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Готові списки джерел за темами / Coalescence and breakup

Добірка наукової літератури з теми "Coalescence and breakup"

Автор: Grafiati

Опубліковано: 7 липня 2024

Оновлено: 7 липня 2024

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Статті в журналах з теми "Coalescence and breakup":

1

de Jong, Emily, John Ben Mackay, Oleksii Bulenok, Anna Jaruga, and Sylwester Arabas. "Breakups are complicated: an efficient representation of collisional breakup in the superdroplet method." Geoscientific Model Development 16, no. 14 (July 26, 2023): 4193–211. http://dx.doi.org/10.5194/gmd-16-4193-2023.

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Abstract. A key constraint of particle-based methods for modeling cloud microphysics is the conservation of total particle number, which is required for computational tractability. The process of collisional breakup poses a particular challenge to this framework, as breakup events often produce many droplet fragments of varying sizes, which would require creating new particles in the system. This work introduces a representation of collisional breakup in the so-called “superdroplet” method which conserves the total number of superdroplets in the system. This representation extends an existing stochastic collisional-coalescence scheme and samples from a fragment size distribution in an additional Monte Carlo step. This method is demonstrated in a set of idealized box model and single-column warm-rain simulations. We further discuss the effects of the breakup dynamic and fragment size distribution on the particle size distribution, hydrometeor population, and microphysical process rates. Box model experiments serve to characterize the impacts of properties such as coalescence efficiency and fragmentation function on the relative roles of collisional breakup and coalescence. The results demonstrate that this representation of collisional breakup can produce a stationary particle size distribution, in which breakup and coalescence rates are approximately equal, and that it recovers expected behavior such as a reduction in precipitate-sized particles in the column model. The breakup algorithm presented here contributes to an open-source pythonic implementation of the superdroplet method, PySDM, which will facilitate future research using particle-based microphysics.

2

Hwa, Rudolph C., and Jicai Pan. "Cluster production with coalescence and breakup." Physical Review C 52, no. 1 (July 1, 1995): 374–79. http://dx.doi.org/10.1103/physrevc.52.374.

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3

Huang, Bingquan, Hong Liang, and Jiangrong Xu. "Lattice Boltzmann simulation of binary three-dimensional droplet coalescence in a confined shear flow." Physics of Fluids 34, no. 3 (March 2022): 032101. http://dx.doi.org/10.1063/5.0082263.

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Small-scale microscopic phenomena determine the behavior of large-scale droplets, which brings great challenges to accurately simulate the droplet coalescence process. In this paper, the mesoscopic lattice Boltzmann method based on the phase field theory is used to simulate the collision and coalescence of binary three-dimensional droplets in a confined shear flow. The numerical prediction of droplet coalescence behavior was first compared with the experimental result, and good agreement was reported. Then, we investigated the influences of a comprehensive range of capillary numbers ([Formula: see text]) and Reynolds numbers ([Formula: see text]) on the shearing dynamics of binary droplets and also provided a quantitative description of droplet behavior in terms of the droplet deformation parameter and relative trajectory. A shearing regime diagram is further constructed based on the coupling effect of Ca and Re, which reveals three distinct types of droplet behaviors, including coalescence, breakup after the coalescence, and non-coalescence. Concretely, three different patterns of droplets can be completely captured with the variation of Ca at low Re; only two types of coalescence and non-coalescence can be observed for a medium Re, and two droplets just slide over each other without the occurrence of the coalescence when Re is sufficiently large. Also, we identified two critical capillary numbers in the lower Re region and one critical capillary number in the middle Re region, respectively, characterizing flow type transitions from the coalescence to breakup, from the breakup to the non-coalescence, and from the coalescence to the non-coalescence. It is found that all the capillary numbers decrease with Re.

4

Chen, Huiting, Shiyu Wei, Weitian Ding, Han Wei, Liang Li, Henrik Saxén, Hongming Long, and Yaowei Yu. "Interfacial Area Transport Equation for Bubble Coalescence and Breakup: Developments and Comparisons." Entropy 23, no. 9 (August 25, 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.

