenon was investigated by computer-treatment of solution pictures recorded every second after the end of insonification. Turbidity appeared to increase with ultrasound power, and also with SDS concentration. During the disappearance of the cloud, a turbidity front appeared rising and spreading upward. This front was studied in the characteristic plane and interpreted as a spatial segregation of different bubble sizes rising with different terminal velocities. The bubble sizes involved were estimated to about 10 microns. Adsorption of surface active species are invoked to explain the cloud formation and its abnormally slow disappearance, but the occurrence of the phenomenon for potassium-sulphate salt remains unexplained.     

Influence of bubble clustering on multibubble sonoluminescence

Influence of clustering of cavitation bubbles on multibubble sonoluminescence (MBSL) in standing wave fields is studied through measurement of MBSL intensity with a photomultiplier tube and observation of corresponding bubble behavior with a high-speed video camera and an intensified charge-coupled device one. It is clarified that, when the SL is quenched suddenly at excessive ultrasonic power, the behavior of bubbles clearly changes; the bubbles which form dendritic branches of filaments change into clusters due to the secondary Bjerknes force. The cluster is composed of several bubbles surrounded by many tiny bubbles, in which bubbles repeatedly coalesce and fragment, and run away from pressure antinodes. When the clusters are broken up by forced fluid motion, the quenching of MBSL is suppressed.     

Finite-amplitude vibration of a bubble and sonoluminescence

Numerical solutions of the differential equation for a bubble performing finite-amplitude vibration are given in detail for a variety of situations. The results demonstrate that in lower acoustic pressure (maximum Mach number very low) its vibration has bounce. When acoustic pressure is in excess of 1.18atm and the instantaneous radius of the bubble approaches its equivalent Van der Waals radius, the maximum velocity and acceleration on the surface of a bubble have a huge increase in a very short period, which seems to favour the sonoluminescence. In vacuum environment (0.1atm), an intensive sonoluminescence could be generated.     

Acoustic cavitation, bubble dynamics and sonoluminescence

Basic facts on the dynamics of bubbles in water are presented. Measurements on the free and forced radial oscillations of single spherical bubbles and their acoustic (shock waves) and optic (luminescence) emissions are given in photographic series and diagrams. Bubble cloud patterns and their dynamics and light emission in standing acoustic fields are discussed.     

Study of single bubble sonoluminescence in phosphoric acid

Sonoluminescence (SL) radiation from different solutions of phosphoric acid has been studied in the framework of a hydro-chemical simulation. By calculating the phase diagrams of an SL bubble in different concentrations of phosphoric acid, the optimum solution for acquiring maximum SL emission has been specified as the solution of around 30 wt.% acid. It is shown that the SL temperature and the number of particles inside the bubble at the time of SL emission are two important factors determining the optimum solution. Numerical calculation of the SL intensity shows that the optimum solution has an intensity of about 20 times greater than that of water. Also, contributions of different energy sources in creation of thermal energy of the bubble have been calculated. The result indicates that the work of external driving pressure is the most important factor to determine the ultimate thermal energy of the bubble at the time of SL emission. Based on this result, we have reasoned out that in the determination of the optimum solution, the role of viscosity of the acid solutions is more important than the vapor pressure.     

Acoustic power dependences of sonoluminescence and bubble dynamics

The decreasing effect of sonoluminescence (SL) in water at high acoustic powers was investigated in relation to bubble dynamics and acoustic emission spectra. The intensity of SL was measured in the power range of 1–18 W at 83.8 kHz for open-end (free liquid surface and film-covered surface) and fixed-end boundaries of sound fields. The power dependence of the SL intensity showed a maximum and then decrease to zero for all the boundaries. Similar results were obtained for sonochemiluminescence in luminol solution. The power dependence of the SL intensity was strongly correlated with the bubble dynamics captured by high-speed photography at 64 k fps. In the low-power range where the SL intensity increases, bubble streamers were observed and the population of streaming bubbles increased with the power. At powers after SL maximum occurred, bubble clusters came into existence. Upon complete SL reduction, only bubble clusters were observed. The subharmonic in the acoustic emission spectra increased markedly in the region where bubble clusters were observed. Nonspherical oscillations of clustering bubbles may make a major contribution to the subharmonic.     

On the dynamics of moving single bubble sonoluminescence

It is well known that the primary Bjerknes force is the origin of the trapping of sonoluminescing bubble in the sound field in liquid. In the present Letter, the quantitative investigation of the behavior of hydrodynamic force on the moving sonoluminescing (SL) bubble introduces the new role of stabilizing the trajectory motion of the bubble for primary Bjerknes force. Using a complete force balanced radial-translational dynamics, it is analytically discussed that by increasing the bubble distance from the antinode of the sound field the increase of the magnitude of inward Bjerknes force, controls the size of the domain of the bubble trajectory. At this time the wake produced by the rapid variation of the bubble's relative translational velocity to the surrounding liquid, changes the bubble direction of motion through the effect of history force. The required momentum for accelerating the SL bubble around the central antinode is produced by the added mass force at the bubble collapse. It is revealed in a re-examination of the coupled radial-translational dynamics for a trapping bubble that because of the bubble lower translational acceleration caused due to the lower added mass force and the bubble attraction towards the acoustic antinodes in presence of inward Bjerknes force, the small bubble will be trapped at the antinode of the sound field.     

