Dissertations / Theses: 'Bubble growth'

1

Robinson, Anthony James Judd R. L. "Bubble growth dynamics in boiling /." *McMaster only, 2003.

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Cyr, David Robert. "Bubble growth behavior in supersaturated liquid solutions." Fogler Library, University of Maine, 2001. http://www.library.umaine.edu/theses/pdf/CyrDR2001.pdf.

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3

Mori, Brian Katsuo. "Studies of bubble growth and departure from artificial nucleation sites." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0009/NQ35258.pdf.

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4

Vidinha, Tania Dos Santos Moreno. "Theoretical and experimental studies of bubble growth at an orifice." Thesis, University of Strathclyde, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275186.

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5

Marshall, Stephen Henry. "Air bubble formation from an orifice with liquid cross-flow." Phd thesis, Faculty of Engineering, 1992. http://hdl.handle.net/2123/5343.

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6

Fan, Jintian. "Bubble growth and starch conversion in extruded and baked cereal systems." Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260706.

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7

Hilton, Matthew. "Rhyolite degassing : an experimental study." Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245574.

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8

Bai, Liping. "Experimental study of bubble growth in Stromboli basalt melts at 1 atmosphere." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101831.

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In order to investigate bubble formation and growth at 1 atmosphere, degassing experiments using a Stromboli basalt with dissolved H2O or H2O + CO2 were performed in a custom furnace on a beamline at the Advanced Photon Source. The glasses were synthesized at 1250°C and 1000 MPa, with ~3.0 wt%, ~5.0 wt%, or ~7.0 wt% H2O or with mixtures of H2O + CO2, ~3.0 wt% H2O and ~440 ppm CO2, ~5.0 wt% H2O and 880 ppm CO2, ~7.0 wt% H2O and ~1480 ppm CO2, then heated on the beamline while recording the bubble growth. The 3D bubble size distributions in the quenched samples were then studied with synchrotron X-ray microtomography.
The experimental results show that bubble nucleation and growth are volatile-concentration dependent. Bubbles can easily nucleate in melts initially containing high volatile concentrations. CO2 has no significant effect on bubble formation and growth because of low CO2 concentrations. Multiple nucleation events occur in most of these degassing samples, and they are more pronounced in more supersaturated melts. Bubble growth is initially controlled by viscosity near glass transition temperatures and by diffusion at higher temperatures where melt viscous relaxation occurs rapidly. Bubble foam forms when bubbles are highly connected due to coalescence, and bubbles begin pop, 10 to 20 seconds after the foam is developed. The degree of bubble coalescence increases with time, and bubble coalescence can significantly change the bubble size distribution. Bubble size distributions follow power-law relations at vesicularities of 1.0% to 65%, and bubble size distributions evolve from power-law relations to exponential relations at vesicularities of 65% to 83%. This evolution is associated with the change from far-from-equilibrium degassing to near-equilibrium degassing.
The experimental results imply that during basaltic eruptions both far-from-equilibrium degassing and near-equilibrium degassing can occur. The far-from-equilibrium degassing generally generates the power-law bubble size distributions whereas the near-equilibrium degassing produces exponential bubble size distributions Bubbles begin to pop when the vesicularities attain 65% to 83%. Bubble expansion in the foam possibly accounts for the mechanism of magma fragmentation.
Afin d'étudier la formation et la croissance de bulle; sous pression d'une atmosphère, desexpériences de dégazage sur un basalte de Stromboli, avec HiO ou H20 + CO2 dissouts,ont été exécutées dans un four pilote sous rayonnement synchrotron à l'APS (AdvancedPhoton Source). Les verres ont été synthétisés à une température de 1250°C et unepression de 1000 MPa, avec des teneurs en eau dissoute de ~ 3.0, ~ 5.0 ou ~ 7.0% (enpoids), et des mélanges H20 + C02 à teneurs de ~ 3.0% H20 (en poids) et 440 ppm CO2,~ 5% H20 et 880 ppm CO2, et de ~ 7.0% H20 et 1480 ppm CO2. La croissance des bullesest enregistrée pendant le chauffage du mélange en utilisant le rayonnement synchrotron.Les distributions tridimensionnelles de la taille des bulles dans les échantillons trempésont été étudiées par microtomographie à rayon X synchrotron.

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Lapeyronie, Octave Serge Christian Marie. "The Brazilian real state market in 2012: robust growth or speculative bubble?" reponame:Repositório Institucional do FGV, 2012. http://hdl.handle.net/10438/10333.

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Rising home prices in Brazil have sparked debate on a possible housing bubble. In light of the credit and housing crisis in the United States, it is fair to question whether or not Brazil’s situation is analogous. Looking at both quantitative and fundamental arguments, we examine the context of the Brazilian housing boom and question its sustainability in the near term. First, home prices tested with basic rental yields and affordability ratios as well an imputed rent model to assess their relative to equilibrium levels. Second, we examine some fundamental factors affecting housing prices – supply and demand, credit and regulation, cultural factors – to find evidence justifying the rising home prices. From these observations, we attempt to draw rational inferences on the likely near future evolution of the Brazilian housing market. While data suggests that home prices are overvalued in comparison to rent levels, there is an evidence of legitimate new housing demand in the rising middle class. A more serious risk may lie in the credit markets in that the Brazilian consumer is already highly leveraged. Nevertheless, we find no evidence suggesting more than a temporary slowdown or correction of home prices.
A forte alta dos imóveis no Brasil nos últimos anos iniciou um debate sobre a possível existência de uma bolha especulativa. Dada a recente crise do crédito nos Estados Unidos, é factível questionar se a situação atual no Brasil pode ser comparada à crise americana. Considerando argumentos quantitativos e fundamentais, examina-se o contexto imobiliário brasileiro e questiona-se a sustentabilidade em um futuro próximo. Primeiramente, analisou-se a taxa de aluguel e o nível de acesso aos imóveis e também utilizou-se um modelo do custo real para ver se o mercado está em equilíbrio o não. Depois examinou-se alguns fatores fundamentais que afetam o preço dos imóveis – oferta e demanda, crédito e regulação, fatores culturais – para encontrar evidências que justificam o aumento dos preços dos imóveis. A partir dessas observações tentou-se chegar a uma conclusão sobre a evolução dos preços no mercado imobiliário brasileiro. Enquanto os dados sugerem que os preços dos imóveis estão supervalorizados em comparação ao preço dos aluguéis, há evidências de uma legítima demanda por novos imóveis na emergente classe média brasileira. Um risco maior pode estar no mercado de crédito, altamente alavancado em relação ao consumidor brasileiro. No entanto, não se encontrou evidências que sugerem mais do que uma temporária estabilização ou correção no preço dos imóveis.

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Li, Weizhong. "A numerical investigation on the behaviour of a rising bubble in a quiescent hot liquid." Thesis, Nottingham Trent University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369237.

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11

Ryan, Amy. "Water solubility and bubble growth dynamics in rhyolitic silicate melts at atmospheric pressure." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/51125.