5

DZWINEL, WITOLD, and DAVID A. YUEN. "MIXING DRIVEN BY RAYLEIGH–TAYLOR INSTABILITY IN THE MESOSCALE MODELED WITH DISSIPATIVE PARTICLE DYNAMICS." International Journal of Modern Physics C 12, no. 01 (January 2001): 91–118. http://dx.doi.org/10.1142/s0129183101001560.

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In the mesoscale, mixing dynamics involving immiscible fluids is truly an outstanding problem in many fields, ranging from biology to geology, because of the multiscale nature which causes severe difficulties for conventional methods using partial differential equations. The existing macroscopic models incorporating the two microstructural mechanisms of breakup and coalescence do not have the necessary physical ingredients for feedback dynamics. We demonstrate here that the approach of dissipative particle dynamics (DPD) does include the feedback mechanism and thus can yield much deeper insight into the nature of immiscible mixing. We have employed the DPD method for simulating numerically the highly nonlinear aspects of the Rayleigh–Taylor (R–T) instability developed over the mesoscale for viscous, immiscible, elastically compressible fluids. In the initial stages, we encounter the spontaneous, vertical oscillations in the incipient period of mixing. The long-term dynamics are controlled by the initial breakup and the subsequent coalescence of the microstructures and the termination of the chaotic stage in the development of the R–T instability. In the regime with high capillary number, breakup plays a dominant role in the mixing whereas in the low capillary number regime, the flow decelerates and coalescence takes over and causes a more rapid turnover. The speed of mixing and the turnover depend on the immiscibility factor which results from microscopic interactions between the binary fluid components. Both the speed of mixing and the overturn dynamics depend not only on the mascrocopic fluid properties but also on the breakup and coalescent patterns, and most importantly on the nonlinear interactions between the microstructural dynamics and the large-scale flow.

6

Taboada, Martha, Nico Leister, Heike Karbstein, and Volker Gaukel. "Influence of the Emulsifier System on Breakup and Coalescence of Oil Droplets during Atomization of Oil-In-Water Emulsions." ChemEngineering 4, no. 3 (August 3, 2020): 47. http://dx.doi.org/10.3390/chemengineering4030047.

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Spray drying of whey protein-based emulsions is a common task in food engineering. Lipophilic, low molecular weight emulsifiers including lecithin, citrem, and mono- and diglycerides, are commonly added to the formulations, as they are expected to improve the processing and shelf life stability of the products. During the atomization step of spray drying, the emulsions are subjected to high stresses, which can lead to breakup and subsequent coalescence of the oil droplets. The extent of these phenomena is expected to be greatly influenced by the emulsifiers in the system. The focus of this study was therefore set on the changes in the oil droplet size of whey protein-based emulsions during atomization, as affected by the addition of low molecular weight emulsifiers. Atomization experiments were performed with emulsions stabilized either with whey protein isolate (WPI), or with combinations of WPI and lecithin, WPI and citrem, and WPI and mono- and diglycerides. The addition of lecithin promoted oil droplet breakup during atomization and improved droplet stabilization against coalescence. The addition of citrem and of mono- and diglycerides did not affect oil droplet breakup, but greatly promoted coalescence of the oil droplets. In order to elucidate the underlying mechanisms, measurements of interfacial tensions and coalescence times in single droplets experiments were performed and correlated to the atomization experiments. The results on oil droplet breakup were in good accordance with the observed differences in the interfacial tension measurements. The results on oil droplet coalescence correlated only to a limited extent with the results of coalescence times of single droplet experiments.

7

Duncan, Christopher C., and Donald L. Turcotte. "On the breakup and coalescence of continents." Geology 22, no. 2 (1994): 103. http://dx.doi.org/10.1130/0091-7613(1994)022<0103:otbaco>2.3.co;2.

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8

Brown, Philip S. "Structural Stability of the Coalescence/Breakup Equation." Journal of the Atmospheric Sciences 52, no. 22 (November 1995): 3857–65. http://dx.doi.org/10.1175/1520-0469(1995)052<3857:ssotce>2.0.co;2.

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9

Hu, Y. T., D. J. Pine, and L. Gary Leal. "Drop deformation, breakup, and coalescence with compatibilizer." Physics of Fluids 12, no. 3 (March 2000): 484–89. http://dx.doi.org/10.1063/1.870254.

