To see the other types of publications on this topic, follow the link: Acoustic and hydrodynamic cavitation.
Dissertations / Theses on the topic 'Acoustic and hydrodynamic cavitation'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Acoustic and hydrodynamic cavitation.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Pamidi, Taraka Rama Krishna. "Process Intensification by Ultrasound Controlled Cavitation." Licentiate thesis, Luleå tekniska universitet, Drift, underhåll och akustik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-73856.
Full textAbstract:
Process industries are cornerstones in today’s industrialized society. They contribute significantly in the manufacturing of various goods and products that are used in our day-to-day life. Our society’s paradigm of consumerism accompanied by a rise in global population drives an ever increasing demand for goods. One of many strategies developed to satisfy these demands and at the same time improve production capabilities is known as process intensification. As an example, this can be accomplished by implementation of devices using the principle of hydrodynamic and acoustic cavitation. High-intensity cavitation in the ultrasonic range can change the physical and chemical properties of a wide range of substances and hence, improve the production rate or quality. Despite the generally accepted benefits of hydrodynamic and acoustic cavitation, applications in the process industry are yet limited. The reasons are that the method requires extensive optimization, which depends on multiple process parameters and encounters problem in the implementation on a larger scale. Scalable cavitation reactor concepts for industrial applications need to meet challenges like stability and robustness, energy efficiency and high flow rates. This thesis focuses on the methodology for the design and optimization of a flow through cavitation reactor. An ultrasound reactor concept has been developed and tested for two different applications: i) Fibrillation processes typical for paper and pulp industry; ii) Metal leaching of mineral concentrates. Simulations were carried out using a commercially available software for multiphysics modeling which combines acoustics, structural dynamics, fluid dynamics and piezoelectrics. However, the optimization procedure requires extensive experimental work in parallel with multi-physical simulations. In general, the application leads to hydrodynamic initiation of small gas bubbles in the fluid to be excited and collapsed by high-intensity ultrasound. This transient collapse of the cavitation bubbles provides both mechanical and chemical effect on materials. The developed reactor has a power conversion efficiency of 36% in batch mode and is well suited for a scale-up. In flow-through mode, the cavitation effect improves extensively and provides stable results. Energy efficiency requires hydrodynamic initiation of cavitation bubbles, high acoustic cavitation intensity by multiple excitation frequencies adapted to the optimized reactor geometry, as well as optimal process pressure and temperature with respect to the materials to be treated. The impact of flow conditions and hydrodynamic cavitation is significant and almost doubles the yield at the same ultrasonic power input. In the case of fibrillation of cellulose fibers, results obtained indicate that generated cavitation intensity changes the mechanical properties of the fiber wall. In the case of leaching, experiments show that six hours of exposure gave a 57% recovery of tungsten from the scheelite concentrate at 80°C and atmospheric pressure. Future research will focus on different types of excitation signals, extended reactor volume, increased flow rates and use of a higher process temperature.
2
Cameron, Peter J. K. "An acoustic countermeasure to supercavitating torpedoes." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29666.
Full textAbstract:
Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009.<br>Committee Chair: Rogers, P. H.; Committee Member: Ferri, A. A.; Committee Member: Ruzzene, M.; Committee Member: Smith, M. K.; Committee Member: Trivett, D.; Committee Member: Zinn, B. T. Part of the SMARTech Electronic Thesis and Dissertation Collection.
3
Kuhn, 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 text
4
Odeyemi, Babatunde O. "Hydrodynamic cavitation : effects of cavitation on inactivation of Escherichia coli (E.coli)." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/11009.
Full text
5
Chanda, Suranjit Kumar. "Disintegration of sludge using ozone-hydrodynamic cavitation." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43105.
Full textAbstract:
In our study we applied hydrodynamic cavitation and ozonation both separately and combined, to determine the synergistic effect of these two technologies for sludge disintegration. A 2 mm orifice was used as a cavitation device. Ozone was injected after cavitation at a concentration of 35 mg/L at a flow of 3 Lpm. The sludge was subjected to treatment for 90 minutes in all three cases. In a final step, combined ozone and cavitation was applied to disintegrate the sludge for 10 hours. It was found that the combination of ozonation and cavitation exhibited higher sludge disintegration capacity than the individual technologies applied alone. About 31% of VSS was reduced by the combined system, whereas 19% was reduced by ozone and only 4% was reduced by cavitation alone after 90 minutes of treatment. Soluble chemical oxygen demand (SCOD) was increased by approximately 1600 mg/L in the combined system, which was much higher than the individual effect observed with either ozone or cavitation alone. About 75% of this SCOD was found to be biodegradable. In the combined system, soluble TOC increased by approximately 1.5 times the amount released by ozone alone, indicating higher release of organic matter from biomass. Only cavitation did not show any significant release of soluble total organic carbon (TOC) compared to the other treatments. In combined application, soluble biochemical oxygen demand (BOD) increased to 420 mg/L, which was significantly higher than the increase of BOD due to the application of ozone alone which was 260 mg/L. Based on the SCOD, it was found that a maximum of 50% of the sludge could be solubilised in 10 hours of combined treatment. It was also found that with ozone-cavitation, approximately 26% of the total sludge phosphorus was released to the solution after 10 hours, although most of the release occured within the first 2 hours. Within the operating conditions applied, cavitation itself was not sufficient for the disintegration of sludge, although better disintegration was found in combined application at higher inlet pressure. In the case of ozonation alone, higher disintegration was obtained at longer ozonation time.
6
Lesko, Timothy Michael McKoy Vincent. "Chemical effects of acoustic cavitation /." Diss., Pasadena, Calif. : California Institute of Technology, 2004. http://resolver.caltech.edu/CaltechETD:etd-04262004-184449.
Full text
7
Skelton, Hedley John. "Applying hydrodynamic cavitation to the activated sludge process." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613352.
Full text
8
Tran, David. "Hydrodynamic cavitation applied to food waste anaerobic digestion." Thesis, Linköpings universitet, Tema Miljöförändring, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-128268.
Full textAbstract:
Innovative pre-treatment methods applied to anaerobic digestion (AD) have developed to enhance the methane yields of food waste. This study investigates hydrodynamic cavitation, which induce disintegration of biomass through microbubble formations, impact on food waste solubilisation and methane production during following AD. Two different sub-streams of food waste (before and after the digestion) pre-treated by hydrodynamic cavitation were evaluated in lab scale for its potential for implementation in a full scale practise. First, the optimum condition for the hydrodynamic cavitation device was determined based on the solids and chemical changes in the food waste. The exposure time was referred to as the number of cycles that the sample was recirculated through the cavitation inducer’s region. The optimal cycles were later tested as a pre-treatment step in a BMP test and semi-CSTR lab scale operation. The tests showed that sufficient impact from the hydrodynamic cavitation was achieved by 20 cavitation cycles. Due to the pre-treatment, food waste solubilisation increased, up to 400% and 48% in terms of turbidity and sCOD measurements, respectively. In the BMP test, the treated samples improved the methane yield by 9-13%, where the digested food waste increased its kinetic constant by 60%. Fresh food waste was then processed in the semi-CSTR operation and the methane yield was increased by up to 17% with hydrodynamic cavitation for two reference periods. These promising results suggest that the hydrodynamic cavitation can be implemented for full scale production with food waste.
9
Abrahamsson, Louise. "Improving methane production using hydrodynamic cavitation as pre-treatment." Thesis, Linköpings universitet, Tema Miljöförändring, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-128783.