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This thesis is a high-temperature, low-pressure experimental study that quantifies the temperature-dependence of water (H₂O) solubility in a rhyolitic melt at atmospheric pressure, and assesses the sensitivity of the water exsolution and bubble growth processes to thermodynamic and kinetic parameters. In the investigation of H₂O solubility I defined the magnitude of retrograde solubility (-7.1x10-³ wt% H₂O per 100°C) and estimated the enthalpy and entropy of the H₂O exsolution reaction (ΔH⁰ = +17.8 kJ mol-¹, ΔS⁰ = 107 J K-¹ mol-¹). I also modelled the implications of retrograde solubility for the glass transition temperature (Tg) and outline the potential effect on cooling volcanic bodies at surface- and conduit-relevant pressures if cooling is slow enough to facilitate H2O resorption. In my investigation of bubble growth dynamics and the vesiculation process in my experimental products I recalibrated the estimates of H₂O exsolution enthalpy and entropy (ΔH⁰ = +18.5 kJ mol-¹, ΔS⁰ = 108 J K-¹ mol-¹). Additionally I identified the viscosity (η) dependence of average volumetric growth rate (dV/dt) (log dV/dt = -0.79 log η + 4.95) and have calculated the time to develop 60% porosity for melts of varying viscosities at conduit-relevant pressures that are up to 15% oversaturated with H₂O. By dismantling a complex system and individually investigating the behaviours of dissolved and exsolved H₂O I have developed models that can be used to study volcanic hazards past, present and future.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate

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12

Kumar, Rajneesh. "Solution-gas drive in heavy oil, gas mobility and kinetics of bubble growth." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0019/MQ49679.pdf.

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13

Wickizer, Gabriel Benjamin. "Experimental System Effects on Interfacial Shape and Included Volume in Bubble Growth Studies." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337716075.

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14

Söder, Mats. "Growth and Removal of Inclusions During Ladle Stirring." Licentiate thesis, KTH, Materials Science and Engineering, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1281.

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The growth and removal of inclusions in stirred ladles hasbeen studied. First, the importance of different growthmechanisms suggested in the literature were studied. Simulationresults from a fundamental model of an induction-stirred ladlehave been used as input in the calculations. Based on thegrowth calculations it was concluded that four of the growthmechanisms need not to be considered since they contribute solittle: i) diffusion of oxygen and aluminum to the inclusionsurface, ii) diffusion coalescence, iii) Brown motioncollision, and iv) laminar shear collision. The majorcontributor to inclusion growth is turbulent collision. Growthdue to Stoke's collisions is also somewhat important if largedifferences among inclusion sizes exist.

Growth of inclusions in gas stirred ladles was studied usinga similar approach as the one for induction stirred ladles, butwith use of simulation results from a fundamental mathematicalmodel of a gas-stirred ladle. Similarly to what was found inthe case of induction stirring, it was found that turbulentcollisions and Stokes collisions appeared to be the majormechanisms for inclusion growth. The contribution of laminarshear collisions to growth was deemed negligible compared tothat of turbulent collisions.

For the gas stirred ladle different removal mechanisms werealso studied, based on input data from a mathematical model ofa gas-stirred ladle. It was found that different modelssuggested to predict the inclusion removal due to bubbleflotation gave very different results. Also, all models assumeda spherical shape of the gas bubbles, which was found to beless realistic. Therefore, a new model for inclusion removal byspherical cap bubble flotation was developed. In the newcalculations, the most important mechanisms of inclusionremoval were found to be removal to the top slag and removal bybubble flotation, assuming spherical-cap bubbles and planecontact. When the bubbles were assumed to be spherical,resulting removal rates were lower than when they were assumedto be spherical caps. Based on these results it is concludedthat more research is needed to obtain a better understandingof the importance of bubble flotation on inclusion removal.Experiments are clearly needed to determine which modelconcepts produce predictions in best agreement withcorresponding data from actual steelmaking processes.

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15

Kalaikadal, Deepak Saagar. "A Parametric Investigation of Gas Bubble Growth and Pinch-Off Dynamics from Capillary-Tube Orifices in Liquid Pools." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342543385.

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16

Bitlloch, Puigvert Pau. "Turbulent bubble suspensions and crystal growth in microgravity. Drop tower experiments and numerical simulations." Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/96295.

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We study the formation and spreading of a turbulent jet of bubbles in microgravity. This has been analyzed from the recordings obtained in previous experimental campaigns of microgravity. Results have been compared with a simplified model of passive bubbles, in which bubbles are advected by the mean flow and dispersed due to the local degree of turbulence at each point of the jet. Thanks to the expertise obtained with this part of the thesis, we have designed and built a new experiment that has been used 36 times in the 4.7 s drop tower of ZARM (“Center of Applied Space Technology and Microgravity”) in Bremen. With this experiment we have obtained, for the first time in history, a monodisperse suspension of bubbles, within a turbulent flow, in microgravity. From the resulting measures we have characterized the relaxation time of pseudo-turbulence (previously generated due to the effect of buoyancy forces upon the injected bubbles in normal gravity conditions). We have also studied the interaction between bubbles and the turbulent medium. Results have been compared with Lattice-Boltzmann simulations of the flow. On the other hand, we have also studied the impact of residual gravitational vibrations (known as g-jitters) upon the quality of semiconductors solidified in microgravity. The quality of the resulting crystals has been studied from the analysis of the inhomogeneities in their dopant concentration. This study has been based entirely on simulations, but g-jitters have been modeled from acceleration signals measured in real space missions.
En la present tesi s’estudia, en primer lloc, la formació d’un doll turbulent de bombolles en condicions de microgravetat. Aquest ha sigut analitzat a partir del tractament de les gravacions obtingudes per altres investigadors en experiments de microgravetat. Els resultats s’han comparat amb un model simplificat de bombolles passives, en el que aquestes són arrossegades pel flux mitjà i, simultàniament, són dispersades degut al grau local de turbulència a cada punt. Gràcies a la experiència obtinguda en aquest anàlisi, s’ha dissenyat un nou experiment que ha sigut utilitzat en 36 llançaments de la torre de caiguda de 4.7 segons del ZARM (“Centre de Tecnologia Espacial Aplicada i Microgravetat”) a Bremen. Amb aquest experiment s’ha aconseguit, per primera vegada a la història, una suspensió monodispersa de bombolles, en el sí d’un flux turbulent, en condicions de microgravetat. A partir dels resultats obtinguts, s’ha caracteritzat per primera vegada el temps de relaxació de la pseudo-turulència (generada prèviament degut a l’efecte de les forces de flotació sobre les bombolles injectades en gravetat normal). També s’ha estudiat l’efecte causat per les bombolles en el medi turbulent. Els resultats han sigut comparats amb simulacions realitzades mitjançant el model de Lattice-Boltzmann. Per altra banda, s’ha estudiat també l’efecte que tenen les vibracions gravitatòries residuals sobre la qualitat de semiconductors solidificats en microgravetat. S’ha analitzat la qualitat dels cristalls resultants a partir de l’estudi de les inhomogeneïtats en la concentració de dopant. Aquest estudi ha sigut realitzat íntegrament a base de simulacions, però s’han establert els paràmetres dominants del soroll gravitatori a partir de valors mesurats en missions espacials reals.

