Relevant bibliographies by topics / Bubble Packing

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  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers

Academic literature on the topic 'Bubble Packing'

Author: Grafiati
Published: 4 June 2021
Last updated: 1 February 2022

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Journal articles on the topic "Bubble Packing"

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Lee, Joon Seong, Dong Keun Park, and Youn Jong Choi. "Automated FE Analysis for Heat Sink of LED Modules." Applied Mechanics and Materials 302 (February 2013): 765–71. http://dx.doi.org/10.4028/www.scientific.net/amm.302.765.

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This paper describes an automatic finite element (FE) mesh generation for FE analysis of LED modules. It is consisting of element generation, bubble packing and solid geometry modeler. This automated FE analysis system including bubble packing method consists of three sub-processes: (a) definition of geometric model, i.e. analysis model, (b) generation of bubbles, and (c) generation of elements. One of commercial solid modelers is employed for three-dimensional solid structures. Bubble is generated if its distance from existing bubble points is similar to the bubble spacing function at the point. The Delaunay method is introduced as a basic tool for element generation. The developed system allows designers to evaluate detailed physical behaviors of structures through some simple interactive operations to their geometry models. To demonstrate practical performances of the present system, the system was used to an analysis of heat sink. Practical performances of the present system are demonstrated through several examples for heat sink of LED modules.
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Qi, Nan, Yufeng Nie, and Weiwei Zhang. "Acceleration Strategies Based on an Improved Bubble Packing Method." Communications in Computational Physics 16, no. 1 (July 2014): 115–35. http://dx.doi.org/10.4208/cicp.080213.151113a.

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AbstractThe bubble packing method can generate high-quality node sets in simple and complex domains. However, its efficiency remains to be improved. This study is a part of an ongoing effort to introduce several acceleration schemes to reduce the cost of simulation. Firstly, allow the viscosity coefficient c in the bubble governing equations to change according the coordinate of the bubble which are defined separately as odd and normal bubbles, and meanwhile with the saw-shape relationship with time or iterations. Then, in order to relieve the over crowded initial bubble placement, two coefficients w1 and w2 are introduced to modify the insertion criterion. The range of those two coefficients are discussed to be w1 = 1, w2 ∈ [0.5,0.8]. Finally, a self-adaptive termination condition is logically set when the stable system equilibrium is achieved. Numerical examples illustrate that the computing cost can significantly decrease by roughly 80% via adopting various combination of proper schemes (except the uniform placement example), and the average qualities of corresponding Delaunay triangulation substantially exceed 0.9. It shows that those strategies are efficient and can generate a node set with high quality.
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Tanaka, Daigo, Kenji Shimada, Michael R. Rossi, and Yoed Rabin. "Cryosurgery planning using bubble packing in 3D." Computer Methods in Biomechanics and Biomedical Engineering 11, no. 2 (April 2008): 113–21. http://dx.doi.org/10.1080/10255840701336653.

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Kim, Jeong-Hun, Hyun-Gyu Kim, Byung-Chai Lee, and Seyoung Im. "Adaptive mesh generation by bubble packing method." Structural Engineering and Mechanics 15, no. 1 (January 25, 2003): 135–49. http://dx.doi.org/10.12989/sem.2003.15.1.135.

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Wu, Weimin, Naiqian Cheng, Lindsay Black, Hendrik Dietz, and Alasdair Steven. "Biphasic Packing of DNA and Internal Proteins in Bacteriophage T4 Heads Revealed by Bubblegram Imaging." Viruses 12, no. 11 (November 10, 2020): 1282. http://dx.doi.org/10.3390/v12111282.