Full textAbstract:
To develop anaerobic digestion (AD), innovative solutions to increase methane yields in existing AD processes are needed. In particular, the adoption of low energy pre-treatments to enhance biomass biodegradability is needed to provide efficient digestion processes increasing profitability. To obtain these features, hydrodynamic cavitation has been evaluated as an innovative solutions for AD of waste activated sludge (WAS), food waste (FW), macro algae and grass, in comparison with steam explosion (high energy pre-treatment). The effect of these two pre-treatments on the substrates, e.g. particle size distribution, soluble chemical oxygen demand (sCOD), biochemical methane potential (BMP) and biodegradability rate, have been evaluated. After two minutes of hydrodynamic cavitation (8 bar), the mean fine particle size decreased from 489- 1344 nm to 277- 381 nm (≤77% reduction) depending of the biomasses. Similar impacts were observed after ten minutes of steam explosion (210 °C, 30 bar) with a reduction in particle size between 40% and 70% for all the substrates treated. In terms of BMP value, hydrodynamic cavitation caused significant increment only within the A. nodosum showing a post treatment increment of 44% compared to the untreated value, while similar values were obtained before and after treatment within the other tested substrates. In contrast, steam explosion allowed an increment for all treated samples, A. nodosum (+86%), grass (14%) and S. latissima (4%). However, greater impacts where observed with hydrodynamic cavitation than steam explosion when comparing the kinetic constant K. Overall, hydrodynamic cavitation appeared an efficient pre-treatment for AD capable to compete with the traditional steam explosion in terms om kinetics and providing a more efficient energy balance (+14%) as well as methane yield for A. nodosum.<br>Det behövs innovativa lösningar för att utveckla anaerob rötning i syfte att öka metangasutbytet från biogassubstrat. Beroende på substratets egenskaper, kan förbehandling möjliggöra sönderdelning av bakterieflockar, uppbrytning av cellväggar, elimination av inhiberande ämnen och frigörelse av intracellulära organiska ämnen, som alla kan leda till en förbättring av den biologiska nedbrytningen i rötningen. För att uppnå detta har den lågenergikrävande förebehandlingsmetoden hydrodynamisk kavitation prövats på biologiskt slam, matavfall, makroalger respektive gräs, i jämförelse med ångexplosion. Effekten på substraten av dessa två förbehandlingar har uppmäts genom att undersöka distribution av partikelstorlek, löst organiskt kol (sCOD), biometan potential (BMP) och nedbrytningshastigheten. Efter 2 minuters hydrodynamisk kavitation (8 bar) minskade partikelstorleken från 489- 1344 nm till 277- 281 nm (≤77 % reduktion) för de olika biomassorna. Liknande påverkan observerades efter tio minuters ångexplosion (210 °C, 30 bar) med en partikelstorlekreducering mellan 40 och 70 % för alla behandlade substrat. Efter behandling med hydrodynamisk kavitation, i jämförelse med obehandlad biomassa, ökade metanproduktionens hastighetskonstant (K) för matavfall (+65%), makroalgen S. latissima (+3%), gräs (+16 %) samtidigt som den minskade för A. nodosum (-17 %). Förbehandlingen med ångexplosion ökade hastighetskonstanten för S. latissima (+50 %) och A. nodosum (+65 %) medan den minskade för gräs (-37 %), i jämförelse med obehandlad biomassa. Vad gäller BMP värden, orsakade hydrodynamisk kavitation små variationer där endast A. nodosum visade en ökning efter behandling (+44 %) i jämförelse med obehandlad biomassa. Biomassa förbehandlade med ångexplosion visade en ökning för A .nodosum (+86 %), gräs (14 %) och S. latissima (4 %). Sammantaget visar hydrodynamisk kavitation potential som en effektiv behandling före rötning och kapabel att konkurrera med den traditionella ångexplosionen gällande kinetik och energibalans (+14%) samt metanutbytet för A. nodosum.
10
Zhang, Siyuan. "Biofilm Removal with Acoustic Cavitation and Lavage." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1356194652.
Full text
11
Power, John Francis. "Electrochemical, photographic, luminescent and acoustic characterisation of cavitation." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274448.
Full text
12
Foley, Thomas. "A study of acoustic cavitation and hydrogen production." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/374705/.
Full textAbstract:
This thesis presents a study of acoustic cavitation generated in an ultrasonic reactor, with the particular aim of enhancing hydrogen gas production and release. The stabilisation of cavitation clusters formed in a set of ultrasonic reactors is demonstrated. The highly stable cluster is induced by the positioning of a rod at the antinode of the sound field employed. These sound fields were characterised with a new technique based on particle imaging. Here adding rheoscopic particles within such reactors revealed a novel and useful method for the characterisation of standing wave fields. This observation was supported by pressure measurements using a hydrophone. In addition the stabilised cluster was investigated using an electrochemical method to monitor the erosion of the surface directly above the cluster, at short (10’s of μs) and long (100’s of s) timescales. Both timescales indicate changes in the stability and nature of the cluster, which in turn is dependent on the local surface conditions (roughness) of the rod/electrode assembly. Low light level imaging of the stabilised cavitation cluster demonstrates the occurrence of sonochemiluminescence (SCL). It is shown that the spatial extent of light emitted via SCL is correlated with the pressure amplitude of the sound field. A visual ‘shimmer’ effect is also shown to be emanating from stabilised cavitation clusters. This is attributed to local heating which in turn induces refractive index changes, which are enhanced through the use of Schlieren imaging. This local cluster induced-heating of the liquid is quantified using a variety of physical measurements. Investigation into the ultrasonic enhancement of the production of molecular hydrogen from aluminium corrosion is made. This study showed that the sonochemical enhancement was insignificant compared to local heating effects associated with the sound field. Analysis of the performance of an electrolysis system, designed and manufactured by the project sponsors (HTOGO Ltd.), is reported. Measurement of the hydrogen gas produced by the system highlights a low Faradaic efficiency and long response time for gas release. An innovative method for the rapid release of gas via ultrasonic outgassing of a liquid reservoir, containing hydrogen and oxygen gas bubbles, is demonstrated. A novel optically isolated Coulter counter system for the in-situ determination of the size distribution of bubbles in a bubbly liquid reservoir is reported. This thesis illustrates the underpinning principles of this technique and the determination of the best calculation method for successful calibration and accurate measurement of the bubble size distributions generated in an electrochemical reactor.
13
Schiffers, Werner Paul. "Optical and acoustic investigation of laser-generated cavitation." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/26862.
Full textAbstract:
Cavitation is the formation of vapour filled bubbles in a liquid. They can be generated either by the reduction of the ambient water pressure at constant temperature or by a temperature increase at constant pressure. In the results of the experiments presented in this work a range of different diameter cavitation bubbles were generated by focusing pulses of near IR radiation (le = 1064 nm) from a Q-switched Nd:YAG laser of varying energy in a small water tank. Single exposure high speed shadow photography and Schlieren techniques are used to visualise the oscillating motion of the cavitation bubbles with high temporal and spatial resolution. The optical analysis of the cavitation bubble in free water shows a smooth symmetrical oscillating motion during the first cycle. When the bubble is collapsing near a solid boundary the motion becomes asymmetrical. The Schlieren images in combination with matching plots of a thin film polyvinylidene fluoride (PVDF) pressure transducer confirm the formation of a liquid jet as well as different shock wave emissions for certain bubble to boundary parameters. They also indicate the importance of the resulting fluid flow to stresses induced in the solid boundary. In an attempt to visualise the fluid flow field around an oscillating cavitation bubble the IR laser radiation is focused in a solution of copper sulphate (CUS04) for contrast enhancement. High speed photography in combination with an accurately positioned Schlieren knife edge displays the heated path of the laser beam and the different shapes of the cavitation bubble. For the case of a bubble in free space the marked laser path indicates radial fluid flow only. For a bubble in front of a solid boundary the marked laser path clearly shows the motion of the fluid into the toroidal shaped bubble during the collapse process. For this case the marked paths are similar to numerically calculated streamline plots. In contrast to the solid boundary a flexible boundary was also used. The interaction of the cavitation bubble with the flexible boundary visualises partially the movement of the water but is found to still destroy some of the symmetry of the bubble.