Water temperature dependence of single bubble sonoluminescence threshold

Water temperature dependence of single bubble sonoluminescence (SBSL) threshold has been experimentally measured to perform measurements at different temperatures on the very same bubble. Results show lower thresholds, i.e. an easier prime of mechanism, of sonoluminescence at lower water temperatures. Dependence is almost linear at lower temperatures while between 14 °C and about 20 °C the curve changes its slope reaching soon a virtual independence from water temperature above about 20 °C.     

Influence of various gases on single bubble sonoluminescence

Influence of various gases on the intensity of single bubble sonoluminescence has been studied. The gases used were air, oxygen, nitrogen, argon and helium. Among these oxygen gave the brightest intensity with nitrogen giving the least.     

Effect of dissolved air content on single bubble sonoluminescence

It has been recently demonstrated that a single gas bubble in a liquid medium can be driven hard enough by an acoustic pressure field to make it emit light which is visible to the naked eye in a dark room. This phenomenon termed as single bubble sonoluminescence has shown some extraordinary physical properties. In the present investigation we have shown that dissolved air content has a significant influence on this phenomenon.     

乙二醇溶液中圆锥泡声致发光的发光特性

利用一种改进后的U形管圆锥泡声致发光装置，研究了乙二醇溶液中圆锥泡声致发光的发光特性.实验结果表明，利用乙二醇溶液可以得到超强的单个发光脉冲，其脉冲宽度可以达到150 μs，其值远远高于其他方式产生的声致发光的脉冲宽度.测量得到的光谱为一从紫外到可见光波长范围的连续谱，在589 nm附近叠加有钠的3P-3S原子发射谱线.在钠的原子发射谱线两侧测量得到了Na-Ar分子激发态跃迁形成的蓝卫星带，并在声致发光实验中测得了Na-Ar的红卫星带以及钠的3S-4S原子发射谱线. 关键词： 圆锥泡声致发光 光脉冲 光谱 卫星带     

The effect of bulk viscosity on single bubble dynamics and sonoluminescence

In our previous paper, we derived a new single bubble model including the effect of bulk viscosity. To confront it to experiments, single bubble dynamics was measured here in 30% (v/v) glycerol-water mixture under different acoustic amplitudes and compared to models including or not the effect of bulk viscosity. The results showed that calculated bubble dynamics were not significantly affected by the bulk viscosity within the experimental conditions used in this study. However, there was a noticeable delay for the first rebound when bulk viscosity was considered. The corresponding sonoluminescence intensities were collected and compared with theoretical predictions. The results did not allow to discriminate between the two models (one includes the effect of bulk viscosity, the other does not), confirming the negligible effect of bulk viscosity in this condition (30% (v/v) glycerol-water mixture). Due to the instability of a single bubble in higher viscosity solutions, we could not implement experiments that can discriminate between the two models.     

Variational approach to hydrodynamics: Application to the sonoluminescence gas bubble

We develop a variational approximation allowing to study under realistic physical conditions the interior dynamics of cavitating gas bubbles in liquids. We discuss in some detail the intricacy of the gas bubble dynamics related to the small size of the system. We also show how to formulate the problem in the framework of the energy equation for non-adiabatic processes.     

Moving single bubble sonoluminescence in phosphoric acid and sulphuric acid solutions

The phenomenon of sonoluminescence still presents some unsolved aspects. Recently [Y.T. Didenko, K. Suslick, Molecular Emission during Single Bubble Sonoluminescence, Nature 407 (2000) 877-879.], it was found that a single cavitating air bubble in polar aprotic liquids (including formamide and adiponitrile) can produce very strong sonoluminescence while undergoing macroscopic translation movements in the resonator, a condition known as moving single bubble sonoluminescing (MSBSL). Here we describe some experiments conducted in aqueous solutions of phosphoric and sulphuric acid. In these liquid media, it is possible to reproduce MSBSL and luminescence is emitted even if a trapped bubble is subjected to a strong shape instability, named in the literature "jittering phase". When a moving and luminescing bubble was present and the acoustic pressure gradually increased, we observed the generation of a discrete lattice of trapped bubbles. The bubbles in the lattice emit very intense light flashes and can change their position while maintaining the overall spatial distribution in time. Some preliminary results, obtained from Mie-scattering and measurements of relative light intensity, are reported.     

Comparison of Xe single bubble sonoluminescence in water and sulfuric acid

Using the equations of fluid mechanics with proper boundary conditions and taking account of the gas properties, we can numerically simulate the process of single bubble sonoluminescence, in which electron-neutral atom bremsstrahlung, electron-ion bremsstrahlung and recombination radiation, and the radiative attachment of electrons to atoms and molecules contribute to the light emission. The calculation can quantitatively or qualitatively interpret the experimental results. We find that the accumulated heat energy inside the compressed gas bubble is mostly consumed by the chemical reaction, therefore, the maximum degree of ionization inside Xe bubble in water is much lower than that in sulfuric acid, of which the vapour pressure is very low. In addition, in sulfuric acid much larger pa and R0 are allowed which makes the bubbles in it much brighter than that in water.