Dissertations / Theses on the topic 'Acoustic Bubbles'
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Hardwick, Andrew John. "The acoustic sizing of bubbles in liquids." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260420.
Full textHarris, Ashley M. "Acoustic properties of toroidal bubbles and construction of a large apparatus." Thesis, Monterey, California. Naval Postgraduate School, 2004. http://hdl.handle.net/10945/1675.
Full textWhen a burst of air is produced in water, the result can be a toroidal bubble. This thesis is concerned with experimental investigations of three acoustical properties of toroidal bubbles: (i) propagation through high-intensity noise, (ii) emission, and (iii) scattering. In (i), an attempt to observe a recent prediction of the acoustic drag on a bubble is described, which is analogous to the Einstein-Hopf effect for an oscillating electric dipole in a fluctuating electromagnetic field. No effect was observed, which may be due to insufficient amplitude of the noise. In (ii), observations of acoustic emissions of volume oscillations of toroidal bubbles are reported. Surprisingly, the emission occurs primarily during the formation of a bubble, and is weak in the case of very smooth toroidal bubbles. In (iii), we describe an experiment to observe the effect of a toroidal bubble on an incident sound field. In addition to the acoustical investigations, we describe the construction of a large hallway apparatus for further investigations and for hands-on use by the public. The tank has cross section 2 feet by 2 feet and height 6 feet, and the parameters of reservoir pressure and time between air bursts are adjustable by the observer.
Lieutenant, United States Navy
Ramble, David Gary. "Characterisation of bubbles in liquids using acoustic techniques." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390369.
Full textSimmons, Stephen Michael. "Non-linear modelling of the acoustic response of bubbles." Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364761.
Full textMcIntyre, Trevor A. "Ultrasonic acoustic characteristics of air bubbles in the surf zone." Thesis, Monterey, California. Naval Postgraduate School, 1995. http://hdl.handle.net/10945/26821.
Full textHarris, Ashley M. "Accoustic properties of toroidal bubbles and contruction of a large apparatus /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Mar%5FHarris.pdf.
Full textSu, Yu-Hsuan 1965. "Numerical study of the nonlinear dynamics of the acoustic drops and bubbles." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9434.
Full textIncludes bibliographical references.
The dynamics of liquid drops and bubbles held together by surface tension and perturbed by small disturbances is of great interest to many researchers. Its essential physical nature is characterized by a nonlinear moving-boundary problem complicated by the interfacial stress interaction between two domains, each governed by their own dynamical systems respectively. In this thesis, the dynamics of an acoustically levitated drop is investigated. A low dimensional phase plane approach is used to interpret the nonlinear dynamics of the drop motions. It is found that the stability of shape oscillations imposes an upper limit on the acoustic bond number that can be used, while the lower limit is set by the stability of translational motion. The static equilibrium shapes can be obtained by incorporating the artificial damping into the system. The static equilibrium shapes thus found agree very well with the experimental data. In addition, that two-to-one internal resonance of a single bubble between the volume mode and one of the shape modes is carefully examined. instability wedges for unstable volume oscillations on the plane of volume oscillation amplitude versus frequency are identified numerically. Furthermore, the dynamical behaviors of the bubbles with parameters within the instability wedges can be divided into stable bubble oscillations and transient bubble oscillations. Attention is focused on the transient bubble oscillations. Numerical simulation shows that liquid jets form at t.he two poles of the transient bubble and lead to the breakup of the bubble. A possible mechanism resulting in the formation of the liquid jets is proposed and demonstrated with numerical simulation examples. Bjerknes forces between two bubbles are also investigated. It is found that the Bjerknes forces between two attracting bubbles can be predicted with a formula derived by Crum with amazing accuracy. However, numerical simulations indicate that a multiplication factor is needed for the cases of two repelling bubbles within short distance. The effect of shape oscillations on the translational motions of two bubbles is also examined. Interestingly, the shape oscillation has little effect on attracting bubbles, while significant effect on the translational motion of two repelling bubbles within short distance is observed.
by Yu-Hsuan Su.
Ph.D.
Parini, Michael R. "Biofilm Removal Using Bubbles and Sound." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd958.pdf.
Full textZhang, Yuning. "Analysis of radial oscillations of gas bubbles in Newtonian or viscoelastic mediums under acoustic excitation." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/55427/.