14
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 textAbstract:
La cavitation est la formation de bulles de vapeur dans un liquide statique ou en écoulement. L’érosion de cavitation se produit quand ces bulles collapsent à cause de la récupération de pression. Ce phénomène peut endommager les parois à proximité desquelles les bulles collapsent. Il s’agit d’un problème majeur dans les machines hydrauliques. Par exemple, les turbines hydrauliques fonctionnent aujourd’hui souvent dans des régions défavorables du point de vue de la cavitation, pour réguler le réseau électrique. Mesurer la cavitation et le taux d’érosion est souvent très difficile voire impossible. L’émission acoustique (EA) est une méthode qui permet la mesure de cavitation sans accès direct à l’écoulement ; toutefois, les données sont difficiles à interpréter. Cette thèse présente quelques possibilités de traitement des données de l’EA pour quantifier les diamètres des indentations créées par impacts individuels de la cavitation et aussi pour évaluer l’érosion de cavitation. De plus, les taux d’érosion de trois matériaux d’aubes de turbine Francis ont été caractérisés. Les raisons pour les différences dans le taux d’érosion de deux aciers inoxydables et martensitiques sont analysées. Tous les essais de cavitation ont été réalisés dans le même tunnel de cavitation haute vitesse. Un premier résultat majeur de cette thèse est le développement d’une méthode pour compter les pics d’EA par une technique d’enveloppe du signal. Les distributions cumulées des pics d’EA sont comparées à celles des diamètres d’indentations. Une relation est proposée entre l’amplitude des pics d’EA et le diamètre des indentations. Le deuxième résultat majeur est le lien entre l’évolution de l’érosion de cavitation et la fréquence de lâcher des nuages de cavitation. Bien que les signaux d’EA soient mesurés en haute fréquence, un processus de démodulation a été mis en œuvre qui permet de mettre en évidence la basse fréquence de lâcher. Cette fréquence augmente avec la rugosité et la déformation de surface au fur et à mesure de la progression de l’endommagement. Par ailleurs, les raisons entre les différences de taux d’érosion des aciers inoxydables et martensitiques ont été identifiées : la taille des grains d’austénite initiale, les tailles des plaques et plaquettes et la quantité d’austénite résiduelle sont les principaux facteurs influants. Cette thèse propose plusieurs résultats directement utilisables, comme la classification entre les aciers inoxydables martensitiques, ainsi que des méthodes pour surveiller la cavitation mises au point en laboratoire dans un tunnel de cavitation et potentiellement applicables aux machines hydrauliques. Le résultat majeur est que l’EA a un fort potentiel pour surveiller la cavitation et l’érosion de cavitation avec l’avantage important qu’elle ne nécessite pas d’accès direct à l’écoulement<br>Cavitation 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
15
Alcock, Robin D. "Transducers for measuring acoustic transients." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/32473.
Full textAbstract:
This thesis is concerned with the design and development of measuring devices for the characterisation of acoustic transients with high temporal and spatial resolution. Three new techniques are demonstrated characterising acoustic transients generated by Nd-YAG laser (1060nm, 30ns, 55mJ) assisted breakdown of water and air. The first technique demonstrates the use of a high power semiconductor laser in a high speed multiple exposure imaging system. This system developed is capable of illuminating an event with up to 10 pulses of light at a maximum repetition rate of 5MHz, with a timing accuracy of ≈5ns. Each semiconductor laser light pulse has a FWHM duration of 50ns, peak power of 30W, and a wavelength of 860nm. Images of individual acoustic transients are displayed on the same CCD camera frame, and it was found that this is best achieved using a dark field imaging technique such as Schlieren imaging.
16
Promasa, Kornpatsitt. "Non-invasive measurement techniques to monitor acoustic cavitation activity." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24419.
Full textAbstract:
High power ultrasound has been used in a number of biomedical and industrial applications. In particular, such systems, when used in chemical processing, modify the course of a chemical reaction. The use of high power ultrasound induces cavitation in the load medium, which then leads to certain mechanical and chemical effects. These effects can cause damage to objects, increase local temperatures and can accelerate chemical reactions. Thus, in order to evaluate an efficient ultrasonic system and to quantify the cavitation activity, it is necessary to measure the cavitation in the reaction under the influence of a high power ultrasonic field. Conventional hydrophone techniques and sensor technologies are not suitable for this type of measurement because the sensor can be damaged and change the acoustic field in the presence of cavitation generated by the high power ultrasound. This Thesis describes the development of a non-invasive technique used to monitor acoustic cavitation activity within a reactor vessel. Both Laser Doppler Velocimetry (LDV) and broadband ultrasonic transducer approaches are considered as potential measurement techniques to measure the acoustic emission (AE) signals associated with a cavitating field. The LDV approach uses laser detection to provide information about cavitation intensity and distribution occurring within a reactor vessel. Next, finite element analysis (FEA) is used to provide a simulation platform to investigate the detection of AE sources from within the reactor vessel. This provides the necessary information to support the design of a broadband transducer appropriate for detection of cavitation generated AE. FEA is then used to design a piezoelectric ceramic composite transducer to develop a non-invasive transducer measurement system. In both approaches, a broadband integrated energy (BIE) approach is used to determine the intensity of the cavitation activity. This technique has been evaluated in different frequency ranges and at various power levels. Interestingly, the BIE in the frequency ranges of 1-5MHz was shown to be sufficient in monitoring the cavitation. Overall, the results reveal that both non-invasive techniques can be used to monitor cavitation activity. Although, neither approach provided adequate spatial resolution to accurately map the cavitation field. These techniques are most appropriate to use when the region of cavitation activity in the reactor vessel is known and the external, non-invasive technique can be targeted at this known position to provide information on the regional cavitation intensity.
17
Ramirez, David A. "Improvement of Ethanol Production on Dry-Mill Process Using Hydrodynamic Cavitation Pretreatment." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354646654.
Full text
18
Lunnbäck, Johan. "Hydrodynamic cavitation applied to anaerobic degradation of fats, oils and greases (FOGs)." Thesis, Linköpings universitet, Tema Miljöförändring, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-140685.
Full textAbstract:
To increase profitability for biogas production, new innovative substrates and condition of operations needs to be implemented. At the current state, fats, oils and greases (FOGs) represent a promising substrate even though it brings operational challenges to the anaerobic digestion process. By utilizing hydrodynamic cavitation (HC) as a pre-treatment of the FOGs, the efficiency of FOGs’ co-digestion with wastewater sludge can be significantly improved. Preliminary experiments conducted on oil and water demonstrates that the HC pre-treatment improves the oil solubilisation as well as forms stable oil and water emulsion that last for several hours. The pre-treatment also improved the soluble chemical oxygen demand (COD) of biosludge (BiSl) by up to 115% and the initial degradation rate by up to 35%. In a semi-continues system, this allowed a significant increment in the specific methane yield depending on the organic loading rate (OLR) applied1. With sufficient process optimization, the HC-pre-treatment may prove to be an energy efficient and effective pre-treatment of FOGs.
19
Ji, Ran. "Study of acoustic cavitation near metal surfaces contaminated by uranium." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS131/document.
