Oscillations Of Gas Bubble Research Articles

Coupling light and sound: giant nonlinearities from oscillating bubbles and droplets

Abstract Nonlinear optical processes are vital for fields including telecommunications, signal processing, data storage, spectroscopy, sensing and imaging. As an independent research area, nonlinear optics began with the invention of the laser, because practical sources of intense light needed to generate optical nonlinearities were not previously available. However, the high power requirements of many nonlinear optical systems limit their use, especially in portable or medical applications, and so there is a push to develop new materials and resonant structures capable of producing nonlinear optical phenomena with low-power light emitted by inexpensive and compact sources. Acoustic nonlinearities, especially giant acoustic nonlinear phenomena in gas bubbles and liquid droplets, are much stronger than their optical counterparts. Here, we suggest employing acoustic nonlinearities to generate new optical frequencies, thereby effectively reproducing nonlinear optical processes without the need for laser light. We critically survey the current literature dedicated to the interaction of light with nonlinear acoustic waves and highly nonlinear oscillations of gas bubbles and liquid droplets. We show that the conversion of acoustic nonlinearities into optical signals is possible with low-cost incoherent light sources such as light-emitting diodes, which would usher new classes of low-power photonic devices that are more affordable for remote communities and developing nations, or where there are demanding requirements on size, weight and power.

ДОСЛІДЖЕННЯ КОЛИВАНЬ ДЕФОРМІВНИХ БУЛЬБАШОК ГАЗУ, РОЗТАШОВАНИХ У РІДИНІ

This paper deals with a problem of the dynamics of deformed gas bubbles in the fluid. Mathematically, bubble model differs from the ideal and destructive one by oscillation equation of gas bubbles (the Rayleigh equation). This, in its turn, brings some extra difficulties in solving the hydrodynamic problem. The paper provides a description of the mathematical model construction of gas bubbles dynamics, the developed techniques and computation algorithms of the oscillation of gas bubbles in the fluid. The results of numerical experiments have been analyzed. The viability of using single bubble model has been proved.

Symmetry Approach in the Evaluation of the Effect of Boundary Proximity on Oscillation of Gas Bubbles

The purpose of the present review is to describe the effect of an interface between media with different mechanical properties on the acoustic response of a gas bubble. This is necessary to interpret sonar signals received from underwater gas seeps and mud volcanoes, as well as in the case of acoustic studies on the Arctic shelf where rising gas bubbles accumulate at the lower boundary of the ice cover. The ability to describe the dynamics of constrained bubble by analytical methods is related to the presence of internal symmetry in the governing equations. This leads to the presence of specific (toroidal and bi-spherical) coordinate systems in which the variables are separated. The existence of symmetry properties is possible only under certain conditions. In particular, the characteristic wavelength should be larger than the bubble size and the distance to an interface. The derived analytical solution allows us to determine how the natural frequency, radiation damping, and bubble shape depend on the distance to the boundary and the material parameters of contacting media.

Amplitude-Frequency Characteristics of the Oscillations of Methane Gas Bubbles in Oil

The author presents an analytical solution to the problem of acoustic-wave-induced oscillations of methane gas bubbles in an oil reservoir at bottom-hole conditions. The amplitude-frequency characteristics are computed for realistic reservoir temperature, pressure, and dissolved gas parameters that make the oil compressibility, density, and viscosity quite different from those of the degassed oil at surface conditions. The author compares the damping decrement of these ultrasonic oscillations to those at normal atmospheric-pressure surface conditions. The solution allowed the author to estimate the ultrasonic vibration frequency range that is optimal and most effective for improving the flow characteristics in a producing reservoir in the near-well zone at a realistic bottom-hole regime.

Underwater noise emitted during small-scale air entrainment events

Abstract The breaking wave phenomenon significantly takes part in the mechanisms of mass, heat and gas exchange at the air-water boundary and depends on the wind velocity. Some of the energy dissipated during this process is converted into underwater sound emitted by oscillating gas bubbles and bubble plumes. However, the underwater noise accompanying the lowest wind speed conditions has received only little attention. This report describes a study aimed at advancing the knowledge of underwater noise emission from air bubbles injected during small-scale breaking events occurring on the water surface. Results of model experiments performed in a small tank are presented. The object of the research is the relationship between the generated noise and the dissipated potential energy of water poured into a tank filled with water of varying physical water properties. Additionally, the impact of various water properties such as salinity, surface tension or microscale gas bubbles was examined. The experiment revealed that noise spectra are affected by different water properties and most likely reflect the varying efficiency of bubble formation and bubble size spectra.