Full textXi, Xiaoyu. "Controlled translation and oscillation of micro-bubbles near a surface in an acoustic standing wave field." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/10981.
Full textDiaz, de la Rosa Mario Alfonso. "High-frequency ultrasound drug delivery and cavitation /." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1679.pdf.
Full textCombriat, Thomas. "Etude d'une assemblée de bulles microfluidiques excitées par une onde ultrasonore : transmission acoustique et phénomène de streaming." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAY052/document.
Full textBecause of the important compressibility of gas bubbles in water, inducing a very low resonance frequency, one can find interest in studying bubbles from an acoustic and a fluid mechanics point of view. Using microfluidics techniques in order to produce assemblies of acoustically driven bi-dimensional bubbles, we are studying their influence on both acoustic waves and the surrounding fluid.Bubbles being sub-wavelength resonators, we show that a micro-bubbles assembly interacts with acoustical waves which wavelengths that are substantially bigger than the bubbles size. Developing a way to extract bubbles contribution to the acoustic signal, we show that their resonance frequency follows a law slightly different from the one Minnaert had found for spherical bubbles. The impact of this medium on the acoustical wave has been studied and we show that a decrease in the acoustical transmission happens in a range of frequencies above the resonance. This decrease can be adjusted in amplitude and in frequency making our system an easily tunable metameterial.Because of the strong response of bubbles induced by acoustical waves, the bubbles surface oscillates with a great amplitude in the surrounding fluid. This oscillation, working together with a coupling present between the bubbles, can drive a strong steady streaming in the fluid. Systems of several bubbles are studied, and a theory is proposed in order to predict the flow they induce. The interaction between the streaming phenomenon and an external flow is also presented, showing that exclusion zones can be present under certain circumstances in these systems. These exclusion zones can be useful in micro-fluidics in order to trap particles or chemicals
Onur, Cagla. "Acoustic Tracking Of Ship Wakes." Phd thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615656/index.pdf.
Full textKapodistrias, Georgios. "A theoretical and experimental study on multiple scattering from bubbles, with emphasis on scattering from a bubble located close to the air-sea interface /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/7150.
Full textChan, Eugene Joseph Pilpa. "Acoustic-induced drag on a bubble." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA360380.
Full text"March 1999". Thesis advisor(s): Andres Larraza, Bruce C. Denardo. Includes bibliographical references (p. 27-28). Also available online.
楊兆麟 and Siu-lun Patrick Yeung. "Effect of bubbly liquid on underwater sound transmission." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31237964.
Full textYeung, Siu-lun Patrick. "Effect of bubbly liquid on underwater sound transmission /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19471221.
Full textZhang, Yuning. "Bubble dynamics under dual-frequency acoustic excitation." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/71098/.
Full textDeymier, P. A., M. Keswani, N. Jenkins, C. Tang, and K. Runge. "Giant frequency down-conversion of the dancing acoustic bubble." NATURE PUBLISHING GROUP, 2016. http://hdl.handle.net/10150/622416.
Full textKuhn, de Chizelle Yan P. Acosta Allan J. Brennen Christopher E. "Hydrodynamics, acoustics and scaling of traveling bubble cavitation /." Diss., Pasadena, Calif. : California Institute of Technology, 1994. http://resolver.caltech.edu/CaltechETD:etd-10202005-152545.
Full textHusin, Shuib. "An experimental investigation into the correlation between Acoustic Emission (AE) and bubble dynamics." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/7318.
Full textMeers, Steven Douglas. "The estimation of bubble populations in the surf-zone by inversion of acoustic propagation." Thesis, University of Southampton, 2005. https://eprints.soton.ac.uk/426770/.
Full textWilson, Preston Scot. "Sound propagation and scattering in bubbly liquids." Thesis, Boston University, 2002. https://hdl.handle.net/2144/1369.
Full textUnited States Navy Office of Naval Research Ocean Acoustics Program
Dogan, Hakan. "Modelling of acoustic pressure waves in bubbly liquids with application to sonochemical reactors." Thesis, Wessex Institute of Technology, 2013. https://eprints.soton.ac.uk/376891/.
Full textHedayetullah, Amin Mohammad. "Optimization of identification of particle impacts using acoustic emission." Thesis, Robert Gordon University, 2018. http://hdl.handle.net/10059/3116.
