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Artykuły w czasopismach na temat "Bubble breakup"
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Zhang, Zheng, Yi Zhang, Guanmin Zhang i Maocheng Tian. "The bubble breakup process and behavior in T-type microchannels". Physics of Fluids 35, nr 1 (styczeń 2023): 013319. http://dx.doi.org/10.1063/5.0131748.
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A double T-type microchannel consisting of two T-junctions is used as the base unit of tree-like microchannels. Studying the breakup process and behavior of bubbles in T-type microchannels can help enhance the capability of microfluidic systems and microchannel heat exchangers. In this study, the bubble breakup process in a double T-type microchannel was simulated using a volume of fluid model via numerical simulation. The simulation results show a total of five regimes of bubble breakup with capillary numbers between 0.001 and 0.008 and dimensionless bubble lengths between 1 and 9, which are the non-breakup, “tunnel” breakup, obstructed breakup, merging symmetric breakup, and merging non-breakup. These five breakup regimes were studied in detail. At a high velocity of the gas phase and with a small size of the generated bubble, the bubble does not break up. Symmetric breakup regimes can be divided into two regimes: tunnel breakup and obstructed breakup. Shear force plays a significant role in the tunnel breakup regime. The obstructed breakup regime is mainly caused by the increase in pressure at the T-junction, which elongates and makes the bubble break up. In the merging symmetrical breakup regime, the bubble has a tunnel breakup process at the beginning. The shear force is small and cannot break up the bubble. The merged bubble breaks up under the action of the obstructed breakup regime. Bubbles are in the merging non-breakup regime mainly because they are too long to break up.
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Pan, Wen-Tao, Lin Wen, Shan-Shan Li i Zhen-Hai Pan. "Numerical study of asymmetric breakup behavior of bubbles in Y-shaped branching microchannels". Acta Physica Sinica 71, nr 2 (2022): 024701. http://dx.doi.org/10.7498/aps.71.20210832.
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Microfluidic technology based on microchannel two-phase flow has been widely used. The precise control of the bubble or droplet size in the channel plays a crucial role in designing the microfluidic systems. In this work, the bubble breakup behavior in Y-shaped microchannel is reconstructed based on the volume of fluid method (VOF), and the effects of bubble dimensionless size (1.2–2.7), outlet flow ratio (1–4) and main channel Reynolds number (100–600) on the bubble breakup behavior are systematically investigated. The bubble asymmetric breakup process is found to be divided into three stages: extension stage, squeeze stage, and rapid pinch-off stage. In the case of small initial bubble size or relatively high outlet flow rate, the bubble does not break, but only experiences the extension stage and the squeezing stage. Four flow patterns of bubble breakup are further revealed for the bubbles with different sizes and outlet flow ratios: tunnel-tunnel breakup, obstruction-obstruction breakup, tunnel-obstruction breakup, and non-breakup. With the increase of outlet flow ratio, the breakup process of the bubble gradually becomes asymmetrical, and the flow pattern shifts along the tunnel-tunnel breakup and the obstruction-obstruction breakup, gradually turns toward the tunnel-obstruction breakup and non-breakup. On this basis, the critical flow ratio of bubble breakup and the variation of daughter bubble volume ratio with outlet flow ratio are obtained for different Reynolds numbers and initial bubble sizes, and the corresponding criterion correlation equation is refined, which can provide theoretical guidance for accurately regulating the daughter bubble size after breakup.
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Chen, Huiting, Shiyu Wei, Weitian Ding, Han Wei, Liang Li, Henrik Saxén, Hongming Long i Yaowei Yu. "Interfacial Area Transport Equation for Bubble Coalescence and Breakup: Developments and Comparisons". Entropy 23, nr 9 (25.08.2021): 1106. http://dx.doi.org/10.3390/e23091106.
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Bubble coalescence and breakup play important roles in physical-chemical processes and bubbles are treated in two groups in the interfacial area transport equation (IATE). This paper presents a review of IATE for bubble coalescence and breakup to model five bubble interaction mechanisms: bubble coalescence due to random collision, bubble coalescence due to wake entrainment, bubble breakup due to turbulent impact, bubble breakup due to shearing-off, and bubble breakup due to surface instability. In bubble coalescence, bubble size, velocity and collision frequency are dominant. In bubble breakup, the influence of viscous shear, shearing-off, and surface instability are neglected, and their corresponding theory and modelling are rare in the literature. Furthermore, combining turbulent kinetic energy and inertial force together is the best choice for the bubble breakup criterion. The reviewed one-group constitutive models include the one developed by Wu et al., Ishii and Kim, Hibiki and Ishii, Yao and Morel, and Nguyen et al. To extend the IATE prediction capability beyond bubbly flow, two-group IATE is needed and its performance is strongly dependent on the channel size and geometry. Therefore, constitutive models for two-group IATE in a three-type channel (i.e., narrow confined channel, round pipe and relatively larger pipe) are summarized. Although great progress in extending the IATE beyond churn-turbulent flow to churn-annual flow was made, there are still some issues in their modelling and experiments due to the highly distorted interface measurement. Regarded as the challenges to be addressed in the further study, some limitations of IATE general applicability and the directions for future development are highlighted.
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Wang, Ziyue, Liansheng Liu, Runze Duan i Liang Tian. "The aerobreakup of bubbles in continuous airflow". Physics of Fluids 34, nr 4 (kwiecień 2022): 043317. http://dx.doi.org/10.1063/5.0086604.
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Floating soap bubbles usually break up owing to gravitational drainage, surface evaporation, environmental disturbances, and collisions with objects. If a gust of wind blows into a bubble, does the bubble break, and, if so, how does it do so? This study reports experiments that use a high-speed camera to examine the dynamic behaviors of a suspended bubble that is suddenly exposed to continuous airflow. Specifically, the behaviors and mechanisms of the aerobreakup of bubbles are explored. The suspended bubble undergoes shedding and deformation under aerodynamic force and flows with airflow. As the Weber number ( We) increases, the parameter of Taylor deformation ( DT) first increases and then decreases. At a higher Reynolds number, K–H waves appear on the surface of the film owing to the strong shear of airflow on the liquid film. Most such bubbles break due to the shear of the wake vortices on the leeward surface or surface waves on the windward surface, both of which are shearing. The aerobreakup of the bubbles becomes more severe with an increase in We, and they successively exhibit modes of wind-flowing, leeward breakup, windward breakup, and multihole breakup.
