Bubble Oscillations Research Articles

Chaos under interface oscillations during boiling and sea surface agitation

Results of investigation of the phase interface fluctuations at film and bubble boiling and sea surface agitation are presented. The vapor film thickness and vapor bubble growing on the wall were determined with the aid of laser diagnostics. Oscillations of a growing vapor bubble and simultaneous pressure oscillations in liquid were detected using optical (laser) and acoustic diagnostics. For the very first time volume and shape oscillations of a vapor bubble growing on a wall were determined. An approached model of volume oscillations of a vapor bubble, growing on a heat transfer surface is presented basing on experimental data. The system of model equations and bubble dynamics were presented considered, accounting simultaneous evaporation and condensation at the interface. It has been found that the growth of a vapor bubble is accompanied by its volume oscillations, which become chaotic under certain circumstances.

Modeling tissue-selective cavitation damage

The destructive growth and collapse of cavitation bubbles are used for therapeutic purposes in focused ultrasound procedures and can contribute to tissue damage in traumatic injuries. Histotripsy is a focused ultrasound procedure that relies on controlled cavitation to homogenize soft tissue. Experimental studies of histotripsy cavitation have shown that the extent of ablation in different tissues depends on tissue mechanical properties and waveform parameters. Variable tissue susceptibility to the large stresses, strains, and strain rates developed by cavitation bubbles has been suggested as a basis for localized liver tumor treatments that spare large vessels and bile ducts. However, field quantities developed within microns of cavitation bubbles are too localized and transient to measure in experiments. Previous numerical studies have attempted to circumvent this challenge but made limited use of realistic tissue property data. In this study, numerical simulations are used to calculate stress, strain, and strain rate fields produced by bubble oscillation under histotripsy forcing in a variety of tissues with literature-sourced viscoelastic and acoustic properties. Strain field calculations are then used to predict a theoretical damage radius using tissue ultimate strain data. Simulation results support the hypothesis that differential tissue responses could be used to design tissue-selective treatments. Results agree with studies correlating tissue ultimate fractional strain with resistance to histotripsy ablation and are also consistent with experiments demonstrating smaller lesion size under exposure to higher frequency waveforms. Methods presented in this study provide an approach for modeling tissue-selective cavitation damage in general.

Numerical Simulations of the Nonlinear Interaction of a Bubble Cloud and a High Intensity Focused Ultrasound Field

We studied the effects of a small bubble cloud located at the pre-focal area of a high-intensity focused ultrasound field. Our objective is to show that bubbles can modify the bioeffects of an ultrasound treatment in muscle tissue. We model a three-dimensional ultrasound field in an idealized configuration of real operating conditions. Simulations are performed using a combined method based on the Khokhlov-Zabolotskaya-Kuznetsov equation, describing the ultrasound propagation, and a Rayleigh-Plesset equation, modeling the bubble oscillations. The nonlinear interaction of the ultrasound field and the bubble oscillations is considered. Results with and without bubbles for different void fractions of the cloud and different acoustic powers are compared. The cloud induces scattering, nonlinear distortion, and shielding of ultrasound, which increase the mechanical index in the pre-focal zone, shift the location, reduce the size, and modify the shape of the volume of tissue of high mechanical index values, and lower the pressure at the intended focus considerably. Although some hypothesis and parameters used in the models do not fit the real HIFU situations, the simulation results suggest that the effects caused by a bubble cloud located in the pre-focal area should be considered and monitored to ensure the safety of high-intensity focused ultrasound treatments.

Numerical analysis of the effect of bubble distribution on multiple-bubble behavior.

Understanding multiple-bubble behavior in a megasonic field is essential for efficient megasonic nanodevice cleaning without pattern damage. In this study, we numerically studied the effects of equilibrium radius and initial void fraction on multiple-bubble behavior and induced pressure. We analyzed the nonspherical collapse, coalescence, and breakup of bubbles in a megasonic field using a compressible, locally homogeneous model of a gas-liquid two-phase medium. Bubbles were simulated with a uniform equilibrium radius or with a bubble size distribution. Our results indicate that the bubble behavior and induced pressure depended mainly on the initial void fraction. For the case of bubbles with uniform equilibrium radius, small bubbles generated high wall pressure at large initial void fractions. When there was a size distribution, bubbles with small equilibrium radii contributed little to the wall pressure because of the damping effect of the oscillation of larger bubbles. Furthermore, the addition of a large bubble suppressed the resonant behavior of the bubbles that induced high wall pressure.