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The virions of tailed bacteriophages and the evolutionarily related herpesviruses contain, in addition to highly condensed DNA, substantial quantities of internal proteins. These proteins (“ejection proteins”) have roles in scaffolding, maturational proteolysis, and cell-to-cell delivery. Whereas capsids are amenable to analysis at high resolution by cryo-electron microscopy, internal proteins have proved difficult to localize. In this study, we investigated the distribution of internal proteins in T4 by bubblegram imaging. Prior work has shown that at suitably high electron doses, radiation damage generates bubbles of hydrogen gas in nucleoprotein specimens. Using DNA origami as a test specimen, we show that DNA does not bubble under these conditions; it follows that bubbles represent markers for proteins. The interior of the prolate T4 head, ~1000 Å long by ~750 Å wide, has a bubble-free zone that is ~100–110 Å thick, underlying the capsid shell from which proteins are excluded by highly ordered DNA. Inside this zone, which is plausibly occupied by ~4 layers of coaxial spool, bubbles are generated at random locations in a disordered ensemble of internal proteins and the remainder of the genome.
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Stride, E., K. Pancholi, M. J. Edirisinghe, and S. Samarasinghe. "Increasing the nonlinear character of microbubble oscillations at low acoustic pressures." Journal of The Royal Society Interface 5, no. 24 (February 19, 2008): 807–11. http://dx.doi.org/10.1098/rsif.2008.0005.

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The nonlinear response of gas bubbles to acoustic excitation is an important phenomenon in both the biomedical and engineering sciences. In medical ultrasound imaging, for example, microbubbles are used as contrast agents on account of their ability to scatter ultrasound nonlinearly. Increasing the degree of nonlinearity, however, normally requires an increase in the amplitude of excitation, which may also result in violent behaviour such as inertial cavitation and bubble fragmentation. These effects may be highly undesirable, particularly in biomedical applications, and the aim of this work was to investigate alternative means of enhancing nonlinear behaviour. In this preliminary report, it is shown through theoretical simulation and experimental verification that depositing nanoparticles on the surface of a bubble increases the nonlinear character of its response significantly at low excitation amplitudes. This is due to the fact that close packing of the nanoparticles restricts bubble compression.
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Zhang, Pengyu, Saizhen Jin, Leming Ou, Wencai Zhang, and Yuteng Zhu. "Fine Bauxite Recovery Using a Plate-Packed Flotation Column." Metals 10, no. 9 (September 2, 2020): 1184. http://dx.doi.org/10.3390/met10091184.

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In this investigation, the fine-grained bauxite ore flotation was conducted in a plate-packed flotation column. This paper evaluated the effects of packing-plates on recovering fine bauxite particles and revealed the fundamental mechanisms. Bubble coalescence and break-up behaviors in the packed and unpacked flotation columns were characterized by combining Computational Fluid Dynamics (CFD) and Population Balance Model (PBM) techniques. Flotation experiments showed that packing-plates in the collection zone of a column can improve bauxite flotation performance and increase the smaller bauxite particles recovery. Using packing-plates, the recovery of Al2O3 increased by 2.11%, and the grade of Al2O3 increased by 1.85%. The fraction of −20 μm mineral particles in concentrate increased from 47.31% to 54.79%. CFD simulation results indicated that the packing-plates optimized the bubble distribution characteristics and increased the proportion of microbubbles in the flotation column, which contributed to improving the capture probability of fine bauxite particles.
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Yamakawa, Soji, and Kenji Shimada. "Anisotropic tetrahedral meshing via bubble packing and advancing front." International Journal for Numerical Methods in Engineering 57, no. 13 (2003): 1923–42. http://dx.doi.org/10.1002/nme.750.

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Deshpande, S. S., J. Walker, J. Pressler, and D. Hickman. "Effect of packing size on packed bubble column hydrodynamics." Chemical Engineering Science 186 (August 2018): 199–208. http://dx.doi.org/10.1016/j.ces.2018.04.045.

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Homan, Tess, Rob Mudde, Detlef Lohse, and Devaraj van der Meer. "High-speed X-ray imaging of a ball impacting on loose sand." Journal of Fluid Mechanics 777 (July 22, 2015): 690–706. http://dx.doi.org/10.1017/jfm.2015.375.