Full textMekki-Berrada, Flore. "Oscillations couplées de microbulles sous champ ultrasonore et conséquences hydrodynamiques." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY069/document.
Full textThe pulsation properties of air bubbles under ultrasound have received much attention since the development of sonoporation and contrast agents. Spherical bubbles are well known to induce streaming when excited by ultrasound.We report in this manuscript the acoustic vibration of microbubbles confined between the two walls of a microfluidic channel. These bubbles exhibit a volumetric pulsation at low intensities of ultrasound, superimposed with a parametric surface mode for higher intensities of the pressure field. Because the channel walls are elastic, the bubble pulsation leads to the generation of Rayleigh waves at the channel wall interface. The bubble coupling induced by these surface waves has hydrodynamic consequences. In fact, a neighbouring bubble will create a translation mode of the bubble, in addition to its volumetric pulsation. It gives rise to a long-range mixed-mode streaming. The Rayleigh waves lead also to a self-organization of the bubbles in a network. In order to study the collective effects of these bubble networks in a controlled manner, bubble positions were fixed by capillarity on micropits. Conditions for an amplification or a synchronization of the bubble pulsations are sought in order to develop new bubble metamaterials
Ylonen, Markku. "Cavitation erosion monitoring by acoustic emission Cavitation Bubble Collapse Monitoring by Acoustic Emission in Laboratory Testing Cavitation Erosion Resistance Assessment and Comparison of Three Francis Turbine Runner Materials Estimation of Cavitation Pit Distributions by Acoustic Emission . Shedding Frequency in Erosion Evolution Tracking." Thesis, Université Grenoble Alpes, 2020. https://tel.archives-ouvertes.fr/tel-02613873.
Full textCavitation is the formation of vapor bubbles either in a static liquid or in a liquid flow due to a drop in static pressure. When these bubbles collapse, as a result of pressure recovery, they may damage adjacent surfaces. These events are major causes of damage and nuisance in hydro machines. Modern hydro turbines are often used to regulate power grids; therefore, they may be operated out of their designed range. The flow-related optimal operation is different from the economic optimal usage. Detecting and characterizing cavitation and assessing damage during operation can be difficult or even impossible. Acoustic emission (AE) measurements provide a way to measure cavitation without access to the flow, but interpreting the data is challenging. This thesis presents insights in the ways of treating the AE data both in characterizing individual pits created by cavitation impacts and in tracking the evolution of cavitation erosion. Additionally, the erosion rates of three turbine materials were compared, and the main reasons behind the differing erosion rates of two martensitic turbine steels were discovered. The same high-speed cavitation tunnel was used in all cavitation experiments. This thesis firstly presents a method for enveloping an AE waveform signal and for counting the peak voltage values. The resulting cumulative distributions were compared to those of cavitation pit diameters, and from this comparison, a connection was proposed between AE peak voltage value and pit diameter. The second result was the connection between cavitation cloud shedding frequency and erosion evolution. The process of demodulating high frequency AE signals effectively promotes the low frequency shedding. The shedding frequency increased with accumulating material loss, and it was concluded that this increase is due to geometry effects, namely surface roughness. In addition to the two proposed methods, it was found that the decisive factors in the differing erosion rates of the martensitic stainless steels are the prior austenite grain size, packet and block sizes and the retained austenite fraction. This thesis provides guidelines directly applicable, such as the martensitic steel classifying, and methods that require further development, if one wishes to utilize them in hydro machine cavitation monitoring instead of laboratory measurements in a cavitation tunnel. The main outcome is that AE is a potential way to monitor cavitation, with the important benefit of not requiring any access to the flow
Scognamiglio, Chiara. "Dynamique de bulles de cavitation dans des systèmes micro-confinés." Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4126.
