Journal articles on the topic 'Acoustic Bubbles'
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1
Desai, Pratik D., Woon Choon Ng, Michael J. Hines, Yassir Riaz, Vaclav Tesar, and William B. Zimmerman. "Comparison of Bubble Size Distributions Inferred from Acoustic, Optical Visualisation, and Laser Diffraction." Colloids and Interfaces 3, no. 4 (December 5, 2019): 65. http://dx.doi.org/10.3390/colloids3040065.
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Bubble measurement has been widely discussed in the literature and comparison studies have been widely performed to validate the results obtained for various forms of bubble size inferences. This paper explores three methods used to obtain a bubble size distribution—optical detection, laser diffraction and acoustic inferences—for a bubble cloud. Each of these methods has advantages and disadvantages due to their intrinsic inference methodology or design flaws due to lack of specificity in measurement. It is clearly demonstrated that seeing bubbles and hearing them are substantially and quantitatively different. The main hypothesis being tested is that for a bubble cloud, acoustic methods are able to detect smaller bubbles compared to the other techniques, as acoustic measurements depend on an intrinsic bubble property, whereas photonics and optical methods are unable to “see” a smaller bubble that is behind a larger bubble. Acoustic methods provide a real-time size distribution for a bubble cloud, whereas for other techniques, appropriate adjustments or compromises must be made in order to arrive at robust data. Acoustic bubble spectrometry consistently records smaller bubbles that were not detected by the other techniques. The difference is largest for acoustic methods and optical methods, with size differences ranging from 5–79% in average bubble size. Differences in size between laser diffraction and optical methods ranged from 5–68%. The differences between laser diffraction and acoustic methods are less, and range between 0% (i.e., in agreement) up to 49%. There is a wider difference observed between the optical method, laser diffraction and acoustic methods whilst good agreement between laser diffraction and acoustic methods. The significant disagreement between laser diffraction and acoustic method (35% and 49%) demonstrates the hypothesis, as there is a higher proportion of smaller bubbles in these measurements (i.e., the smaller bubbles ‘hide’ during measurement via laser diffraction). This study, which shows that acoustic bubble spectrometry is able to detect smaller bubbles than laser diffraction and optical techniques. This is supported by heat and mass transfer studies that show enhanced performance due to increased interfacial area of microbubbles, compared to fine bubbles.
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Ammari, Habib, Brian Fitzpatrick, David Gontier, Hyundae Lee, and Hai Zhang. "Sub-wavelength focusing of acoustic waves in bubbly media." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 473, no. 2208 (December 2017): 20170469. http://dx.doi.org/10.1098/rspa.2017.0469.
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The purpose of this paper is to investigate acoustic wave scattering by a large number of bubbles in a liquid at frequencies near the Minnaert resonance frequency. This bubbly media has been exploited in practice to obtain super-focusing of acoustic waves. Using layer potential techniques, we derive the scattering function for a single spherical bubble excited by an incident wave in the low frequency regime. We then propose a point scatterer approximation for N bubbles, and describe several numerical simulations based on this approximation, that demonstrate the possibility of achieving super-focusing using bubbly media.
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Reeder, D. Benjamin, John E. Joseph, Thomas A. Rago, Jeremy M. Bullard, David Honegger, and Merrick C. Haller. "Acoustic spectrometry of bubbles in an estuarine front: Sound speed dispersion, void fraction, and bubble density." Journal of the Acoustical Society of America 151, no. 4 (April 2022): 2429–43. http://dx.doi.org/10.1121/10.0009923.
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Estuaries constitute a unique waveguide for acoustic propagation. The spatiotemporally varying three-dimensional front between the seawater and the outflowing freshwater during both flood and ebb constitutes an interfacial sound speed gradient capable of supporting significant vertical and horizontal acoustic refraction. The collision of these two water masses often produces breaking waves, injecting air bubbles into the water column; the negative vertical velocities of the denser saltwater often subduct bubbles to the bottom of these shallow waveguides, filling the water column with a bubbly mixture possessing a significantly lower effective sound speed. A field experiment was carried out in the mouth of Mobile Bay, Alabama in June 2021 to characterize estuarine bubble clouds in terms of their depth-dependent plume structure, frequency-dependent sound speed and attenuation, bubble size distribution, bubble number density, and void fraction. Results demonstrate that sound speed in the bubbly liquid consistently falls below the intrinsic sound speed of bubble-free water; specifically, the bubbly liquid 1.3 m below the surface in a front in this environment possesses effective sound speeds, void fractions, and bubble number densities of approximately 750 m/s, 0.001%, and 2 × 106 bubbles/m3, respectively.
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Simaciu, Ion, Gheorghe Dumitrescu, Zoltan Borsos, and Anca Baciu. "Mach’s Principle in the Acoustic World." BULETINUL INSTITUTULUI POLITEHNIC DIN IAȘI. Secția Matematica. Mecanică Teoretică. Fizică 67, no. 4 (December 1, 2021): 59–69. http://dx.doi.org/10.2478/bipmf-2021-0020.
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Abstract The aim of this paper is to investigate the coupled oscillations of multiple bubbles within a cluster. The interaction between a bubble and the other bubbles in a cluster produces an additional mass. For a fixed number of bubbles and uniformly distributed (N ---gt------gt--- 1), in case of a certain value of the bubbles number density, we deduce the relations analogous to the Eddington relation (between the cluster radius and the bubble radius) and the Sciama relation (between the cluster radius and the gravitoacoustic radius) according to Mach’s Principle.
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Wang, Yu, Dehua Chen, Xueshen Cao, and Xiao He. "Theoretical and Experimental Studies of Acoustic Reflection of Bubbly Liquid in Multilayer Media." Applied Sciences 12, no. 23 (November 30, 2022): 12264. http://dx.doi.org/10.3390/app122312264.
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Bubbly liquids are widely present in the natural environment and industrial fields, such as seawater near the ocean bottom, the multiphase flow in petroleum reservoirs, and the blood with bubbles resulting in decompression sickness. Therefore, accurate measurement of the gas content is of great significance for hydroacoustic physics, oil and gas resources exploration, and disease prevention and diagnosis. Trace bubbles in liquids can lead to considerable changes in the acoustic properties of gas–liquid two-phase media. Acoustic measurements can therefore be applied for trace bubble detection. This study derived the reflection coefficient of acoustic waves propagating in a sandwich layering model with liquid, bubbly liquid, and liquid. The influences of gas contents on the reflection coefficient at the layer interface were analyzed based on theoretical calculations. It was revealed that the magnitude of the reflection coefficient and the frequency interval between its valleys have a quantitative correlation with the gas contents. Thus, a novel means to detect the contents of trace bubbles was proposed by evaluating the reflection coefficients. The reflection features of a thin layer with bubbly liquid were then studied through experiments. It was validated by acoustical measurements and theories that the reflection coefficient is considerably sensitive to the change of gas contents as long as the gas content is tiny. With the increasing gas content, the maximum value of the reflection coefficient increases; meanwhile, the frequency intervals between the valleys become smaller. However, when the gas content is extensive enough, e.g., greater than 1%, the effect of the change of gas content on the reflection coefficient becomes inapparent. In that case, it is not easy to measure the gas content by the acoustic reflection signals with satisfying precision. This proposed method has potential applications for the detection of trace gas bubble content in several scenarios, e.g., decompression illness prevention and diagnosis.
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Li, Fan, Xian-Mei Zhang, Hua Tian, Jing Hu, Shi Chen, Cheng-Hui Wang, Jian-Zhong Guo, and Run-Yang Mo. "Structure stability of cyclic chain-like cavitation cloud in thin liquid layer." Acta Physica Sinica 71, no. 8 (2022): 084303. http://dx.doi.org/10.7498/aps.71.20212257.