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Li, Linyu. "Economic growth in Sweden, 2000-2010 : The dot-com bubble and the financial crisis." Thesis, Högskolan Dalarna, Nationalekonomi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:du-14883.

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Economic growth is the increase in the inflation-adjusted market value of the goods and services produced by an economy over time. The total output is the quantity of goods or servicesproduced in a given time period within a country. Sweden was affected by two crises during the period 2000-2010: a dot-com bubble and a financial crisis. How did these two crises affect the economic growth? The changes of domestic output can be separated into four parts: changes in intermediate demand, final domestic demand, export demand and import substitution. The main purpose of this article is to analyze the economic growth during the period 2000-2010, with focus on the dot-com bubble in the beginning of the period 2000-2005, and the financial crisis at the end of the period 2005-2010. The methodology to be used is the structural decomposition method. This investigation shows that the main contributions to the Swedish total domestic output increase in both the period 2000-2005 and the period 2005-2010 were the effect of domestic demand. In the period 2005-2010, financial crisis weakened the effect of export. The output of the primary sector went from a negative change into a positive, explained mainly by strong export expansion. In the secondary sector, export had most effect in the period 2000-2005. Nevertheless, domestic demand and import ratio had more effect during the financial crisis period. Lastly, in the tertiary sector, domestic demand can mainly explain the output growth in the whole period 2000-2010.

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McIntosh, Iona Margaret. "Bubble growth and resorption in magma : insights from dissolved water distributions in volcanic glass." Thesis, Durham University, 2013. http://etheses.dur.ac.uk/8505/.

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Volcanic eruptions are driven by the growth of gas bubbles in magma, which grow and shrink as volatile species exsolve from and dissolve back into the melt in response to changes in the local environment, particularly in pressure and temperature. This movement of volatiles, particularly water, is recorded in the glass around vesicles and recent studies have used this record to interpret natural samples. This thesis investigates the processes that control bubble growth and resorption in magma, by measuring the distribution of dissolved H2O in experimentally-vesiculated volcanic glasses. H2O concentration profiles obtained using SIMS-calibrated BSEM imaging and H2O speciation data obtained using FTIR spectroscopy, are interpreted in the context of the known pressure and temperature history of the samples. Samples are found to have undergone partial bubble resorption during the quench to glass at the end of experiments, as a result of increasing H2O solubility with decreasing temperature. Analysis of the lengthscale and timing of the resulting H2O concentration profiles demonstrates that the majority of resorption occurs above the glass transition. This quench resorption is associated with a reduction in bubble volumes which creates characteristic textures, such as buckled melt films between adjacent vesicles and reoriented cracks around resorption halos. Highly disequilibrium H2O speciation ratios within resorption halos are found to be diagnostic of quench resorption and can preserve evidence of pre-quench bubble growth Quench resorption can increase sample H2O concentrations and H2Om:OH ratios and reduce bubble volumes and sample porosities. Studies based on these parameters must therefore consider the potential impact of quench resorption, which is expected to be greatest for samples with high H2O concentrations, slow quench and low initial sample porosities. H2O speciation data offer a way to investigate these impacts in unconstrained natural samples and could provide a tool for forensic interrogation of their eruptive history.

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19

Deodhar, Anirudh M. "Computational Study of Adiabatic Bubble Growth Dynamics from Submerged Orifices in Aqueous Solutions of Surfactants." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337100942.

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20

Gokhale, Omkar S. "Experimental Study of Chamber Volume Effect on Bubble Growth from Orifice Plates Submerged in Liquid Pools." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1554217036036588.

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21

Meder, Stephan. "Study on bubble growth rate in a single microchannel heat exchanger with high-speed CMOS-camera." Zürich : ETH, Eidgenössische Technische Hochschule Zürich, Department of Mechanical and Process Engineering, 2007. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=335.

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22

Smith, Ian Heaton. "A study of foam stability and the kinetics of bubble growth in glass at high temperature." Thesis, University of Salford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359882.

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23

Bradley, Aoibhinn Maire. "Analysis of nonlinear spatio-temporal partial differential equations : applications to host-parasite systems and bubble growth." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24405.

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The mountain hare population currently appears to be under threat in Scotland. The natural population cycles exhibited by this species are thought to be, at least in part, due to its infestation by a parasitic worm. We seek to gain an understanding of these population dynamics through a mathematical model of this system and so determine whether low population levels observed in the field are a natural trough associated with this cycling, or whether they point to a more serious decline in overall population densities. A generic result, that can be used to predict the presence of periodic travelling waves (PTWs) in a spatially heterogeneous system, is reported. This result is applicable to any two population host-parasite system with a supercritical Hopf bifurcation in the reaction kinetics. Application of this result to two examples of well studied host-parasite systems, namely the mountain hare and the red grouse systems, predicts and illustrates, for the first time, the existence of PTWs as solutions for these reaction advection diffusion schemes. One method for designing bone scaffolds involves the acoustic irradiation of a reacting polymer foam resulting in a final sample with graded porosity. The work in this thesis represents the first attempt to derive a mathematical model, for this empirical method, in order to inform the experimental design and tailor the porosity profile of samples. We isolate and study the direct effect of the acoustic pressure amplitude as well as its indirect effect on the reaction rate. We demonstrate that the direct effect of the acoustic pressure amplitude is negligible due to a high degree of attenuation by the sample. The indirect effect, on reaction rate, is significant and the standing wave is shown to produce a heterogeneous bubble size distribution. Several suggestions for further work are made.

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Manoharan, Sanjivan. "Bubble Growth from Submerged Orifices: Investigating the Influence of Surface Wettability, Liquid Properties, and Design Conditions." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479819854513389.

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Dethloff, Christian [Verfasser], and Jarir [Akademischer Betreuer] Aktaa. "Modeling of Helium Bubble Nucleation and Growth in Neutron Irradiated RAFM Steels / Christian Dethloff ; Betreuer: Jarir Aktaa." Karlsruhe : KIT Scientific Publishing, 2012. http://d-nb.info/1185581049/34.

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Samaroo, Randy. "The effects of geometric, flow, and boiling parameters on bubble growth and behavior in subcooled flow boiling." Thesis, The City College of New York, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10159915.

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Air bubble injection and subcooled flow boiling experiments have been performed to investigate the liquid flow field and bubble nucleation, growth, and departure, in part to contribute to the DOE Nuclear HUB project, Consortium for Advanced Simulation of Light Water Reactors (CASL). The main objective was to obtain quantitative data and compartmentalize the many different interconnected aspects of the boiling process — from the channel geometry, to liquid and gas interactions, to underlying heat transfer mechanisms.

The air bubble injection experiments were performed in annular and rectangular geometries and yielded data on bubble formation and departure from a small hole on the inner tube surface, subsequent motion and deformation of the detached bubbles, and interactions with laminar or turbulent water flow. Instantaneous and ensemble- average liquid velocity profiles have been obtained using a Particle Image Velocimetry technique and a high speed video camera. Reynolds numbers for these works ranged from 1,300 to 7,700.