Full textThe present thesis focuses on cavitation process, meaning nucleation and dynamics of a bubble within a liquid as a result of pressure decrease. In particular, we investigate the growth of the vapor phase in micrometric volumes of water confined by a poro-elastic material. In systems where water is encapsulated in a porous medium, molecules can evaporate from the pores resulting in a remarkable pressure reduction and bubbles nucleation. Once a vapor bubble nucleates, it can trigger within few microseconds the appearance of other bubbles in the neighbor cavities, activating an ultra-fast avalanche-like phenomenon. We resolved the dynamics and acoustics of cavitation bubbles, in case of singles or multiple nucleation events. The realization of an innovative device where water is encapsulated between a porous material and a glass window opens the way for metastable water investigation. A second part of the manuscript is devoted to a new project where microfluidics and biology are combined and applied to drug delivery. The device consists of an artificial blood vessel in communication with the target tissue accommodated in a purposely designed compartment (tissue-on-a-chip). The walls of the microfluidic channel mimicking the vessel are lined with endothelial cells to reproduce the actual walls of in vivo blood vessels. This device allows to investigate the effects of ultrasound-activated bubbles on the blood vessels wall
Elsey, Justin Rae. "Dynamic Modelling, Measurement and Control of Co-rotating Twin-Screw Extruders." University of Sydney. Department of Chemical Engineering, 2003. http://hdl.handle.net/2123/687.
Full textCavaro, Matthieu. "Apport de l'accoustique non linéraire à la caractérisation de l'engagement du sodium liquide : application aux réacteurs nucléaires de quatrième génération." Thesis, Aix-Marseille 2, 2010. http://www.theses.fr/2010AIX22106/document.
Full textThe SFR system chosen (Sodium Fast Reactor: fast neutron reactors cooled by liquid sodium) by France led to afourth-generation prototype named ASTRID. The development of this kind of reactors presents several challenges, particularly in terms of improving the safety and monitoring operation. This involves, among other things, characterization of the bubbles presence in liquid sodium. The characterization of the bubbles presence is the subject of this thesis. It involves the determination of void fraction (gas volume fraction) and histogram of the radiiof bubbles. The bibliographic work done has shown that linear acoustic techniques for the characterization of bubble clouds are inadequate to achieve this. However promising leads have been identified by studying nonlinear acoustic techniques. This last idea has therefore been explored. An experimental water bench for the generation and optical control of microbubbles cloudallowed us to validate finely the reconstruction of histograms of radii through a technique of nonlinear mixing of a high frequency with a low frequency. The potential of the mixing of two high frequencies, more interesting for the industrial point of view has also been demonstrated. Finally, the bases of the transposition of an original technique of nonlinear resonance spectroscopy applied to a bubbles cloud were explored through the introduction of acoustic resonators. The results offer many interesting opportunities, both in terms of industrial applications and formore fundamental understanding of non-linear behavior of a bubble excited by multiple frequencies and of bubbles clouds excited at low frequency
Diaz, Mario Alfonso. "High-Frequency Ultrasound Drug Delivery and Cavitation." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1050.
Full textMontes, Quiroz William. "Étude expérimentale de la stabilité d'une bulle unique de cavitation acoustique : application à la nucléation de la glace déclenchée par cavitation." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2014. http://www.theses.fr/2014EMAC0002/document.
Full textThis study of the stability of an acoustic cavitation bubble is part of an ANR project started in September 2009 (SONONUCLICE ANR-09-BLAN-0040-02). It takes place in the continuity of the works on the optimization process of lyophilisation of pharmaceutical products conducted by the “Transferts couplés de matière et de chaleur” team of LAGEP (ESCPE/UCB, Lyon) laboratory, which is the project’s team leader, and the studies of ultrasound-assisted crystallization in the RAPSODEE Centre. The application of power ultrasound into liquids produces thousands of bubbles. This phenomenon is called acoustic cavitation. The bubbles formed don’t have the same size, their oscillations are not in phase, and their spatial density in the fluid is not homogeneous: this phenomenon is very complex and involves multiple variables very difficult to isolate. Even if this phenomenon is chaotic, it allows to observe macroscopic effects on the nucleation and crystal growth of ice in undercooled solutions. These effects have a capital importance for industrial applications such as freezing and lyophilisation (also called freeze drying). Although ultrasound has a noticeable influence on crystallization, the origin of these effects remains unclear. The multi-bubble approach doesn’t give any hint on the microscopic mechanisms involved. In order to isolate the main actor of these effects, this study aims at isolating a single cavitation bubble. To do that, a cubic levitation cell made of optical glass was build. In this cell, an acoustic pressure is applied by a piezoelectric glued to the bottom’s external face of the cell. With this cell is possible to rebuild all the oscillations states of the bubble, and in combination with our optical system we can see the bubble’s dynamics and its stages like: expansion, collapse and rebounds. For the crystallization part of this study, a crystal’s detection system was developed. It is based on the variations of the bubble’s periodicity (measured by a microphone pill) introduced by the sudden appearance of a foreign body in its vicinity. This method requires the correlation of the signals from a filtered microphone and the harmonics signals from a microphone, in order to known the oscillation state of the bubble and detect variations on the bubble’s dynamics. Experiments of bubble perturbations by a thin wire were made. The detection system was used to trigger the image recording of a fast camera, in order to capture the final moments of the bubble. This method should be allowing the early detection of new crystals in the proximity of the bubble. Around the levitation cell, various systems have been developed. A degassing and filling system for the cavitation cell allow us to work with degased water around the 20 % of its saturated concentration of air. An illumination system based in a power LED and a set of optical lenses was used to view the bubble correctly
Looten-Baquet, Isabelle. "Etude et caractérisation de l'activité des champs de bulles générées par cavitation ultrasonore." Valenciennes, 1996. https://ged.uphf.fr/nuxeo/site/esupversions/1c0a52f3-bfd0-437a-8d3c-877eb1bb54f7.