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When a ball is dropped in fine very loose sand, a splash and subsequently a jet are observed above the bed, followed by a granular eruption. To directly and quantitatively determine what happens inside the sand bed, high-speed X-ray tomography measurements are carried out in a custom-made set-up that allows for imaging of a large sand bed at atmospheric pressures. Herewith, we show that the jet originates from the pinch-off point created by the collapse of the air cavity formed behind the penetrating ball. Subsequently, we measure how the entrapped air bubble rises through the sand, and show that this is consistent with bubbles rising in continuously fluidized beds. Finally, we measure the packing fraction variation throughout the bed. From this we show that there is (i) a compressed area of sand in front of and next to the ball while the ball is moving down, (ii) a strongly compacted region at the pinch-off height after the cavity collapse and (iii) a relatively loosely packed centre in the wake of the rising bubble.
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Dissertations / Theses on the topic "Bubble Packing"

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Shimada, Kenji. "Physically-based mesh generation : automated triangulation of surfaces and volumes via bubble packing." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12332.

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Andrade, Diego Fernando. "Patterning and Customization: Evaluating Tensor Field Generation For Mechanical Design On Free-Form Surfaces." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/889.

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This dissertation delivers a new computational framework for the automatic generation of geometric feature patterns for industrial design and architectural facades on free-form surfaces. Such patterns include holes in a speaker grill, showerhead holes, protrusions on ceramics or bumpy textures on a panel. These patterns play a key role in making a designed object aesthetically pleasing as well as functional. Computer Aided Design (CAD) systems currently offer tools for generating simple patterns, such as uniformly spaced rectangular or radial patterns. However, they are not applicable to more general cases required in industrial design, including arbitrarily shaped target geometry and graded feature sizes. These tools are limited in several ways: (1) They cannot be applied to free-form geometries used in industrial design, (2) Patterning of these features happens within a single working plane and is not applicable to highly curved surfaces, and (3) Created features lack anisotropy and spatial variations, such as changes in the size and orientation of geometric features within a given region. This thesis proposes a new method of taking input for a target region along with sizing metrics. It will generate feature patterns automatically in three steps: (1) packing isotropic or anisotropic cells tightly in a target region, (2) scaling features according to the specified sizing metrics, and (3) adding features on the base geometry. This approach automatically generates complex patterns that conform to the boundary of any specified region. User input of a small number of geometric features (called “seed features”) of desired size and orientation in preferred locations also can be specified within the target domain. These geometric seed features are then transformed into tensors and used as boundary conditions to generate a Riemannian metric tensor field. A form of the Laplace heat equation is used to generate the field over the target domain, subject to specified boundary conditions. The field represents the anisotropic pattern of the geometric features. The system is implemented as a plugin module in a commercial CAD package to add geometric features to the target region of the model using two set operations, union and subtraction. This method facilitates the creation of a complex pattern of hundreds of geometric features in minutes. All the features are accessible from the CAD system and can be manipulated individually if required by the user. This allows the industrial designer or architect to explore more alternatives by avoiding the tedious and time-consuming manual generation of these geometric patterns.
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Khadra, Rami. "Nouvelle génération de transformateurs de chaleur, sélection de fluides de travail et optimisation des équipements du cycle en employant des technologies innovantes." Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0083.