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In this paper, the evolution of the cavitation bubbles is investigated. A model is developed to describe the cyclic chain-like cavitation cloud and analyze its structure stability in a thin liquid layer. By considering the effect of secondary acoustic radiation of bubbles, the dynamic equations of the bubbles in three zones of the cyclic chain are obtained. The secondary Bjerknes force is selected and used to explore the interaction between the bubbles in different regions. Numerical results show that the newborn bubbles inside the pure liquid zone of the thin layer can be attracted by the bubbles at the cyclic chain-like bubble chain. The bubble number density can affect the coupling strength between bubbles, and it is closely related to the driving pressure. Therefore, the structure stability of cyclic chain-like cavitation cloud can be disrupted by the perturbations of the acoustic pressure. To verify our analysis, we observe the structure of cavitation cloud in a thin liquid layer in a strong acoustic field by using a high speed camera. It is observed that the simultaneous collapse of local bubbles occurs, and pure liquid-like thin layers are distributed in the bubble cloud randomly. The boundary of the pure liquid-like thin layers oscillates with the acoustic field, and these liquid zones sustain about 4 acoustic cycles. The experimental results accord well with theoretical results.
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Altay, Rana, Abdolali K. Sadaghiani, M. Ilker Sevgen, Alper Şişman, and Ali Koşar. "Numerical and Experimental Studies on the Effect of Surface Roughness and Ultrasonic Frequency on Bubble Dynamics in Acoustic Cavitation." Energies 13, no. 5 (March 3, 2020): 1126. http://dx.doi.org/10.3390/en13051126.
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With many emerging applications such as chemical reactions and ultrasound therapy, acoustic cavitation plays a vital role in having improved energy efficiency. For example, acoustic cavitation results in substantial enhancement in the rates of various chemical reactions. In this regard, an applied acoustic field within a medium generates acoustic streaming, where cavitation bubbles appear due to preexisting dissolved gas in the working fluid. Upon cavitation inception, bubbles can undergo subsequent growth and collapse. During the last decade, the studies on the effects of different parameters on acoustic cavitation such as applied ultrasound frequency and power have been conducted. The bubble growth and collapse mechanisms and their distribution within the medium have been classified. Yet, more research is necessary to understand the complex mechanism of multi-bubble behavior under an applied acoustic field. Various parameters affecting acoustic cavitation such as surface roughness of the acoustic generator should be investigated in more detail in this regard. In this study, single bubble lifetime, bubble size and multi-bubble dynamics were investigated by changing the applied ultrasonic field. The effect of surface roughness on bubble dynamics was presented. In the analysis, images from a high-speed camera and fast video recording techniques were used. Numerical simulations were also done to investigate the effect of acoustic field frequency on bubble dynamics. Bubble cluster behavior and required minimum bubble size to be affected by the acoustic field were obtained. Numerical results suggested that bubbles with sizes of 50 µm or more could be aligned according to the radiation potential map, whereas bubbles with sizes smaller than 10 µm were not affected by the acoustic field. Furthermore, it was empirically proven that surface roughness has a significant effect on acoustic cavitation phenomena.
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Mekki-Berrada, F., T. Combriat, P. Thibault, and P. Marmottant. "Interactions enhance the acoustic streaming around flattened microfluidic bubbles." Journal of Fluid Mechanics 797 (May 26, 2016): 851–73. http://dx.doi.org/10.1017/jfm.2016.289.
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The vibration of bubbles can produce intense microstreaming when excited by ultrasound near resonance. In order to study freely oscillating bubbles in steady conditions, we have confined bubbles between the two walls of a silicone microchannel and anchored them on micropits. We were thus able to analyse the microstreaming flow generated around an isolated bubble or a pair of interacting bubbles. In the case of an isolated bubble, a short-range microstreaming occurs in the channel gap, with additional in-plane vortices at high amplitude when Faraday waves are excited on the bubble periphery. For a pair of bubbles, we have observed long-range microstreaming and large recirculations describing a ‘butterfly’ pattern. We propose a model based on secondary acoustic Bjerknes forces mediated by Rayleigh waves on the silicone walls. These forces lead to attraction or repulsion of bubbles and thus to the excitation of a translational mode in addition to the breathing mode of the bubble. The mixed-mode streaming induced by the interaction of these two modes is shown to generate fountain or anti-fountain vortex pairs, depending on the relative distance between the bubbles.
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Ouyang, Di-Hua, Wen-Rong Yan, Qian-Tao Zhang, and Chun-Hai Yang. "Movement and acoustic radiation of a rising bubble from combustion of pyrotechnic mixtures using experiment and image processing method." Physics of Fluids 33, no. 10 (October 2021): 105114. http://dx.doi.org/10.1063/5.0063854.
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Bubble volume and bubble geometry are key parameters that affect the movement and acoustic radiation performance of bubble columns. This paper proposes an image processing method to study the movement and acoustic radiation characteristics of the rising bubbles originating from the combustion of a pyrotechnic composition based on high-speed photography. Results showed that during the rise of bubbles, their shape gradually changed from spherical to irregular, and their rising trajectory presented a curvilinear form. After the rising velocities of the bubbles in the z and x directions were compared, the results revealed that the rising velocity of the bubbles was unstable. The velocity of the rising bubbles in the direction of the z axis was much higher than that of the x axis. Meanwhile, the acceleration of bubble volume decreased first and then increased. This process was repeated; however, the amplitude of increase or decrease was inconsistent, which led to the generation of a certain amount of acoustic radiation effect, and it had a similar trend of change with the acceleration of bubble volume.
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Boziuk, Thomas R., Marc K. Smith, and Ari Glezer. "Dynamics of vapor bubble condensation under directional ultrasonic actuation." Physics of Fluids 35, no. 1 (January 2023): 017126. http://dx.doi.org/10.1063/5.0134326.
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Direct-contact condensation of vapor bubbles injected into a subcooled liquid is enhanced using ultrasonic O(1 MHz) acoustic actuation. In the absence of actuation, the surface tension-driven pinch-off process of the vapor bubble from the injection orifice induces a liquid spear that travels upward through the bubble and ruptures the top interface to form a toroidal bubble. Similarly, the acoustic actuator produces a narrow high-intensity acoustic beam that deforms the top interface of the vapor bubble via radiation pressure to form a liquid spear that travels downward though the bubble and ruptures the bottom interface to form a toroidal bubble. Comparisons between the growth and collapse of vapor bubbles in these two cases were performed using high-speed video imaging and particle image velocimetry. The results show that the actuated bubble collapsed about 35% faster than the unactuated bubble. The flow fields around the bubbles induced by the motion of the liquid spears are similar in both cases. By comparing vapor bubbles under different subcooling conditions with an unactuated, noncondensing air bubble, it was shown that condensation at the liquid–vapor interface strongly influences bubble collapse times and the velocity field surrounding each of the bubbles and that these effects increase as the level of subcooling increases.
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Doinikov, Alexander A., and Ayache Bouakaz. "Microstreaming generated by two acoustically induced gas bubbles." Journal of Fluid Mechanics 796 (May 4, 2016): 318–39. http://dx.doi.org/10.1017/jfm.2016.270.
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A theory is developed that describes microstreaming generated by two interacting gas bubbles in an acoustic field. The theory is used in numerical simulations to compare the characteristics of acoustic microstreaming at different frequencies, separation distances between the bubbles and bubble sizes. It is shown that the interaction of the bubbles leads to a considerable increase in the intensity of the velocity and stress fields of acoustic microstreaming if the bubbles are driven near the resonance frequencies that they have in the presence of each other. Patterns of streamlines for different situations are presented.
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Rychert, Kevin M., and Thomas C. Weber. "Tests of Acoustic Target Strength and Bubble Dissolution Models Using a Synthetic Bubble Generator." Journal of Atmospheric and Oceanic Technology 37, no. 1 (January 2020): 129–40. http://dx.doi.org/10.1175/jtech-d-19-0133.1.
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AbstractTo test methods used for converting observations of acoustic backscatter to estimates of the volume and transport of free gas escaping the seabed, a bubble generator has been constructed and used at sea. The bubble generator creates individual bubbles of the sizes commonly associated with methane seeps, 1–5-mm radii, which can be released at preplanned rates. The bubble generator was deployed off the coast of New Hampshire at a depth of 55 m, and acoustic backscatter between 16 and 24 kHz was collected from a shipboard echo sounder while transiting over the rising bubbles. Bubble sizes and compositions (either Ar or N2) were known at the source. A model for bubble evolution, accounting for changes in bubble size and composition due to hydrostatic pressure and gas diffusion across the gas–liquid boundary, was coupled with an acoustic target strength (TS) model to generate predictions of the acoustic backscatter from bubbles that had risen to different depths. These predictions were then compared with experimental observation. Good agreement between prediction and observation was found in most cases, with the exception of the largest (4 mm) gas bubbles at depths of 30 m or less. The exact cause of this bias is unknown, but may be due to incorrect assumptions in models for the bubble TS, rise velocity, or mass transfer rate.