Full textAbstract:
Le démantèlement des réacteurs UNGG produit un grand volume de matériaux métalliques contaminés. Parmi ceux-ci, les alliages à base de magnésium, connus comme métaux hautement réactifs, présentent un risque élevé de corrosion et peuvent générer de l'hydrogène gazeux qui peut causer de graves dommages pendant le stockage. Afin de réduire le volume des effluents radioactifs générés et de déclasser les déchets nucléaires, la sonochimie peut être mise en œuvre comme technologie efficace pour la décontamination des surfaces métalliques. La sonochimie traite des effets des ondes ultrasonores sur les réactions chimiques en solution. Les effets observés en sonochimie proviennent du phénomène de cavitation acoustique, qui est la nucléation, la croissance et l'effondrement implosif rapide de microbulles remplies de gaz et de vapeur. Des espèces et des radicaux excités peuvent être générés dans le plasma formé, qui émet de la lumière (sonoluminescence). Lorsque l’effondrement des bulles a lieu à proximité d'une surface solide, il produit des ondes de choc violentes et des microjets dirigés vers la surface. Ces effets physiques contribuent fortement au nettoyage par ultrasons, à la dépassivation de surfaces et à la décontamination.Cette étude se concentre sur : 1) les comportements de cavitation près d'une surface solide ; 2) la structuration ultrasonore des surfaces étendues de magnésium ; 3) la décontamination par ultrasons de surfaces métalliques radioactives. L'activité sonochimique est évaluée en mesurant les rendements en H2O2, la distribution de sonochimiluminescence et les spectres de sonoluminescence. Les effets de la structuration et de la décontamination des surfaces sont suivis au moyen de MEB, EDS, FTIR, Raman, DRX, analyse du comportement de mouillage, spectrométrie de masse et ICP-AES.Ce travail a mis en évidence le fort impact de la fréquence ultrasonore sur l'activité sonochimique, sa distribution spatiale et sur les effets générés sur les échantillons de magnésium. Une répartition spatiale homogène de l'activité sonochimique est observée aux fréquences ≥ 100 kHz. L'effondrement asymétrique des bulles est plus susceptible de se produire près de la surface solide aux ultrasons à haute fréquence. La formation d’une structure allongée semblable à une balle de golf est observée à des fréquences comprises entre 100 et 362 kHz. De telles architectures résultent de la dissolution contrôlée par ultrasons de la surface Mg. Il est probable que la nucléation hétérogène assurée par la création de défauts par les ultrasons et la libération de gaz H2 soient à l'origine de la formation des cratères. La décontamination des surfaces radioactives de Mg et d’alliages de Mg ont d'abord démontré un nettoyage rapide par les ultrasons suivi d’un lent processus de recontamination due à l'adsorption de brucite formée sur les surfaces de Mg ou de ses alliages<br>The dismantling of UNGG reactors produces large volumes of contaminated metallic materials. Among these, magnesium-based alloys which are known as highly reactive metals, have a high risk of corrosion and can generate hydrogen gas that can cause serious damages during storage. In order to reduce the volume of generated radioactive effluents and downgrade nuclear wastes, sonochemistry can be applied as an efficient technology for metallic surface decontamination. Sonochemistry deals with the effects of ultrasound waves on chemical reactions in solution. The effects observed in sonochemistry originate from the acoustic cavitation phenomenon, which is the nucleation, growth and rapid implosive collapse of gas and vapor filled microbubbles. Excited species and radicals can be generated in the formed plasma and light (sonoluminescence) is emitted. When the bubble collapse takes place in the vicinity of a solid surface, it produces violent shock waves and microjets directed towards the surface. These physical effects strongly contribute in ultrasonic cleaning, surface depassivation and decontamination.This study focuses on: 1) the cavitation behaviors near a solid surface; 2) the ultrasonic structuration of extended magnesium surfaces; 3) the ultrasonic decontamination of radioactive metal surfaces. The sonochemical activity is evaluated by measuring H2O2 yields, sonochemiluminescence distribution and sonoluminescence spectra. Surface structuration and decontamination effects are followed by means of SEM, EDS, FTIR, Raman, XRD, wetting behavior analysis, mass spectrometry and ICP-AES.The investigations reveal a strong ultrasonic frequency dependency of the cavitation activity and distribution and of the effects generated on the Mg samples. A homogeneous spatial repartition of sonochemical activity is observed at frequencies ≥ 100 kHz. Asymmetrical bubble collapse is found more likely to happen near the solid surface at high frequency ultrasound. A golf-ball like extended structure is observed at frequencies between 100 and 362 kHz. It is shown that such architectures result from the ultrasonically controlled dissolution of the Mg surface. Heterogeneous nucleation provided by the creation of defects by ultrasound and the release of H2 gas are supposed to be at the origin of the crater formation. Decontamination of radioactive surfaces of Mg and Mg alloys demonstrate rapid ultrasonic cleaning followed by a slow recontamination process which is due to the adsorption of brucite formed on the surfaces of Mg or its alloys
20
Salgaonkar, Vasant A. "Passive imaging & measurements of acoustic cavitation during ultrasound ablation." Cincinnati, Ohio : University of Cincinnati, 2009. http://rave.ohiolink.edu/etdc/view.cgi?acc_num=ucin1259075197.
Full textAbstract:
Thesis (Ph.D.)--University of Cincinnati, 2009.<br>Advisor: T. Douglas Mast. Title from electronic thesis title page (viewed Jan. 19, 2010). Keywords: Ultrasound Ablation; Acoustic cavitation; Passive cavitation detection;High-intensity focused ultrasound;Passive cavitation imaging;guidance and control. Includes abstract. Includes bibliographical references.
21
McInnes, James Christopher. "Low-frequency acoustic energy, cavitation, and their effects on bacteria /." Thesis, Connect to this title online; UW restricted, 1992. http://hdl.handle.net/1773/8041.
Full text
22
Altizer, Chase Duncan. "Hydroxyl Radical Production via Acoustic Cavitation in Ultrasonic Humidifier Systems." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/95935.
Full textAbstract:
Ultrasonic humidifiers use sound vibrations at frequencies higher than can be heard by humans (> 20,000 Hz) to generate aerosolized water also have potential for inducing sonochemical reactions for chemicals present in water. This research focuses on examining oxidants formed within ultrasonic humidifiers, as well as the oxidants effects of contaminants in water used in the systems. Hydroxyl radicals were found using DMPO as a spin trap. Caffeine and 17β-estradiol, as pharmaceutical contaminants of drinking water, were both emitted from the humidifier when present in the water reservoir and would enter breathing air. Emitted 17β-estradiol was found at 60% of the initial concentration filled in the ultrasonic humidifier after 480 minutes. Caffeine exhibited less degradation than 17β-estradiol. Degradation of both pharmaceuticals was attributed to ultrasonic processes, most likely oxidation with hydroxyl radicals produced. Bromide as a contaminant of the fill water was found to remain constant over time.<br>MS
23
Salgaonkar, Vasant Anil. "Passive Imaging and Measurements of Acoustic Cavitation during Ultrasound Ablation." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1259075197.
Full text
24
Seth, Duvall S. "A Study in Biofouling Prevention and Removal via Acoustic Cavitation." University of Toledo / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1554854930764174.
Full text
25
Hill, D. C. "Energy and momentum transfer between acoustic and hydrodynamic fields." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233256.