Boiling experiments have been performed with subcooled water at atmospheric pres- sure in the same annular channel geometry as the air injection experiments. A second flow loop with a slightly larger annular channel was constructed to perform further boiling experiments at elevated pressures up to 10 bar. High speed video and PIV measurements of turbulent velocity profiles in the presence of small vapor bubbles on the heated rod are presented. The liquid Reynolds number for this set of experiments ranged from 5,460 to 86,000. It was observed that as the vapor bubbles are very small compared to the injected air bubbles, further experiments were performed using a microscopic objective to obtain higher spatial resolution for velocity fields near the heated wall. Multiple correlations for the bubble liftoff diameter, liftoff time and bub- ble history number were evaluated against a number of experimental datasets from previous works, resulting in a new proposed correlations that account for fluid prop- erties that vary with pressure, heat flux, and variations in geometry.

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Romanchuk, Bradley J. "Computational Modeling of Bubble Growth Dynamics in Nucleate Pool Boiling for Pure Water and Aqueous Surfactant Solutions." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406809980.

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Zajíc, Jiří. "Dot-com bubble - faktor hospodářského úspěchu USA v 90. letech 20. století?" Master's thesis, Vysoká škola ekonomická v Praze, 2014. http://www.nusl.cz/ntk/nusl-201947.

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This thesis deals with the impacts of information and communication technology investment surge on USA economic growth in the 1990s. Besides others, rapid development of these technologies also led to the creation of a stock market bubble, which affected the expansion phase of the economic cycle. Its burst in 2000-2001 resulted in economic slow-down and end of the longest recorded economic expansion in the history of the United States. Main part of the thesis discusses the benefits of information technology for economy and further evaluates the role of the speculative bubble in the development of consumption and investment expenditures. The thesis results suggest that the increase in capital intensity and sharp stock market price inflation significantly accelerated the dynamics of the economic growth in the second half of the described cycle.

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Jani, Parth K. "Experimental Investigation of Influence of Liquid Physicochemical Properties on Adiabatic Bubble Growth from Submerged Capillary Orifice under Constant Flow Rate Conditions." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1623169715636338.

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30

Potgieter, Jarryd. "Numerical investigation on the effect of gravitational orientation on bubble growth during flow boiling in a high aspect ratio microchannel." Diss., University of Pretoria, 2019. http://hdl.handle.net/2263/79642.

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Recent technological developments, mostly in the fields of concentrated solar power and microelectronics, have driven heat transfer requirements higher than current heat exchangers are capable of producing. Processing power is increasing, while processor size simultaneously decreases and the heat flux requirements of concentrating solar power plants are being driven up by the high temperatures that produce the best thermal efficiency. Heat transfer in microchannels, specifically when utilising flow boiling, has been shown to produce significantly higher heat fluxes than their macro-scale counterparts and could have a large impact on many industrial fields. This high heat transfer characteristic is caused by a number of factors, including the large difference between the sensible and latent heat of the working fluid and the evaporation of a thin liquid film that forms between the microchannel walls and the vapour bubbles. These phenomena occur at incredibly small scales. Flow visualisations, temperature and pressure measurements are therefore difficult to obtain. Many experiments that cover a wide range of microchannel sizes, shapes and orientations, and utilise different working fluids and heat fluxes have been reported. However, the correlations between confined boiling, heat flux and pressure drop have mostly been produced for macro-scale flow. Many different criteria have been developed to distinguish the macro scale from the micro scale, but the general consensus is that macro-scale heat transfer correlations do not perform well when used in the micro scale. Heat transfer correlations are typically created by performing physical experiments over a wide range of parameters and then quantifying the effect that varying these parameters has on the performance of the system. The small scale and high complexity of microchannel-based heat exchangers make visualising the flow within them difficult and inaccurate because both the working fluid and the microchannel walls distort light. The use of numerical modelling via computational fluid dynamics software allows phenomena that occur within the channel to be simulated, which provides valuable insight into how rapid bubble growth affects the surrounding fluid, which can lead to the design of better heat exchangers. This study focused on numerically modelling the growth of a single bubble during the flow boiling of FC-72 in a microchannel with a hydraulic diameter of 0.9 mm and an aspect ratio of 10. The numerical domain was limited to a 10 mm section of the microchannel where bubble nucleation and detachment were observed in an experimental study on a similar microchannel setup. The high cost of 3D simulations was offset by an interface-tracking mesh refinement method, which refined cells not only at the interface, but also a set distance on either side of the interface. To focus on the effects of gravity, a simplified approach is used, which isolates certain phenomena. Density gradients, material roughness and multiple bubble interaction are ignored so that the effects of buoyancy and bubble detachment can be analysed. Simulations are first performed in a 2D section through the centre of the microchannel, and then in the full 3D domain. In both the 3D numerical and experimental cases (Meyer et al., 2020), the bottom heated case had the lowest maximum temperature and the highest heat transfer characteristics, which were influenced by the detachment of the bubble from the heated surface. This observation indicates that the gravitational orientation of the channel can have a significant effect on the heat transfer characteristics of microchannel-based heat exchangers, and that more investigation is required to characterise the extent of this effect.
Dissertation (MEng)--University of Pretoria, 2019.
Mechanical and Aeronautical Engineering
MEng
Unrestricted

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31

Kalaikadal, Deepak Saagar. "Investigation of Bubble Dynamics in Pure Liquids and Aqueous Surfactant / Polymer Solutions Under Adiabatic and Diabatic Conditions." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1525167893347615.

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32

Franz, Benjamin [Verfasser], Peter [Akademischer Betreuer] Stephan, and Catherine [Akademischer Betreuer] Colin. "Numerical simulation of bubble growth in subcooled pool and flow boiling under microgravity conditions / Benjamin Franz ; Peter Stephan, Catherine Colin." Darmstadt : Universitäts- und Landesbibliothek, 2021. http://d-nb.info/1237050197/34.

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33

Sugrue, Rosemary M. "The effects of orientation angle, subcooling, heat flux, mass flux, and pressure on bubble growth and detachment in subcooled flow boiling." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76974.

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Thesis (S.M. and S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 119-122).
The effects of orientation angle, subcooling, heat flux, mass flux, and pressure on bubble growth and detachment in subcooled flow boiling were studied using a high-speed video camera in conjunction with a two-phase flow loop that can accommodate a wide range of flow conditions. Specifically, orientation angles of 0' (downward-facing horizontal), 30°, 45°, 60°, and 90° (vertical); mass flux values of 250, 300, 350, and 400 kg/m²s, with corresponding Froude numbers in the range of 0.42 to 1.06; pressures of 101 (atmospheric), 202, and 505 kPa; two values of subcooling (10°C to 20°C); and two heat fluxes (0.05 to 0.10 MW/m²) were explored. The combination of the test section design, high-speed video camera, and LED lighting results in high accuracy (order of 20 microns) in the determination of bubble departure diameter. The data indicate that bubble departure diameter increases with increasing heat flux, decreasing mass flux, decreasing levels of subcooling, and decreasing pressure. Also, bubble departure diameter increases with decreasing orientation angle, i.e. the largest bubbles are found to detach from a downward-facing horizontal surface. The mechanistic bubble departure model of Klausner et al. and its recent modification by Yun et al. were found to correctly predict all the observed parametric trends, but with large average errors and standard deviation: 35.7+/-24.3% for Klausner's and 16.6±11.6% for Yun's. Since the cube of the bubble departure diameter is used in subcooled flow boiling heat transfer models, such large errors are clearly unacceptable, and underscore the need for more accurate bubble departure diameter models to be used in CFD.
by Rosemary M. Sugrue.
S.M.and S.B.