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10

Shikhmurzaev, Yulii D. "Coalescence and capillary breakup of liquid volumes." Physics of Fluids 12, no. 10 (2000): 2386. http://dx.doi.org/10.1063/1.1288513.

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Дисертації з теми "Coalescence and breakup":

1

Vold, Truls Chr. "Droplet breakup and coalescence in compact wellstream seperation." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for kjemisk prosessteknologi, 2000. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2323.

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2

Hunt, William E. "Breakup and coalescence in turbulent two-phase flows." Thesis, Virginia Tech, 1995. http://hdl.handle.net/10919/40633.

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Many engineering processes involve a gas and a liquid or two immiscible liquids in turbulent flow. The turbulent flows present in two-phase systems will cause the bubbles or drops of a dispersion to undergo breakup and coalescence, and the resulting changes in the dispersion may significantly affect the engineering process under consideration. For this reason, many researchers have studied breakup and coalescence in turbulent two phase flows. Models that can be used to simulate changes in a dispersion over time have been proposed, but these models contain constants that change with experimental conditions and empirical equations that can only be considered valid for certain experimental setups. The goal of this study was to develop general models that could be used to predict changes in bubble or drop size distributions over time for turbulent flows in agitated vessels and pipes.

Computer programs were written to reproduce the results of three agitated vessel studies. These programs used existing population balance models to approximate the changes in a dispersion over time measured in previous experiments. A new model for breakup in agitated vessels was then developed and verified with existing experimental data. A new model for coalescence in agitated vessels was also developed and verified with existing experimental data. Both of these models are based on theory and are more readily extendible than previous breakup and coalescence models. The work for agitated vessels was then extended to turbulent two-phase pipe flow. Since there was only a limited amount of experimental data available for breakup and coalescence in pipes, the model for turbulent pipe flow could not be verified.
Master of Science

3

Liao, Yixiang. "Development and validation of models for bubble coalescence and breakup." Helmholtz-Zentrum Dresden-Rossendorf, 2013. https://hzdr.qucosa.de/id/qucosa%3A22180.

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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.

4

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.

5

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.

6

Lee, Joshua. "Experimental Investigation of Breakup and Coalescence Characteristics of a Hollow Cone Swirling Spray." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5974.

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Atomization can be achieved by discharging liquid at relative high velocities into a slow moving environment (hydraulic nozzles) or by discharging liquid at low velocities into a fast moving gas flow (air-blast nozzles). These two types of injector nozzles are featured in majority of the industry applications such as power generation, food or pharmaceutical powder formation, spray painting, petroleum refining, and thermal sprays. The most common atomizer used in combustion engines is the pressure-swirl nozzle (Simplex nozzle) to obtain a homogenous mixture at different equivalence ratios. The experimental studies performed with pressure-swirl nozzles have reported contradictory results over the last few years. Thus, the fundamentals of spray dynamics, such as spray formation, liquid breakup length, droplet breakup regimes, and coalescence still need to be understood for a pressure-swirl nozzle. An experimental study of the breakup characteristics of various liquids and fuels with different thermal physical properties emanating from hollow cone hydraulic injector nozzles induced by pressure-swirling was investigated. The experiments were conducted using two nozzles with different orifice diameters 0.3mm and 0.5mm and injection pressures (0.3-4MPa) which correspond to Rep = 7,000-31,000 depending on the liquids being tested. Three laser-based techniques, i.e., Shadowgraph, Particle Image Velocimetry (PIV) and Phase Doppler Particle Anemometry (PDPA) were utilized in this study. Although each technique had its limitation in different flow regimes, the results were cross-validated, and generally showed correct trends in axial and radial measurements of velocity and diameter for different nozzles, Weber and Reynolds numbers. The spatial variation of diameter and velocity arises principally due to primary breakup of liquid films and subsequent secondary breakup of large droplets due to aerodynamic shear. Downstream of the nozzle, coalescence of droplets due to collision is also found to be significant. Different types of liquid film break up was considered and found to match well with the theory. The spray is subdivided into three zones: near the nozzle, a zone consisting of film and ligament regime, where primary breakup and some secondary breakup take place; a second zone where the secondary breakup process continues, but weakens, and the centrifugal dispersion becomes dominant, and a third zone away from the spray where coalescence is dominant. Each regime has been analyzed in detail to understand the effect of surface tension and viscosity. Surface tension and viscosity were engineered to mimic fuels, which were then compared with real fuels such as Ethanol, Jet-A and Kerosene. Results show similarity in the diameter in the beginning stages of breakup but in the coalescence regime, the values deviate from each other, indicating that the vapor pressure also plays a major role in this regime.
Ph.D.
Doctorate
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering

7

Regnault, Paul. "Front-Tracking mesh adaptation for the simulation of two-phase flows with coalescence and breakup." Electronic Thesis or Diss., Université Gustave Eiffel, 2023. http://www.theses.fr/2023UEFL2076.

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Dans le cadre des écoulements diphasiques à phases séparées, ce travail porte sur la gestion dynamique du maillage de l'interface (constitué de triangles en 3D) et son impact sur l'approximation des propriétés géométriques que sont la position et la courbure. Les équations de conservation de la mécanique des fluides sont résolues sur des grille fixes, décalées et structurées. L'interface est suivie de façon lagrangienne au cours du temps avec un maillage mobile et déformable : on parle de méthode de type « Front-Tracking ». En plus des opérations de remaillage classiques (suppression et échange d'arêtes, insertion de sommets notamment), on étudiera l'adaptation du maillage à la courbure de l'interface et l'utilisation d'une approximation polynomiale pour améliorer l'insertion de sommets ou la suppression d'arêtes. Ces méthodes sont évaluées sur des surfaces analytiques mobiles et déformables, sans résolution des équations de Navier-Stokes ni changement topologique. Dans les écoulements diphasiques, des changements topologiques peuvent avoir lieu : la coalescence et la rupture. Nous proposons une méthode de coalescence et une méthode de rupture d'interface. Ces deux méthodes sont activées selon des critères de distance et sont basées uniquement sur le maillage de l'interface, sans recourir au maillage eulérien. Ces méthodes sont utilisées sur des configurations numériques et expérimentales de la littérature pour apprécier leur robustesse et leurs performances
In the context of two-phase flows with separated phases, this work focuses on dynamic management of the interface mesh (made up of connected triangles in 3D) and its impact on the approximation of geometrical properties that are position and curvature. The conservation equations of fluid mechanics are solved on fixed, staggered and structured grids. The interface is tracked in a Lagrangian fashion with a moving and deformable mesh: this method is known as the"Front-tracking" method. In addition to classical remeshing operations (edgesplitting, collapsing and swapping for instance), we will study the adaptation of the mesh to the curvature of the interface and the use of polynomial approximation to improve edge splitting and collapsing. These methods are evaluated on analytical, mobile and deformable surfaces, with neither the resolution of the Navier-Stokes equations nor topological changes. In two-phaseflows, topological changes may happen: coalescence and breakup. We propose a method for coalescence and a method for breakup. These two methods are activated by distance criteria and rely only on the interface mesh, without resorting to the Eulerian mesh. These methods are employed on numerical and experimental configurations from the literature to appreciate their robustness and performances

8

Suwa, Akihiko 1972. "Simulation of phase domain breakup and coalescence in strong shear and transient flows using lattice-Boltzmann method." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50408.

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9

Krepper, Eckhard, and 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.

10

Krepper, Eckhard, and 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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Книги з теми "Coalescence and breakup":

1

Hu, Zailiang. A numerical study of the evolution of raindrop size distribution by coalescence, breakup, and evaporation. 1993.

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Частини книг з теми "Coalescence and breakup":

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Shikhmurzaev, Yulii D. "Coalescence and Breakup: Solutions Without Singularities." In Fluid Mechanics and Its Applications, 281–88. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-010-0796-2_34.

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Eggers, Jens. "Breakup and Coalescence of Free Surface Flows." In Handbook of Materials Modeling, 1403–16. Dordrecht: Springer Netherlands, 2005. http://dx.doi.org/10.1007/1-4020-3286-2_70.

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Eggers, Jens. "Breakup and Coalescence of Free Surface Flows." In Handbook of Materials Modeling, 1403–16. Dordrecht: Springer Netherlands, 2005. http://dx.doi.org/10.1007/978-1-4020-3286-8_70.