Full textSchneider, Julia. "Characterisation of Single and Multibubble Cavitation Through Analysis of Molecular, Atomic and Ionic Line Emissions." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20011.
Full textThe importance of acoustic cavitation, i.e., the formation, growth and collapse of gaseous cavities in liquid exposed to ultrasound, in sonochemistry is based on the generation of extreme conditions upon bubble collapse. Temperatures and pressures inside the collapsing bubble are approximated to reach 104 K and 1000 atm, respectively [suslick-1999]. Under such conditions chemical bonds of the solvent vapour or volatile solutes present in the bubble core are easily cleaved, which in the case of aqueous systems, leads to the formation of chemically reactive OH and H radicals. These primary radicals either recombine leading to chemiluminescence, or diffuse into solution, where they are liable to react with other species. Of particular importance in this work is the light emission that accompanies cavitation, termed sonoluminescence (SL). This emission is a broad continuum ranging from 200nm to 900 nm, resembling the emission of a blackbody, which can be superimposed with atomic or molecular emission lines comparable to bremsstrahlung. It is necessary to distinguish two forms of SL, single-bubble (SBSL) and multibubble (MBSL). In general, MBSL spectra differ from SBSL spectra in that they contain emission lines, e.g., from alkali atoms or hydroxyl radicals [matula-1995]. Consequently, it was, until recently considered that the mechanisms of light emission, and the nature of the bubble interior upon collapse were fundamentally different for the single and multibubble systems. Considering that MBSL is a cloud of single bubbles a bridging theory is desired.With this background the objective of the present work was to conduct a comparative spectroscopic analysis of SBSL, driven at 27 kHz, and MBSL generated from low and high ultrasonic frequencies (20, 203 and 607 kHz) of aqueous electrolyte solutions. Therefore a single bubble sonoreactor was developed, where the temperature, gas content and type, as well as the acoustic pressure could be controlled. The electrolytes of choice were: sodium chloride and chlorides of the luminescent lanthanide ions, Ce3+, Tb3+, Eu3+ and Gd3+, which can be excited by UV light absorption and collisions with energetic particles [kulmala-1995]. In the first part of this work the conditions upon bubble collapse were approximated by fitting the broad-band continuum of SBSL spectra of water with 70 mbar of argon and a 0.5 M NaCl solution with 70 mbar of argon using Planck's law of blackbody radiation. The obtained blackbody temperatures are in the range of 104 K, which is in good agreement with previous studies, but with the discrepancy of being independent of the presence of NaCl and the acoustic pressure, whereas the SL intensity increased by a factor of more than 10 upon increased acoustic pressure. The different trends followed by SL intensity and blackbody temperatures question the blackbody model. Another observation questioning the blackbody model is the appearance of atomic and molecular emission lines in MBSL and as recently observed also in SBSL [liang-2007, young-2001]. The present work proofed that the key factors for line emission in SBSL are small amounts of argon and low acoustic pressure. Moreover, the work revealed that the shape of the OH• radical emission is very similar to that in MBSL spectra, indicating the strong similarity of intrabubble conditions in MBSL and SBSL under certain experimental conditions [schneider-2011]. An increase of the acoustic pressure caused the continuum to overlap the lines until they become indistinguishable giving the usually in SBSL observed featureless continuum. This advance is a big step toward bridging the gap between SBSL and MBSL. Furthermore this study reveals that the concentration of the sodium ion at the interface of a single bubble can be enriched with a surface active counterion and the concentration is crucial for the observation of the sodium line in SBSL, suggesting that excitation of sodium either takes place at the interface of the
Monloubou, Martin. "Interaction d'une onde de souffle avec une mousse liquide : atténuation et rupture." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S067/document.