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34

Diana, Antoine. "Liquid-vapour phase change : nucleate boiling of pure fluid and nanofluid under different gravity levels." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/65842/1/Antoine_Diana_Thesis.pdf.

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This research was a step towards the comprehension of the nano-particles interaction with bubbles created during boiling. It was aimed at solving the controversies of whether the heat transfer is enhanced or deteriorated during the boiling of the nanofluid. Experiments were conducted in normal gravity and reduced gravity environments on-board the European Space Agency Parabolic Flight Program. The local modification of the thermo-physical properties of the fluid and moreover the modification experienced in the liquid microlayer under the growing vapour bubble were the dominant factors in explaining the mechanisms of the boiling behaviour of the nanofluid.

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35

Dib, Jawhar Marie-Claire. "Study of the Coalescence Mechanisms during Silicone Foaming." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10051.

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Le principe d’élaboration des mousses de silicone est basé sur une compétition entre deux réactions mettant en jeu les fonctions hydrogénosilane portées par le polymère précurseur : la première provoque le dégagement d’un gaz (à l’origine de la formation des cellules) et la deuxième, l’hydrosilylation, bien connue et maîtrisée dans les silicones, conduit à la réticulation du milieu réactionnel. De ce fait, le contrôle des propriétés finales de la mousse nécessite la maîtrise de ces deux cinétiques de synthèse du gaz et de réticulation. D’autre part, les propriétés finales des mousses (type de porosité, densité apparente,…) dépendent également de la rhéologie (propriétés élongationnelles adéquates) ainsi que des charges ajoutées à la formulation. L’étude de la nucléation et la croissance cellulaire a été faite sous microscope optique. Les résultats montrent que le phénomène fondamental contrôlant la croissance des bulles est la coalescence. Sous l’influence couplée des effets de surface et viscoélastiques, les bulles se rapprochent et se déforment pour donner naissance à une forme intermédiaire avant d’atteindre leur forme finale. D’autre part, on a montré que l’air initialement dissous dans les formulations ainsi que l’air introduit par agitation permettent de réduire l’effet de peau, d’avoir une distribution de taille homogène et une meilleure structure cellulaire. D'autres facteurs ont également été étudiés dans le but de rendre la distribution de taille plus homogène et améliorer certaines propriétés
A foam sample is assumed to be a set of bubbles embedded into a polymeric matrix with an initial gas overpressure. Silicon foams are produced by a competition between two reactions involving the hydrogenosilane functions carried by the polymer precursor: the first reaction generates gas (initiating cell formation) while the other one, hydrosilylation, well known and controlled in silicon, leads to the crosslinking of the rising foam. Thus, obtaining enhanced foam properties requires a good balance between two reactions, crosslinking and gas generation. On the other hand, the final characteristics of the foam (porosity, bulk density…) largely depend on the rheology of the mix (appropriate elongational properties) as well as the added fillers. Nucleation and cell growth were carried out under optical microscopy. The experiments show that the main phenomenon controlling cell growth is bubble coalescence. Due to the surface effects and the viscoelastic properties, bubbles approach from each other and get deformed giving birth to an intermediate shape before reaching their final geometry. Many parameters have direct effect on foam properties. In fact, dissolved gas in formulas as well as the air introduced during manual mixing, reduce the skin effect and guarantee a homogeneous cell size distribution and a better foam structure. Other factors have also been studied in order to render size distribution more homogeneous and improve certain properties

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36

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.

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Co-rotating twin-screw extruders are unique and versatile machines that are used widely in the plastics and food processing industries. Due to the large number of operating variables and design parameters available for manipulation and the complex interactions between them, it cannot be claimed that these extruders are currently being optimally utilised. The most significant improvement to the field of twin-screw extrusion would be through the provision of a generally applicable dynamic process model that is both computationally inexpensive and accurate. This would enable product design, process optimisation and process controller design to be performed cheaply and more thoroughly on a computer than can currently be achieved through experimental trials. This thesis is divided into three parts: dynamic modelling, measurement and control. The first part outlines the development of a dynamic model of the extrusion process which satisfies the above mentioned criteria. The dynamic model predicts quasi-3D spatial profiles of the degree of fill, pressure, temperature, specific mechanical energy input and concentrations of inert and reacting species in the extruder. The individual material transport models which constitute the dynamic model are examined closely for their accuracy and computational efficiency by comparing candidate models amongst themselves and against full 3D finite volume flow models. Several new modelling approaches are proposed in the course of this investigation. The dynamic model achieves a high degree of simplicity and flexibility by assuming a slight compressibility in the process material, allowing the pressure to be calculated directly from the degree of over-fill in each model element using an equation of state. Comparison of the model predictions with dynamic temperature, pressure and residence time distribution data from an extrusion cooking process indicates a good predictive capability. The model can perform dynamic step-change calculations for typical screw configurations in approximately 30 seconds on a 600 MHz Pentium 3 personal computer. The second part of this thesis relates to the measurement of product quality attributes of extruded materials. A digital image processing technique for measuring the bubble size distribution in extruded foams from cross sectional images is presented. It is recognised that this is an important product quality attribute, though difficult to measure accurately with existing techniques. The present technique is demonstrated on several different products. A simulation study of the formation mechanism of polymer foams is also performed. The measurement of product quality attributes such as bulk density and hardness in a manner suitable for automatic control is also addressed. This is achieved through the development of an acoustic sensor for inferring product attributes using the sounds emanating from the product as it leaves the extruder. This method is found to have good prediction ability on unseen data. The third and final part of this thesis relates to the automatic control of product quality attributes using multivariable model predictive controllers based on both direct and indirect control strategies. In the given case study, indirect control strategies, which seek to regulate the product quality attributes through the control of secondary process indicators such as temperature and pressure, are found to cause greater deviations in product quality than taking no corrective control action at all. Conversely, direct control strategies are shown to give tight control over the product quality attributes, provided that appropriate product quality sensors or inferential estimation techniques are available.

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37

Benage, Mary Catherine. "The thermal evolution and dynamics of pyroclasts and pyroclastic density currents." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53962.