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Pruppacher, H. R., and J. D. Klett. "Growth of Cloud Drops by Collision, Coalescence and Breakup." In Microphysics of Clouds and Precipitation, 617–58. Dordrecht: Springer Netherlands, 2010. http://dx.doi.org/10.1007/978-0-306-48100-0_15.

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Biswas, Subhajit, and Raghuraman N. Govardhan. "Bubble Capture, Breakup, and Coalescence in Vortex–Bubble Interaction." In 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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Heinemann, Moritz, Filip Sadlo, and Thomas Ertl. "Interactive Visualization of Droplet Dynamic Processes." In Fluid Mechanics and Its Applications, 29–46. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-09008-0_2.

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AbstractThis article presents an overview of visual analysis techniques specifically developed for high-resolution direct numerical multiphase simulations in the droplet dynamic context. Visual analysis of such data covers a large range of tasks, starting from observing physical phenomena such as energy transport or collisions for single droplets to the analysis of large-scale simulations such as sprays and jets. With an increasing number of features, coalescence and breakup events might happen, which need to be visually presented in an interactive explorable way to gain a deeper insight into physics. But also the task of finding relevant structures, features of interest, or a general dataset overview becomes non-trivial. We present an overview of new approaches developed in our SFB-TRR 75 project A1 covering work from the last decade to the current work-in-progress. They are the basis for relevant contributions to visualization research as well as useful tools for close collaborations within the SFB.

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Gnotke, O., R. Jeschke, and R. Loth. "Experimental and theoretical investigation of bubble break-up and coalescence in bubbly flows." In 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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Hagesaether, Lars, Hugo A. Jakobsen, Kai Hjarbo, and Hallvard F. Svendsen. "A coalescence and breakup module for implementation in CFD-codes." In Computer Aided Chemical Engineering, 367–72. Elsevier, 2000. http://dx.doi.org/10.1016/s1570-7946(00)80063-2.

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Tabeling, Patrick. "Hydrodynamics of microfluidics 2: droplets." In Introduction to Microfluidics, 162–244. 2nd ed. Oxford University PressOxford, 2023. http://dx.doi.org/10.1093/oso/9780192845306.003.0004.

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Abstract This concerns the hydrodynamics of microfluidics, in the presence of free interfaces. In particular bubbles an droplets in microchannels. Basics of interfaces are shown, including discussions on capillarity, surface tension Laplace law, wetting. Surfactants, which play a major role in microfluidics, are presented. Various laws are discussed: Washburn law, Landau Levich, Breteherton, Rayleigh Plateau. These notions are used to discuss the behaviour of droplets in microfluidic systems: breakup, coalescence, bubble pressure drop, droplet production.

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Borom, Marcus P. "Role of Earth-Moon rotational dynamics in the shaping of the surface of our planet." In In the Footsteps of Warren B. Hamilton: New Ideas in Earth Science. Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2553(22).

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ABSTRACT The age of the Moon (1.55–1.78 b.y. old) as calculated from its regression as a function of geological time is much younger than the currently accepted age (ca. 4.52 Ga) determined by radiometric dating of lunar samples collected by Apollo astronauts. This discrepancy has posed a serious challenge for planetary scientists to account satisfactorily for the formation and subsequent breakup of Pangea. Conventional orbital models of the Earth-Moon system cannot explain why Pangea formed on only one hemisphere of Earth, whereas this study’s proposed two-stage rotation model can provide a plausible explanation. Calculations and a plot of the Earth-Moon separation distance against geologic age suggest that, during their first ~3.0 b.y., Earth and the Moon were mutually tidally locked, rotating as an integrated unit about a barycenter (designated as stage I rotation). Beginning 1.55 Ga, however, Earth disengaged from its tidal lock with the Moon and entered its current orbital mode (designated as stage II rotation). The dynamics associated with the two rotational modes of the Earth-Moon system throughout Earth’s history are hypothesized to constitute the driving forces for the migration and coalescence of landmasses during stage I rotation to create Pangea, and its ultimate breakup and drifting during stage II rotation.

Тези доповідей конференцій з теми "Coalescence and breakup":

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Yuan, Shuxia, Ramin Dabirian, Ram S. Mohan, and Ovadia Shoham. "Simulation of Coalescence and Breakup of Dispersed Water Droplets in Continuous Oil Phase." In ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/fedsm2018-83314.