Full textAbstract:
A prominent feature of many practical flows is the hydrodynamic wave system attached to moving bodies or concentrations of vorticity. Sound waves are usually present, and these act as a mechanism for energy and momentum transport. With their source rooted in the unsteadiness of the flow, they can sometimes play an important role in determining the general flow structure, particularly if the flow is unstable. In this thesis we investigate the basic connection between sound, and hydrodynamic waves. By analysing the waves attached to boundaries which are in prescribed unsteady motion, details emerge concerning the linear production of sound from hydrodynamic motions. We show that the abrupt arrest or commencement of a steady hydrodynamic wave causes the production of a quantity of sound energy exactly equalling that of the hydrodynamic wave. For more gentle modulations of the steady state, we identify those aspects of the evolving hydrodynamic field which determine how much sound is produced. These results are used to suggest ways to improve procedures for minimising the noise from vibrating surfaces. According to linear theory, when waves on an infinite fluid boundary travel at sonic speed the fluid response is infinite. We use the ideas developed to cope with the sound generation problem to investigate the effects of unsteady transonic motion. We give a detailed analysis of acoustic 'Cerenkov radiation', which would occur if a body travelled through an inviscid medium supersonically, and decelerated to a subsonic speed. We assess the degree to which non-linear transonic effects are important. Sound waves are known to be a critical factor leading to the destabilisation of line vortices, and we were intrigued to know whether compressibility has a corresponding effect on the stability of a rigid body moving steadily in an irrotational, inviscid flow. Our investigation reveals that the motion is always stable.
26
Mirhadizadeh, S. A. "Monitoring hydrodynamic bearings with acoustic emission and vibration analysis." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7888.
Full textAbstract:
Acoustic emission (AE) is one of many available technologies for condition
health monitoring and diagnosis of rotating machines such as bearings. In
recent years there have been many developments in the use of Acoustic
Emission technology (AET) and its analysis for monitoring the condition of
rotating machinery whilst in operation, particularly on high speed machinery.
Unlike conventional technologies such as oil analysis, motor current signature
analysis (MCSA) and vibration analysis, AET has been introduced due to its
increased sensitivity in detecting the earliest stages of loss of mechanical
integrity.
This research presents an experimental investigation that is aimed at
developing a mathematical model and experimentally validating the influence of
operational variables such as film thickness, rotational speed, load, power loss,
and shear stress for variations of load and speed conditions, on generation of
acoustic emission in a hydrodynamic bearing. It is concluded that the power
losses of the bearing are directly correlated with acoustic emission levels. With
exponential law, an equation is proposed to predict power losses with
reasonable accuracy from an AE signal.
This experimental investigation conducted a comparative study between AE
and Vibration to diagnose the rubbing at high rotational speeds in the
hydrodynamic bearing. As it is the first known attempt in rotating machines. It
has been concluded, that AE parameters such as amplitude, can perform as a
reliable and sensitive tool for the early detection of rubbing between surfaces of
a hydrodynamic bearing and high speed shaft.
The application of vibration (PeakVue) analysis was introduced and compared
with demodulation. The results observed from the demodulation and PeakVue
techniques were similar in the rubbing simulation test. In fact, some defects on
hydrodynamic bearings would not have been seen in a timely manner without
the PeakVue analysis.In addition, the application of advanced signal processing and statistical
methods was established to extract useful diagnostic features from the acquired
AE signals in both time and frequency domain. It was also concluded that the
use of different signal processing methods is often necessary to achieve
meaningful diagnostic information from the signals. The outcome would largely
contribute to the development of effective intelligent condition monitoring
systems which can significantly reduce the cost of plant maintenance.
To implement these main objectives, the Sutton test rig was modified to assess
the capability of AET and vibration analysis as an effective tool for the detection
of incipient defects within high speed machine components (e.g. shafts and
hydrodynamic bearings).
The first chapter of this thesis is an introduction to this research and briefly
explains motivation and the theoretical background supporting this research.
The second and third chapters, summarise the relevant literature to establish
the current level of knowledge of hydrodynamic bearings and acoustic emission,
respectively. Chapter 4 describes methodologies and the experimental
arrangements utilized for this investigation. Chapter 5 discusses different NDT
diagnosis. Chapter 6 reports on an experimental investigation applied to
validate the relationship between AET on operational rotating machines, such
as film thickness, speed, load, power loss, and shear stress. Chapter 7 details
an investigation which compares the applicability of AE and vibration
technologies in monitoring a rubbing simulation on a hydrodynamic bearing.
27
Hallow, Daniel Martin. "Measurement and Correlation of Acoustic Cavitation with Cellular and Tissue Bioeffects." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/19741.
Full textAbstract:
Targeted intracellular delivery is a goal of many novel drug delivery systems to treat site-specific diseases thereby increasing the effectiveness of drugs and reducing side effects associated with current drug administration. The development of ultrasound-enhanced delivery is aimed at providing a targeted means to deliver drugs and genes intracellularly by utilizing ultrasound s ability to non-invasively focus energy into the body and generate cavitation, which has been found to cause transient poration of cells. To address some of the current issues in this field, the goals of this study were (i) to develop a measurement of cavitation to correlate with cellular bioeffects and (ii) to evaluate the ability of ultrasound to target delivery into cells in viable tissue. In addition, this study sought to exploit the shear-based mechanism of cavitation by (iii) developing a simplified device to expose cells to shear stress and cause intracellular uptake of molecules. This study has shown that broadband noise levels of frequency spectra processed from cavitation sound emissions can be used to quantify the kinetic activity of cavitation and provide a unifying parameter to correlate with the cellular bioeffects. We further demonstrated that ultrasound can target delivery of molecules into endothelial and smooth muscle cells in viable arterial tissue and determined approximate acoustic energies relevant to drug delivery applications. Lastly, we developed a novel device to expose cells to high-magnitude shear stress for short durations by using microfluidics and demonstrated the ability of this method to cause delivery of small and macromolecules into cells. In conclusion, this work has advanced the field of ultrasound-enhanced delivery in two major areas: (i) developing a real-time non-invasive measurement to correlate with intracellular uptake and viability that can be used as means to predict and control bioeffects in the lab and potentially the clinic and (ii) quantitatively evaluating the intracellular uptake into viable cells in tissue due to ultrasound that suggest applications to treat cardiovascular diseases and dysfunctions. Finally, by using shear forces generated in microchannels, we have fabricated a simple and inexpensive device to cause intracellular uptake of small and large molecules, which may have applications in biotechnology.
28
Cochran, Stephen Andrew. "Sonoluminescence as an indicator of cell membrane disruption by acoustic cavitation." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/15496.
Full text
29
Höchemer, Ralf H. Hoffmann Michael R. "Degradation of organic compounds by acoustic cavitation and pulsed-power discharges /." Diss., Pasadena, Calif. : California Institute of Technology, 1996. http://resolver.caltech.edu/CaltechETD:etd-06262006-111213.
Full text
30
Sesis, Achilleas. "Influence of acoustic cavitation on the controlled ultrasonic dispersion of nanomaterials." Thesis, University of Surrey, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.654750.
Full textAbstract:
Processing of nanoparticles is a core research area of nanotechnology. Carbon nanotubes (CNTs) are a prototype high aspect ratio nanomaterial and have been extensively studied due to their remarkable properties and the wide range of potential applications. Ultrasonication is the most widely used technique for the dispersion of a range of nanomaterials but the underlying mechanism is poorly understood, with the role of acoustic cavitation largely ignored by the materials science community despite its critical role in the dispersion process. As a consequence, many of the dispersion strategies in the literature are empirical in nature and typically specify only the solute concentrations, the electrical input power of the device and the exposure time. Having as an aim the need to clarify, standardise and optimise these processes, this thesis presents new in sights into the dispersion mechanism of CNTs in aqueous surfactant solutions using a novel sono-reactor and an in situ technique for the measurement of acoustic cavitation activity during sono-processing. Distinction is made between stable cavitation, which leads to chemical attack on the surface of the CNTs, and inertial cavitation, which favours CNT exfoliation and length reduction. These main conclusions are supported by a range of characterisation techniques, including measurement of sonochemically generated hydrogen peroxide, characterisation of CNT quality using Raman spectroscopy and of dispersion efficiency using absorption spectroscopy and atomic force microscopy. This work highlights that careful measurement and control of cavitation rather than blind application of input power is essential in the production of nanomaterial dispersions with tailored properties. The results have major implications for enhanced control and scale-up of nanoparticle dispersion using ultrasonic processing.