Numerical study on mechanism of condensation oscillation of unstable steam jet

Submerged steam jet condensation is widely used in many industries. However, this process may cause damage to equipment due to pressure oscillation, especially at low steam mass flux. The dynamic process of steam bubble and different pressure oscillation types were investigated in this numerical study. Five typical stages were observed, which were bubble growth stage, bubble slow necking stage, bubble rapid necking stage, bubble detachment stage and secondary bubble oscillation stage. Two pressure oscillation types were found by the synchronization analysis of bubble pattern and pressure field. The mechanisms of condensation oscillation of unstable steam jet were revealed. As for the first type, two pressure peaks existed in the fluctuation process of secondary bubble volume. The higher pressure peak was generated when secondary bubble was oscillated to its minimum volume, and the other was generated when secondary bubble was collapsed. As for the second type, only one pressure peak existed and secondary bubble was quickly contracted without volume fluctuation. Pressure peak was generated when secondary bubble was quickly contracted to its minimum volume. Moreover, analyses of flow field pressure at different locations were carried out. Results indicated that the pressure fluctuation was mainly induced by the condensation oscillation of secondary bubble for both types. The trends of pressure at different locations were the same as that of secondary bubble internal pressure.

Infrasound from giant bubbles during explosive submarine eruptions

Shallow submarine volcanoes pose unique scientific and monitoring challenges. The interaction between water and magma can create violent explosions just below the surface, but the inaccessibility of submerged volcanoes means they are typically not instrumented. This both increases the risk to marine and aviation traffic and leaves the underlying eruption physics poorly understood. Here we use low-frequency sound in the atmosphere (infrasound) to examine the source mechanics of shallow submarine explosions from Bogoslof volcano, Alaska. We show that the infrasound originates from the oscillation and rupture of magmatic gas bubbles that initially formed from submerged vents, but that grew and burst above sea level. We model the low-frequency signals as overpressurized gas bubbles that grow near the water–air interface, which require bubble radii of 50–220 m. Bubbles of this size and larger have been described in explosive subaqueous eruptions for more than a century, but we present a unique geophysical record of this phenomenon. We propose that the dominant role of seawater during the effusion of gas-rich magma into shallow water is to repeatedly produce a gas-tight seal near the vent. This resealing mechanism leads to sequences of violent explosions and the release of large, bubble-forming volumes of gas—activity we describe as hydrovulcanian. During the submarine eruption of gas-rich magma into shallow water, a gas-tight seal forms, breaks and reseals, a process that results in violent explosions and the release of large gas bubbles, suggest low-frequency sound data from Bogoslof volcano, Alaska.

Experiments on pool boiling regimes and bubble departure characteristics of single vapor bubble under subcooled bulk conditions

An experimental study for understanding the effects of subcooling of bulk fluid on the phenomenon of nucleate boiling heat transfer was carried out. The whole field experimental data was recorded in a purely non-intrusive manner using rainbow schlieren deflectometry as the optical diagnostic tool. Boiling experiments were conducted over a range of heat flux conditions (1⩽q′′⩽40 kW/m2) and for varying levels of subcooling (0 K ≤ ΔTsubcooling ≤ 10 K). The recorded images were first been interpreted to understand the effect of subcooling on various regimes of boiling phenomenon, which include convection, isolated nucleate boiling and vertical coalescence of the departing bubbles. Observations on convection regime showed an increasing influence of natural convection heat transfer. Based on the formation of vapor bubble and its departure characteristics, the isolated nucleate boiling regime of the classical boiling curve was further segmented into three sub-regimes namely, stable vapor bubbles, oscillating vapor bubbles and oscillating-departing vapor bubbles. A mechanism explaining the oscillations of vapor bubbles under subcooled condition was proposed that takes into account the relative dominance of condensing apex region and evaporating microlayer region. Various bubble dynamic parameters such as equivalent bubble diameter, departure frequency, aspect ratio and oscillation frequency were determined quantitatively to understand the effect of subcooling on the bubble departure characteristics. Based on the experimental results, an empirical correlation for predicting the bubble departure diameter and evaporative heat flux was developed and proposed.