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The thermal evolution of pyroclastic density currents (PDCs) is the result of entrainment of ambient air, particle concentration, and initial eruptive temperature, which all impact PDC dynamics and their hazards, such as runout distance. The associated hazards and opaqueness of PDCs make it impossible for in-situ entrainment efficiencies or concentration measurements that would provide critical information on the thermal evolution and physical processes of PDCs. The thermal evolution of explosive eruptive events such as volcanic plumes and pyroclastic density currents (PDCs) is reflected in the textures of the material they deposit. A multiscale model is developed to evaluate how the rinds of breadcrust bombs can be used as a unique thermometer to examine the thermal evolution of PDCs. The multiscale, integrated model examines how bubble growth, pyroclast cooling, and dynamics of PDC and projectile pyroclasts form unique pyroclast morphology. Rind development is examined as a function of transport regime (PDC and projectile), transport properties (initial current temperature and current density), and pyroclast properties (initial water content and radius). The model reveals that: 1) rinds of projectile pyroclasts are in general thicker and less vesicular than those of PDC pyroclasts; 2) as the initial current temperature decreases due to initial air entrainment, the rinds on PDC pyroclasts progressively increase in thickness; and 3) rind thickness increases with decreasing water concentration and decreasing clast radius. Therefore, the modeled pyroclast’s morphology is dependent not only on initial water concentration but also on the cooling rate, which is determined by the transport regime. The developed secondary thermal proxy is then applied to the 2006 PDCs from the Tungurahua eruption to constrain the entrainment efficiency and thermal evolution of PDCs. A three-dimensional multiphase Eulerian-Eulerian-Lagrangian (EEL) model is coupled to topography and field data such as paleomagnetic data and rind thicknesses of collected pyroclasts to study the entrainment efficiency and thus the thermal history of PDCs at Tungurahua volcano, Ecuador. The modeled results that are constrained with observations and thermal proxies demonstrate that 1) efficient entrainment of air to the upper portion of the current allows for rapid cooling, 2) the channelized pyroclastic density currents may have developed a stable bed load region that was inefficient at cooling and 3) the PDCs had temperatures of 600-800K in the bed load region but the upper portion of the currents cooled down to ambient temperatures. The results have shown that PDCs can be heterogeneous in particle concentration, temperature, and dynamics and match observations of PDCs down a volcano and the thermal proxies. Lastly, the entrainment efficiencies of PDCs increases with increasing PDC temperature and entrainment varies spatially and temporally. Therefore, the assumption of a well-mixed current with a single entrainment coefficient cannot fully solve the thermal evolution and dynamics of the PDC.

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38

Elsey, Justin Rae. "Dynamic Modelling, Measurement and Control of Co-rotating Twin-Screw Extruders." Thesis, The University of Sydney, 2002. http://hdl.handle.net/2123/687.

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Co-rotating twin-screw extruders are unique and versatile machines that are used widely in the plastics and food processing industries. Due to the large number of operating variables and design parameters available for manipulation and the complex interactions between them, it cannot be claimed that these extruders are currently being optimally utilised. The most significant improvement to the field of twin-screw extrusion would be through the provision of a generally applicable dynamic process model that is both computationally inexpensive and accurate. This would enable product design, process optimisation and process controller design to be performed cheaply and more thoroughly on a computer than can currently be achieved through experimental trials. This thesis is divided into three parts: dynamic modelling, measurement and control. The first part outlines the development of a dynamic model of the extrusion process which satisfies the above mentioned criteria. The dynamic model predicts quasi-3D spatial profiles of the degree of fill, pressure, temperature, specific mechanical energy input and concentrations of inert and reacting species in the extruder. The individual material transport models which constitute the dynamic model are examined closely for their accuracy and computational efficiency by comparing candidate models amongst themselves and against full 3D finite volume flow models. Several new modelling approaches are proposed in the course of this investigation. The dynamic model achieves a high degree of simplicity and flexibility by assuming a slight compressibility in the process material, allowing the pressure to be calculated directly from the degree of over-fill in each model element using an equation of state. Comparison of the model predictions with dynamic temperature, pressure and residence time distribution data from an extrusion cooking process indicates a good predictive capability. The model can perform dynamic step-change calculations for typical screw configurations in approximately 30 seconds on a 600 MHz Pentium 3 personal computer. The second part of this thesis relates to the measurement of product quality attributes of extruded materials. A digital image processing technique for measuring the bubble size distribution in extruded foams from cross sectional images is presented. It is recognised that this is an important product quality attribute, though difficult to measure accurately with existing techniques. The present technique is demonstrated on several different products. A simulation study of the formation mechanism of polymer foams is also performed. The measurement of product quality attributes such as bulk density and hardness in a manner suitable for automatic control is also addressed. This is achieved through the development of an acoustic sensor for inferring product attributes using the sounds emanating from the product as it leaves the extruder. This method is found to have good prediction ability on unseen data. The third and final part of this thesis relates to the automatic control of product quality attributes using multivariable model predictive controllers based on both direct and indirect control strategies. In the given case study, indirect control strategies, which seek to regulate the product quality attributes through the control of secondary process indicators such as temperature and pressure, are found to cause greater deviations in product quality than taking no corrective control action at all. Conversely, direct control strategies are shown to give tight control over the product quality attributes, provided that appropriate product quality sensors or inferential estimation techniques are available.

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39

Bogojević, Dario. "Flow boiling and two-phase flow instabilities in silicon microchannel heat sinks for microsystems cooling." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/3791.

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Flow boiling in microchannels, while very promising as a cooling technology in electronics thermal management, is still a subject being explored that requires further investigation. Before applying this technology for high heat flux computer chip cooling, challenging issues such as fully understanding boiling mechanisms in confined spaces, extending and stabilising the nucleate boiling regime, suppressing flow boiling instabilities, maintaining uniform flow distribution among microchannels, have to be addressed. If flow boiling is to be used as a thermal management method for high heat flux electronics it is necessary to understand the behaviour of a non-uniform heat distribution, which is typically the case observed in a real operating computer chip. In this study, flow boiling of deionised water in a silicon microchannel heat sink under uniform and non-uniform heating has been investigated with particular attention to flow boiling instabilities. An experimental system was designed and constructed to carry out the experimental investigations. The experimental heat sink consisting of forty parallel rectangular microchannels with 194 μm hydraulic diameter together with integrated inlet and outlet manifold was fabricated on a silicon wafer using inductive coupled plasma dry etching, in conjunction with photolithographic techniques. A design with integrated temperature sensors made from a thin nickel film allows local temperature measurements with a much faster response time and smaller thermal resistance as compared to temperature measurements using thermocouples. The integrated heater was designed to enable either uniform or non-uniform heating (hotspot investigation) with a low thermal resistance between the heater and the channels. Numerical simulations for single phase flow in adiabatic conditions were used to assist the design of the manifold geometry in the microchannels heat sink. Microfabricated temperature sensors were used together with simultaneous high speed imaging in order to obtain a better insight related to temperature fluctuations caused by two-phase flow instabilities under uniform and non-uniform heating. Two types of two-phase instabilities with flow reversal were identified and classified into flow stability maps. The effect of inlet water temperature on flow boiling instabilities was experimentally studied, with the influence of different subcooling conditions on the magnitude of temperatures as well as the influence on temperature uniformity over the heat sink being assessed. The effect of various hotspot locations on flow boiling instabilities has been investigated, with hotspots located in different positions along the heat sink. Bubble growth and departure size have been experimentally investigated. The results of this study demonstrate that bubble growth in microchannels is different from that in macroscale channels. Furthermore, the effects of bubble dynamics on flow instabilities and heat transfer coefficient have been investigated and discussed.