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THO, PAUL, RICHARD MANASSEH, and ANDREW OOI. "Cavitation microstreaming patterns in single and multiple bubble systems." Journal of Fluid Mechanics 576 (March 28, 2007): 191–233. http://dx.doi.org/10.1017/s0022112006004393.
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Cavitation microstreaming is a well-known phenomenon; however, few flow visualizations or measurements of the velocity fields have been conducted. In this paper micro-PIV (particle image velocimetry) measurements and streak photography were used to study the flow field around a single and two oscillating bubbles resting on a solid boundary. The mode of oscillation of the bubble was also measured in terms of the variation in the radius of the bubble and the movement of the bubble's centroid so that the streaming flow field could be accurately related to the bubble's oscillatory motion. The mode of oscillation was found to vary primarily with the applied acoustic frequency. Several modes of oscillation were investigated, including translating modes where the bubble's centroid moves along either a single axis, an elliptical orbit or a circular orbit. The flow field resulting from these oscillation modes contains closed streamlines representing vortical regions in the vicinity of the bubble. The translating modes were observed to occur in sequential order with the acoustic excitation frequency, changing from a translation along a single axis, to an elliptical orbit and finally to a circular orbit, or vice versa. Following this sequence, there is a corresponding transformation of the streaming pattern from a symmetrical flow structure containing four vortices to a circular vortex centred on the bubble. Despite some inconsistencies, there is general agreement between these streaming patterns and those found in existing theoretical models. Volume and shape mode oscillations of single bubbles as well as several different cases of multiple bubbles simultaneously oscillating with the same frequency and phase were also investigated and show a rich variety of streaming patterns.
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Nasibullaeva, E. Sh, and I. Sh Akhatov. "Modeling of oscillations of a bubble cluster in an acoustic field." Proceedings of the Mavlyutov Institute of Mechanics 4 (2006): 174–85. http://dx.doi.org/10.21662/uim2006.1.016.
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A mathematical model describing the dynamics of nonlinear oscillations of gas bubbles in a cluster under the influence of an acoustic field is proposed. On the basis of this model, small bubble oscillations in a cluster were analyzed, the bubble oscillations in a monodisperse cluster were compared with the oscillations of a single bubble, the effects of the interaction of bubbles in a polydisperse cluster were studied, and the diffusion stability of bubbles in mono- and polydisperse clusters was investigated.
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Mettin, Robert, P. E. Frommhold, X. Xi, F. Cegla, H. Okorn-Schmidt, A. Lippert, and F. Holsteyns. "Acoustic Bubbles: Control and Interaction with Particles Adhered to a Solid Substrate." Solid State Phenomena 195 (December 2012): 161–64. http://dx.doi.org/10.4028/www.scientific.net/ssp.195.161.
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Applications of acoustic cavitation [ frequently suffer from certain random aspects (e.g., stochastic bubble nucleation events) as well as from its sensitivity to external parameters (like gas content in the liquid). This renders for example a prediction of bubble distributions in size and space still a difficult task. To improve this situation by a better understanding of the fundamentals, a "bottom-up" approach has recently been followed which tried to model collective bubble phenomena and bubble structures on the basis of single bubbles and their interaction [. If the behavior of individual bubbles can be well captured by the models, it is hoped to gain significant insight into a larger system of acoustically driven bubbles. Indeed, several aspects of multi-bubble systems and structures could be explained by single bubble dynamics, for instance by the inversion of the primary Bjerknes force in strong ultrasonic fields. Nevertheless, many details of bubble dynamics stay partly unclear, and considerable efforts are undertaken to improve our understanding and to optimize applications of acoustic bubbles.
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ZERAVCIC, ZORANA, DETLEF LOHSE, and WIM VAN SAARLOOS. "Collective oscillations in bubble clouds." Journal of Fluid Mechanics 680 (June 6, 2011): 114–49. http://dx.doi.org/10.1017/jfm.2011.153.
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In this paper the collective oscillations of a bubble cloud in an acoustic field are theoretically analysed with concepts and techniques of condensed matter physics. More specifically, we will calculate the eigenmodes and their excitabilities, eigenfrequencies, densities of states, responses, absorption and participation ratios to better understand the collective dynamics of coupled bubbles and address the question of possible localization of acoustic energy in the bubble cloud. The radial oscillations of the individual bubbles in the acoustic field are described by coupled linearized Rayleigh–Plesset equations. We explore the effects of viscous damping, distance between bubbles, polydispersity, geometric disorder, size of the bubbles and size of the cloud. For large enough clusters, the collective response is often very different from that of a typical mode, as the frequency response of each mode is sufficiently wide that many modes are excited when the cloud is driven by ultrasound. The reason is the strong effect of viscosity on the collective mode response, which is surprising, as viscous damping effects are small for single-bubble oscillations in water. Localization of acoustic energy is only found in the case of substantial bubble size polydispersity or geometric disorder. The lack of localization for a weak disorder is traced back to the long-range 1/r interaction potential between the individual bubbles. The results of the present paper are connected to recent experimental observations of collective bubble oscillations in a two-dimensional bubble cloud, where pronounced edge states and a pronounced low-frequency response had been observed, both consistent with the present theoretical findings. Finally, an outlook to future possible experiments is given.
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Ostrovsky, Ilia. "The acoustic quantification of fish in the presence of methane bubbles in the stratified Lake Kinneret, Israel." ICES Journal of Marine Science 66, no. 6 (April 20, 2009): 1043–47. http://dx.doi.org/10.1093/icesjms/fsp103.
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Abstract Ostrovsky, I. 2009. The acoustic quantification of fish in the presence of methane bubbles in the stratified Lake Kinneret, Israel. – ICES Journal of Marine Science, 66: 1043–1047. Methane ebullition from bottom sediments is common in many productive bodies of water. During acoustic surveys, the methane bubbles can be mistaken as fish. In the stratified Lake Kinneret, the densities and target-strength (TS) values of acoustic targets were measured with a 120-kHz, dual-beam echosounder at night, when the fish schools were dispersed and single targets could be detected. The density and TS of methane bubbles were estimated in the anoxic hypolimnion, where there were no fish. A discrete-bubble model was applied in combination with a TS vs. methane bubble-size relationship to estimate the methane bubble TS at different depths. This information was used to quantify the densities of methane bubbles and fish, and the fish TS in the epilimnion where both types of target were found. During periods of rapid decrease in water level, methane bubbles could be the principal acoustic targets in the epilimnion, and their TS strongly overlapped that of fish. In some strata, they contributed up to 90–95% of all targets. The amount of methane bubbles in the water column depends on the type of sediment, bottom depth, and the history of sediment degassing. Their presence could be a serious obstacle to the accurate assessment of fish abundance in lakes and reservoirs with varying water levels, where intensive gas emission is a common feature. For such situations, backscattering by methane bubbles must be taken into account to avoid the erroneous quantification of fish abundance.
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Shi, Hui-Min, Run-Yang Mo, and Chen-Hui Wang. "Oscillation behavior of bubble pair in magnetic fluid tube under magneto-acoustic complex field." Acta Physica Sinica 71, no. 8 (2022): 084302. http://dx.doi.org/10.7498/aps.71.20212150.