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Ce travail contribue aux efforts de l'Union Européenne pour réduire les émissions de CO2. Son objectif est d'aider les industries produisant de la chaleur fatale à récupérer cette énergie perdue, d'augmenter sa température et de la réutiliser in situ. Les transformateurs de chaleur (Absorption Heat Transformers ou AHT), machines à absorption consommant très peu d'électricité, sont alors ici étudiés. Les AHTs existants rencontrent des problèmes comme la corrosion, la cristallisation, la toxicité et les niveaux de pression éloignés de la pression atmosphérique. Ceux-ci sont causés par les fluides conventionnels (Eau/LiBr et Ammoniaque/Eau) et s'aggravent à des températures supérieures à 120°C. Des modèles de conception ainsi que des solutions techniques, applicables avec tous mélanges de fluides organiques, sont alors proposés dans cette thèse. Ces modèles sont validés avec des données de la littérature et implémentés dans des outils d'aide à la décision.Tout d'abord, un modèle de sélection de paires de fluides organiques (parmi une liste de fluides) est développé. Les contraintes prises en compte sont, entre autres, les types et les profils de températures des sources et puits de chaleur, et les propriétés du fluide. Pour chaque type de fluide, la méthode la plus adaptée au calcul des propriétés physiques des fluides est choisie.En second lieu, pour effectuer la séparation des 2 constituants du mélange de fluides organiques, le générateur (composant recevant la chaleur fatale) et le condenseur de l'AHT sont fusionnés pour former une colonne de distillation. Un modèle d'une colonne de distillation nommée « hybride » est alors développé en adaptant la méthode de Ponchon-Savarit et en la combinant avec la méthode ETD (Equal Thermodynamic Distance). Cette colonne associe les avantages des 2 types de colonnes adiabatiques et diabatiques. Elle allie réduction de production d'entropie et meilleure exploitation des sources de chaleur à températures glissantes. La conception mécanique de la colonne hybride est aussi incluse.Troisièmement, pour atteindre la température théorique maximale du mélange de fluide déjà choisi, l'absorbeur de l'AHT (où la chaleur à haute température est libérée) est divisé en sections adiabatiques suivies par des sections diabatiques. De plus, les modèles détaillés des colonnes à bulles (fonctionnant en co-courant ou en contre-courant) ainsi que de la colonne à garnissage sont présentés et comparés entre eux.Les principaux résultats de ces travaux consistent en une nouvelle méthodologie de choix de fluides organiques pouvant remplacer les mélanges classiques surtout à températures élevées (supérieures à 130 °C). En ce qui concerne la colonne de distillation, il est montré que la colonne adiabatique constitue un meilleur choix lorsqu'une source de chaleur latente est disponible tandis qu'avec une source de chaleur sensible, la colonne hybride engendre moins de pertes exergétiques. En passant à l'absorbeur, le nouveau mode d'opération de celui-ci permet à l'utilisateur d'atteindre des températures plus élevées que celles réalisées avec les technologies actuellement disponibles. Enfin, les modèles développés permettent de choisir les technologies de distillation (adiabatique, diabatique ou hybride) et d'absorption (colonne à bulles ou à garnissage) les plus appropriées en s'adaptant à différentes problématiques industrielles
This work is part of the European union efforts to reduce its CO2 emissions. It aims to assist any waste heat producing industry in recuperating this lost thermal energy, pumping it to higher temperature levels and reusing it on site. Absorption Heat Transformers (AHT), that consume little electricity, are used for this task. Current AHT problems such as corrosion, crystallization, toxicity and inconvenient pressure levels are caused by conventionally used H2O/LiBr and NH3/ H2O working fluids and get worse at temperatures exceeding 120°C. Potential solutions are thus suggested. According to them, models are developed; they are all able to operate with any organic mixture and are customized to accompany the industrialist from start to finish. These solutions were validated by comparing them with literature data and are implemented into several tools.Firstly, a model selects the optimal organic binary mixture -among a list of fluids- in terms of the real case application's constraints: Heat transfer fluids used, Heat source's and heat sink's types and temperature profiles, mixtures transport properties among other parameters. Suitable thermodynamic model is selected for different fluid group types.Secondly, in order to separate the 2 components of the chosen mixture of organic compounds, the AHT generator (component which receives waste heat) is merged with the AHT condenser thus forming a distillation column. A “hybrid column” is designed by modifying the Ponchon-Savarit method and combining it with the Equal Thermodynamic Distance (ETD) method. This new column associates the best features of the two columns. It reduces entropy production rates and best exploits temperature gliding heat sources. Mechanical design for the hybrid column is also included.Thirdly, to ensure that the maximum theoretical temperature of the working fluid is reached, the AHT absorber (where high temperature heat is released) is divided into consecutive adiabatic parts followed by diabatic ones. Detailed Models for co-current and counter-current bubble columns as well as packing columns are presented and compared.Main results consist in a selection methodology of organic compounds mixtures, capable of replacing conventional ones specially at temperatures higher than 130 °C. It's also shown that adiabatic columns are better options when latent type heat sources are available while hybrid columns lose less exergy when used with sensible heat sources. As for the absorber, the new operating mode provides the user with higher temperatures than currently reached by available technologies. Finally, using the developed models, tailored and most suitable distillation (adiabatic, diabatic or hybrid columns) and absorber (bubble or packing columns) technologies can be proposed depending on the industrial specific cases and requirements
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Eriksson, Victoria. "All-inclusive hotels’ packaging of the northern coast of Jamaica: creating and maintaining an environmental bubble." Thesis, Stockholms universitet, Latinamerikainstitutet, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-182493.