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40

Runevall, Odd. "Helium Filled Bubbles in Solids : Nucleation, Growth and Swelling." Doctoral thesis, KTH, Reaktorfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-90960.

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When nuclear fuel, fabricated for the purpose of transmuting spent fuel is irradiated, significant amounts of He is produced from alpha particles mainly emitted when 242Cm decays into 238Pu. From irradiation experiments it is known that the presence of He in the solids alters the swelling behaviour of the material. The thesis presents the theoretical background from which nucleation models of He bubbles can be formulated. Such models are presented for He in metals, and the case of He in Mo is studied as an example. MgO, which together with Mo is suggested as a matrix material in transmutation fuel is also studied and the stability of He containing bubbles in this material is discussed. By calculating parameters for a rate theory model derived from atomistic modelling, it is shown that He can stabilise vacancy clusters and cause cluster growth at temperatures and irradiation doses where nucleation and growth would not otherwise occur. At the initial stages of nucleation He can stabilise small bubbles while larger bubbles are unstable. This results in an incubation time of swelling, which implies that He does not always cause increased swelling, but can at certain irradiation conditions slow down the growth of large vacancy clusters and thereby delay swell\-ing beyond the time of the irradiation. When comparing the behaviour of bubble nucleation in Mo and MgO, it is found that He has a significant impact even at very low concentrations in Mo. In contrast, the concentration of He has to be considerably higher in MgO to affect the swelling behaviour. For an inert matrix fuel, designed for transmutation purposes, this implies that the Mo matrix will have a tendency to swell considerably at rather high temperatures due to He stabilised vacancy clusters. If operated at lower temperatures, the swelling could instead be reduced due to the incubation time. In a MgO matrix, the swelling behaviour will instead depend largely on the production rate of He. For a low production rate, the material will have a swelling behaviour similar to the one seen when He is not present in the material. A high production rate implies that He will remain in vacancy clusters, thereby stabilising the clusters and enhancing the growth and swelling.

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41

Brandon, Nigel Peter. "The growth kinetics and interfacial properties of electrogenerated bubbles." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37645.

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42

Forestier-Coste, Louis. "Croissance et coalescence de bulles dans les magmas : analyse mathématique et simulation numérique." Phd thesis, Université d'Orléans, 2012. http://tel.archives-ouvertes.fr/tel-00736634.

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Cette thèse est consacrée à l'étude mathématiques et numérique d'un problème physique issu de la volcanologie. On s'intéresse à la modélisation polydisperse de croissance de bulles par exsolution, décompression et coalescence. Un modèle de croissance polydisperse a été proposé dans la litérature, mais ne prenait en compte que le volume des bulles, ce qui restreint le domaine d'application car la croissance par exsolution dépend également de la masse d'eau présente dans la bulle. Pour améliorer ce modèle, nous sommes parti d'une description monodisperse adimensionnelle de la croissance d'une bulle par décompression et exsolution, donnée par le couplage de deux EDO et une EDP. Un code numérique est proposé pour résoudre le problème monodisperse et est actuellement utilisé. Après avoir validé numériquement ce code et considéré plusieurs cas limites, nous avons étudié les solutions du problème et défini une approximation du flux qui nous permet de découpler le système d'équations. Ensuite, nous avons étendu le modèle polydisperse de une à deux dimensions. Une résolution de la coalescence est proposée et couplée avec le modèle de croissance polydisperse. La résolution de la coalescence est confrontée à d'autres schémas numériques en une et deux dimensions afin de valider le schéma numérique proposé. Les premiers test numériques appliqués au problème physique donnent de bon résultats.

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43

Hilton, Anne Marie. "The formation and growth of COâ†2 gas bubbles from supersaturated aqueous solutions." Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334502.

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44

Ramachandran, Sai Manohar. "Computational Studies of Stable and Unstable Growth of Vapor bubbles in Superheated Liquid." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/dissertations/1379.

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Two thermo-fluid problems of physical and practical significance are studied; (i) growth of a vapor bubble in a superheated liquid and (ii) thermocapillary-driven fluid flow of two superimposed fluids. In the first, the dynamics of stable and unstable growth of a vapor bubble in a superheated liquid is investigated using Direct Numerical Simulations. A one-field formulation is used wherein one set of equations for conservation of mass, momentum, and energy are solved using the front tracking/finite difference method. The governing equations are solved on a fixed grid and the phase boundary is tracked explicitly by a moving front. The numerical method is validated by comparison with benchmark analytical solutions. Unstable growth leads to wrinkling at the surface of the bubbles and evaporative mass fluxes that are several order of magnitude larger than those of stable boiling. Stable/unstable growth of vapor bubble is studied, by changing the governing nondimensional parameters and the material property ratio. The effect of the ratio of the bubble radii, and the distance between the center of two bubbles on the growth rate, and bubble surface area are studied. The growth of the vapor bubble is considerably influenced by density ratio, conductivity ratio and Jacob number. The hydrodynamic and thermal interactions of two vapor bubbles significantly reduces the bubble radius and bubble surface area. In the second problem, the thermocapillary-driven convection of two-superimposed fluids occupying the space between the walls of a microchannel, heated from below with a sinusoidal nonuniform temperature and imposing a uniform temperature on the top wall, in zero gravity is studied. The problem is studied to explore the effect of the thickness ratio, conductivity ratio, and the viscosity ratio on fluid flow and interface deformation. This is achieved, by solving the equation of conservation of mass, momentum, and the energy balance analytically using the domain perturbation analysis and numerically using a front tracking/finite difference method, in the limit of creeping flow regime, and negligible convection of heat. The relative thickness of the fluid, and the ratio of the material properties, have direct effect on the flow strength. The sense of the interface deformation is studied, by varying the thickness ratio, and the viscosity ratio. The flow strength decreased, with an increase in the conductivity ratio ekc = ka/kb, and the viscosity ratio. The relative thickness, and the viscosity ratio determine the sense of deformation. It is seen that the deformation decreases with increase in the conductivity ratio. It is also seen that as the viscosity ratio increases for different thickness ratio, at lower eμ the deformation is towards the bottom wall, and further increase in viscosity ratio achieves a zero deformation and then reverses the sense of deformation, towards the top wall increasing the deformation.

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45

Motohashi, Atsushi. "Studies on Asset Bubbles, Economic Growth, and Bailout Policy in an Open Economy." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263411.

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46

Zhu, Lin. "Three essays on asset bubbles and economic growth in a small open economy." Thesis, University of Macau, 2018. http://umaclib3.umac.mo/record=b3959330.

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47

Patey, Julia. "Is the housing market in Sweden overrated? : A Study Of The Hypothetical Yield Of The Residential Real Estate In Stockholm." Thesis, Uppsala universitet, Nationalekonomiska institutionen, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-355240.