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Zhang, Chengbin, Xuan Zhang, Qianwen Li i Liangyu Wu. "Numerical Study of Bubble Breakup in Fractal Tree-Shaped Microchannels". International Journal of Molecular Sciences 20, nr 21 (5.11.2019): 5516. http://dx.doi.org/10.3390/ijms20215516.
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Hydrodynamic behaviors of bubble stream flow in fractal tree-shaped microchannels is investigated numerically based on a two-dimensional volume of fluid (VOF) method. Bubble breakup is examined in each level of bifurcation and the transition of breakup regimes is discussed in particular. The pressure variations at the center of different levels of bifurcations are analyzed in an effort to gain further insight into the underlying mechanism of bubble breakup affected by multi-levels of bifurcations in tree-shaped microchannel. The results indicate that due to the structure of the fractal tree-shaped microchannel, both lengths of bubbles and local capillary numbers decrease along the microchannel under a constant inlet capillary number. Hence the transition from the obstructed breakup and obstructed-tunnel combined breakup to coalescence breakup is observed when the bubbles are flowing into a higher level of bifurcations. Compared with the breakup of the bubbles in the higher level of bifurcations, the behaviors of bubbles show stronger periodicity in the lower level of bifurcations. Perturbations grow and magnify along the flow direction and the flow field becomes more chaotic at higher level of bifurcations. Besides, the feedback from the unequal downstream pressure to the upstream lower level of bifurcations affects the bubble breakup and enhances the upstream asymmetrical behaviors.
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MARTÍNEZ-BAZÁN, C., J. L. MONTAÑÉS i J. C. LASHERAS. "On the breakup of an air bubble injected into a fully developed turbulent flow. Part 1. Breakup frequency". Journal of Fluid Mechanics 401 (25.12.1999): 157–82. http://dx.doi.org/10.1017/s0022112099006680.
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The transient evolution of the bubble-size probability density functions resulting from the breakup of an air bubble injected into a fully developed turbulent water ow has been measured experimentally using phase Doppler particle sizing (PDPA) and image processing techniques. These measurements were used to determine the breakup frequency of the bubbles as a function of their size and of the critical diameter Dc defined as Dc = 1.26 (σ/ρ)3/5ε−2/5, where ε is the rate of dissipation per unit mass and per unit time of the underlying turbulence. A phenomenological model is proposed showing the existence of two distinct bubble size regimes. For bubbles of sizes comparable to Dc, the breakup frequency is shown to increase as (σ/ρ)−2/5ε−3/5 √D/Dc−1, while for large bubbles whose sizes are greater than 1.63Dc, it decreases with the bubble size as ε1/3D−2/3. The model is shown to be in good agreement with measurements performed over a wide range of bubble sizes and turbulence intensities.
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ENTOV, VLADIMIR, i PAVEL ETINGOF. "On the breakup of air bubbles in a Hele-Shaw cell". European Journal of Applied Mathematics 22, nr 2 (21.12.2010): 125–49. http://dx.doi.org/10.1017/s095679251000032x.
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We study the problem of breakup of an air bubble in a Hele-Shaw cell. In particular, we propose some sufficient conditions of breakup of the bubble, and ways to find the contraction points of its parts. We also study regulated contraction of a pair of bubbles (in which the rates of air extraction from the bubbles are controlled) and study various asymptotic questions (such as the asymptotics of contraction of a bubble to a degenerate critical point, and asymptotics of contraction of a small bubble in the presence of a big bubble)
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Ekambara, K., R. Sean Sanders, K. Nandakumar i J. H. Masliyah. "CFD Modeling of Gas-Liquid Bubbly Flow in Horizontal Pipes: Influence of Bubble Coalescence and Breakup". International Journal of Chemical Engineering 2012 (2012): 1–20. http://dx.doi.org/10.1155/2012/620463.
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Modelling of gas-liquid bubbly flows is achieved by coupling a population balance equation with the three-dimensional, two-fluid, hydrodynamic model. For gas-liquid bubbly flows, an average bubble number density transport equation has been incorporated in the CFD code CFX 5.7 to describe the temporal and spatial evolution of the gas bubbles population. The coalescence and breakage effects of the gas bubbles are modeled. The coalescence by the random collision driven by turbulence and wake entrainment is considered, while for bubble breakage, the impact of turbulent eddies is considered. Local spatial variations of the gas volume fraction, interfacial area concentration, Sauter mean bubble diameter, and liquid velocity are compared against experimental data in a horizontal pipe, covering a range of gas (0.25 to 1.34 m/s) and liquid (3.74 to 5.1 m/s) superficial velocities and average volume fractions (4% to 21%). The predicted local variations are in good agreement with the experimental measurements reported in the literature. Furthermore, the development of the flow pattern was examined at three different axial locations ofL/D= 25, 148, and 253. The first location is close to the entrance region where the flow is still developing, while the second and the third represent nearly fully developed bubbly flow patterns.
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Solsvik, Jannike, i Hugo A. Jakobsen. "Single Air Bubble Breakup Experiments in Stirred Water Tank". International Journal of Chemical Reactor Engineering 13, nr 4 (1.12.2015): 477–91. http://dx.doi.org/10.1515/ijcre-2014-0154.
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Abstract Single gas bubbles have been injected into an stirred liquid tank and the eventual breakup process of the bubbles was examined through high-speed imaging. Experimental observations of the breakup probability, breakup time, number of daughter bubbles and daughter bubble size distribution have been collected. The occurrence of non-equal-size breakup events dominated over equal-size breakup events. The frequency of binary and multiple breakup events was about equal. The largest uncertainty is associated with the determination of the breakup time because the bubbles take continuously altering deformed shapes already from the point of injection into the tank. The present experimental data do not support the standard model assumption regarding the number of daughter particles. The active breakup zone in the stirred tank was in the large velocity field close to the radial impeller. It is not evident whether the breakup events are due to time average shear or pressures and velocity fluctuations.