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This study contributes to the existing discussion about international tourism by exploring the role of all-inclusive hotels in the creation of an environmental bubble on the northern coast of Jamaica. Moreover, it examines what type of Jamaica is being sold by the hotels and who is included and who is excluded from the environmental bubble. The purpose of this study is to analyze how all-inclusive hotels on the northern coast of Jamaica are selling their travel packages. In order to do that, this study makes a qualitative media analysis of digital website advertisement from all-inclusive hotel’s websites. Social scientists agree that one characteristic of all-inclusive type of tourism is the separation between guest and host. I argue that the website advertisements by all-inclusive hotels are contributing to this separation.
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Kuo, Jia-yi, and 郭嘉儀. "Research on Mechanism of Bubble Formation in Liquid Lens Packaging." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/89032778307330564272.

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碩士
國立臺灣科技大學
機械工程系
96
In all kinds of auto focus technology, the liquid lens is newly developing in auto focus technology, although it possibly will achieve module microminiaturization, in power consumption, response time and fall down test have excellent performance, due to optic medium of the liquid lens is liquid, so optic quality and environment temperature test are still interesting, and the liquid lens of discussion in this research is also in developing beginning. In room and high temperature environment test, formed bubbles cause imaging twist to reduce product reliability, so this research discuss and analyze for formed bubbles possible factors, and further try to improve it. Before packaged the liquid lens in this research, it build up vacuum process equipment to reduce air content and outgas phenomenon cause by liquid lens components, learnt by the experimental result, the 70 torr’s vacuum process equipment is sure that outgassing performance, then discuss and analyze variety of possibility of formed bubbles. Learnt by the experimental result, in room temperature, the liquid separates the distance of the gas room to be insufficient additionally capillarity phenomenon, so formed bubbles .And in high temperature formed bubbles caused by existent solution’s vapor pressure, then led to structure of sealed by glue could not resist hydraulic pressure in high temperature, and then caused to leak solution at the same time formed bubbles. Eventually we discuss and analyze what the major reason of formed bubbles in this research, and then try different rubber o-ring packaged structures and constantly improve them, and further discuss its gastightness.
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Books on the topic "Bubble Packing"

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Nyberg, Tim, and Joey Green. The Bubblewrap Book: Hundreds of Creative and Wacky Uses for the World's Favorite Packing Material. Perennial (HarperCollins), 1998.

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Parker, Philip M. The 2007-2012 World Outlook for Plastics Blister and Bubble Formed Packaging. ICON Group International, Inc., 2006.

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The 2006-2011 World Outlook for Plastics Blister and Bubble Formed Packaging. Icon Group International, Inc., 2005.

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Book chapters on the topic "Bubble Packing"

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Yamakawa, Soji, and Kenji Shimada. "Anisotropic terahedral meshing via bubble packing and advancing front." In Computational Fluid and Solid Mechanics, 1676–79. Elsevier, 2001. http://dx.doi.org/10.1016/b978-008043944-0/50997-5.

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"Bubbles in Beijing." In The Pursuit of Perfect Packing, Second Edition, 107–10. Taylor & Francis, 2008. http://dx.doi.org/10.1201/9781420068184.ch12.