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Based on the dynamic model of a single bubble in a magnetic fluid tube, the dynamic equation of a bubble pair system in a magneto-acoustic field is established by introducing the secondary sound radiation between bubbles and considering the magnetic field effect of the viscosity of the magnetic fluid. The effects of magnetic field intensity, bubble pair’s size, bubble interaction (including secondary Bjerknes force <i>F</i><sub>B</sub> and magnetic attraction <i>F</i><sub>m</sub>) and fluid characteristics on the vibration characteristics of double bubbles are analyzed. The results show that magnetic field increases the amplitude of bubbles, and the influence of magnetic field on the large bubble is greater than on the small bubble. When the center distance between the two bubbles is constant and the relative size of two bubbles is larger, or when the size of the two bubbles is constant and the surface distance between two bubbles is small, the interaction between two bubbles is stronger. In the magneto-acoustic composite field, magnetic field can affect <i>F</i><sub>B</sub>, <i>F</i><sub>m</sub>, magnetic pressure <i>P</i><sub>m</sub> and viscosity resistance, and the influence degrees are different. There is competition between <i>F</i><sub>B</sub> and <i>F</i><sub>m</sub> and between <i>P</i><sub>m</sub> and viscosity resistance, and the forces acting on the microbubble jointly affect the movement of the bubbles. By studying the dynamic behavior of paired bubbles, it can provide a theoretical basis for improving the therapeutic effect of targeted regulation of microbubbles on biological tissues by adjusting the magneto-acoustic field in practical application.
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Nelli, Filippo, Grant Deane, Andrew Ooi, and Richard Manasseh. "Analysis of sound pressure levels generated by nozzle-emitted large bubbles." JASA Express Letters 2, no. 5 (May 2022): 054002. http://dx.doi.org/10.1121/10.0010377.
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The sound radiated by newly formed bubbles can be used to determine their properties. However, details of the fluid dynamics driving the acoustic emission remain unclear. A neck-collapsing model has been proposed to explain the sound generation at bubble pinch-off. The model uses a forcing function which drives the Rayleigh-Plesset equation and is linked to the bubble acoustic pressure. Here, the model is tested on bubbles of diameter up to 7 mm generated in distilled water, tap water, and alcohol-water solution. The model works well for bubbles less than 2.2 mm radius but the error increases up to 71% for larger diameters.
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Hou, Jiacheng, Zhongquan Charlie Zheng, and John S. Allen. "Immersed-boundary time-domain simulation of acoustic pulse scattering from a single or multiple gas bubble(s) of various shapes." Journal of the Acoustical Society of America 152, no. 4 (October 2022): A118. http://dx.doi.org/10.1121/10.0015738.
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Acoustic scattering and resonances resulting from a point pulse on a single or multiple gas bubbles are simulated using a time-domain simulation. The time histories of scattering pressure and velocity, both outside and inside the bubbles, are obtained simultaneously with an immersed-boundary method implementation. The acoustic resonances of the bubbles are investigated for various bubble numbers, sizes, shapes and interior gas parameters. For several cases, the scattering and resonance behaviors are compared with the existing theoretical and experimental results.
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Li, Qi, Shu Liu, and Dajing Shang. "Prediction of Acoustic Energy Radiated by Bubble Produced by Raindrops." Mathematical Problems in Engineering 2020 (December 14, 2020): 1–12. http://dx.doi.org/10.1155/2020/4581937.
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Underwater noise produced by rainfall is an important part of underwater ambient noise. The bubbles produced by raindrops are the main noise source of underwater noise. Generally, the sound pressure signal of individual bubbles is easily contaminated by tank reverberation, hydrodynamic flow, and laboratory electrical noise. In order to solve this problem, this study proposes a method for calculating the acoustic energy of the bubble produced by a raindrop when the latter falls onto a plane water surface. For this purpose, a series of experiments was conducted in a 15 m × 9 m × 6 m reverberation tank filled with tap water. The bubble produced by a raindrop behaves as a simple exponentially damped sinusoidal oscillator. Based on the dipole radiation pattern, a formula was derived to predict the sound energy of these bubbles. The damping coefficient of the bubble formed by raindrops is found to differ appreciably from the empirical value of the bubble formed by other mechanisms. The resonance frequency of the bubbles is found to decrease with time. It is due to the rapid increase in the distance between the bubble and the interface. Then, the formula is optimized by using these two improved variables. The experimental results agree well with the theoretical derivation.
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Zhang, Jingjing, Tengfei Zheng, Lin Tang, Hui Qi, Xiaoyu Wu, and Linlong Zhu. "Bubble-Enhanced Mixing Induced by Standing Surface Acoustic Waves (SSAWs) in Microchannel." Micromachines 13, no. 8 (August 18, 2022): 1337. http://dx.doi.org/10.3390/mi13081337.
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BAW-based micromixers usually achieve mixing enhancement with acoustic-induced bubbles, while SAW-based micromixers usually enhance mixing efficiency by varying the configuration of IDTs and microchannels. In this paper, bubble-enhanced acoustic mixing induced by standing surface acoustic waves (SSAWs) in a microchannel is proposed and experimentally demonstrated. Significant enhancement in the mixing efficiency was achieved after the bubbles were stimulated in our acoustofluidic microdevice. With an applied voltage of 5 V, 50 times amplified, the proposed mixing microdevice could achieve 90.8% mixing efficiency within 60 s at a flow rate of 240 μL/h. The bubbles were generated from acoustic cavitation assisted by the temperature increase resulting from the viscous absorption of acoustic energy. Our results also suggest that a temperature increase is harmful to microfluidic devices and temperature monitoring. Regulation is essential, especially in chemical and biological applications.
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BARBAT, TIBERIU, NASSER ASHGRIZ, and CHING-SHI LIU. "Dynamics of two interacting bubbles in an acoustic field." Journal of Fluid Mechanics 389 (June 25, 1999): 137–68. http://dx.doi.org/10.1017/s0022112099004899.
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This paper contains theoretical and experimental results on the relative motion of two pulsating spherical bubbles along their line of centres, in a liquid subjected to an acoustic field. The motion is caused only by the secondary Bjerknes forces. The linear theory for the secondary Bjerknes forces is modified by introducing a model for the coupling between the pulsations of the interfaces. The secondary effects introduced by this model are determined by the frequency indices of the bubbles, defined as the ratio of the forcing frequency to the resonance frequency of each bubble. The equations of motion are set up with the conservative Lagrangian formalism. This approach allows an analytical study of all the possible patterns of motion and the identification of the set of governing parameters: total energy and interaction coefficient. A pair of bubbles driven far from their resonance frequencies may attract or repel, depending on whether their frequency indices are respectively on the same side or on either side of unity. For forcing frequencies close to resonance, the proposed model predicts a new pattern of relative motion, namely a periodic motion (oscillations) around an equilibrium bubble separation. The experimental study identifies this new periodic pattern of motion, for acoustically levitated bubbles of nearly equal sizes, forced near their resonance frequency. A quantitative study on the variation of the relative velocity with the separation between the bubbles shows that the conservative model for the motion holds for large and moderate separations. The following information is reported: (a) a classification of the pairs of bubbles, based upon their phase difference in oscillations; (b) a model for the coupling of the pulsations of two bubbles; (c) formulas for the interaction force field of two pulsating bubbles, for all of the categories; (d) a study of all possible patterns of relative motion (collisions, scattering and oscillations), with their conditions of occurrence; (e) experimental data for two attracting bubbles; (f) experimental data for two oscillating bubbles.
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Wang, Yi-Chun. "Effects of Nuclei Size Distribution on the Dynamics of a Spherical Cloud of Cavitation Bubbles." Journal of Fluids Engineering 121, no. 4 (December 1, 1999): 881–86. http://dx.doi.org/10.1115/1.2823550.
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The nonlinear dynamics of a spherical bubble cloud with nuclei size distribution are studied numerically. The spectrum of nuclei is assumed uniform initially. The simulations employ a nonlinear continuum bubbly mixture model with consideration of the presence of bubbles of different sizes. This model is then coupled with the Rayleigh-Plesset equation for the dynamics of bubbles. A numerical method based on the integral representation of the mixture continuity and momentum equations in the Lagrangian coordinates is developed to solve this set of integro-differential equations. Computational results show that the nuclei size distribution has significant effects on the cloud dynamics in comparison to the results for a single bubble size. One important effect is that the bubble collapse is always initiated near the surface of the cloud, even if the cloud has a very small initial void fraction. This effect has an important consequence, namely that the geometric focusing of the bubbly shock wave is always a part of the nonlinear dynamics associated with the collapse of a spherical cloud with nuclei size distribution. The strength of the shock and the oscillation structure behind the shock front are suppressed due to the effects of multiple bubble sizes. Far-field acoustic pressures radiated by two bubble clouds, one of equal-size bubbles and the other with bubble size distribution, are also compared. It is found that the cloud containing bubbles of different sizes emits a larger noise than the cloud of identical bubbles. Explanations for this effect are also presented.