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Yang, Weidong, Zhiguo Luo, Nannan Zhao i Zongshu Zou. "Numerical Analysis of Effect of Initial Bubble Size on Captured Bubble Distribution in Steel Continuous Casting Using Euler-Lagrange Approach Considering Bubble Coalescence and Breakup". Metals 10, nr 9 (27.08.2020): 1160. http://dx.doi.org/10.3390/met10091160.
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A mathematic model considering the bubble coalescence and breakup using the Euler-Lagrange approach has been developed to study the effect of the initial bubble size on the distribution of bubbles captured by the solidification shell. A hard sphere model was applied for dealing with the bubble collision. Advanced bubble coalescence and breakup models suitable for the continuous casting system and an advanced bubble captured criteria have been identified established with the help of user-defined functions of FLUENT. The predictions of bubble behavior and captured bubble distribution agree with the water model and plant measurements well respectively. The results show that the number of small bubbles captured by solidification shell is much higher than that of large bubbles. What is more, the number of captured bubbles at the sidewalls decreases with the distance from the meniscus. For the case of large gas flow rate (gas flow fraction of 8.2%), the initial size of bubbles has little effect on bubble captured distribution under various casting speeds. When the gas flow rate is small (gas flow fraction of 4.1%), the number density of captured bubbles increases as the initial bubble size increases, and the effect of initial bubbles size on captured bubble number density is amplified when the casting speed decreases. The average captured bubble diameter is about 0.12–0.14 mm. Additionally, for all cases, the initial bubble size hardly affects the average size of captured bubbles.
Rozprawy doktorskie na temat "Bubble breakup"
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Kang, In Seok Leal L. Gary Leal L. Gary. "Bubble dynamics and breakup in straining flows /". Diss., Pasadena, Calif. : California Institute of Technology, 1988. http://resolver.caltech.edu/CaltechETD:etd-11072007-112829.
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Liao, Yixiang. "Development and validation of models for bubble coalescence and breakup". Helmholtz-Zentrum Dresden-Rossendorf, 2013. https://hzdr.qucosa.de/id/qucosa%3A22180.
Pełny tekst źródłaStreszczenie:
A generalized model for bubble coalescence and breakup has been developed, which is based on a comprehensive survey of existing theories and models. One important feature of the model is that all important mechanisms leading to bubble coalescence and breakup in a turbulent gas-liquid flow are considered. The new model is tested extensively in a 1D Test Solver and a 3D CFD code ANSYS CFX for the case of vertical gas-liquid pipe flow under adiabatic conditions, respectively. Two kinds of extensions of the standard multi-fluid model, i.e. the discrete population model and the inhomogeneous MUSIG (multiple-size group) model, are available in the two solvers, respectively. These extensions with suitable closure models such as those for coalescence and breakup are able to predict the evolution of bubble size distribution in dispersed flows and to overcome the mono-dispersed flow limitation of the standard multi-fluid model.
For the validation of the model the high quality database of the TOPFLOW L12 experiments for air-water flow in a vertical pipe was employed. A wide range of test points, which cover the bubbly flow, turbulent-churn flow as well as the transition regime, is involved in the simulations. The comparison between the simulated results such as bubble size distribution, gas velocity and volume fraction and the measured ones indicates a generally good agreement for all selected test points. As the superficial gas velocity increases, bubble size distribution evolves via coalescence dominant regimes first, then breakup-dominant regimes and finally turns into a bimodal distribution. The tendency of the evolution is well reproduced by the model. However, the tendency is almost always overestimated, i.e. too much coalescence in the coalescence dominant case while too much breakup in breakup dominant ones. The reason of this problem is discussed by studying the contribution of each coalescence and breakup mechanism at different test points. The redistribution of the gaseous phase from the injection position at the pipe wall to the whole cross section is overpredicted by the Test Solver especially for the test points with high superficial gas velocity. Besides the models for bubble forces, the simplification of the Test Solver to a 1D model has an influence on the redistribution process. Simulations performed using CFX show that a considerable improvement is achieved with comparison to the results delivered by the standard closure models. For the breakup-dominant cases, the breakup rate is again overestimated and the contribution of wake entrainment of large bubbles is underestimated. Furthermore, inlet conditions for the liquid phase, bubble forces as well as turbulence modeling are shown to have a noticeable influence, especially on the redistribution of the gaseous phase.
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Liao, Yixiang. "Development and validation of models for bubble coalescence and breakup". Forschungszentrum Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-134760.
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A generalized model for bubble coalescence and breakup has been developed, which is based on a comprehensive survey of existing theories and models. One important feature of the model is that all important mechanisms leading to bubble coalescence and breakup in a turbulent gas-liquid flow are considered. The new model is tested extensively in a 1D Test Solver and a 3D CFD code ANSYS CFX for the case of vertical gas-liquid pipe flow under adiabatic conditions, respectively. Two kinds of extensions of the standard multi-fluid model, i.e. the discrete population model and the inhomogeneous MUSIG (multiple-size group) model, are available in the two solvers, respectively. These extensions with suitable closure models such as those for coalescence and breakup are able to predict the evolution of bubble size distribution in dispersed flows and to overcome the mono-dispersed flow limitation of the standard multi-fluid model.
For the validation of the model the high quality database of the TOPFLOW L12 experiments for air-water flow in a vertical pipe was employed. A wide range of test points, which cover the bubbly flow, turbulent-churn flow as well as the transition regime, is involved in the simulations. The comparison between the simulated results such as bubble size distribution, gas velocity and volume fraction and the measured ones indicates a generally good agreement for all selected test points. As the superficial gas velocity increases, bubble size distribution evolves via coalescence dominant regimes first, then breakup-dominant regimes and finally turns into a bimodal distribution. The tendency of the evolution is well reproduced by the model. However, the tendency is almost always overestimated, i.e. too much coalescence in the coalescence dominant case while too much breakup in breakup dominant ones. The reason of this problem is discussed by studying the contribution of each coalescence and breakup mechanism at different test points. The redistribution of the gaseous phase from the injection position at the pipe wall to the whole cross section is overpredicted by the Test Solver especially for the test points with high superficial gas velocity. Besides the models for bubble forces, the simplification of the Test Solver to a 1D model has an influence on the redistribution process. Simulations performed using CFX show that a considerable improvement is achieved with comparison to the results delivered by the standard closure models. For the breakup-dominant cases, the breakup rate is again overestimated and the contribution of wake entrainment of large bubbles is underestimated. Furthermore, inlet conditions for the liquid phase, bubble forces as well as turbulence modeling are shown to have a noticeable influence, especially on the redistribution of the gaseous phase.