Modulation of the secondary Bjerknes force in multi-bubble systems.

The behaviours of insonated bubble clusters are regulated by the secondary Bjerknes force between bubble pairs. While the force has been investigated extensively for two-bubble systems, the modulation of the force by nearby bubbles remains unclear. This problem is investigated in this paper by theoretical analyses and numerical simulations of a three bubble system. For weak oscillations, the third bubble is found to have strong effects when its radius is close to the resonant radius. The equilibrium distance between the bubble pair is reduced when the radius of the third bubble is smaller than the resonant threshold, and increased when it is larger. For strong oscillations of bubbles with radii of a few microns, the third bubble reduces the magnitude of the force, hence increasing the equilibrium distance. The modulation effects depend strongly on the relative sizes of the bubbles. Stronger effects can be produced when the third bubble is placed closer to the smaller bubble in the bubble pair. The findings highlight the need for a more accurate parametrization of the secondary Bjerknes force in the simulation and manipulation of bubble clusters.

Experimental study of bubble sources localization in a water tank for oil spill detection

Since the Deepwater Horizon oil spill in 2010, there have been increasing demand for a real-time monitoring system that can detect, locate, and assess oil leakages. To this goal, we launched a three-year research project to develop a passive acoustic technique in 2017. The leaked crude oil creates underwater sound through bubble oscillations in an oil spill event. This paper focuses on studying the localization of the source of bubble-induced sounds in an experimental environment. Hydrophone arrays were deployed randomly and used to receive the acoustic signals in a 2 m × 2 m × 2 m water tank. We used spatial spectrum analysis algorithms such as Multiple Signal Classification (MUSIC) and Estimation of Signal Parameters by Rotational Invariance Techniques (ESPRIT) to determine the direction of arrival (DOA) by a hydrophone Uniform Linear Array (ULA), and utilized the multiple 2-D angles to localize the bubbles in 3-D space. We will also investigate the sensitivity of the localization algorithm with respect to the variations of physical features such as the cluster of frequency components and noise level. Experiment results will be presented and discussed.Since the Deepwater Horizon oil spill in 2010, there have been increasing demand for a real-time monitoring system that can detect, locate, and assess oil leakages. To this goal, we launched a three-year research project to develop a passive acoustic technique in 2017. The leaked crude oil creates underwater sound through bubble oscillations in an oil spill event. This paper focuses on studying the localization of the source of bubble-induced sounds in an experimental environment. Hydrophone arrays were deployed randomly and used to receive the acoustic signals in a 2 m × 2 m × 2 m water tank. We used spatial spectrum analysis algorithms such as Multiple Signal Classification (MUSIC) and Estimation of Signal Parameters by Rotational Invariance Techniques (ESPRIT) to determine the direction of arrival (DOA) by a hydrophone Uniform Linear Array (ULA), and utilized the multiple 2-D angles to localize the bubbles in 3-D space. We will also investigate the sensitivity of the localization algorithm with respect...

Characterization of sound induced by bubbles released from nozzles

In an oil spill event, the leaked crude oil creates underwater sound through bubble oscillations and fluid jets. In this laboratory study, sound induced by bubbles in two types of oil leakage were simulated: a few bubbles and constant flow bubbles. We investigated sound emitted by bubbles released from nozzles, aiming to obtain the characteristics of the oil leakage from the recorded sound signals. For the few bubble case, the dependences of bubble size and frequency on the nozzle diameter were measured. A relation between the average size of bubble and acoustic frequency with the nozzle diameter was used to explain the measurements. In the case of constant flow bubbles, different flow rate was tested. The relation of acoustic energy with the flow rate was obtained from the experimental data. Bubble size distribution was obtained from the spectrum of recorded sound signals. The physical modeling of the bubble sound will be presented and discussed. [Funded by the Gulf Research Program of the National Academy of Sciences.]