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Yoon, Dongik, Hyun Jin Park, Yuji Tasaka, and Yuichi Murai. "Lift coefficient of bubble sliding inside turbulent boundary layers in an inclinable channel flow." Physics of Fluids 34, no. 5 (May 2022): 053301. http://dx.doi.org/10.1063/5.0086777.
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The behavior of bubbles traveling in the proximity of a tilted wall is studied experimentally to understand the fundamental sliding motion of bubbles inside turbulent boundary layers along an inclined wall. The qualitative visualization of sliding bubbles confirms the contribution of bubble buoyancy on the sliding motion for negative and positive inclinations of the channel. An opto-acoustic combined measurement technique is adopted to explore the sliding motion. Liquid velocity profiles in the bubbly flow and the distance between the wall and bottom of the bubble are obtained using the ultrasound pulsed Doppler method, while the bubble diameters and velocities are obtained from particle-tracking type image processing. The combined measurements reveal that the velocity of bubbles decreases under the negative slope condition and increases under the positive slope condition due to opposite buoyancy effects. In addition, the distance between the wall and bottom of the bubble increases with an increase in negative inclination. The lift coefficient is derived from the measured variables using a force–balance equation among the buoyancy, lift, and surface tension. Finally, we propose modeling equations for the lift coefficient expressed in terms of the Reynolds, Weber, and Bond numbers, which apply to the bubbles inside boundary layers.
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Gubaidullin, Damir, and Anatolii Nikiforov. "Interaction acoustic waves with a layered structure containing layer of bubbly liquid." MATEC Web of Conferences 148 (2018): 15006. http://dx.doi.org/10.1051/matecconf/201814815006.
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The results of a theoretical study of the effect of a bubble layer on the propagation of acoustic waves through a thin three-layered barrier at various angles of incidence are presented. The barrier consists of a layer of gel with polydisperse air bubbles bounded by layers of polycarbonate. It is shown that the presence of polydisperse air bubbles in the gel layer significantly changes the transmission and reflection of the acoustic signal when it interacts with such an obstacle for frequencies close to the resonant frequency of natural oscillations of the bubbles. The frequency range is identified where the angle of incidence has little effect on the reflection and transmission coefficients of acoustic waves.
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Gubaidullin, Damir Anvarovich, and Ramil Nakipovich Gafiyatov. "Reflection and Transmission of Acoustic Waves through the Layer of Multifractional Bubbly Liquid." MATEC Web of Conferences 148 (2018): 15001. http://dx.doi.org/10.1051/matecconf/201814815001.
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The mathematical model that determines reflection and transmission of acoustic wave through a medium containing multifractioanl bubbly liquid is presented. For the water-water with bubbles-water model the wave reflection and transmission coefficients are calculated. The influence of the bubble layer thickness on the investigated coefficients is shown. The theory compared with the experiment. It is shown that the theoretical results describe and explain well the available experimental data. It is revealed that the special dispersion and dissipative properties of the layer of bubbly liquid can significantly influence on the reflection and transmission of acoustic waves in multilayer medium
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Gavrilev, Stepan, Mikhail Ivanov, and Semen Totunov. "THE MONITORING OF THE LIQUID-GAS MIXTURE PARAMETERS BY THE PASSIVE ACOUSTIC METHOD." VOLUME 39, VOLUME 39 (2021): 148. http://dx.doi.org/10.36336/akustika202139148.
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The considers the actual problem of determining the dispersed composition of the gas phase in a liquid medium. The work uses a passive acoustic method based on the interaction between the vibration frequency of bubbles and their size. On the experimental setup, acoustic waves emitted by air bubbles in water were recorded using a hydrophone. The sizes of the bubbles were determined by the spectra of the recorded signal. In the course of the experiments, the bubble radius was varied from 1.7 to 2.4 mm. The spectrogram of the signal was used to estimate the intensity of the release of bubbles in the volume of the experimental apparatus. Using the technique of synchronous filming, a video recording of the process of bubbles allocation at the apparatus was made. The analysis of the recorded video showed the correspondence of the determination of the parameters of the liquid-gas mixture. There are proposed various application scenarios of the passive acoustic method in the oil and gas industry.
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Denner, Fabian, and Sören Schenke. "Modeling acoustic emissions and shock formation of cavitation bubbles." Physics of Fluids 35, no. 1 (January 2023): 012114. http://dx.doi.org/10.1063/5.0131930.
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Despite significant progress in understanding and foretelling pressure-driven bubble dynamics, models that faithfully predict the emitted acoustic waves and the associated shock formation of oscillating or collapsing bubbles have received comparably little attention. We propose a numerical framework using a Lagrangian wave tracking approach to model the acoustic emissions of pressure-driven bubbles based on the Kirkwood–Bethe hypothesis and under the assumption of spherical symmetry. This modeling approach is agnostic to the equation of the state of the liquid and enables the accurate prediction of pressure and velocity in the vicinity of pressure-driven bubbles, including the formation and attenuation of shock fronts. We validate and test this new numerical framework by comparison with solutions of the full Navier–Stokes equations and by considering a laser-induced cavitation bubble as well as pressure-driven microbubbles in excitation regimes relevant to sonoluminescence and medical ultrasound, including different equations of state for the liquid. A detailed analysis of the bubble-induced flow field as a function of the radial coordinate r demonstrates that the flow velocity u is dominated by acoustic contributions during a strong bubble collapse and, hence, decays predominantly with [Formula: see text], contrary to the frequently postulated decay with [Formula: see text] in an incompressible fluid.
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Hua, Zhi Li, and Zhong Hai Zhou. "Numerical Simulation of Deep Sea Gas Hydrate Plumes." Advanced Materials Research 1010-1012 (August 2014): 1719–22. http://dx.doi.org/10.4028/www.scientific.net/amr.1010-1012.1719.
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Plume is closely related to the presence of gas hydrates which can often be found in plume development area. By acoustic detection, plumes of bubbles in the seawater from shallow gas have been found by marine surveying instruments in some areas over the world. Based on the existed theory of plume porosity, acoustic echo profile of sedbed seep plumes are numerically calculated. Within the simulation results, according to the pattern of gas bubble change and movement in the seawater, process of methane plumes generation is simulated and directs the distribution of bubble radius and plume boundary as depth. Acoustic features of plume bubbles seeping from shallow gas are shown to be consistent with the field results.
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WANG, Q. X., and J. R. BLAKE. "Non-spherical bubble dynamics in a compressible liquid. Part 1. Travelling acoustic wave." Journal of Fluid Mechanics 659 (July 27, 2010): 191–224. http://dx.doi.org/10.1017/s0022112010002430.
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Micro-cavitation bubbles generated by ultrasound have wide and important applications in medical ultrasonics and sonochemistry. An approximate theory is developed for nonlinear and non-spherical bubbles in a compressible liquid by using the method of matched asymptotic expansions. The perturbation is performed to the second order in terms of a small parameter, the bubble-wall Mach number. The inner flow near the bubble can be approximated as incompressible at the first and second orders, leading to the use of Laplace's equation, whereas the outer flow far away from the bubble can be described by the linear wave equation, also for the first and second orders. Matching between the two expansions provides the model for the non-spherical bubble behaviour in a compressible fluid. A numerical model using the mixed Eulerian–Lagrangian method and a modified boundary integral method is used to obtain the evolving bubble shapes. The primary advantage of this method is its computational efficiency over using the wave equation throughout the fluid domain. The numerical model is validated against the Keller–Herring equation for spherical bubbles in weakly compressible liquids with excellent agreement being obtained for the bubble radius evolution up to the fourth oscillation. Numerical analyses are further performed for non-spherical oscillating acoustic bubbles. Bubble evolution and jet formation are simulated. Outputs also include the bubble volume, bubble displacement, Kelvin impulse and liquid jet tip velocity. Bubble behaviour is studied in terms of the wave frequency and amplitude. Particular attention is paid to the conditions if/when the bubble jet is formed and when the bubble becomes multiply connected, often forming a toroidal bubble. When subjected to a weak acoustic wave, bubble jets may develop at the two poles of the bubble surface after several cycles of oscillations. A resonant phenomenon occurs when the wave frequency is equal to the natural oscillation frequency of the bubble. When subjected to a strong acoustic wave, a vigorous liquid jet develops along the direction of wave propagation in only a few cycles of the acoustic wave.