31
Lyka, Erasmia. "Passive acoustic mapping for improved detection and localisation of cavitation activity." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:d99dd0b6-3777-4506-9ef5-1b613433de58.
Full textAbstract:
Passive acoustic mapping (PAM) is a novel method for monitoring ultrasound therapies by mapping sources of acoustic activity, and in most cases cavitation activity, using an array of detectors. Although the range of its applications is indicative of its great potential, clinical adoption is currently hindered by its limited spatial resolution and the inherent difficulty of distinguishing, at depth, between nonlinear signals arising from nonlinear propagation and those arising from processes such as cavitation. The objective of this thesis is to address this limitation, by improving both the detection of the signal-of-interest and the source localisation. An optimum data-adaptive array beamforming algorithm is proposed, Robust Beamforming by Linear Programming (RLPB), which exploits the higher-orderstatistics of the recorded signals, aiming at improving PAM source localisation. Both simulations and in vitro experimentation demonstrated improvement in PAM spatial resolution compared to a previously introduced algorithm, Robust Capon Beamformer. More specifically, under the in vitro conditions examined here, a 22% and 14% increase in the axial and transverse PAM resolution is respectively achieved. In terms of reliable signal-of-interest detection amongst interfering signals, a time-domain data-adaptive parametric model, Sum-of-Harmonics (SOH) model, is developed. This model enables accurate estimation of time-varying-amplitude narrowband components in the presence of broadband signals. Respectively, it can recover a weak broadband signal in the presence of a dominant narrowband component. Compared to conventional comb filtering, SOH model enables PAM of cavitation sources that better reflect their physical location and extent. PAM performance enhancement achieved by combining the proposed beamforming and filtering approaches is assessed in a context where spatial resolution really matters, namely for distinguishing between cavitation activity occurring inside a channel and perivascularly following cavitation-mediated extravasation. Adoption of the proposed method results in more accurate isolation of the broadband emissions from inertially cavitating sources, and more reliable localisation of these sources despite the long source-to-array distance has been observed. Such an improvement to the spatial accuracy of PAM paves the way towards its clinical translation, and in vivo experimentation is the next step for further validation of PAM in conjunction with the proposed methods under clinically relevant conditions.
32
Diaz, 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 text
33
Bangaru, Balasundaram. "A detailed investigation of microbial cell disruption by hydrodynamic cavitation for selective product release." Doctoral thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/5345.
Full textAbstract:
Includes bibliographical references.<br>Hydrodynamic cavitation is a novel method for microbial cell disruption, mediated by intense pressure fluctuations caused by cavity oscillation and collapse. Selective release of intracellular microbial products is desirable to reduce the cost involved in their downstream processing. A study of the process variables that affect microbial cell disruption by hydrodynamic cavitation is presented in order to ascertain the conditions required for a selective release. Two model systems were considered (yeast and E. coil). Enzymes from different locations of the cell were studied and the release compared with other methods of disruption.
34
Kubina, Dávid. "Dynamika kavitujícího proudění za clonou." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-378401.
Full textAbstract:
Cavitating flow through five perforated plates with different number of holes with preserved constant flow cross-section area in sum were experimentally examined. Dynamic characteristics such as dependence of pressure amplitudes and dominant frequencies on cavitation number in all regimes of cavitating flow: incipient cavitation, partial cavitation, fully developed cavitation and supercavitation are obtained. For determination of dominant frequencies several pressure transducers in two regimes of measurement were used. Results were validated with frequency spectra obtained from picture analysis based on high-speed camera records.
35
Hockham, Natalie. "Spatio-temporal control of acoustic cavitation during high-intensity focused ultrasound therapy." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:1dd3c105-6b6e-49e0-a948-0fa7c07fc642.
Full textAbstract:
High-intensity focused ultrasound (HIFU) is rapidly emerging as a viable alterna- tive to conventional therapies in the treatment of deep-seated, solid tumours. In contrast to surgical methods, extracorporeal HIFU transducers non-invasively tar- get pathogenic tissue deep beneath the skin, inducing thermal necrosis of a volume of tissue typically coincident with the ultrasound focus. More recently, cavitation activity has been observed to enhance focal heating, whilst providing a unique op- portunity for real-time treatment monitoring. Unfortunately, the stochastic nature of cavitation makes it difficult to initiate and sustain the level of cavitation activity required for enhanced heating, and to confine the spatial extent of cavitation to the focal volume. The overall aim of this thesis is to design and implement a real-time, closed- loop controller for sustaining thermally relevant cavitation within the HIFU focal region. This is intended to improve the speed and reproducibility of tissue ablation, whilst providing clinicians with real-time feedback as to the extent and location of the ablated region. A quantitative relationship between the level of cavitation activity and asso- ciated temperature rise is first sought experimentally, by investigating cavitation- enhanced heating in two different tissue-mimicking materials (TMM) that yield dif- ferent levels of cavitation for the same HIFU exposure conditions. It is found that a minimum level of inertial cavitation activity is required for cavitation-enhanced heating to dominate the heating process, which is achieved in the first material but not the second. However, the introduction of exogenous, artificial nuclei to the second material is seen to augment cavitation levels to the extent that cavitation- enhanced heating becomes dominant. Subsequently, HIFU experimentation is extended to non-perfused, ex vivo bovine liver, into which a variety of cavitation nuclei are introduced to augment cav- itation levels, and hence heating. Commercially available lipid-shelled microbub- bles are contrasted with custom-made sonosensitive nanoparticles for their ability to seed cavitation events, culminating in an empirical relationship between iner- tial cavitation and heating that is common to both types of exogenous nuclei, and which agrees with the in vitro results. Moreover, the abnormally large lesions pro- duced are found to correlate with a broad spatial distribution of inertial cavitation events, as seen on two-dimensional passive acoustic maps. Based on these encouraging results, a novel negative-feedback, real-time con- trol system is implemented to sustain inertial cavitation within the focal region for extended periods of time. The controller is designed to be both asymmetric and adaptive, deploying different feedback gains to adjust the peak rarefactional focal pressure (PRFP), depending on whether cavitation activity is above or below the level required for cavitation-enhanced heating. With active cavitation control in vitro, the associated focal temperature elevation is maintained at a cytotoxic level for 20 seconds using less than half the energy input required in the absence of cavi- tation control. In order to test the applicability of the novel controller to a near-physiological environment, HIFU exposures are eventually performed in a unique normothermic perfused liver model that accounts for both heat advection and nuclei replenish- ment. Following preliminary experimentation, the controller is modified to account for the inherent variability in the cavitation threshold of perfused tissue, whilst the cavitation demand is also increased to account for heat advection. Following these modifications, use of the controller is found to enable greatly improved re- producibility of HIFU-induced lesions compared to those achieved without cavita- tion control, with a lesion size that is directly related to the cavitation demand. A cost-effective method for enabling caviation-enhanced, cavitation-controlled and cavitation-monitored HIFU therapy has thus been developed, which enables suc- cessful tissue ablation at acoustic energies lower than in current clinical use.
36
Schlicher, Robyn. "Size and lifetime of transient cell membranes disruptions created by acoustic cavitation." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/11905.
Full text
37
Wang, Qi. "Electromagnetic acoustic source (EMAS) for generating shock waves and cavitation in mercury." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12882.