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Mawson, Ryan A. "Bubble Coalescence and Breakup Modeling for Computing Mass Transfer Coefficient". DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1330.
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There exist several different numerical models for predicting bubble coalescence and breakup using computational fluid dynamics (CFD). Various combinations of these models will be employed to model a bioreactor process in a stirred reactor tank. A mass transfer coefficient, Kla, has been calculated and compared to those found experimentally by Thermo-Fisher Scientific, to validate the accuracy of currently available mathematical models for population balance equations. These include various combinations of bubble breakup and coalescence models coupled with the calculation of mass transfer coefficients.
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Krepper, Eckhard, i Dirk Lucas. "CFD models for polydispersed bubbly flows". Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-28052.
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Many flow regimes in Nuclear Reactor Safety Research are characterized by multiphase flows, with one phase being a continuous liquid and the other phase consisting of gas or vapour of the liquid phase. In dependence on the void fraction of the gaseous phase the flow regimes e.g. in vertical pipes are varying from bubbly flows with low and higher volume fraction of bubbles to slug flow, churn turbulent flow, annular flow and finally to droplet flow. In the regime of bubbly and slug flow the multiphase flow shows a spectrum of different bubble sizes. While disperse bubbly flows with low gas volume fraction are mostly mono-disperse, an increase of the gas volume fraction leads to a broader bubble size distribution due to breakup and coalescence of bubbles. Bubbles of different sizes are subject to lateral migration due to forces acting in lateral direction different from the main drag force direction. The bubble lift force was found to change the sign dependent on the bubble size. Consequently this lateral migration leads to a de-mixing of small and large bubbles and to further coalescence of large bubbles migrating towards the pipe center into even larger Taylor bubbles or slugs. An adequate modeling has to consider all these phenomena. A Multi Bubble Size Class Test Solver has been developed to investigate these effects and test the influence of different model approaches. Basing on the results of these investigations a generalized inhomogeneous Multiple Size Group (MUSIG) Model based on the Eulerian modeling framework has been proposed and was finally implemented into the CFD code CFX. Within this model the dispersed gaseous phase is divided into N inhomogeneous velocity groups (phases) and each of these groups is subdivided into Mj bubble size classes. Bubble breakup and coalescence processes between all bubble size classes Mj are taken into account by appropriate models. The inhomogeneous MUSIG model has been validated against experimental data from the TOPFLOW test facility.
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Krepper, Eckhard, i Dirk Lucas. "CFD models for polydispersed bubbly flows". Forschungszentrum Dresden-Rossendorf, 2007. https://hzdr.qucosa.de/id/qucosa%3A21632.
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Many flow regimes in Nuclear Reactor Safety Research are characterized by multiphase flows, with one phase being a continuous liquid and the other phase consisting of gas or vapour of the liquid phase. In dependence on the void fraction of the gaseous phase the flow regimes e.g. in vertical pipes are varying from bubbly flows with low and higher volume fraction of bubbles to slug flow, churn turbulent flow, annular flow and finally to droplet flow. In the regime of bubbly and slug flow the multiphase flow shows a spectrum of different bubble sizes. While disperse bubbly flows with low gas volume fraction are mostly mono-disperse, an increase of the gas volume fraction leads to a broader bubble size distribution due to breakup and coalescence of bubbles. Bubbles of different sizes are subject to lateral migration due to forces acting in lateral direction different from the main drag force direction. The bubble lift force was found to change the sign dependent on the bubble size. Consequently this lateral migration leads to a de-mixing of small and large bubbles and to further coalescence of large bubbles migrating towards the pipe center into even larger Taylor bubbles or slugs. An adequate modeling has to consider all these phenomena. A Multi Bubble Size Class Test Solver has been developed to investigate these effects and test the influence of different model approaches. Basing on the results of these investigations a generalized inhomogeneous Multiple Size Group (MUSIG) Model based on the Eulerian modeling framework has been proposed and was finally implemented into the CFD code CFX. Within this model the dispersed gaseous phase is divided into N inhomogeneous velocity groups (phases) and each of these groups is subdivided into Mj bubble size classes. Bubble breakup and coalescence processes between all bubble size classes Mj are taken into account by appropriate models. The inhomogeneous MUSIG model has been validated against experimental data from the TOPFLOW test facility.
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Liao, Y., i D. Lucas. "Entwicklung und Validierung von Modellen für Blasenkoaleszenz und -zerfall". Forschungszentrum Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-113883.
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Ein neues, verallgemeinertes Modell für Blasenkoaleszenz und –zerfall wurde entwickelt. Es basiert auf physikalischen Überlegungen und berücksichtigt verschiedene Mechanismen, die zu Blasenkoaleszenz und –zerfall führen können. In einer ausführlichen Literaturrecherche wurden zunächst die verfügbaren Modelle zusammengestellt und analysiert. Es zeigte sich, dass viele widersprüchliche Modelle veröffentlicht wurden. Keins dieser Modelle erlaubt die Vorhersage der Entwicklung der Blasengrößenverteilungen entlang einer Rohrströmung für einen breiten Bereich an Kombinationen von Volumenströmen der Gas- und der Flüssigphase.