Full textLiquid foams are used in various domains in our everyday life. Their excellent ability to dissipate energy makes foams widely used in the military domain to mitigate blast waves produced after an explosion. In this Thesis, we have designed an original experimental setup allowing us to image the deformation of a liquid foam after the impact of a blast wave exiting a shock tube. We also measure the overpressure in the foam, within a range of 5 to 50\,kPa. We evidence a pressure attenuation, increasing and then saturating at increasing bubble size, while all the other parameters of the foam, especially liquid fraction, are kept constant. Those results are interpreted with a thermal dissipation model at the bubble scale, suggesting the existence of a maximum dissipation for a given bubble size. We then characterise the wave velocity in the foam. At small amplitudes, the velocity follows Wood's model, based on linear propagation in an effective continuous medium. At greater amplitudes, we show the apparition of a non-linear regime, with a higher propagation velocity and a lower attenuation, those two features being captured theoretically and numerically. Close to the source, the foam is destroyed by the shock. We close our study with more qualitative results on the quantity of destroyed foam and the propagation velocity of the rupture front, which have been evidenced for the first time in a three-dimensional foam
Thieury, Margaux. "Développement de métamatériaux super-absorbants pour l’acoustique sous-marine." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLS004.
Full textThe constant evolution of sonar performance requires new designs of absorbent coatings for underwater acoustics. Such coatings are used to improve stealth of submarines but can also improve the efficiency of on-board detection systems. Bubble meta-screens (reminiscent of the so-called Alberich coatings) are a possible solution to tackle this issue. A bubble meta-screen consists of a periodic distribution of sub-wavelength air cavities trapped in a visco-elastic matrix. The cavities acoustically behave as bubbles and exhibit a low frequency resonance, known as the Minnaert resonance. Under certain conditions, the meta-screen can achieve a total absorption when placed in front of a perfect reflector. This doctoral work allowed us to build a phenomenological model, validated by numerical simulations and experiments, which can predict the reflection and transmission coefficients of the meta screen as a function of its geometric and rheological characteristics. Our model takes into account the influence of the temperature and static pressure on the performance of a meta-screen, as well as the role played by the shape of the cavities
Pham, Tuyet Mai. "La mesure des populations de germes de cavitation : qualification et optimisation d'un compteur dynamique à ogive centrale." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10235.
Full textKrefting, Dagmar. "Untersuchung von Einzel- und Mehrblasensystemen in akustischen Resonatoren." Doctoral thesis, [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=97074675X.
Full textGreene, Chad Allen. "Low-frequency acoustic classification of methane hydrates." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-12-2632.
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Zhang, Songhua. "Nonlinear acoustic method for gas bubbles identification in marine sediments." Thesis, 2006. http://hdl.handle.net/1828/2084.
Full textSilva, João Pedro Santos Parente da. "Acoustic methods for assessment of bubbles produced by marine plants." Master's thesis, 2018. http://hdl.handle.net/10400.1/12166.
Full textLiao, Chen-Ting, and 廖振廷. "Microscopic Particle Dynamics in Dust Acoustic Waves and Dusty Plasma Bubbles." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/64206471954393897580.