Investigation of the effect of characteristics of gas­containing suspensions on the parameters of the process of ultrasonic wave propagation

In the course of present study, we have investigated patterns of connection between fluctuations in the number and size of particles, suspended in a fluid, and characteristics of the field of volumetric ultrasonic waves. The presence of particles of the solid phase and gas bubbles introduces certain features to the process of attenuation and scattering of ultrasonic wave energy. The scattering of waves on the solid phase particles becomes considerable when the wavelength is commensurate with the size of the particles themselves. In order to characterize the absorption and scattering of acoustic oscillations by oscillating gas bubbles, we applied the concepts of effective cross-sections of damping, absorption and scattering. The dependence is presented of the magnitude of cross-section of ultrasound damping by air bubbles on frequency of the sound wave. It was established that the magnitude of attenuation of volumetric ultrasonic oscillations of high frequency (≥5 MHz) in an actual pulp depends almost only on the concentration of the solid phase and particle size of the crushed material. The frequency of volumetric ultrasonic waves, at which the components of their absorption and scattering by particles of the solid phase in suspension are equal, characterizes the average particle size. A given frequency does not depend on the particle concentration and can be applied to estimate their mean size

Study of the effect of thermobaric conditions on the process of formation of propane hydrate

The study presents results of the development of a mathematical model of an oscillating gas bubble. It takes into account inertial and thermodynamic components of oscillation of gas bubbles in a liquid, mass transfer processes near a surface of a bubble and phase transition processes in a liquid. Considering mentioned features in the mathematical model, it is possible to get values of temperatures of gas, liquid and solid phases, pressure of a gas medium and a size of a bubble, a rate of a side movement, localization and a rate of phase transitions in a liquid, intensity of heat and mass transfer processes at a bubble boundary and many other data at any time. We performed a series of estimating calculations of the hydrate formation of the propane-butane mixture with the help of the proposed mathematical model. We investigated the influence of initial temperature and pressure of the gas mixture on the hydrate formation process. We obtained graphs of the hydration formation and temperature regime of a gas bubble, distribution of temperature fields in a liquid under conditions of phase transition processes and accumulation of hydrate in separate layers of a liquid. The performed studies show that the whole period of hydrate formation consists of three parts: the initial heating of gas in a bubble, the period of oscillations and the period of stationary heat transfer. The maximum rate of hydrate formation is observed during the period of heating of a gas in a bubble. It has a short duration of 2÷40 μs, but it is the most productive. The duration of the oscillation period depends on thermobaric conditions and may exceed 200 μs. We established that there exists a region of gas temperatures where the rate of the hydrate formation is maximal. We can use the proposed mathematical model to determine thermophysical characteristics of gas bubbles, liquid and steam in various technological processes associated with the formation of gas hydrates, dissolution of gases in liquid, hardening of foam, and others. The conducted study can be useful for optimization of technological processes connected with formation of gas hydrates.

Chaotic oscillations of gas bubbles under dual-frequency acoustic excitation

Chaotic oscillation of bubbles in liquids reduces the efficiency of the sonochemical system and should be suppressed in the practical applications. In the present paper, a chaos control method based on the dual-frequency approach is numerically investigated and is proved to be an effective method even for cases with intensive energy input. It was found that the chaos could be successfully suppressed by the application of dual-frequency approach in a wide range of parameter zone (even with high acoustic pressure amplitude). Furthermore, influences of power allocation between two waves on the chaos control are quantitatively discussed with clear descriptions of the routes from stable oscillations to chaos.

Two-Dimensional Numerical Simulations of Ultrasound in Liquids with Gas Bubble Agglomerates: Examples of Bubbly-Liquid-Type Acoustic Metamaterials (BLAMMs)

This work deals with a theoretical analysis about the possibility of using linear and nonlinear acoustic properties to modify ultrasound by adding gas bubbles of determined sizes in a liquid. We use a two-dimensional numerical model to evaluate the effect that one and several monodisperse bubble populations confined in restricted areas of a liquid have on ultrasound by calculating their nonlinear interaction. The filtering of an input ultrasonic pulse performed by a net of bubbly-liquid cells is analyzed. The generation of a low-frequency component from a single cell impinged by a two-frequency harmonic wave is also studied. These effects rely on the particular dispersive character of attenuation and nonlinearity of such bubbly fluids, which can be extremely high near bubble resonance. They allow us to observe how gas bubbles can change acoustic signals. Variations of the bubbly medium parameters induce alterations of the effects undergone by ultrasound. Results suggest that acoustic signals can be manipulated by bubbles. This capacity to achieve the modification and control of sound with oscillating gas bubbles introduces the concept of bubbly-liquid-based acoustic metamaterials (BLAMMs).