Full textAbstract:
Thesis (Ph.D.)--Boston University
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.<br>In the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory a vessel of liquid mercury is subjected to a proton beam. The resulting nuclear interaction produces neutrons that can be used for materials research, among other things, but also launches acoustic waves with pressures in excess of 10 MPa. The acoustic waves have high enough tensile stress to generate cavitation in the mercury which results in erosion to the steel walls of the vessel. In order to study the cavitation erosion and develop mitigation schemes it would be convenient to have a way of generating similar pressures and cavitation in mercury, without the radiation concerns associated with a proton beam. Here an electromagnetic acoustic source (EMAS) has been developed which consisted of a coil placed close to a metal plate which is in turn is in contact with a fluid. The source is driven by discharging a capacitor through the coil and results in a repulsive force on the plate launching acoustic waves in the fluid. A theoretical model is presented to predict the acoustic field from the EMAS and compares favorably with measurements made in water. The pressure from the EMAS was reported as a function of capacitance, charging voltage, number of coils, mylar thickness, and properties of the plates. The properties that resulted in the highest pressure were employed for experiments in mercury and a maximum pressure recorded was 7.1 MPa. Cavitation was assessed in water and mercury by high speed camera and by detecting acoustic emissions. Bubble clouds with lifetimes on the order of 100 p,s were observed in water and on the order of 600 µs in mercury. Based on acoustic emissions the bubble radius in mercury was estimated to be 0.98 mm. Experiments to produce damage to a stainless steel plate in mercury resulted in a minimal effect after 2000 shock waves at a rate of 0.33 Hz -- likely because the pressure amplitude was not high enough. In order to replicate the conditions in the SNS it is necessary to generate 40 MPa acoustic pulses in mercury at a rate of 60 Hz and it was estimated that a 20 kV power supply in excess of 100 kW would be needed to achieve that.
38
Schlimpert, Stephan [Verfasser]. "Numerical Analysis of Hydrodynamic and Acoustic Flame Response Mechanisms / Stephan Schlimpert." München : Verlag Dr. Hut, 2016. http://d-nb.info/1113334649/34.
Full text
39
Azencott, Harold R. "Influence of the cell wall on intracellular delivery by electroporation and acoustic cavitation." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/11294.
Full text
40
Jamshidi, Rashid [Verfasser]. "Modeling and numerical investigation of acoustic cavitation with applications in sonochemistry / Rashid Jamshidi." Clausthal-Zellerfeld : Universitätsbibliothek Clausthal, 2014. http://d-nb.info/1049593693/34.
Full text
41
Kopechek, Jonathan A. "The Role of Acoustic Cavitation in Ultrasound-triggered Drug Release from Echogenic Liposomes." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1318878799.
Full text
42
Mylonopoulou, Eleonora. "Enhancement and mapping of ultrasonic drug release from thermosensitive liposomes by acoustic cavitation." Thesis, University of Oxford, 2011. https://ora.ox.ac.uk/objects/uuid:f31e4020-a3e0-41e3-9bfa-a6d2c9b04aa1.
Full textAbstract:
One of the major limiting factors of cancer therapy is the inability to deliver a sufficient dose of drugs to a target tumour without incurring significant side effects. Recent advances in nano-sized liposome formulations have enabled encapsulation of anti-cancer agents that simultaneously reduce off-target toxicity and allow increased accumulation in tumours due to the enhanced permeability and retention effect. Yet, a method for reliably releasing the drug from encapsulation has yet to be found. In this work, low-temperature sensitive liposomes, which release an encapsulated anti-cancer agent (doxorubicin) in the temperature range of 39-45±C, are combined with focused ultrasound-induced mild hyperthermia to deliver a predictable, site-specific, and high dose of anti-cancer agents that has the potential of overcoming the current limitations of targeted drug delivery for cancer. To reach this aim, acoustic cavitation-enhanced heating was harnessed to produce rapid and efficient temperature rises that could be spatiotemporally monitored and eventually controlled. For this purpose, a reproducible, non-exothermic, cell-embedding tissue-mimicking model was first developed to have an attenuation coefficient, thermal response and cavitation threshold similar to liver. The phantom platform was then utilised to allow for high-throughput optimisation of ultrasound exposure parameters that efficiently and safely produced mild hyperthermia and drug release. Inertial cavitation-enhanced heating was successfully shown to enhance drug release from the liposomes and subsequent cancer cell death due to release of the encapsulated agents, using a 25% Duty Cycle, 1Hz PRF 6 s sonication sequence. The remotely detectable acoustic emissions associated with cavitation were then exploited to enable real-time monitoring and spatial mapping of drug release using a novel passive acoustic mapping method. Finally, these developments and techniques were combined to demonstrate the feasibility of cavitation enhanced drug release and delivery in a world-unique isolated normothermic liver perfusion model that provides blood-flow rates comparable to those encountered in humans.
43
Hilares, Ruly Terán. "Hydrodynamic cavitation as a new approach for sugarcane bagasse pretreatment aiming to second generation ethanol production." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/97/97131/tde-07082018-153234/.
Full textAbstract:
Renewable energy sources have been proposed as a viable option to mitigate the consumption and the dependence of fossil fuels. Among the available alternatives, lignocellulosic biomass has shown great potential for bioenergy generation, and biofuels as ethanol can be obtained by fermentation from sugars present in cellulosic and hemicellulosic fractions of biomass. However, for the efficient release of fermentable sugars during the enzymatic hydrolysis step, a pretreatment process is required to modify the material in its structure and composition. In this context, hydrodynamic cavitation (HC) was proposed in this work as a new and promising alternative for pretreatment of sugarcane bagasse. Firstly, the variables NaOH concentration, solid/liquid (S/L) ratio and HC process time were optimized in HC assisted pretreatment. In optimized conditions (0.48 mol/L of NaOH, 4.27% of S/L ratio and 44.48 min), high lignin removal (60.4%) and enzymatic digestibility of cellulose fraction (97.2%) were obtained. Based in those results, new variables (inlet pressure, temperature, alkali concentration) were included for evaluation in a second stage of the study aiming to reduce the HC pretreatment time. In this case, temperature and álcali concentration showed more significance on lignin removal and hydrolysis yield of carbohydrate fraction in pretreated biomass. No significant difference in pretreatment efficiency was observed in 20 and 30 min of process time in the best conditions (70 °C, 3 bar of inlet pressure and 0.3 mol/L of NaOH). The dimensionless cavitation number influence also was evaluated in two levels (0.017 and 0.048), resulting higher efficiency using low cavitation number which was obtained using orifice plate with 16 holes (1 mm of diameter). Using the last optimized conditions and lower temperature (60 °C instead 70 °C) in order to avoid the foam formation when black liquor is reused, other alkalis (Ca(OH)2, Na2CO3, KOH) were evaluated in combination with HC and compared to the use of NaOH. High enzymatic conversions of carbohydrate fraction were observed in biomass pretreated using KOH-HC and NaOH-HC; additionally, NaOH black liquor was reused in 10 sequential batches. The pretreated biomass using fresh and reused black liquor were mixed and used for simultaneous saccharification and fermentation process (SSF) in interconnected column reactors, resulting in 62.33% of hydrolysis of total carbohydrate fractions and 17.26 g/L of ethanol production (0.48 g of ethanol/g of glucose and xylose consumed). Finally, the addition of oxidant agent (H2O2) in the alkali HC-process was optimized. In selected conditions (0.29 mol/L of NaOH, 0.78 % v/v of H2O2 and 9.8 min), 95,43% and 81.34% of enzymatic hydrolysis yield of cellulose and hemicellulose fraction were achieved respectively, using 5% of solid loading (S/L) in the hydrolysis process. When packed bed flow-through column reactor using 20% of S/L was used, 74.7% cellulose hydrolysis yield was reached. Sugars present in hydrolysate were also fermented into ethanol in bubble column reactor resulting in a yield value of 0.49 g/g and 0.68 g/L.h of productivity. By analyzing the results as a whole, HC was shown as a promising technology to accelerate the pretreatment time under mild conditions, showing advantages as simplicity of system and possibility to application in industrial scale.