Bubble Lifetime Research Articles

Research on Micro Heater Efficiency for Thermal Inkjet Head

Micro heaters for thermal inkjet print heads are investigated to estimate the effects of heater size and operating condition on its thermal efficiency. Tantalum Aluminum (TaAl) heaters, 0.15μm in thickness, are prepared on silicon oxide layer. Silicon nitride film of 0.4μm thickness covers the heater. Visualization technique is applied to observe bubbles in open pool condition. Volume and life time of bubble are measured from CCD images of plane and side views of the bubble generated at the heat flux range of 0.5∼5.0GW/m2.Thermal conduction simulation for the heater provides bubble nucleation pressure. Bubble work is calculated with Asai's pressure model and the visualization results; bubble life time and volume. Then, thermal efficiency of the heater defined as the ratio of bubble work to the electric input energy can be estimated.

Properties of Electron Bubbles in Liquid Helium

We present calculations of a number of properties of electron bubbles in liquid helium. The size and shape of bubbles containing electrons in different quantum states is determined based on a simplified model. We then find how the geometry of these bubbles changes with the applied pressure. The radiative lifetime of bubbles with electrons in excited states is calculated. Finally, we use a quantum Monte Carlo method to determine the properties of a bubble containing two electrons. We show that this object is unstable against fission.

Measurement of cavitation bubble lifetime and size distribution and its correlation with bioeffects

Ultrasound-induced disruption of cell membranes can be used to deliver drugs and genes into cells. Because ultrasound bioeffects are governed by cavitation, measurement and control of cavitation bubble lifetime and size distribution should afford greater control over ultrasound’s effects on cells. In this study, 500 kHz ultrasound was focused onto suspensions of albumin-stabilized gas bubbles (Optison) either with or without DU145 prostate cancer cells bathed in calcein. Bubble size and lifetime were determined by Coulter counting, while uptake of calcein and cell viability (i.e., bioeffects) were quantified by flow cytometry. We found that the lifetime and size of Optison bubbles decreased with increasing acoustic energy exposure. Moreover, bioeffects were shown to correlate well with disappearance of bubbles. For example, cell viability remained above 90% until approximately 75% of bubbles were destroyed; viability then dropped dramatically as more bubbles disappeared. Additionally, Optison solutions presonicated to destroy all detectable bubbles also caused significant bioeffects. These observations suggest that bioeffects were caused by the cavitation dynamics of free, short-lived, and/or very small daughter bubbles liberated from albumin-stabilized Optison parent bubbles. Regulation of bubble size distribution, possibly by presonication of Optison solutions, could provide a means to optimize high uptake and cell viability.

Self-consistent coupling of cavitation bubbles in aqueous systems

The dynamics of an ensemble of cavitation voids initiated by laser-produced stress waves in aqueous systems is considered. Aqueous systems have large similarity to soft tissues. Laser-initiated stress waves are reflected from tissue boundaries, thereby inducing a tensile stress that is responsible for tissue damage. The early stage of damage is represented by an ensemble of voids or bubbles that nucleate and grow around impurities under stress wave tension. For impurity densities larger than 105 cm−3 the bubbles growth reduces the tensile wave component and causes the pressure to oscillate between tension and compression. For impurity densities below 108 cm−3 the bubbles grow on a long time scale (∼10 μs) relative to the wave interaction time (∼100 ns). For bubble densities above 108 cm−3 the bubble lifetime is greatly shortened because of the reduced tensile component. On a long time scale the growing bubbles cause a significant reduction in the liquid average compression pressure below the ambient atmospheric pressure. This effect increases the bubble lifetime by almost a factor of 2 relative to the low impurity density case when the bubbles are growing independently, in agreement with experiment [Paltauf and Schmidt-Kloiber, Appl. Phys. A: Mater. Sci. Process. 62, 303 (1996)]. As the collapse stage starts, small bubbles collapse first and the compression pressure screening becomes less effective, thereby accelerating the collapse of the larger bubbles and reducing the spread of the bubble lifetimes.