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Kerboua, Kaouther, Oualid Hamdaoui, and Abdulaziz Alghyamah. "Numerical Characterization of Acoustic Cavitation Bubbles with Respect to the Bubble Size Distribution at Equilibrium." Processes 9, no. 9 (August 30, 2021): 1546. http://dx.doi.org/10.3390/pr9091546.
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In addition to bubble number density, bubble size distribution is an important population parameter governing the activity of acoustic cavitation bubbles. In the present paper, an iterative numerical method for equilibrium size distribution is proposed and combined to a model for bubble counting, in order to approach the number density within a population of acoustic cavitation bubbles of inhomogeneous sizing, hence the sonochemical activity of the inhomogeneous population based on discretization into homogenous groups. The composition of the inhomogeneous population is analyzed based on cavitation dynamics and shape stability at 300 kHz and 0.761 W/cm2 within the ambient radii interval ranging from 1 to 5 µm. Unstable oscillation is observed starting from a radius of 2.5 µm. Results are presented in terms of number probability, number density, and volume probability within the population of acoustic cavitation bubbles. The most probable group having an equilibrium radius of 3 µm demonstrated a probability in terms of number density of 27%. In terms of contribution to the void, the sub-population of 4 µm plays a major role with a fraction of 24%. Comparisons are also performed with the homogenous population case both in terms of number density of bubbles and sonochemical production of HO•,HO2•, and H• under an oxygen atmosphere.
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SHAW, S. J., and P. D. M. SPELT. "Shock emission from collapsing gas bubbles." Journal of Fluid Mechanics 646 (March 8, 2010): 363–73. http://dx.doi.org/10.1017/s0022112009993338.
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The origin and the resultant properties of the strong pulses or shocks emitted by collapsing gas bubbles into a surrounding liquid are investigated numerically. The compressible flow in both phases is resolved. Results are presented for micron- and millimetre-sized bubbles and for bubble collapse triggered either by an acoustic driving or by an initially imposed spherical shock in the liquid. The origin of the diverging shocks is investigated, and the results of a parametric study for the acoustically driven collapse reveal a predominant linear dependence of the shock strength and width on the maximum bubble radius. The results compare favourably with experimental data and agree well with acoustic theory in the limit of weak forcing.
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Yao, X. L., X. H. Huang, Z. Y. Shi, and W. Xiao. "Reducing bubble generation and sweepdown effect on a research vessel with a moonpool." Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 235, no. 2 (February 25, 2021): 303–10. http://dx.doi.org/10.1177/1475090221997247.
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Some research vessels set moonpools for sonars installation. The moonpool provides a relatively good working environment for sonar in a harsh marine environment. At the same time, other acoustic detection equipment are installed along the ship bottom behind the moonpool. Due to the exist of the sonar with a variable cross-section, the number of bubbles generated in the moonpool increases. The bubbles generated in the moonpool expel and flow along the vessel bottom to the stern, which leads to the sweepdown effect. The performance of the sonar and other acoustic detection equipment degrades by the bubbles around. However, the research on reducing bubble generation in the moonpool and sweepdown effects is rare. So in present paper the reduction effects of damping devices such as the flange and choke deck on the bubble generation in the moonpool are investigated experimentally. Then, in order to reduce the sweepdown effects of bubbles on the ship bottom, three other damping devices which are double flaps, diversion channel and wedge are investigated. It can be seen that through reducing the area of bubble leakage in the moonpool the distribution position of bubbles can be effectively restricted and the width and thickness of the bubbles reduce.
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Ballard, Megan, Kevin M. Lee, Kyle Capistrant-Fossa, Preston S. Wilson, Andrew R. McNeese, and Kenneth H. Dunton. "Long-term monitoring of a seagrass meadow using wideband acoustic measurements." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A149. http://dx.doi.org/10.1121/10.0010932.
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Seagrasses are sentinel species whose sensitivity to changing water conditions makes them an indicator for sea level rise and climate change. The biological processes and physical characteristics associated with seagrass are known to affect acoustic propagation due to gas bodies contained within the seagrass tissue as well as photosynthesis-driven bubble production that results in free gas bubbles in the water. In this work, acoustical methods are applied to monitor seagrass biomass and gas ebullition with an autonomous field-deployed system using broadband acoustic measurements. Supporting environmental measurements including water temperature and salinity, dissolved oxygen, and photosynthetically active radiation (PAR) were also collected and used to interpret the acoustic data. A ray-based propagation model that includes losses due to the dispersion, absorption, and scattering of sound is applied to relate the measured acoustic signals to the gas bodies in the seagrass tissue and free bubbles in the water. This talk will present preliminary results from the first six months of a year-long deployment of the acoustic system in a dense seagrass meadow dominated by Thalassia testudinum (turtle grass) in Corpus Christi Bay, Texas (Gulf of Mexico). [Work supported by NSF.]
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Longuet-Higgins, Michael S., Bryan R. Kerman, and Knud Lunde. "The release of air bubbles from an underwater nozzle." Journal of Fluid Mechanics 230 (September 1991): 365–90. http://dx.doi.org/10.1017/s0022112091000836.
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Air bubbles released from an underwater nozzle emit an acoustical pulse which is of interest both for the study of bubble detachment and for elucidating the mechanism of sound generation by a newly formed bubble. In this paper we calculate theoretically the sequence of bubble shapes from a given nozzle and show that there is for each nozzle a bubble of maximum volume vmax Assuming that the bubble becomes detached at its ‘neck’, and that the volume of the detached bubble equals the volume V* of the undetached bubble above its ’neck’, we determine for each nozzle diameter D an acoustic frequency f* corresponding to 'slow’ bubble release.Experiments show that the acoustic frequency, hence the bubble size, depends on the rate of air.flow to the bubble, but for slow rates of flow the frequency f is very close to the theoretical frequency f*.High-speed photographs suggest that when the bubble pinches off. the limiting form of the surface is almost a cone. This is accounted for by assuming a line sink along the axis of symmetry. Immediately following pinch-off there is evidence of the formation of an axial jet going upwards into the bubble. This may play a part in stimulating the emission of sound.
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VANHILLE, CHRISTIAN, and CLEOFÉ CAMPOS-POZUELO. "SIMULATION OF NONLINEAR ULTRASONIC PULSES PROPAGATING THROUGH BUBBLY LAYERS IN A LIQUID: FILTERING AND CHARACTERIZATION." Journal of Computational Acoustics 18, no. 01 (March 2010): 47–68. http://dx.doi.org/10.1142/s0218396x1000405x.
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This paper deals with the nonlinear propagation of ultrasonic pulses in a homogeneous medium in which a bubbly layer is placed. The medium we use is air bubbles in water. During the propagation of a pulse, the interaction of the acoustic field and bubbles vibration is assured via the coupling of a nonlinear differential system. The solution is tracked in the time domain by means of the SNOW-BL code. In the biphasic fluid, attenuation and nonlinear effects are due to the bubbles only. The study addresses to two applications: filter effects of the layer and nonlinear characterization of liquid–gas mixtures. We study the filter effects (screen effect) a layer has for some frequency ranges present in the initial ultrasonic pulses, in the linear and nonlinear regimes, i.e. for low and high pressure amplitude. One (or several) simple layer is contemplated in numerical experiments with different bubble densities, bubble sizes, layer thicknesses, for different kinds of pulse.
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Bull, Joseph L. "Acoustic droplet vaporization and gas embolotherapy." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A78. http://dx.doi.org/10.1121/10.0010715.