The vibration behavior of submicron gas vesicles in response to acoustic excitation as determined via laser doppler vibrometry

Gas vesicles (GVs) are remarkably stable nano-sized gas-filled protein shells proven effective in ultrasonic imaging. The many potential benefits of GVs arise from their strong gas equilibrium at a submicron size as produced by bacteria or algae, producing significant contrast in ultrasound imaging. The actual vibration behavior of GVs, including buckling and collapse, is poorly understood since the GVs are too small for observation methods of sufficient speed to produce details of the GV deformation during exposure to ultrasound. Traditional optical or acoustic microscopy methods are, in any case, not useful, and ex-situtransmission electron microscopy produces useful images but without sufficient time resolution. We propose to instead use laser Doppler vibrometry (LDV) to observe the vibration behavior of GVs. Employing interferometry, LDV offers a far better spatiotemporal resolution. While the typical GV is smaller than 1 μm, an agglomeration of GVs may be used with the LDV to produce a measurable displacement response from a controlled, acoustically delivered pressure. In this talk, we report the fundamental and first harmonic resonance frequencies of GVs and vibration to buckling and collapse at the clinically relevant frequency of 6.5 MHz. We also compare these results with predictions from classic theories of bubble and particle oscillations and finite difference-based computations.

GHz ultrasound propagation with a high speed in compressible liquids containing many microbubbles

This paper theoretically deals with weakly nonlinear (i.e., neither linear nor strong nonlinear) propagation of plane progressive quasi-monochromatic waves in an initially quiescent compressible liquid containing a tremendously large number of spherical gas bubbles on the basis of the derivation of two types of amplitude evolution equations (nonlinear wave equations). The important points are as follows: (i) the compressibility of the liquid phase, which has long been neglected, is taken into account; (ii) The incident wave frequency is very larger than an eigenfrequency of single bubble oscillations; (iii) bubbles are neither created nor annihilated; and (iv) the thermal effect is not considered and wave dissipation are then owing to liquid compressibility and liquid viscosity. By the use of the method of multiple scales with an appropriate choice of scaling relations of threenondimensional parameters, we can derive two types of the complex Ginzburg-Landau equations (or nonlinear Schrodinger equations), where the phase velocity is larger than the speed of sound in a pure liquid.

Application of two-branch deep neural network to predict bubble migration near elastic boundaries

Compared to the drawbacks of traditional experimental and numerical methods for predicting bubble migration, such as high experimental costs and complex simulation operations, the data-driven approach of using deep neural network algorithms can provide an alternative method. The objective of this paper is to construct a two-branch deep neural network (TBDNN) model in order to improve the high-fidelity bubble migration results and further reduce dependence on the quantity of experimental data. A TBDNN model is obtained by embedding the features of the Kelvin impulse into a basic deep neural network (BDNN) system. The results show that compared to the original BDNN model, TBDNN performs much better in accurately predicting bubble migration based on the same amount of training data. Using the TBDNN model, the critical condition of bubble oscillation at a fixed location can be detected under the influence of boundary properties (normalized stiffness and mass) and bubble standoff. Furthermore, the initial position of the bubble and normalized stiffness of boundaries have a positive correlation with bubble migration, whereas normalized mass has a negative impact. It was found that the normalized mass of boundaries plays the most important role in affecting bubble migration compared to the standoff and stiffness when using the method of variable sensitivity analysis.