Bubble behavior in subcooled flow boiling of water at low pressures and low flow rates

This study presents experimental data for subcooled flow boiling of water at pressures from 1.05 to 3 bar, bulk liquid velocities ranging from 0.08 to 0.8 m/s, and subcooling from 10 to 30 K. Experiments were carried out on a vertical, annular test section with inner heating surface and upward water flow. High-speed photography at rates of 6000–8000 frames/s captured bubble behavior from inception to collapse, bubble shapes during lifetime, detachment from the wall and typical bubble size. Bubble growth and condensation rates, and variation of bubble lifetime and size with flow rate, subcooling, heat flux and pressure were, further, examined and new correlations proposed.

Influence of adsorption kinetics and bubble motion on stability of the foam films formed at n-octanol, n-hexanol and n-butanol solution surface

Lifetimes of single bubbles at surface of n-octanol solutions of various concentrations were determined for two different locations of the surface in respect to the capillary orifice at which the bubbles were formed. It was found that when solution surface was located ‘far’ ( L=39.5 cm) the average lifetimes of bubbles were shorter than that ones at the solution surface located ‘close’ ( L=4 cm) to the point of the bubbles formation. The bubble departing from the capillary orifice has the adsorption coverage determined by the mutual ratio of velocity of its formation and kinetics of surfactant adsorption. The degree of surfactant coverage over the surface of the growing bubble was calculated assuming that the surfactant adsorption at the surface of the departing bubble is governed by convective–diffusion. It was demonstrated that for the time of bubble growth t growth=0.16 s encountered in our experiments the departing bubbles had practically equilibrium coverage's in n-butanol and n-hexanol solutions, while in n-octanol solutions the adsorption coverage was much smaller than the equilibrium one. Thus, unlike for shorter chain n-alkanols, even for the location ‘close’ the partially non-symmetrical film is formed when in n-octanol solutions the bubble arrives at the free solution surface. For the location ‘far’, the bubble motion through the solution causes further disequilibration of the surfactant coverage over its surface. The bubble reaches the solution surface with its upstream pole practically devoid of surfactant and the fully non-symmetrical film is formed. Such fully non-symmetrical film is less stable than the film formed at the location ‘close’. Our results show that the lifetime of the foam film formed by a single bubble arriving at the solution surface strongly depends on ‘history’ of the bubble formation and motion.

Bubble, Bubble, Toil and Trouble

Soap bubbles burst when their walls thin because of evaporation or the effects of gravity. Glycerin is thought to increase the lifetime of bubbles because it is hygroscopic and very viscous. Since it is hygroscopic, it helps to prevent evaporation of the water. Its high viscosity increases the time that it takes for downward flow of the material in the bubble. Other substances such as corn syrup, liquid fruit pectin, and sugar appear to work similarly. When added to soap solution, rubbing alcohol results in short-lived bubbles, possibly because it greatly increases the solution's evaporation rate. In this activity, students first create a standard solution by mixing water with liquid dishwashing detergent. They then add glycerin, rubbing alcohol, and one or more additional substances (corn syrup, liquid fruit pectin [Certo], or sugar) to samples of the detergent solution. The solutions are compared to see which produces the longest-lasting bubbles.Bubbles are a fun way to introduce the concepts of surface...

Acoustic droplet vaporization for therapeutic and diagnostic applications

A phase shift droplet emulsion is introduced as an aid to unusual ultrasound (US) applications. The transpulmonary droplet emulsion (90% < 6 μm diameter) is made by mixing saline, bovine albumin and dodecafluoropentane. It has been observed that an acoustic pressure threshold exists, above which the droplets vaporize into bubbles approximately 25 times the original diameter. For frequencies between 1.5 and 8 MHz, the threshold decreases from 4.5 to 0.75 MPa peak rarefactional pressure. This paper presents preliminary results for droplet preparation and their evaporation as a function of applied acoustic pressure and frequency, as well as simulations of the lifetime of these gas bubbles based on gas diffusion. In vivo experiments were simulated by the evaporation of droplets in blood flowing under attenuating material. We propose that this agent might be useful for tissue occlusion in cancer treatment, as well as for phase aberration corrections in acoustic imaging.