Das neue Modell wurde ausführlich in einem vereinfachten Testsolver untersucht. Dieser erfasst zwar nicht alle Einzelheiten einer sich entlang des Rohres entwickelten Strömungen, erlaubt aber im Gegensatz zu den CFD-Simulationen eine Vielzahl von Variationsrechnungen zur Untersuchung des Einflusses einzelner Größen und Modelle. Koaleszenz und Zerfall kann nicht getrennt von anderen Phänomenen und Modellen, die diese widerspiegeln, betrachtet werden. Es bestehen enge Wechselwirkungen mit der Turbulenz der Flüssigphase und dem Impulsaustausch zwischen den Phasen. Da die Dissipationsrate der turbulenten kinetischen Energie ein direkter Eingangsparameter für das neue Modell ist, wurde die Turbulenzmodellierung besonders genau untersucht.
Zur Validierung des Modells wurde eine TOPFLOW-Experimentalserie zur Luft-Wasser-Strömungen in einem 8 m langen DN200-Rohr genutzt. Die Daten zeichnen sich durch eine hohe Qualität aus und wurden im Rahmen des TOPFLOW-IIVorhabens mit dem Ziel eine Grundlage für die hier vorgestellten Arbeiten zu liefern, gewonnen. Die Vorhersage der Entwicklung der Blasengrößenverteilung entlang des Rohrs konnte im Vergleich zu den bisherigen Standardmodellen für Blasenkoaleszenz und -zerfall in CFX deutlich verbessert werden. Einige quantitative Abweichungen bleiben aber bestehen.
Die vollständigen Modellgleichungen sowie eine Implementierung über „User-FORTRAN“ in CFX stehen zur Verfügung und können für weitere Arbeiten zur Simulation polydisperser Blasenströmungen genutzt werden.
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Pellacani, Filippo [Verfasser], Rafael [Akademischer Betreuer] Macián-Juan i Vicent Sergio [Akademischer Betreuer] Chiva. "Development and Validation of Bubble Breakup and Coalescence Constitutive Models for the One-Group Interfacial Area Transport Equation / Filippo Pellacani. Gutachter: Sergio Chiva Vicent ; Rafael Macián-Juan. Betreuer: Rafael Macián-Juan". München : Universitätsbibliothek der TU München, 2012. http://d-nb.info/104199480X/34.
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Wu, Yining. "Étude des phénomènes interfaciaux à micro-échelle". Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0330/document.
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Cette thèse a étudié de façon systématique les processus de la rupture et de la coalescence impliquant une interface liquide-liquide (gouttelettes) ou gaz-liquide (bulles) en présence ou pas d’un champ magnétique dans des dispositifs microfluidiques, à l’aide d’une caméra rapide. Les mécanismes de la rupture d’une interface ferrofluide sous différents champs magnétiques ont été étudiés et comparés. On a constaté que la structure morphologique et la vitesse d’amincissement du cou peuvent être contrôlées activement par la force magnétique. Ainsi, le volume et la fréquence de formation de gouttelettes de ferrofluide peuvent être pilotés aisément. La rupture de l'interface liquide-liquide a généralement conduit à la formation de gouttelettes satellites avec sa taille proportionnelle au nombre capillaire de la phase continue. La coalescence des gouttelettes ont aussi été étudiée avec l’analyse de l'évolution du cou reliant deux gouttelettes. Il a été constaté que la formation du pont ou du cou liquide pouvait se produire dans la gamme de l'ordre de dizaines de micromètres entre les bords d'attaque sous champ magnétique. L'inertie d’origine d'attraction magnétique sur des gouttelettes de ferrofluide devenait la force motrice pour la coalescence lors de la première étape au détriment de la force capillaireThis thesis systematically investigates the breakup and coalescence processes of the involved droplet (bubble) interface under magnetic field or not in two-phase microfluidic flow, by using a high speed digital camera. The whole breakup processes of ferrofluid interface under different magnetic fields were investigated and compared. It was found that the morphological structure and necking velocity of the interface can be actively controlled by the magnetic force. Thus the volumes and the formation frequencies of ferrofluid droplets can be actively adjusted. The breakup of Liquid-Liquid interface usually leads to the formation of satellite droplet with its size proportional to the capillary number of the continuous phase. The coalescences of droplets were investigated. The evolution of the neck connecting two droplets was analyzed. It was found that the formation of liquid bridge or neck could occurs with a visible gap in the order of tens of micrometers between the leading edges under magnetic field and the inertia of the ferrofluid originating from the magnetic attraction fields becomes the driving force at the initial stage of coalescence instead of capillary force
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Zschau, Jochen, Winfried Zippe, Cornelius Zippe, Horst-Michael Prasser, Dirk Lucas, Ulrich Rohde, Arnd Böttger i in. "Strömungskarten und Modelle für transiente Zweiphasenströmungen". Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-29111.
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Experimente mit neuartigen Messverfahren lieferten Daten über die Struktur von transienten Flüssig-keits-Gas-Strömungen für die Entwicklung und Validierung von mikroskopischen, d.h. geometrieunabhängigen Konstitutivbeziehungen zur Beschreibung des Impulsaustauschs zwischen Flüssig-phase und Gasblasen sowie zur Quantifizierung der Häufigkeit von Blasenkoaleszenz und -zerfall. Hierzu wurde eine vertikale Testsektion der Zweiphasentestschleife MTLoop in Rossendorf genutzt, wobei erstmals Gittersensoren mit einer Auflösung von 2-3 mm bei einer Messfrequenz von bis zu 10 kHz angewandt wurden. Dabei wurde die Evolution von Gasgehalts-, Geschwindigkeits- und Bla-sengrößenverteilungen entlang des Strömungsweges und bei schnellen Übergangsprozessen aufge-nommen und so die für die Modellbildung erforderlichen Daten bereitgestellt. Für den Test der Mo-dellbeziehungen wurde ein vereinfachtes Verfahren zur Lösung der Strömungsgleichungen entlang des Strömungswegs erstellt. Es basiert auf der Betrachtung einer größeren Anzahl von Blasengrö-ßenklassen. Die erhaltenen numerische Lösungen haben erstmals gezeigt, dass der bei Erhöhung der Gasvolumenstromdichte stattfindende Übergang von einer Blasenströmung mit Randmaximum zu einem Profil mit Zentrumsmaximum und anschließend zu einer Pfropfenströmung ausgehend von einem einheitlichen Satz physikalisch begründeter und geometrieunabhängiger Konstitutivgleichun-gen modelliert werden kann. Die Modellbeziehungen haben sich in einem abgegrenzten Gebiet der Volumenstromdichten als generalisierungsfähig erwiesen und sind für den Einbau in CFD-Modelle geeignet. Weiterhin wurden Arbeiten zur Kondensation durchgeführt, die direkten Bezug zu den Kon-densationsmodellen haben, die in Thermohydraulik-Codes enthalten sind. Die Untersuchung liefert darüber hinaus experimentelle Daten für die Modellvalidierung hinsichtlich des Verhaltens und des Einflusses nichtkondensierbarer Gase. Hierfür wurden spezielle Sonden für die Bestimmung der Konzentration und für die Lokalisierung von Pfropfen nichtkondensierbarer Gase entwickelt und bei transienten Kondensationsversuchen in einem leicht geneigten Wärmeübertragerrohr eingesetzt.