Investigation of a rupture-induced underwater sound source

Underwater acoustic experiments, surveys, and sonar often require a repeatable, predictable, and broadband sound source. In many instances, a high amplitude, impulsive sound source is utilized to produce a broad-band event capable of penetrating the seabed and propagating to long range. Prior experimentation at the Applied Research Laboratories at the University of Texas at Austin (ARL:UT) has demonstrated the viability of a device that utilizes a rupture disk as an underwater acoustic source. A rupture disk is an expendable diaphragm used in industrial applications, which is designed to break at a specified pressure differential. Placing a rupture disk over an evacuated chamber and mechanically breaking the disk (either by striking on demand or via hydrostatic pressure) at a specified depth was demonstrated to produce high-amplitude, broadband waveforms as the cavity collapses and inflowing water impacts the bottom of the chamber. Residual bubble oscillations are greatly reduced due to the fact that the collapse chamber is initially evacuated. This source also has the advantage that it is solely comprises inert materials—no explosives or combustive gases are required. Discussion will focus on new and expanded source level measurements and preliminary comparisons to model predictions.

Learning and teaching acoustics through bubbles

By a lark, I started my acoustics career as a graduate student studying a single big bubble in the form of the combustive sound source. By at least the luck of being in a certain place at a certain time, I finished my graduate education by studying bubbles in the form of the acoustics of bubbly liquids. It turns out that the subject of bubbles provides an excellent lens through which to learn and teach acoustics. One starts with lumped element approximations which lead to simple harmonic oscillators and resonance. You can study the bubble oscillator as linear system and encounter increasingly complex nonlinear behavior at comparatively low amplitudes. A bubble is a source of sound initially modeled as a simple spherical source and can of course behave as a spherical scatterer. Add one or many bubbles and one can study more complex scattering and propagation that includes dispersion and loss. Along the way one encounters effective medium theories of varying complexity and statistical descriptions of acoustic phenomena. There are also applications that require inference and inverse techniques. You can even apply a model of a single bubble to study the expansion and contraction of the universe. Examples of these including demos and videos will be presented.By a lark, I started my acoustics career as a graduate student studying a single big bubble in the form of the combustive sound source. By at least the luck of being in a certain place at a certain time, I finished my graduate education by studying bubbles in the form of the acoustics of bubbly liquids. It turns out that the subject of bubbles provides an excellent lens through which to learn and teach acoustics. One starts with lumped element approximations which lead to simple harmonic oscillators and resonance. You can study the bubble oscillator as linear system and encounter increasingly complex nonlinear behavior at comparatively low amplitudes. A bubble is a source of sound initially modeled as a simple spherical source and can of course behave as a spherical scatterer. Add one or many bubbles and one can study more complex scattering and propagation that includes dispersion and loss. Along the way one encounters effective medium theories of varying complexity and statistical descriptions of acoust...

Modeling three dimensional gas bubble dynamics between two curved rigid plates using boundary integral method

High speed liquid jet forms when a bubble collapses near a solid boundary. The formation of the jet has both advantages and disadvantages as it causes erosion and damage in the nearby turbomachinery and can be beneficially applied in surface cleaning, fluid pumping, etc. In this paper, three-dimensional bubble oscillation between two curved rigid plates is modeled using boundary integral method (BIM). The bubble is incepted at different locations between the plates to investigate the eccentricity effects on the bubble shape, jet formation, etc. The modified Laplacian smoothing technique is implemented on the bubble surface during the jet development to reduce element distortion. The new model is validated with the Rayleigh–Plesset equation as well as with the available experimental data. It was found that the jet velocity increases, and the number of jets is reduced from two to one as the bubble is horizontally shifted away from the centroid. When the bubble is incepted on the horizontal axisymmetric line the jet is horizontal. However, the jet direction changes as the bubble is incepted closer to one of the plates. Finally, the pressure and velocity fields of the fluid surrounding the bubble are provided for better interpretation of the results.

Acoustic microstreaming produced by nonspherical oscillations of a gas bubble. II. Case of modes 1 and m.

This paper continues a study that was started in our previous paper [A. A. Doinikov etal., Phys. Rev. E 100, 033104 (2019)10.1103/PhysRevE.100.033104]. The overall aim of the study is to develop a theory for modeling the velocity field of acoustic microstreaming produced by nonspherical oscillations of an acoustically driven gas bubble. In the previous paper, general equations were derived that describe the velocity field of acoustic microstreaming produced by modes n and m of bubble oscillations. In the present paper, the above equations are solved analytically in the case that acoustic microstreaming is the result of the interaction of the translational mode (mode 1) with a mode of arbitrary order m≥1. Solutions are expressed in terms of complex mode amplitudes, which means that the mode amplitudes are assumed to be known and serve as input data for the calculation of the velocity field of acoustic microstreaming. No restrictions are imposed on the ratio of the bubble radius to the viscous penetration depth. Analytical results are illustrated by numerical examples.