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"Toils and troubles with bubbles." In The Pursuit of Perfect Packing. Taylor & Francis, 2000. http://dx.doi.org/10.1201/noe0750306485.ch7.

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"Toils and Troubles with Bubbles." In The Pursuit of Perfect Packing, Second Edition, 87–105. Taylor & Francis, 2008. http://dx.doi.org/10.1201/9781420068184.ch11.

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Conference papers on the topic "Bubble Packing"

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Ren Ming, Zhang Weiwei, Li Shouying, and Nie Yufeng. "A bubble packing algorithm for parametric surface delaunay triangulation." In IET International Conference on Information Science and Control Engineering 2012 (ICISCE 2012). Institution of Engineering and Technology, 2012. http://dx.doi.org/10.1049/cp.2012.2459.

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Chung, Soon, and Seung Kim. "Numerical simulation of localized damage through automatic finite element remeshing based on bubble packing method." In 19th AIAA Applied Aerodynamics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2001. http://dx.doi.org/10.2514/6.2001-1254.

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Yamakawa, Soji, and Kenji Shimada. "Quad-Layer: Layered Quadrilateral Meshing of Narrow Two-Dimensional Domain by Bubble Packing and Chordal Axis Transformation." In ASME 2001 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/detc2001/dac-21149.

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Abstract This paper presents a new computational method for quadrilateral meshing of a thin, or narrow, two-dimensional domain. An output mesh of our method is well-shaped and either single-layered, multi-layered, or partially multi-layered. Element sizes can be uniform or graded. A high quality, layered quadrilateral mesh is often required for finite element analyses of a narrow two-dimensional domain with a large deformation such as the analysis of rubber deformation or sheet metal forming. Our method consists of two steps: (1) extraction of the skeleton of a given domain by the discrete chordal axis transformation, and (2) discretization of the chordal axis into a set of line segments and conversion of each of the line segments to a single quadrilateral element or multiple layers of quadrilateral elements. In both steps we use a physically-based computational method called bubble packing to discretize a curve into a set of line segments of specified sizes. Experiments show that the accuracy of a large-deformation FEM analysis can be significantly improved by using a well-shaped quadrilateral mesh created by the proposed method.
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Shoykhet, Nissan, Elena S. Di Martino, David A. Vorp, and Kenji Shimada. "Assessment of Hex-Dominant Mesh Efficacy for Nonlinear Finite Element Method Structural Analyses." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-61773.

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The objective of this study is to compare different types of meshes for the solution of static structural problems under large deformation conditions, using nonlinear materials. The three types of mesh used in this study are a structured hexahedral mesh, an unstructured tetrahedral mesh, and a hex-dominant mesh generated automatically by the bubble packing algorithm, [1]. The two geometries tested were a hypothetical, partially symmetric model of an Abdominal Aortic Aneurysm (AAA), and a three dimensional representation of an in vivo AAA reconstructed from CT scan images (Fig 1). In order to evaluate the accuracy of the finite element approximation the mean square (or L2) norm of the error was estimated.
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Lane, C. D., and A. A. Donaldson. "Flow Profiles and Gas/Liquid Separation in First and Second Generation Designs for Ebullated Reactors." In ASME/JSME/KSME 2015 Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ajkfluids2015-03227.