Surface supercooling and stability of n-alkane films

The surface tension of n-octadecane was studied in the vicinity of the bulk melting point using both the maximum bubble pressure and Wilhelmy plate methods. The bubble surfaces were found to be supercooled below the surface freezing point. The onset of surface freezing is indicated by a sharp drop in surface tension at a constant temperature. This transition is accompanied by an increased film stability resulting in longer bubble lifetimes at the liquid surface. Variations in bubble lifetime reflect changes in the interfacial mechanical properties of the film from liquidlike to solidlike.

Growth Rate, Lifetime, and Maximum Diameter of Bubbles in Silicate Melt Film

The growth rate, lifetime, and maximum diameter of bubbles in a silicate melt film are measured at 770°C in an argon atmosphere with the use of a video complex consisting of a high-temperature microscope, a video camera, an input–output video card, and an IBM-486 personal computer.

Dynamics of microscopic bubbles generated by a corona discharge in insulating liquids: influence of pressure

In this paper, we present an experimental study of the successive rebounds of a bubble as a function of several parameters, hydrostatic pressure P ∞ (in the range 0.1–10 MPa), electrical energy W i deposited by the current pulse (1–20 nJ) and nature of the liquid. Two loss mechanisms have been clearly identified, viscous losses and losses correlated with the acoustically radiated energy. However, the very important damping of the successive rebounds of the bubble cannot be quantitatively explained by only these two mechanisms. Our experiments show that other important dissipative processes are to be considered during the bubble life time.

Measurements of the lifetimes of electron bubbles in large size selected HeN−4 droplets

The lifetimes of electron bubbles in large size selected HeN−4 droplets have been measured in a molecular beam experiment to lie between 2⋅10−3 and 0.2 s in droplets with sizes between N≈105 and 107 atoms, respectively. The dependence of the lifetimes on the electric fields used to size select the droplets, on the energies of the incident electrons, and on the infrared radiation emitted from the apparatus walls were investigated and taken into account. The experimental lifetimes are many orders of magnitude smaller than predicted by earlier theories but consistent with a recent theory published by the authors in Phys. Rev. Lett. 81, 3892 (1998).

Modelling Foamy Oil Flow in Porous Media

This paper describes a dynamic model for the simulation of foamy oil flow in porous media. The model includes expressions for the rate processes of nucleation, bubble growth and disengagement of dispersed gas bubbles from the oil. The model is used to simulate experimental results pertaining to primary depletion tests conducted in a sand pack. Using the model to interpret experimental results indicated that, although the lifetimes of supersaturation and dispersed gas bubbles may be short, supersaturated conditions are likely to exist, and dispersed gas bubbles are likely to be present during the entire production period, as long as the pressure continues to decline at a high rate. The model developed in this paper gave better agreement with experimental data than other proposed models. The effect of foamy oil flow increases as the rate of pressure decline increases.

Effect of motion on lifetime of bubbles at n-butanol solution surface

A simple experimental technique was developed to measure lifetimes of single bubbles at an n-butanol solution surface located far and close to the point of bubble formation. It was found that when the free surface of the n-butanol solution was located far ( L=39.5 cm) from the point of bubble formation, the average lifetimes of bubbles were shorter than those of bubbles on the solution surface located close ( L=4 cm) to the point of bubble formation. According to theoretical predictions, the motion of a bubble through a surfactant solution leads to a non-uniform surfactant distribution over the bubble surface with substantially lowered adsorption coverage on its upstream part. When the solution surface was far, the distance travelled by the bubble was long enough for such a non-uniform distribution to develop and so a non-symmetrical foam film with its lower interface depleted of surfactant was formed at the solution surface. The stability of such a non-symmetrical film is lower than that of a symmetrical foam film formed by a bubble with equilibrium surface coverage undisturbed by motion. Therefore, lifetimes of bubbles were shorter at the n-butanol solution surface located far from the point of bubble formation. A good agreement was found between the lifetimes of bubbles and the lifetimes of foam films calculated from a simple theoretical model based on the velocity of thinning of the symmetrical and fully non-symmetrical foam film with one surface devoid of n-butanol molecules.

ディジタル画像処理の二相流への適用 第２報 気泡の動的解析

In the second report, the extraction technique of the bubble boundary described in the first report is applied to analyze the subcooled flow boiling in the vertical annular tube. The procedure determines bubble size and shape, interfacial area, information about void formation, bubble growth or collapse, position and velocity of bubbles, bubble life time and bubble trajectory for particular condition. These parameters are of fundamental importance in two fluid model formulation, especially in relation to the rational design and effective operation of facilities in the energy power systems and in various industrial processes.