Książki na temat "Bubble breakup"
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Zhou, Su-min. Interface dynamics: Bubble growth and droplet breakup in the Hele-Shaw cell. 1992.
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HAWLEY, George. Tangled Wires: A Telecom Career Spanning the Bell System Breakup to the Internet Bubble. Independently Published, 2017.
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Patterson, Brandon, Marc Henry de Frahan i Erika Lazar. Brooke Bubble Breaks Things. BrookeBubble, 2018.
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A Dream and a Dollar: Strategies That Will Help You Break Out of Your "Dream Bubble.". Point of Grace Entertainment, 2005.
Znajdź pełny tekst źródłaCzęści książek na temat "Bubble breakup"
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Avdeev, Alexander A. "Bubble Breakup". W Mathematical Engineering, 371–415. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-29288-5_10.
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Biswas, Subhajit, i Raghuraman N. Govardhan. "Bubble Capture, Breakup, and Coalescence in Vortex–Bubble Interaction". W Lecture Notes in Mechanical Engineering, 33–41. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-15-5183-3_4.
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Gärtner, Jan Wilhelm, Daniel D. Loureiro i Andreas Kronenburg. "Modelling and Simulation of Flash Evaporation of Cryogenic Liquids". W Fluid Mechanics and Its Applications, 233–50. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-09008-0_12.
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AbstractRocket engine manufacturers attempt to replace toxic, hypergolic fuels by less toxic substances such as cryogenic hydrogen and oxygen. Such components will be superheated when injected into the combustion chamber prior to ignition. The liquids will flash evaporate and subsequent mixing will be crucial for a successful ignition of the engine. We now conduct a series of DNS and RANS-type simulations to better understand this mixing process including microscopic processes such as bubble growth, bubble-bubble interactions, spray breakup dynamics and the resulting droplet size distribution. Full scale RANS simulations provide further insight into effects associated with flow dynamic such as shock formation behind the injector outlet. Capturing these gas dynamic effects is important, as they affect the spray morphology and droplet movements.
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Senhaji, R., A. Abdelqari i J. M. Rosant. "Characterization of Turbulent Properties in Relation with Bubble/Drop Breakup Process". W Fluid Mechanics and Its Applications, 460–64. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0457-9_84.
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Sadhal, S. S., P. S. Ayyaswamy i J. N. Chung. "Formation and Breakup of Bubbles and Drops". W Transport Phenomena with Drops and Bubbles, 311–401. New York, NY: Springer New York, 1997. http://dx.doi.org/10.1007/978-1-4612-4022-8_7.
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Gnotke, O., R. Jeschke i R. Loth. "Experimental and theoretical investigation of bubble break-up and coalescence in bubbly flows". W Bubbly Flows, 85–99. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-642-18540-3_8.
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Chen, Shyh-Wei, i Zixiong Xie. "Smooth break, non-linearity, and speculative bubbles". W International Financial Markets, 133–59. Abingdon, Oxon ; New York, NY : Routledge, 2019. | Series: Routledge advances in applied financial econometrics ; volume 1: Routledge, 2019. http://dx.doi.org/10.4324/9781315162775-6.
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Vrijenhoek, Sanne, i Natali Helberger. "Pitch Proposal: Recommenders with a Mission - Assessing Diversity in News Recommendations". W ECML PKDD 2020 Workshops, 554–61. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-65965-3_38.
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AbstractBy helping the user find relevant and important online content, news recommenders have the potential to fulfill a crucial role in a democratic society. Simultaneously, recent concerns about filter bubbles, fake news and selective exposure are symptomatic of the disruptive potential of these digital news recommenders. Recommender systems can make or break filter bubbles, and as such can be instrumental in creating either a more closed or a more open internet. This document details a pitch for an ongoing project that aims to bridge the gap between normative notions of diversity, rooted in democratic theory, and quantitative metrics necessary for evaluating the recommender system. Our aim is to get feedback on a set of proposed metrics grounded in social science interpretations of diversity.
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Liovic, Petar, Djamel Lakehal i Jong-Leng Liow. "LES of Turbulent Bubble Formation and Break-Up Based on Interface Tracking". W Direct and Large-Eddy Simulation V, 261–70. Dordrecht: Springer Netherlands, 2004. http://dx.doi.org/10.1007/978-1-4020-2313-2_28.
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Kakuno, Shohachi, Douglas B. Moog, Tetsuya Tatekawa, Kenji Takemura i Tatsuya Yamagishi. "The Effect of Bubbles on Air-Water Oxygen Transfer in the Breaker Zone". W Gas Transfer at Water Surfaces, 265–70. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm127p0265.
Pełny tekst źródłaStreszczenia konferencji na temat "Bubble breakup"
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Jo, Daeseong, i Shripad T. Revankar. "Study of Bubbly Flow Through a Packed Bed". W ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64767.