Model for oscillating gas bubbles

Model for oscillating gas bubbles

Linear oscillation of gas bubbles in a viscoelastic material under ultrasound irradiation

Acoustically forced oscillation of spherical gas bubbles in a viscoelastic material is studied through comparisons between experiments and linear theory. An experimental setup has been designed to visualize bubble dynamics in gelatin gels using a high-speed camera. A spherical gas bubble is created by focusing an infrared laser pulse into (gas-supersaturated) gelatin gels. The bubble radius (up to 150 μm) under mechanical equilibrium is controlled by gradual mass transfer of gases across the bubble interface. The linearized bubble dynamics are studied from the observation of spherical bubble oscillation driven by low-intensity, planar ultrasound driven at 28 kHz. It follows from the experiment for an isolated bubble that the frequency response in its volumetric oscillation was shifted to the high frequency side and its peak was suppressed as the gelatin concentration increases. The measurement is fitted to the linearized Rayleigh–Plesset equation coupled with the Voigt constitutive equation that models the behavior of linear viscoelastic solids; the fitting yields good agreement by tuning unknown values of the viscosity and rigidity, indicating that more complex phenomena including shear thinning, stress relaxation, and retardation do not play an important role for the small-amplitude oscillations. Moreover, the cases for bubble-bubble and bubble-wall systems are studied. The observed interaction effect on the linearized dynamics can be explained as well by a set of the Rayleigh–Plesset equations coupled through acoustic radiation among these systems. This suggests that this experimental setup can be applied to validate the model of bubble dynamics with more complex configuration such as a cloud of bubbles in viscoelastic materials.

Ultrasounds in Bubbly Liquids: Unidirectional Propagation and Switch

The presence of oscillating gas bubbles in a liquid generates attenuation, dispersion, and nonlinearity. We take advantage of these effects to set the theoretical basis for two new devices. An acoustic diode that blocks the propagation of ultrasonic waves in one direction and let them pass in the other direction is proposed. The system is based on two adjacent layers made up of two bubbly liquids of different bubble sizes. This acoustic diode is an alternative system to other devices previously proposed by other groups and that rely on periodical structures (sonic crystals, metal plates). An acoustic switch that allows the control (switch-on or switch-off) of the propagation of the main ultrasonic wave by means of a secondary ultrasonic field able to generate a cavitation field (at low or high ultrasonic frequency) is also presented. This system is an alternative to an acoustic switch set previously by our group. The theoretical design of both structures relies on experimental observations and numerical simulations.

Thermal effects on nonlinear radial oscillations of gas bubbles in liquids under acoustic excitation

Modeling of nonlinear radial oscillations of gas bubbles in liquids under acoustic excitation is an important subject for understanding of many acoustic bubble related phenomena (e.g., sonoluminescence, sonochemistry and sonoporation). In the present paper, numerical simulations of the oscillations of gas bubbles in liquids based on a more complete polytropic model are performed with heat transfer across bubble interfaces considered. By comparing with predictions given in the literature that using a constant polytropic exponent and ignoring energy dissipation through a heat transfer across bubble interfaces, our simulations reveal that the polytropic exponent and thermal dissipation mechanism significantly influence the predictions of nonlinear bubble behavior (e.g., locations and magnitudes of resonances, thresholds of subharmonics and ultraharmonics).

A General Approach for Rectified Mass Diffusion of Gas Bubbles in Liquids Under Acoustic Excitation

Rectified mass diffusion serves as an important mechanism for dissolution or growth of gas bubbles under acoustic excitation with many applications in acoustical, chemical and biomedical engineering. In this paper, a general approach for predicting rectified mass diffusion phenomenon is proposed based on the equation of bubble motion with liquid compressibility. Nonuniform pressure inside gas bubbles is considered in the approach through employing a well-established framework relating with thermal effects during gas bubble oscillations. Energy dissipation mechanisms (i.e., viscous, thermal, and acoustic dissipation) and surface tension are also included in the approach. Comparing with previous analytical investigations, present approach mainly improves the predictions of rectified mass diffusion in the regions far above resonance and regions with frequencies megahertz and above. Mechanisms for the improvements are shown and discussed together with valid regions and limitations of present approach.

Mass transfer during radial oscillations of gas bubbles in viscoelastic mediums under acoustic excitation

The generation of acoustic cavitation in viscoelastic mediums (e.g. human or animal tissue) is an essential topic for facilitating non-invasive therapeutic ultrasonic treatment of serious diseases (e.g. tumors). In present paper, mass transfer during radial oscillations of gas bubbles in viscoelastic mediums under acoustic excitation is theoretically investigated and influences of several parameters (e.g. shear modulus, saturation condition and viscosity) on the mass diffusion across bubble interfaces are discussed. The characteristics of acoustic cavitation generated in vivo are also explained based on our predictions by re-visiting the pioneering studies in the field. Comparing with previous predictions in the literature, our predictions reveal that values of maximum bubble sizes growing through mass diffusion is larger and required time reaching above maximum bubble size is longer, suggesting that medium viscoelasticity is one of paramount parameters for predicting mass diffusion of cavitation bubbles in tissue.