Realcinematographic Visualization of Droplet Ejection in Thermal Ink Jets

In thermal ink jets a complete understanding of the physical processes in ink-jet firing chambers still requires research. The experimental investigation of these high-speed dynamic processes is difficult due to the extremely short durations of the different phenomena in the ink chamber. For example, the bubble lifetime is approximately 15 &#x3BC;s. A new experimental setup is presented to record phenomena of very short durations, like bubble nucleation, bubble growth, bubble collapse, and the beginning of droplet ejection. This setup allows realcinematographic visualization of such processes with a spatial resolution of less than 1 &#x3BC;m and a time resolution of 10 ns. The apparatus also offers the possibility of studying transient processes such as droplet ejection at high printing frequencies. The essential part of the setup is a new highspeed camera. With an exact evaluation of the digitized images the locus, velocity, and acceleration distributions of the phase interface from liquid to vapor/air can be measured. In addition to experimental work simulation results of a dynamic numerical model with realistic geometric data of the firing chamber and the nozzle of a commercially available printhead are presented. A comparison of experiment and simulation leads to conclusions for pressure propagation in the vapor bubble.

Hydrodynamic processes in dynamic bubble pressure experiments 1. A general analysis

The transition of the bubble lifetime in maximum bubble pressure experiments to milliseconds and submilliseconds can be arranged by decreasing the capillary length. In this time range, a transitional hydrodynamic regime results with spatial inhomogeneities of the gas flow. As a consequence, a considerable increase of the calculated deadtime of a growing bubble can be expected as compared to the Poiseuille regime. An equation has been derived and discussed qualitatively for estimating the bubble lifetime and a correction Δt d to the deadtime. The given approach neglects the variation of surface tension during the bubble growth, and the growth of the bubble is assumed to be purely hydrodynamic. Also, surfactant adsorption accompanied by a decrease in capillary pressure was not considered in the present approach.

Experimental evidence of the existence of non-equilibrium coverages over the surface of the floating bubble

According to earlier theoretical works, viscous drag over the surface of a floating bubble causes the top part of the bubble to have a surface coverage which is lower than the equilibrium one. This paper reports measurements of average lifetimes of single bubbles at the free surface of n-nonanol solutions located close to and far away from the point of the bubbles' formation. It was found that the average lifetimes on bubbles at free surfaces located far away were shorter than the lifetimes at the interface located close to the capillary orifice. Shorter bubble lifetimes at the interface far away from the point of the bubbles' formation show that the bubble motion indeed causes the lowering of n-nonanol surface coverage at the top pole of the floating bubbles.

Infrared multiwavelength laser system for establishing a surgical delivery path through water

A multiwavelength laser system designed for precise and efficient tissue ablation under water was realized by simultaneously coupling radiation of a holmium:YAG laser, emitting at a wavelength of 2.12 μm and an erbium: YSGG laser at 2.79 μm into the same zirconium fluoride (ZrF4) fiber. The beam paths of the two lasers were collinearly combined taking advantage of the dispersion of an Infrasil prism. Fast video flash photographs and laser induced pressure transients simultaneously recorded with a PVDF pressure transducer were used to study the dynamics of bubble formation at the submerged fiber tip. The bubble size and the bubble lifetime were determined as a function of the wavelength and the delay time between the two different laser pulses. The results indicate that the combination of 2 and 3 μm radiation takes specific advantage of both wavelengths and strongly enhances the ablation efficiency of tissue under water.

Macroscopic ESWL-induced cavitation: in vitro studies

The rarefaction shock wave results in a liquid failure at the target/fluid interface. In the wake of the reflected ESWL-induced shock wave, a macroscopic cavity is generated in filtered water. The cavity implosion induces a large shock wave, divulging the bubble existence and lifetime. The existence of this shock wave is revealed by the diffraction of a HeNe laser beam. The induced cavitation bubbles are registered by a camera, illuminated by an externally triggered stroboscope (exposure time 10 μs). The radius of the large cavity bubble, generated at the stone surface, is time dependent as theoretically predicted.