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We present an overview of our research group’s work in acoustic droplet vaporization and gas embolotherapy, including bubble and droplet dynamics, bioeffects, targeting of droplets, localized drug delivery, and selective occlusion of blood flow to tumors. In these applications, transvascular liquid perfluorocarbon droplets are injected intravenously and, subsequently, vaporized with ultrasound to selectively form vascular micro- and nano-bubbles that are used for therapy. The resulting bubbles are approximately 125 times the volume of the droplets from which they originate. Embolization of tumors with this methodology involves droplets that are sufficiently large to produce bubbles that will lead to occlusion. Drug-loaded droplet may be used without occlusion if they are sufficiently small. We have used a combination of theoretical, computational, and experimental approaches to elucidate the behaviors and mechanisms involved in acoustic droplet vaporization. In a murine model of hepatocellular carcinoma, we have demonstrated that the combination of gas embolization and chemotherapy can result in complete tumor regression.
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Baranowska, Anna. "Theoretical Studies of Nonlinear Generation Efficiency in a Bubble Layer." Archives of Acoustics 37, no. 3 (November 1, 2012): 287–94. http://dx.doi.org/10.2478/v10168-012-0037-0.
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Abstract The aim of the paper is a theoretical analysis of propagation of high-intensity acoustic waves throughout a bubble layer. A simple model in the form of a layer with uniformly distributed mono-size spherical bubbles is considered. The mathematical model of the pressure wave’s propagation in a bubbly liquid layer is constructed using the linear non-dissipative wave equation and assuming that oscillations of a single bubble satisfy the Rayleigh-Plesset equation. The models of the phase sound speed, changes of resonant frequency of bubbles and damping coefficients in a bubbly liquid are compared and discussed. The relations between transmitted and reflected waves and their second harmonic amplitudes are analyzed. A numerical analysis is carried out for different environmental parameters such as layer thicknesses and values of the volume fraction as well as for different parameters of generated signals. Examples of results of the numerical modeling are presented.
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Hauptmann, Marc, Steven Brems, Elisabeth Camerotto, Paul W. Mertens, Marc M. Heyns, Stefan de Gendt, Christ Glorieux, and Walter Lauriks. "Stroboscopic Schlieren Study of Bubble Formation during Megasonic Agitation." Solid State Phenomena 187 (April 2012): 185–89. http://dx.doi.org/10.4028/www.scientific.net/ssp.187.185.
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An important problem in megasonic cleaning is the nucleation process of bubbles, which act as the cleaning agents. A fundamental understanding of this nucleation process will help to optimize the cleaning parameters for future applications to achieve damage free cleaning. In this work, we use quantitative stroboscopic Schlieren imaging to study the interaction of nucleating bubbles with a travelling acoustic wave. The advantage of this method is that it is non-interfering, meaning that it does not disturb the bubble nucleation. It is revealed that nucleation mechanism is a 2 step process, where a regime of slow bubble growth due to rectified diffusion is subsequently followed by a transient cavitation cycle, where bubbles grow explosively. The latter is accompanied by broadband acoustic emission and enhanced thermal dissipation, leading to the occurrence of thermal convection visible in the Schlieren images.
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Agisheva, U. O., I. I. Vdovenko, and M. N. Galimzyanov. "The effect of diffusion on the acoustic properties of a bubble fluid." Multiphase Systems 14, no. 3 (2019): 165–75. http://dx.doi.org/10.21662/mfs2019.3.023.
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The problems of wave propagation in bubble media have been of great interest to researchers for almost half a century in connection with the wide distribution of these systems in nature and their intensive use in modern technologies. It is known from the literature that the intensity of attenuation of sound disturbances in the gas-liquid media under consideration is mainly determined by the thermophysical characteristics of the gas in the bubbles. It turns out that these effects are significantly enhanced with increasing vapor concentration due to an increase in the temperature of the system. There are a large number of publications in the literature in which various statements of the wave action on bubble media have been considered. In the present work, the propagation of small perturbations in a liquid with bubbles filled with vapor and a gas insoluble in the liquid phase is considered in the plane one-dimensional and single-velocity approximations. The rate of liquid evaporation (condensation) inside the bubble was determined from the condition of heat balance. To take into account interphase heat and mass transfer, the heat conduction and diffusion equations inside the bubble and the heat conduction equation in the fluid around the bubble are used. From the condition for the existence of a solution in the form of a decaying traveling wave, taking into account the effects of acoustic unloading of bubbles, the dispersion equation is written. From the condition for the existence of a solution in the form of a decaying traveling wave, taking into account the effects of acoustic unloading of bubbles, the dispersion equation is written. Based on the obtained dispersion equation, relations are written for the equilibrium speed of sound depending on the thermophysical parameters of the medium and numerical calculations are performed for water with vapor-gas bubbles. The features of the reflection of harmonic waves from the interface between the “pure” liquid and liquid with vapor-gas bubbles are studied. The influence of the perturbation frequency and the temperature of the medium on the attenuation coefficient of the acoustic wave is studied. The influence of diffusion on the evolution of harmonic waves is analyzed.
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Topolnikov, A. S., and S. I. Konovalova. "Dynamics of Vapor Bubbles in Cluster in the Strong Acoustic Field." Proceedings of the Mavlyutov Institute of Mechanics 5 (2007): 289–94. http://dx.doi.org/10.21662/uim2007.1.037.
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The radial and translational motion of spherical vapor bubbles in a cluster under the influence of ultrasound field of high amplitude (about 10 atmospheres) is studied. In mathematical describing of the problem the discrete model is used, according to which the dynamics of single bubble in a cluster is considered separately, and the interaction between bubbles is implemented by secondary Bjerknes forces. The possibility of amplification of radial pulsations of the bubbles by their joined motion is studied. The process of structure formation in a cluster and stability of oscillations (positional and radial) is investigated.
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Memoli, Gianluca, Kate Baxter, Helen Jones, Ken Mingard, and Bajram Zeqiri. "Acoustofluidic Measurements on Polymer-Coated Microbubbles: Primary and Secondary Bjerknes Forces." Micromachines 9, no. 8 (August 15, 2018): 404. http://dx.doi.org/10.3390/mi9080404.
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The acoustically-driven dynamics of isolated particle-like objects in microfluidic environments is a well-characterised phenomenon, which has been the subject of many studies. Conversely, very few acoustofluidic researchers looked at coated microbubbles, despite their widespread use in diagnostic imaging and the need for a precise characterisation of their acoustically-driven behaviour, underpinning therapeutic applications. The main reason is that microbubbles behave differently, due to their larger compressibility, exhibiting much stronger interactions with the unperturbed acoustic field (primary Bjerknes forces) or with other bubbles (secondary Bjerknes forces). In this paper, we study the translational dynamics of commercially-available polymer-coated microbubbles in a standing-wave acoustofluidic device. At increasing acoustic driving pressures, we measure acoustic forces on isolated bubbles, quantify bubble-bubble interaction forces during doublet formation and study the occurrence of sub-wavelength structures during aggregation. We present a dynamic characterisation of microbubble compressibility with acoustic pressure, highlighting a threshold pressure below which bubbles can be treated as uncoated. Thanks to benchmarking measurements under a scanning electron microscope, we interpret this threshold as the onset of buckling, providing a quantitative measurement of this parameter at the single-bubble level. For acoustofluidic applications, our results highlight the limitations of treating microbubbles as a special case of solid particles. Our findings will impact applications where knowing the buckling pressure of coated microbubbles has a key role, like diagnostics and drug delivery.
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Pelekasis, Nikolaos A., and John A. Tsamopoulos. "Bjerknes forces between two bubbles. Part 2. Response to an oscillatory pressure field." Journal of Fluid Mechanics 254 (September 1993): 501–27. http://dx.doi.org/10.1017/s002211209300223x.
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The motion of two gas bubbles in response to an oscillatory disturbance in the ambient pressure is studied. It is shown that the relative motion of bubbles of unequal size depends on the frequency of the disturbance. If this frequency is between the two natural frequencies for volume oscillations of the individual bubbles, the two bubbles are seen to move away from each other; otherwise attractive forces prevail. Bubbles of equal size can only attract each other, irrespective of the oscillation frequency. When the Bond number, Bo (based on the average acceleration) lies above a critical region, spherical-cap shapes appear with deformation confined on the side of the bubbles facing away from the direction of acceleration. For Bo below the critical region shape oscillations spanning the entire bubble surface take place, as a result of subharmonic resonance. The presence of the oscillatory acoustic field adds one more frequency to the system and increases the possibilities for resonance. However, only subharmonic resonance is observed because it occurs on a faster timescale, O(1/ε), where ε is the disturbance amplitude. Furthermore, among the different possible periodic variations of the volume of each bubble, the one with the smaller period determines which Legendre mode will be excited through subharmonic resonance. Spherical-cap shapes also occur on a timescale O(1/ε). When the bubbles are driven below resonance and for quite large amplitudes of the acoustic pressure, ε ≈ 0.8, a subharmonic signal at half the natural frequency of volume oscillations is obtained. This signal is primarily associated with the zeroth mode and corresponds to volume expansion followed by rapid collapse of the bubbles, a behaviour well documented in acoustic cavitation experiments.