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Ebullated bed reactor technology is found in the oil and gas industry as part of the hydrocracking process, within which heavy oils are cracked under elevated temperatures and pressures to produce increased fractions of refinable petroleum products. A unique feature of these types of reactors is the presence of an internal gas/liquid separation and liquid recycle line, through which 60 to 90% of the net liquid flow through the column is recycled to maintain fluidized conditions within the internal catalyst bed. The separation efficiency within these systems has a significant impact on overall unit profitability, whereby high levels of gas recirculation results in lower liquid throughput and increased potential of over-cracking of product gases and production of light ends [1]. These units typically operate at gas holdups above 30%, with even small reductions in gas entrainment potentially leading to significant increases in profitability. Due to the severe conditions present within operating units (several MPa pressures, >300°C), pilot-scale experimental systems exploring fluid flow phenomena have typically employed nitrogen and kerosene as analogous fluids[2]. Even within these systems, the ability to visualize flow patterns and parametrically evaluate the effects of separator modifications on gas recirculation has been limited. In an effort to provide strategic focus for future process improvements, Dalhousie University has been collaborating with Ottawa University and Syncrude Canada Ltd. to develop 3D CFD-based simulations of older generation designs to explore fundamental flow characteristics and sensitivity of gas-liquid separation efficiency to changes in geometry and process conditions. This work explores the sensitivity of gas separation efficiency to operational parameters (bubble size, processing rate, gas holdup), geometric design (two generations of separator designs), and computational model choices (drag correlations and packing limiters). Of particular note is the sensitivity of the predicted performance to drag models, for which there is limited empirical validation under the high gas fraction conditions present in this industrial unit, and the sensitivity to packing limiters, which reflect foam formation (an issue observed within operating units). The trends predicted within this work show significant similarities to current operational trends observed in commercial ebullated bed reactors, and provide a basis for predicting the effects of operational changes on the overall performance of these units.
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Pan, Liang-Ming, Chuan He, Ming-Dao Xin, Tien-Chien Jen, and Qinghua Chen. "Bubbles Coalescence and Condensation of Subcooled Flow Boiling in Vertical Narrow Channels." In ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72860.

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Compared with conventional channels, narrow and micro channels have significant heat transfer enhancement characteristic. With smooth internal surface, such channels can efficiently avoid encrustation at the washing of the high-speed liquid. Moreover, heat transfer elements can be easily assembled. This type of channels have been adopted extensively in many engineering applications, e.g. microelectronic cooling, Advanced Nuclear Reactor, cryogenic, aviation and space technology and thermal engineering. In recent years, many efforts have been done which focused upon flow patterns, heat transfer and pressure drop. Almost every researcher thought the heat transfer enhancement mechanism of narrow and micro channels to be bubble’s deformation and disturbance, but the proposed mechanism is insufficient to explain the heat transfer enhancement of narrow channel. In present paper, an experimental flow visualization study has been performed under pressured conditions. Microscopic high-speed video visualization revealed that initial bubbles growth accompanied with slipping on heating wall in flow direction with slip velocity less than 0.1m/s. Several important parameters, such as heat flux and subcooling of cross-section, have important effects on the behavior of bubbles. At higher heat flux, it resulted shifting of the ONB point to the upstream and thus generated larger population of bubbles. It was observed that small bubbles (d = 0.01∼0.07mm) slipped on heating wall at a speed of 0.1 to 0.2m/s, and the velocity of larger bubbles (d = 0.1∼0.3mm) was increased to 0.25 ∼ 0.7 m/s. From flow visualization, it is showed that the process of large bubbles coalescing with small ones is the dominating mechanism of bubble growing. In some situation, the speed-increasing bubble’s size even formed vapor layer near the heating wall.
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Christopher, David M., Hao Wang, and Xiaofeng Peng. "Comparison of Heat Transfer Rates Around Moving and Stationary Bubbles During Nucleate Boiling." In ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72625.

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Nucleate boiling is known to be a very efficient method for generating high heat transfer rates from solid surfaces into liquids; however, the fundamental physical mechanisms governing nucleate boiling heat transfer are not well understood. This paper describes a numerical analysis of the heat transfer mechanisms around stationary and moving bubbles on a very thin microwire. The numerical analysis accurately models the experimentally observed bubble movement and fluid velocities. The analytical model was then used to study the heat transfer mechanisms around the bubbles. The analysis shows that the primary heat transfer mechanism is not the direct heat transfer to the bubble, but rather the large amount of convection around the outside of the bubble induced by the Marangoni flow that transfers at least twice as much energy from the wire than the heat transfer directly under the bubble. The enhanced heat transfer due to the Marangoni flow was evident for both stationary and moving bubbles.
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8

Christopher, David M., Hao Wang, and Xiaofeng Peng. "Experimental and Numerical Investigation of the Dynamics of Moving Vapor Bubbles." In ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72415.