Heat transfer across interfaces of oscillating gas bubbles in liquids under acoustic excitation

Heat transfer across interfaces of oscillating gas bubbles in liquids is a fundamental issue of bubble dynamics with many applications. The current formulas in the literature relating with heat transfer are either too complex to be used for calculation or not valid for some regions of interest. In this communication, a group of formulas is proposed to predict heat transfer across bubble interfaces accurately for a wide range of parameters. An exact solution is used to validate the accuracy of the present formulas. Finally, energy dissipation during gas bubble oscillations in liquids through heat transfer is quantitatively compared with those through viscosity and acoustic radiation.

Towards an Improved Megasonic Cleaning Process: Influence of Surface Tension on Bubble Activity in Acoustic Fields

Removal of particulate residues represents a very challenging step in current CMOS-technology nodes. The continued miniaturization and the introduction of novel materials in the semiconductor industry have resulted in very stringent requirements for device fabrication steps such as cleaning processes [. Physical forces, acting directly on the surface to be cleaned, are currently employed for delicate particle removal as an alternative to more aggressive chemistries [2]. High frequency ultrasounds (500 kHz 4 MHz), or megasonics, rely on the action of oscillating bubbles created during the ultrasonic agitation of the cleaning liquid. Strongly oscillating gas bubbles are able to generate shear forces, which are considered to be responsible for cleaning [3]. However, collapsing bubbles close to a surface can also produce water jets and shockwaves which lead to damage of fragile structures. Fundamental research is needed in order to overcome these issues by improving the understanding of the physical parameters playing a role in the acoustic cavitation of bubbles. This study reports the effects of lowering the surface tension of the liquid bulk on the bubble activity in the MHz range. A lower surface tension (45 mN/m) with respect to water (72 mN/m) is obtained by adding a non-ionic surface-active agent (TritonX-100). After fully characterizing its wettability, a cleaning solution containing surfactant is investigated under pulsed and continuous acoustic fields, for different acoustic amplitudes and gas concentrations. The aim is to increase bubble activity while reducing the strength of the bubble collapse. The results obtained can be useful in tuning megasonic cleaning systems towards more efficient processes.

Effects of liquid compressibility on radial oscillations of gas bubbles in liquids

For forced radial oscillations of gas bubbles in liquids, a more rigorous expression of the acoustic damping constant based on Keller's equation is developed. Comparison with those in published papers is also made. The expression offered in this paper will improve the predictions of total damping constant in particular for high frequencies and large bubbles, i.e., large ωR0/c1 (ω is the frequency of driving sound field, R0 is the equilibrium bubble radius, c1 is the sound speed in the liquid). Examples in ultrasound imaging and acoustical oceanography are demonstrated.

Nonlinear oscillations of gas bubbles submerged in water: implications for plasma breakdown

Gas bubbles submerged in a dielectric liquid and driven by an electric field can undergo dramatic changes in both shape and volume. In certain cases, this deformation can enhance the distribution of the applied field inside the bubble as well as decrease the internal gas pressure. Both effects will tend to facilitate plasma formation in the gas volume. A practical realization of these two effects could have a broad impact on the viability of liquid plasma technologies, which tend to suffer from high voltage requirements. In this experiment, bubbles of diameter 0.4–0.7 mm are suspended in the node of a 26.4 kHz underwater acoustic standing wave and excited into nonlinear shape oscillations using ac electric fields with amplitudes of 5–15 kV cm−1. Oscillations of the deformed bubble are photographed with a high-speed camera operating at 5130 frames s−1 and the resulting images are decomposed into their axisymmetric spherical harmonic modes, , using an edge detection algorithm. Overall, the bubble motion is dominated by the first three even modes l = 0, 2 and 4. Electrostatic simulations of the deformed bubble's internal electric field indicate that the applied field is enhanced by as much as a factor of 2.3 above the nominal applied field. Further simulation of both the pure l = 2 and l = 4 modes predicts that with additional deformation, the field enhancement factors could reach as much as 10–50.

Oscillations of gas bubbles in liquid at resonance of frequencies 2:1 of radial and arbitrary axisymmetrical modes

Oscillations of gas bubbles in liquid at resonance of frequencies 2:1 of radial and arbitrary axisymmetrical modes