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Titov, Aleksei, Yilin Fan, Kagan Kutun, and Ge Jin. "Distributed Acoustic Sensing (DAS) Response of Rising Taylor Bubbles in Slug Flow." Sensors 22, no. 3 (February 7, 2022): 1266. http://dx.doi.org/10.3390/s22031266.
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Slug flow is one of the most common flow types encountered in surface facilities, pipelines, and wellbores. The intermittent gas phase, in the form of a Taylor bubble, followed by the liquid phase can be destructive to equipment. However, commonly used point flow sensors have significant limitations for flow analysis. Distributed acoustic sensing (DAS) can turn optical fibers into an array of distributed strain rate sensors and provide substantial insights into flow characterization. We built a 10 m vertical laboratory flow loop equipped with wrapped fiber optic cables to study the DAS response of rising Taylor bubbles. Low-passed DAS data allow for velocity tracking of Taylor bubbles of different sizes and water velocities. Moreover, we measured the velocity of the wake region following the Taylor bubble and explored the process of Taylor bubbles merging. The amplitude analysis of DAS data allows for the estimation of Taylor bubble size. We conclude that DAS is a promising tool for understanding Taylor bubble properties in a laboratory environment and monitoring destructive flow in facilities across different industries to ensure operations are safe and cost-effective.
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Schenke, Sören, Rishav Saha, and Fabian Denner. "Predicting acoustic emissions of ultrasound-driven lipid-coated microbubbles." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A30. http://dx.doi.org/10.1121/10.0010556.
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Lipid-coated microbubbles excited by ultrasound are utilized in an increasing number of diagnostic and therapeutic medical applications, in which the acoustic waves emitted by the oscillating or collapsing bubbles are the main protagonist. The emitted acoustic waves cause bioeffects, enable contrast enhancement for ultrasonic imaging, and serve as a reference to monitor cavitation activity in situ. However, quantifying the acoustic waves emitted by cavitation bubbles turns out to be difficult: the small and extremely transient phenomenon is challenging to measure in experiments with sufficient accuracy and state-of-the-art computational methods are limited in their ability to predict acoustic emissions reliably. In this contribution, we present our recent work on predicting acoustic emissions of microbubbles based on Rayleigh–Plesset models and, more generally, reduced-order models. Using the nonlinear Westervelt equation including the motion of the bubble wall and the background medium as a result of the bubble oscillations, we investigate the amplitude and frequency modulation (e.g., due to nonlinear Doppler effects, thermoviscous attenuation or geometric distortion) of acoustic waves emitted by lipid-coated microbubbles. Additionally, we explore the capabilities of a reduced-order modeling approach that drastically simplifies the computational complexity of simulating these acoustic emissions.
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HARKIN, ANTHONY, TASSO J. KAPER, and ALI NADIM. "Coupled pulsation and translation of two gas bubbles in a liquid." Journal of Fluid Mechanics 445 (October 16, 2001): 377–411. http://dx.doi.org/10.1017/s0022112001005857.
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We present and analyse a model for the spherical pulsations and translational motions of a pair of interacting gas bubbles in an incompressible liquid. The model is derived rigorously in the context of potential flow theory and contains all terms up to and including fourth order in the inverse separation distance between the bubbles. We use this model to study the cases of both weak and moderate applied acoustic forcing. For weak acoustic forcing, the radial pulsations of the bubbles are weakly coupled, which allows us to obtain a nonlinear time-averaged model for the relative distance between the bubbles. The two parameters of the time-averaged model classify four different dynamical regimes of relative translational motion, two of which correspond to the attraction and repulsion of classical secondary Bjerknes theory. Also predicted is a pattern in which the bubbles exhibit stable, time-periodic translational oscillations along the line connecting their centres, and another pattern in which there is an unstable separation distance such that bubble pairs can either attract or repel each other depending on whether their initial separation distance is smaller or larger than this value. Moreover, it is shown that the full governing equations possess the dynamics predicted by the time-averaged model. We also study the case of moderate-amplitude acoustic forcing, in which the bubble pulsations are more strongly coupled to each other and bubble translation also affects the radial pulsations. Here, radial harmonics and nonlinear phase shifting play a significant role, as bubble pairs near resonances are observed to translate in patterns opposite to those predicted by classical secondary Bjerknes theory. In this work, dynamical systems techniques and the method of averaging are the primary mathematical methods that are employed.
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Itkulova, Yu A., O. A. Abramova, N. A. Gumerov, and I. Sh Akhatov. "Direct numerical simulation of three-dimensional dynamics of compressible bubbles in acoustic field using boundary element method." Proceedings of the Mavlyutov Institute of Mechanics 10 (2014): 59–65. http://dx.doi.org/10.21662/uim2014.1.011.
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In the present work the dynamics of bubbles containing compressible gas is studied in the presence of an acoustic field at low Reynolds numbers. The numerical approach is based on the boundary element method (BEM), which is effective for three-dimensional simulation. The application of the standard BEM to the compressible bubble dynamics faces the problem of the degeneracy of the algebraic system. To solve this problem, additional relationships based on the Lorentz reciprocity principle are used. Test calculations of the dynamics of one and several bubbles in an acoustic field are presented.
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Ohl, Siew-Wan, Evert Klaseboer, and Boo Cheong Khoo. "Bubbles with shock waves and ultrasound: a review." Interface Focus 5, no. 5 (October 6, 2015): 20150019. http://dx.doi.org/10.1098/rsfs.2015.0019.
Full textAbstract:
The study of the interaction of bubbles with shock waves and ultrasound is sometimes termed ‘acoustic cavitation'. It is of importance in many biomedical applications where sound waves are applied. The use of shock waves and ultrasound in medical treatments is appealing because of their non-invasiveness. In this review, we present a variety of acoustics–bubble interactions, with a focus on shock wave–bubble interaction and bubble cloud phenomena. The dynamics of a single spherically oscillating bubble is rather well understood. However, when there is a nearby surface, the bubble often collapses non-spherically with a high-speed jet. The direction of the jet depends on the ‘resistance' of the boundary: the bubble jets towards a rigid boundary, splits up near an elastic boundary, and jets away from a free surface. The presence of a shock wave complicates the bubble dynamics further. We shall discuss both experimental studies using high-speed photography and numerical simulations involving shock wave–bubble interaction. In biomedical applications, instead of a single bubble, often clouds of bubbles appear (consisting of many individual bubbles). The dynamics of such a bubble cloud is even more complex. We shall show some of the phenomena observed in a high-intensity focused ultrasound (HIFU) field. The nonlinear nature of the sound field and the complex inter-bubble interaction in a cloud present challenges to a comprehensive understanding of the physics of the bubble cloud in HIFU. We conclude the article with some comments on the challenges ahead.
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Sametov, S. P. "Experimental study of interaction of bubble media with acoustic field." Proceedings of the Mavlyutov Institute of Mechanics 12, no. 2 (2017): 180–86. http://dx.doi.org/10.21662/uim2017.2.027.
Full textAbstract:
In the paper, the procedure for performing experimental measurements and the results of studies on the dynamics of interaction of ultrasonic fields with a bubble liquid in a closed volume with reflecting walls and a free surface were detailed description. The influence of different concentrations of bubbles in the liquid on the nature of the purification of the medium from them is considered. In a bubble liquid, the velocity of acoustic waves decreases substantially, which leads to a redistribution of the conditions for the formation of standing waves. It was found that an increase in concentration leads to a more intensive displacement of air bubbles by an ultrasonic field with forming of a displacement front.