Full text國立中央大學
物理研究所
95
Dust acoustic wave (DAW) can be self excited at low pressure in the dusty plasma liquid due to some instabilities. Particle motions are directly observed and analyzed in DAW by a high speed micro image system with suitable illumination. We investigate their interactions and dynamics as a connection between macroscopic and microscopic pictures of the longitudinal wave. Various instabilities and collective behaviors can be self generated, such as DAW, or driven externally such as plasma bubble. In experiments, we can measure the global behaviors of the wave including spatiotemporal evolution of the particle number density, the spatial distribution of the power spectrum, phase space portrait, etc. In microscopic viewpoint, individual particle trajectories are traced in DAW to get its displacement and velocity. It is found that when the particle colliding the wave crest, it may be carried by the wave front and travels together for a short time or it may be repelled by the wave front and turns back. Most particles behave as long time aperiodic or quasi periodic chaotic motion instead of the simple harmonic motion. Particles oscillate in their potential wells may have opportunity to jump to nearby potential wells as the hopping motion. Furthermore, all particle trajectories are traced at the same time to study the velocity distribution of the particles in the wave. In another part of the experiment, the same methods are used to observe the spatiotemporal evolution and particle dynamics for pulsed laser ablation induced plasma bubble, i.e., spherical dust cavity. The collapsing plasma bubble can be considered as a downward propagating supersonic dust shock wave. Consequently, we further investigate some interesting phenomena such as the wave-bubble interactions and the induced dust wake field behind the bubble when plasma bubble traveling through DAW.
Schoen, Scott Joseph Jr. "Acoustic characterization of encapsulated microbubbles at seismic frequencies." Thesis, 2013. http://hdl.handle.net/2152/23911.
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Chan, Hsiang-Chih, and 湛翔智. "Acoustic Analysis of Nearshore Breaking Wave Bubbles Simulated by Piston-Type Wavemaker." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/96263626936033802781.
Full text國立中山大學
海下技術研究所
90
This article studies ambient noise in the surf zone that was simulated by piston-type wavemaker in the tank. The experiment analyzed the bubbles of breaking wave by using a hydrophone to receive the acoustic signal, and the images of bubbles were recorded by a digital video camera to observe distribution of bubbles. The tank is in College of Marine Sciences, National Sun Yat-sen University, the dimensions of water tank are 35 m ×1 m ×1.2 m, and the slope of the simulated seabed is 1:5. The studied parameters of ambient noise generates by breaking wave bubbles were wave height, period, and water depth. Short-time Fourier Transform was applied to obtain the acoustic spectrum of bubbles, MATLAB programs were used to calculate mean sound pressure level, and determine number of bubbles. Bubbles with resonant frequency from 0.5 to 10 kHz were studied, counted from peaks in the spectrum. The number of bubbles generated by breaking waves could be estimated by bubbles energy distributions. The sound pressure level of ambient noise was highly related to the wave height and period, with correlation coefficient 0.7. The results were compared with other studies of ambient noise in the surf.
Hay, Todd Allen 1979. "A model of the interaction of bubbles and solid particles under acoustic excitation." 2008. http://hdl.handle.net/2152/18109.
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Wu, Cheng-kang, and 吳政剛. "The Study of Effects of Gas Bubbles on Acoustic Wave Attenuation Using AST-Sonar System." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/69204416925635398037.
Full text國立中山大學
海下技術研究所
95
Bubbles are often present in the natural ocean. Bubbly liquid will have the significant influence the sound propagation, and creates a significant disturbance to under water target''s detection. Therefore, it is an important research subject of bubble influence to the sound wave propagation. This study used the sonar training system which developed by British''s iTP corporation, through suitable additional design discuss the attenuation of sound propagating through a bubble screen. At first this study collects and infers the formula by the literature review. Secondly, the experimental design of measuring the attenuation of sound wave. The experiment process by using two parallel iron boards to carry on the measurement of gas-volume fraction. Then correlate with the sound pressure from the measurement of hydrophone. After curve fitting, we can clearly know the each other correlation. Finally taking the result compare with the attenuation coefficient formula. The experimental consists of two parts. The first part is to measure the gas-volume fraction of the bubbly liquid contained in the screen; while the second part is to measure the sound attenuation of the bubble screen. The result display that the bubble screen can attenuate about 8 dB per centimeter as the gas-volume fraction stay at 1 percent. At high gas-volume fraction the coefficient of attenuation has increased, and is different from theoretical value. This is because the bubble''s correlation has not been considered. In addition, the low frequency sound wave is close to theoretical value, but the high frequency sound wave has big different to theoretical value. Because the high frequency sound wave''s wavelength is too small to satisfy the condition. At experiment I suggest to use more appropriate transducers and precise bubble''s tube. Thus the experimental result will be better.
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Gilbert, Jeffrey. "Study of the self noise generated by supercavitating vehicles." Thesis, 2015. https://hdl.handle.net/2144/16307.
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