Acoustic microstreaming produced by nonspherical oscillations of a gas bubble. I. Case of modes 0 and m.

A theory is developed that allows one to model the velocity field of acoustic microstreaming produced by nonspherical oscillations of an acoustically driven gas bubble. It is assumed that some of the bubble oscillation modes are excited parametrically and hence can oscillate at frequencies different from the driving frequency. Analytical solutions are derived in terms of complex amplitudes of oscillation modes, which means that the mode amplitudes are assumed to be known and serve as input data when the velocity field of acoustic microstreaming is calculated. No restrictions are imposed on the ratio of the bubble radius to the viscous penetration depth. The present paper is the first part of our study in which a general theory is developed and then applied to the case that acoustic microstreaming is generated by the interaction of the breathing mode (mode 0) with a mode of arbitrary order m≥1. Examples of numerical simulations and a comparison with experimental results are provided.

Numerical study on dual-frequency ultrasonic enhancing cavitation effect based on bubble dynamic evolution.

Ultrasonic cavitation is a physical dynamic phenomenon of bubbles inflation, compression, and collapse in liquid. A dual-frequency ultrasonic cavitation dynamics model is established in this paper to investigate dynamic evolution of bubble under single and dual frequency ultrasonic modes. The variation of bubble radius, pressure, energy, temperature, and number of water vapor molecules inside the bubble in single and dual frequency ultrasonic modes are analyzed, respectively. The results show the oscillation of cavitation bubbles is more unstable and easier to collapse in dual-frequency ultrasound field than those in single-frequency ultrasound field. With the increase of the ultrasonic frequency, cavitation effect is weakened due to the shortage of oscillation period. Under the same ultrasonic power, the maximums of bubble radius, pressure, and water vapor molecules number inside the bubble in the dual-frequency mode are larger than those in the single-frequency mode. Under the ultrasonic excited by 50 kHz + 70 kHz, the maximum bubble radius and pressure can reach 36.061 μm and 2285.9 MPa, respectively, which are much larger than 18.183 μm, 730.61 MPa at 50 kHz and 14.576 μm, 332.25 MPa at 70 kHz. The calculation results of three different frequency combinations (30 kHz + 50 kHz, 40 kHz + 60 kHz and 50 kHz + 70 kHz) indicate dual-frequency ultrasound can significantly enhance the cavitation effect.

A perturbed ghost model for estimating air-gun array signatures

Source designature for seismic data acquired using an air-gun array aims to remove the effects of pulse asymmetry, bubble oscillation, array directivity, and ghosting at the sea surface. For the process to be successful, we require an accurate representation of the source signature in the far field over the full data bandwidth. The well-established approach to this problem is to derive signatures from hydrophone data recorded in the near field of the source array. We perform a least-squares inversion of the near-field data, using a representation of the physics of propagation within the vicinity of the array, according to the measured geometry and incorporating bubble motion and source ghost formation. While ghost formation is typically treated using a simple linear model of propagation and reflection at the sea surface, observations suggest that this may be too simplistic. For example, ghost amplitudes are often found to be lower than expected, and features indicative of acoustically induced cavitation are observed. Hence there is interest in developing approaches that allow us to solve for the ghost directly using additional measurements made in the near field. We present an approach that builds on the standard method of inverting for notional sources and that seeks to take account of nonlinear perturbations to the downgoing wavefield, including attenuation of the ghost. Perturbation of the ghost is described using a series of virtual notional sources situated in the water column between the guns and the sea surface. This is found to provide a more accurate treatment of the ghost and does not require optimization of model parameters as is often necessary in practice with the standard approach. It is also found that the inversion is more stable than an alternative parameter-free approach that solves directly for real and mirror virtual notional sources. The improved performance and stability are demonstrated with a field data example.