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Jet flows have been observed flowing from the tops of vapor bubbles during nucleate boiling in a variety of situations. This paper analyzes the physical mechanisms that cause jet flows to emanate from the tops of bubbles moving along microwires. The flows were analyzed by numerically solving the governing differential equations for the 3-D velocity and temperature distributions around the bubble and the heated wire as the bubble moves along the wire. The results show that the flow is most likely driven by the temperature difference from the front to the back of the bubble resulting from the bubble motion which would cause Marangoni flow. The Marangoni flow provides thrust to push the bubble forward. Comparisons with experimental observations suggests that the condensation heat transfer at the bubble interface must be restricted by noncondensable gases would increase the surface temperature gradient which would in turn increase the resulting Marangoni flow.
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9

Tollkoetter, Alexander, Norbert Kockmann, Florian Schirmbeck, and Jens Wesholowski. "High Flow Rate Micro Orifice Dispersion of Gas-Liquid Flow." In ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels collocated with the ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/icnmm2015-48221.

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The flow of microbubbles in millichannels with typical dimensions in the range of few millimeters offers a reduced pressure loss with simultaneous large specific contact surface. By flowing through micro orifices, the transformation of pressure into kinetic energy creates a desired secondary flow pattern, which results in continuous dispersion. Differences in velocity and pressure act on the phase boundary of the bubbles and lead to deformations and break-up. In this work, bubble dispersion and bubbly flow in different orifices and channel modules with widths up to 7 mm are studied experimentally and by CFD simulations. The effect of the orifice dimensions on bubble sizes are evaluated for hydraulic diameters of 0.25 to 0.5 mm with different aspect ratios. Several channel structures are analyzed to offer less coalescence and larger residence times. The modules are arranged in a holder and are fixed under a view glass for optical characterization via high-speed camera. Volume flow rates of 10 to 250 mL/min are studied with various phase ratios. Bubble diameters are generated in the range of less than 0.1 to 0.7 mm with narrow size distributions depending on the entire flow rate through the device. The first break-up point is shifted closer to the outlet of the orifices for increasing velocities and smaller hydraulic diameters, but the whole break-up region stays nearly constant for each orifice indicating stronger velocity oscillations acting on the bubble surface. Generally, a linear relation of smaller bubble diameters with larger energy input was identified. Opening angles of the orifices above 6° resulted in flow detachments and recirculation zones around the effluent jet. Independence of the Reynolds number was determined contrary to existing literature models. Flow detachment and coalescence in curves was avoided by an additional bend within the curve based on systematically varied geometrical dimensions.
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10

Thiagarajan, Naveenan, Florian Kapsenberg, Vinod Narayanan, Sushil H. Bhavnani, and Charles Ellis. "On the Lateral Motion of Bubbles Generated From Re-Entrant Cavities Located on Asymmetrically Structured Surfaces." In ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems. ASMEDC, 2011. http://dx.doi.org/10.1115/ipack2011-52056.

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This paper describes a novel concept of lateral motion of bubbles in pool boiling, which has the potential to be translated into a liquid propulsion system when used in a closed loop. The lateral motion of bubbles is achieved due to nucleation from cavities on an asymmetric saw-tooth profile created on a silicon surface. The surface modification involves etching a 3D sawtooth structure with a nominal angle of approximately 24° using gray-scale lithography. The downstream slope of each sawtooth structure features re-entrant cavity structures that act as controlled nucleation sites. The angle of the surface thus obtained causes a net imbalance of forces acting in concert on the flow field around the bubbles departing from the surface. The first part of the paper discusses the steps involved in fabricating such a heat sink with a saw-tooth structure augmented by re-entrant cavities. This is followed by description of the experimental facility used for studying the feasibility of the concept. High-speed photography in conjunction with bubble tracking is used to determine the bubble velocities. Results for a subcooled condition show substantial axial bubble velocities on the order of up to 68.5 cm/s near the cavities and a far-field velocity of up to 4 cm/s.
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