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A two phase bubbly flow through a packed bed was studied for dominant bubble breakup and coalescence mechanisms through experiments and CFD modeling. Data on various two-phase parameters, such as local void fraction, bubble velocity, size, number, and shape were obtained from the high speed video images. Results indicated that when a flow regime changed from bubbly to either trickling or pulsing flow, the number of average size bubbles significantly decreased and the shape of majority of bubbles was no longer spherical. The bubble coalescence and breakup mechanisms depend on local conditions such as local velocity of the bubble and pore geometry. The CFD analysis using CFX software package was carried out to study bubble size distributions. In the analysis the models for interactions were examined for each case of bubble breakup flow and bubble coalescence. A comparative study was performed on the resulting bubble size distributions, breakup and coalescence rates estimated by individual models. For change of bubble size distributions along the axial direction medians was used as an comparative parameter and the CFD results on bubble medians were compared against the experimental data. This comparative study showed that the predictions estimated by CFD analyses with the bubble breakup and coalescence models currently available in the literature do not agree with the experimental data.
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Fujiwara, A., K. Okamoto, K. Hashiguchi, J. Peixinho, S. Takagi i Y. Matsumoto. "Bubble Breakup Phenomena in a Venturi Tube". W ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37243.
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Microbubble generation techniques have been proposed in former investigations. Here, we study an effective technique using air bubbly flow into a convergent-divergent nozzle (venturi tube). Pressure change in the diverging section induces bubble breakup. The purpose of this study is to clarify the effect of flow velocity at the throat with respect to the bubble breakup process and the bubble behavior in a venturi tube. Relations between generated bubble diameter and bubble breakup process are also described. Using high speed camera for detailed observation of bubble behavior, the following features were obtained. The velocity at the throat is expected to be of the order of the magnitude of the speed of sound of bubbly flow and a drastic bubble expansion and a shrink is induced. Besides, a liquid column appeared after the bubble flowing into the throat, and it grew up to stick to the bubble like in the form of a jet. This jet induced both unstable surface waves and the breakup of a single large bubble into several pieces.
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Yoshida, Kohei, Kota Fujiwara, Akiko Kaneko i Yutaka Abe. "Experimental Study on Bubble and Aerosol Behavior During Pool Scrubbing". W 2021 28th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/icone28-61490.
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Abstract Understanding radioactive aerosol behavior is important during severe accidents in nuclear power plants. In particular, pool scrubbing at a suppression pool is a key factor for estimating the leakage of radioactive aerosol into the environment. Therefore, we have to elucidate the mechanism of the aerosol transfer from the gas phase to the liquid phase during bubbly flow. Currently, models to evaluate the amount of aerosol removal by pool scrubbing have been incorporated into integrated severe accident analysis codes such as MELCOR. However, the models for bubbles and aerosols behavior have not been validated enough by experiment. Therefore, the measurement of bubbles and aerosols behavior is required for validation and reconstruction pool scrubbing model. However, the quantitative measurement of bubbly flow is very difficult by complicated bubble shape and overlapping of bubbles in visualization. The wire-mesh sensor (WMS) is one of the most effective measuring methods for complicated bubbly flow. The reconstruction method of bubbly flow by WMS measurement is suggested by Prasser et al. This method can measure the bubble surface, meanwhile, individual bubble velocity and volume are not one-to-one correspondence because bubble volume is calculated by using radial average velocity. Kanai et al. proposed a method for acquisition bubble three-dimensional velocity method by bubble tracking. In this method, bubble velocity and volume are one-to-one correspondence. Thus, we suggested an algorithm of bubble surface measurement by applying a bubble tracking method. The bubble three-dimensional velocity and surface area is obtained by this algorithm. As a result, bubble rising velocity in bubbly flow is higher than bubble terminal velocity according to causing liquid phase velocity. In addition, the gas-liquid total interfacial area is overestimated in MELCOR predict by overestimating bubble breakup. This result suggests that the overestimating of DF at downstream is caused by overestimating bubble breakup in MELCOR model.
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Zima, Patrik, i Milan Sedlář. "Modeling Bubble Collapse Aggressiveness in Traveling Bubble Cavitation using Bubble Breakup Model". W 8th International Symposium on Cavitation. Singapore: Research Publishing Services, 2012. http://dx.doi.org/10.3850/978-981-07-2826-7_209.
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Maekawa, Munenori, Naoki Shimada, Kouji Kinoshita, Akira Sou i Akio Tomiyama. "Numerical Simulation of Heterogeneous Bubbly Flow in a Bubble Column". W ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98178.
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Numerical methods for predicting heterogeneous bubbly flows are indispensable for the design of a Fisher-Tropsh reactor for GTL (Gas To Liquid). It is necessary to take into account bubble size distribution determined by bubble coalescence and breakup for the accurate prediction of heterogeneous bubbly flows. Hence we implemented several bubble coalescence and breakup models into the (N+2) field model, which is a hybrid combination of an interface tracking method and a multi-fluid model. Void and bubble size distributions in an open rectangular bubble column were measured and compared with predicted ones. As a result, the following conclusions were obtained: (1) Void and bubble size distributions were not affected by inlet bubble sizes because the bubble size distribution reaches an equilibrium state at which the birth rate is equal to the death rate, and (2) the combination of Luo’s bubble breakup model and a coalescence model consisting of Prince & Blanch’s model and Wang’s wake entrainment model gave good predictions.
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Nomura, Yasumichi, Shin-ichiro Uesawa, Akiko Kaneko i Yutaka Abe. "Study on Bubble Breakup Mechanism in a Venturi Tube". W ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-10024.
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Microbubbles are expected to be applied in various subjects such as engineering and medical fields. Thus, on-demand microbubble generation techniques with high efficiently are required. In the present study, the microbubble generator using a venturi tube (converging-diverging nozzle) is focused. Although this technique realizes generation of many tiny bubbles with less than several-hundred-micrometer diameter, there are several unsolved parts of flow structure in a venturi tube on bubble breakup behavior. The purpose of this study is to clarify the bubble breakup mechanism in a venturi tube for practical use. In the present study, using a high speed camera for detailed observation of bubble behavior, the following features were obtained. In low velocity conditions, bubbles are divided in several pieces with a jet penetrating from the top (downstream) to the bottom (upstream) part of the bubble. In high velocity conditions, bubbles collapse in countless microbubbles with a drastic bubble expansion and shrinkage. Also, in order to clarify the flow structure in a venturi tube, pressure profile is measured in detail. Under chocking condition, the pressure profile shows the tendency of supersonic flow in a Laval nozzle and sudden pressure gradient appears in the diverging section. There are strong correlations between bubble fission points and pressure recovery points. It is suggested that bubble collapse is strongly influenced with pressure recovery in the diverging section.