<br>O uso de fontes de energia renováveis tem sido proposto como uma alternativa viável para reduzir o consumo e a dependência de combustíveis fósseis. Entre as alternativas disponíveis, a biomassa lignocelulósica apresenta grande potencial para geração de bioenergia, sendo que biocombustíveis como o etanol podem ser obtidos por fermentação a partir de açúcares presentes em suas frações celulósicas e hemicelulósicas. No entanto, para a liberação eficiente de açúcares fermentáveis na etapa de hidrólise enzimática, é necessário um processo prévio de pré-tratamento para modificar a estrutura e composição do material. Neste contexto, no presente trabalho a cavitação hidrodinâmica (CH) foi proposta como uma nova e promissora alternativa para o pré-tratamento do bagaço de cana-de-açúcar. Em uma primeira etapa, as variáveis concentração de NaOH, relação sólido/líquido (S/L) e tempo de processo foram otimizadas no pré-tratamento assistido por CH. Em condições otimizadas (0,48 mol/L de NaOH, 4,27% de relação S/L e 44,48 min), elevados valores de remoção de lignina (60,4%) e digestibilidade enzimática da fração de celulose (97,2%) foram obtidos. Com base nesses resultados, novas variáveis (pressão à montante, temperatura e concentração de álcali) foram incluídas para avaliação em uma segunda etapa do estudo com o objetivo de reduzir o tempo de pré-tratamento com CH. Neste caso, a temperatura e a concentração de álcalis foram as mais importantes na remoção de lignina e influenciaram na hidrólise das frações carboidrato da biomassa pré-tratada. Não houve diferença significativa na eficiência do pré-tratamento em 20 e 30 minutos de tempo de processo nas melhores condições (70 ° C, 3 bar de pressão a montante e 0,3 mol/L de NaOH). A influência do adimensional -número de cavitação? também foi avaliada em dois níveis (0,017 e 0,048), resultando em maior eficiência usando o número de cavitação mais baixo, que foi obtido usando placa de orifício com 16 furos (1 mm de diâmetro). Usando estas condições otimizadas e menor temperatura (60 ° C ao invés de 70 ° C) para evitar a formação de espuma quando o licor negro é reutilizado, outros álcalis (Ca (OH)2, Na2CO3, KOH) foram avaliados em combinação com CH e comparados com o uso de NaOH. Conversões enzimáticas elevadas das frações carboidrato foram observadas em material pré-tratado utilizando KOH-CH e NaOH-CH; além disso, o licor negro de NaOH foi reutilizado em 10 bateladas sequenciais. As biomassas pré-tratadas com licor negro reutilizado e fresco foram misturadas e utilizadas em processo de sacarificação e fermentação simultâneas (SSF) em reatores de coluna interligados, resultando em 62,33% de hidrólise das frações carboidrato e 17,26 g/L de produção de etanol (0,48 g de etanol/g de glicose e xilose consumidos). Finalmente, a adição de agente oxidante (H2O2) no processo alcalino-CH foi otimizado. Nas condições selecionadas (0,29 mol/L de NaOH, 0,78% v/v de H2O2 e 9,8 min), 95,43% e 81,34% de rendimento de hidrólise enzimática das frações de celulose e hemicelulose, respectivamente, foram obtidos utilizando 5% de carregamento de sólidos (S/L) no processo de hidrólise. Quando foi utilizado reator de coluna de leito fixo com 20% de S/L, atingiu-se 74,7% de rendimento de hidrólise de celulose. Os açúcares presentes no hidrolisado também foram fermentados em etanol em um reator de coluna de bolhas, resultando em um valor de rendimento de 0,49 g/g e 0,68 g/L.h de produtividade. Analisando-se os resultados de uma forma global, demonstrou-se que a CH é uma tecnologia promissora para acelerar o tempo de pré-tratamento em condições amenas, mostrando vantagens como simplicidade do sistema e possibilidade de aplicação em escala industrial.
44
SWANSON, LUKE A. "A DETAILED EXAMINATION OF THE PRESSURE PRODUCED BY A HYDRODYNAMIC RAM EVENT." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1195587339.
Full text
45
Diaz, Mario Alfonso. "High-Frequency Ultrasound Drug Delivery and Cavitation." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1050.
Full textAbstract:
The viability of a drug delivery system which encapsulates chemotherapeutic drugs (Doxorubicin) in the hydrophobic core of polymeric micelles and triggers release by ultrasound application was investigated at an applied frequency of 500 kHz. The investigation also included elucidating the mechanism of drug release at 70 kHz, a frequency which had previously been shown to induce drug release. A fluorescence detection chamber was used to measure in vitro drug release from both Pluronic and stabilized micelles and a hydrophone was used to monitor bubble activity during the experiments. A threshold for release between 0.35 and 0.40 in mechanical index was found at 70 kHz and shown to correspond with the appearance of the subharmonic signal in the acoustic spectrum. Additionally, drug release was found to correlate with increase in subharmonic emission. No evidence of drug release or of the subharmonic signal was detected at 500 kHz. These findings confirmed the role of cavitation in ultrasonic drug release from micelles. A mathematical model of a bubble oscillator was solved to explore the differences in the behavior of a single 10 um bubble under 70 and 500 kHz ultrasound. The dynamics were found to be fundamentally different; the bubble follows a period-doubling route to chaos at 500 kHz and an intermittent route to chaos at 70 kHz. It was concluded that this type of "intermittent subharmonic" oscillation is associated with the apparent drug release. This research confirmed the central role of cavitation in ultrasonically-triggered drug delivery from micelles, established the importance of subharmonic bubble oscillations as an indicator, and expounded the key dynamic differences between 70 and 500 kHz ultrasonic cavitation.
46
Schröder, Thorben Hans Jürgen [Verfasser]. "Advanced computational aeroacoustics based on hydrodynamic/acoustic splitting / Thorben Hans Jürgen Schröder." Düren : Shaker, 2019. http://d-nb.info/1196492409/34.
Full text
47
Berger, Thomas K. "Hydrodynamic properties of air entraining flows : a study using new acoustic techniques /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 1999. http://wwwlib.umi.com/cr/ucsd/fullcit?p9944221.
Full text
48
Schröder, Thorben [Verfasser]. "Advanced computational aeroacoustics based on hydrodynamic/acoustic splitting / Thorben Hans Jürgen Schröder." Düren : Shaker, 2019. http://nbn-resolving.de/urn:nbn:de:101:1-2019100610595768566368.
Full text
49
Čupr, Pavel. "Hydroelastic Response of Hydrofoil Under Cavitation Conditions." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-446789.
Full textAbstract:
Tato disertační práce se zabývá experimentálním a výpočtovým výzkumem přídavných účinků od proudu kapaliny na obtékaný hydraulický profil. Dynamická odezva profilu byla analyzována pro dva typy buzení: buzení odtržením mezní vrstvy a Kármánových vírů a dále buzení pomocí externího budiče připojeného k lopatce. Experimentální měření dynamické odezvy profilu na oba typy buzení bylo provedeno pro lopatku umístěnou v kavitujícím a nekavitujícím proudění. Získané výsledky byly použity pro verifikaci přídavných účinků stanovených s využitím numerického modelování.
50
Walker, Daniel Lloyd Norris. "The influence of blockage and cavitation on the hydrodynamic performance of ice class propellers in blocked flow." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23111.pdf.
Full text