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This paper presents a method to value the residential real estate portfolio of an economy by summarizing the future discounted values of the net operating income. The motivation for this choice of subject is the concern for a house bubble in Sweden due to the double-digit rise in housing prices which the economy has experienced during many consecutive years. However, the method is general and can be applied anywhere where relevant statistics is available. The challenge to use an income approach to residential real estate valuation lies in the fact that there is no obvious net operating income, as the owner and the end user is in many cases the same person. To solve this challenge, we determine the maximum possible net operating income by taking the households’ disposable incomes and subtracting their expenses. This will be a fictional value for the maximum possible net operating income or the imputed income for real estate owners. When this fictional net operating income is compared to the mean prices of properties, a maximum potential yield to capital invested in residential real estate is extracted. The current number for this maximal potential yield on the Stockholm market seem to be 6,4 percent, 2017. The main contribution of this paper to the science of economy is that it presents a way to use classical fundamental valuation methods to evaluate the price level of residential real estate, that, due to lack of tangible net operating income is not as straightforward as the valuation of the commercial real estate market.

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Modini, Robin Lewis. "Investigation of the effect of organics on the water uptake of marine aerosols." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/46884/1/Robin_Modini_Thesis.pdf.

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Water uptake refers to the ability of atmospheric particles to take up water vapour from the surrounding atmosphere. This is an important property that affects particle size and phase and therefore influences many characteristics of aerosols relevant to air quality and climate. However, the water uptake properties of many important atmospheric aerosol systems, including those related to the oceans, are still not fully understood. Therefore, the primary aim of this PhD research program was to investigate the water uptake properties of marine aerosols. In particular, the effect of organics on marine aerosol water uptake was investigated. Field campaigns were conducted at remote coastal sites on the east coast of Australia (Agnes Water; March-April 2007) and west coast of Ireland (Mace Head; June 2007), and laboratory measurements were performed on bubble-generated sea spray aerosols. A combined Volatility-Hygroscopicity-Tandem Differential Mobility Analyser (VH-TDMA) was employed in all experiments. This system probes the changes in the hygroscopic properties of nanoparticles as volatile organic components are progressively evaporated. It also allows particle composition to be inferred from combined volatility-hygroscopicity measurements. Frequent new particle formation and growth events were observed during the Agnes Water campaign. The VH-TDMA was used to investigate freshly nucleated particles (17-22.5 nm) and it was found that the condensation of sulphate and/or organic vapours was responsible for driving particle growth during the events. Aitken mode particles (~40 nm) were also measured with the VH-TDMA. In 3 out of 18 VH-TDMA scans evaporation of a volatile, organic component caused a very large increase in hygroscopicity that could only be explained by an increase in the absolute water uptake of the particle residuals, and not merely an increase in their relative hygroscopicity. This indicated the presence of organic components that were suppressing the hygroscopic growth of mixed particles on the timescale of humidification in the VH-TDMA (6.5 secs). It was suggested that the suppression of water uptake was caused by either a reduced rate of hygroscopic growth due to the presence of organic films, or organic-inorganic interactions in solution droplets that had a negative effect on hygroscopicity. Mixed organic-inorganic particles were rarely observed by the VH-TDMA during the summer campaign conducted at Mace Head. The majority of particles below 100 nm in clean, marine air appeared to be sulphates neutralised to varying degrees by ammonia. On one unique day, 26 June 2007, particularly large concentrations of sulphate aerosol were observed and identified as volcanic emissions from Iceland. The degree of neutralisation of the sulphate aerosol by ammonia was calculated by the VH-TDMA and found to compare well with the same quantity measured by an aerosol mass spectrometer. This was an important verification of the VH-TMDA‘s ability to identify ammoniated sulphate aerosols based on the simultaneous measurement of aerosol volatility and hygroscopicity. A series of measurements were also conducted on sea spray aerosols generated from Moreton Bay seawater samples in a laboratory-based bubble chamber. Accumulation mode sea spray particles (38-173 nm) were found to contain only a minor organic fraction (< 10%) that had little effect on particle hygroscopicity. These results are important because previous studies have observed that accumulation mode sea spray particles are predominantly organic (~80% organic mass fraction). The work presented here suggests that this is not always the case, and that there may be currently unknown factors that are controlling the transfer of organics to the aerosol phase during the bubble bursting process. Taken together, the results of this research program have significantly improved our understanding of organic-containing marine aerosols and the way they interact with water vapour in the atmosphere.

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49

Marchal, Antoine. "Modélisation du gonflement radiolytique d'enrobés bitumineux." Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0038/document.

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L'objectif de ce travail est de prédire le gonflement de fûts d'enrobés bitumineux contenant des déchets radioactifs en condition d'entreposage, de transport et de stockage. L'incorporation de radionucléides dans du bitume provoque en effet sa radiolyse et du dihydrogène est ainsi généré dans le matériau. Ce gaz est solubilisé dans la matrice jusqu'à ce que sa concentration atteigne une valeur limite, la saturation. Au-delà de celle-ci, un mécanisme de germination a lieu : des bulles sont formées. Elles vont par la suite croître grâce à l'apport de gaz par radiolyse et migrer sous l'effet de la poussée d'Archimède. Le gonflement du matériau résulte alors de la compétition entre création et évacuation de gaz. Un modèle a été construit pour décrire l'évolution d'une population de bulles. Sa résolution analytique n'étant pas possible, un code numérique a été développé. Les résultats montrent qu'une augmentation de la viscosité du fluide, du terme source de gaz apporté par radiolyse ou de la hauteur du récipient induisent une augmentation du gonflement et qu'une augmentation du coefficient de diffusion du gaz dans la matrice diminue le gonflement. Lorsque le fluide présente un seuil d'écoulement, le comportement de la population de bulles est modifié et l'évacuation de gaz par migration des bulles se fait par à-coups, contrairement au cas d'un fluide newtonien où une évacuation stationnaire est atteinte. Cette dernière a enfin servi à l'optimisation des conditions opératoires
The aim of this PhD thesis is to predict the swelling of bitumen barrels in which radioactive salts are mixed. The bitumen exposed to radioactivity undergoes a chemical reaction: the radiolys. This implies a generation of dihydrogen. The created is solubilized until the concentration reaches a limit value which is called saturation. Over this limit nucleation of bubbles is observed. Then they will grow thank to the contribution of the gas generated by radiolys and they will be submitted to Archimede's principle so that they will rise in the fluid. The swelling is the result of the competition between generation and evacuation of gas. A model has been built to describe theevolution of a bubble population. Because of it is not possible to solve it analitically, a numerical program was developed. The results show that an increase of the fluid viscosity, the gas generation or the container height lead to an increase of the swelling and that an increase of the diffusioncoefficient contributes to a decrease of the swelling. In the particular case of a yield stress fluid, the behavior of the bubble population is modified and the evacuation of gas is done with several shots, at the opposite of the case of a Newtonian fluid for which a stationary evacuation is reached

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50

Carr, Matthew William. "A study of the kinetics of nucleation, growth and detachment of carbon dioxide and chlorine bubbles using pressure release nucleation and the quartz crystal microbalance." Thesis, University of Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335381.

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Dissertations / Theses on the topic 'Bubble growth'

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