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Li, Xianguo, i Jihua Shen. "Experiments on Annular Liquid Jet Breakup". W ASME 2001 Engineering Technology Conference on Energy. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/etce2001-17010.
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Abstract Experimental investigations have been carried out for the breakup process of an annular water jet exposed to an inner air stream by videographic and photographic techniques. Three flow regimes for the jet breakup process have been identified, i.e., bubble formation, annular jet formation and atomization. Within the bubble formation regime, the jet breakup characteristics measured from the photographs taken under various liquid and gas velocities indicate that nearly uniform bubbles are observed for various air-to-water velocity ratios; both the jet breakup length and the wavelength for bubble formation decrease as the air-to-water velocity ratio is increased. The measurements are compared with the predictions by the linear instability analysis, and fair agreement is obtained.
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Guan, Shunran, Jinyu Han, Chenru Zhao i Hanliang Bo. "Assessment and Analysis of Various Mechanisms in the Coalescence and Breakup Models for Upward Bubbly Flow". W 2021 28th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/icone28-64436.
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Abstract Accurate three-dimensional CFD simulation is of great importance to the flow and heat transfer of flow boiling in the steam generator in nuclear power plant, in which bubbly flow is the main flow pattern. One of the biggest challenges for the CFD simulation is the coalescence and breakup model for bubbles dispersed in the continuous fluid. Recently, several new bubble coalescence and breakup models have been developed combined with the inhomogeneous Multi-Size-Group (MUSIG) model in the Eulerian framework in addition to the standard closure model (Luo and Svendsen (1996), and Prince and Blanch (1990)), which has been widely adopted in the CFD simulations in bubbly flow using the Eulerian method. For example, Liao had developed a comprehensive closure model (2015), in which five collision mechanisms and four breakup mechanisms have been included in the model. However, proper coefficients for the Liao model must be determined to properly address the proportion for various mechanism in the coalescence and breakup models. In this paper, we compared the predictions using the standard closure model and the Liao model (2015) combined with the iMUSIG model for the case of adiabatic upward bubbly flow in vertical pipe, as well as the corresponding experimental results reported by Lucas et al (2008) which were obtained at TOPFLOW test facilities. Six simulated working conditions are chosen. The significance of various mechanisms on the bubble coalescence and breakup were analyzed based on the bubble size distributions in various heights obtained in the CFD predictions and experiments. Finally, a set of proper coefficients for various mechanisms in the coalescence and breakup models of Liao (2015) was developed for the simulated conditions.
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Ding, Guodong, Jiaqing Chen i Zhenlin Li. "An Investigation on the Bubble Breakup Characteristics by Recirculation Flow in a Venturi Channel". W ASME 2021 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/fedsm2021-65716.
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Abstract Discrete bubbles can be effectively cracked and dispersed in a Venturi channel with its unique structural characteristics, and the general Venturi channel has been widely used in the practical engineering. Bubble breakup mechanisms based on Venturi channels have been extensively studied, but most of them are based on single bubble or bubble flow pattern. In this paper, the transport process of slug flow in a Venturi channel was explored through visualization experiments, and the characteristics of recirculation flow were indicated by numerical simulation method. The liquid velocity sensitively affects the bubble generation process. With the increase of the liquid velocity, the initial bubble is no longer detached from the gas injector hole, and the gas-liquid flow pattern changes from bubbly flow to slug flow. The slug bubble extends to the diverging section and experiences the process of interface instability, sub-bubble detachment and bubble collapse. The average Sauter bubble diameter decreases with the increase of liquid velocity, and the fitting function is Log Normal. There is a recirculation flow in the side wall region of the diverging section, and the area of the recirculation flow increases with the increase of the liquid velocity at the inlet. The numerical simulation results indicated that there is a large velocity gradient in the boundary region of the recirculation flow under slug flow pattern, which contribute to the bubble collapse.
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Li, J., A. M. Castro i P. M. Carrica. "Progress on Prediction of Bubbly Flows Around Ships". W ASME 2016 Fluids Engineering Division Summer Meeting collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/fedsm2016-7665.
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This paper presents recent progress on prediction of bubbly flows around ships, including bubble entrainment modeling, bubble transport and numerical issues. The bubbly flow is described by a polydisperse two-fluid model that can predict the bubble entrainment locations and rates, bubble dissolution, breakup and coalescence rates, bubble velocities, turbulence quantities and bubble size distribution. To test the performance of the two phase flow model, several simulations are conducted on canonical bubbly flows with wave breaking. These well experimentally studied flows provide important information for the design of the bubble entrainment model, which is the weakest link in the model chain but crucial for prediction of the bubbly wake. The results are compared with experimental data to study the model’s accuracy and to calibrate the entrainment model constants. Full scale simulations for the flat bottom Kann boat and the Athena R/V are performed to evaluate the model under more complex flows of naval relevance that have considerable data available. It is found that the model calibrated with canonical problems predicts good results for Athena R/V, but the current turbulent entrainment model significantly underestimates the entrainment at the bow of Kann boat due to other entrainment mechanisms involved (entrainment due to impact, droplets, etc.). The breakup model, which currently considers turbulent mechanisms, underestimates the population of small bubbles in the boundary layer where strong shear is present. Finally, a grid study is carried on Athena R/V to test grid convergence. Void fraction and size distribution are compared against available experimental data and discussed in detail. Overall, the simulations show encouraging results considering the complexity of two phase flow involved in ship applications, and the model is proven to be grid independent, a very important property for practical applications.
Raporty organizacyjne na temat "Bubble breakup"
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McLaughlin, J. B. Bubble Motion, Deformation, and Breakup. Final Report. Office of Scientific and Technical Information (OSTI), sierpień 2003. http://dx.doi.org/10.2172/823827.
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