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Petroleum industry uses shear devices such as chokes, valves, orifices and pumps, which cause droplet coalescence and breakup making the downstream separation process very challenging. Droplet-droplet coalescence leads to formation of larger droplets, which accelerate the phase separation, whereas the breakup of larger droplets into smaller ones delays the separation process. Computational Fluid Dynamic (CFD) simulations are conducted by ANSYS-Fluent software to track the droplet breakup and droplet-droplet coalescence, where the interfaces between the two phases are tracked by the Volume of Fluid (VOF) model. The material of droplet is water, while the continuous phase is oil. In this study, the effect of variables such as droplet diameter, droplet relative velocities as well as droplet motion directions on the time evolution of droplet-droplet coalescence and breakup is evaluated. The simulation results confirm that smaller droplet collisions lead to coalescence under wide ranges of droplet relative velocities, while larger droplet collisions result in droplet breakup at higher relative velocities. During coalescence, two droplets combine into one droplet, which deform in several times from one direction to orthogonal direction until recovering its shape or breakup. In addition, the simulation results show that fastest coalescence takes place when droplet collisions occur at optimum relative velocity, whereas droplet breakup occurs at higher velocities than the optimum velocity, and delay in coalescence happens at lower velocity. Furthermore, the simulation results clearly show that droplet moving direction play an important role in the occurrence of droplet coalescence and breakup. Comparison of the simulation results with the collected experimental data from literature confirm that the simulations are capable of predicting the evolution time of the droplet coalescence and breakup with high accuracy.

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Wu, Kejia, Johnathan Green, and Subajan Sivandran. "Bubble Breakup and Coalescence Modelling for Subsea Gas Releases Using Computational Fluid Dynamics." In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-77293.

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Bubble breakup and coalescence is a phenomenon which occurs within a developing subsea gas plume. A Computational Fluid Dynamics (CFD) model incorporating bubble breakup and coalescence was developed to describe the behaviour of a subsea gas release and the subsequent rising gas plume. The model was assessed for its suitability in capturing the characteristic behaviour of a rising gas plume by comparing the CFD results with experimental data obtained from underwater gas release experiments. The study shows bubble breakup and coalescence plays a key role in determining the shape and the behaviour of a subsea gas release. Without the bubble breakup and coalescence included in the CFD model a narrower plume width and higher rising velocity is observed when compared to the experimental data. With bubble breakup and coalescence included the results obtained from the CFD model more accurately match the experimental data. Breakup and coalescence is a mechanism which redistributes the energy within the core of the gas plume towards the edge of the plume. This has a significant impact on the plume characteristics and is vital to be included in the CFD model to describe the behaviour of the released gas. The study was carried out using air as the released gas. This was done to compare with the available experimental data where air was used as the source. However the CFD model developed is applicable for hydrocarbon subsea gas releases.

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Asiagbe, K. S., Michael Fairweather, Derrick O. Njobuenwu, and M. Colombo. "Microbubble coalescence and breakup in turbulent vertical channel flows." In THMT-18. Turbulence Heat and Mass Transfer 9 Proceedings of the Ninth International Symposium On Turbulence Heat and Mass Transfer. Connecticut: Begellhouse, 2018. http://dx.doi.org/10.1615/thmt-18.520.

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Jo, Daeseong, and Shripad T. Revankar. "Study of Bubbly Flow Through a Packed Bed." In 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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Guan, Shunran, Jinyu Han, Chenru Zhao, and Hanliang Bo. "Assessment and Analysis of Various Mechanisms in the Coalescence and Breakup Models for Upward Bubbly Flow." In 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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Park, Ki Sun, and Stephen D. Heister. "Numerical Simulation of Particle Breakup/Coalescence Processes in Shock Waves." In 49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2013. http://dx.doi.org/10.2514/6.2013-4084.

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Maekawa, Munenori, Naoki Shimada, Kouji Kinoshita, Akira Sou, and Akio Tomiyama. "Numerical Simulation of Heterogeneous Bubbly Flow in a Bubble Column." In 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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Rosero, Cristian, and E. do A. Soares. "Modeling of bubble breakup and coalescence rates in sudden expansions and contractions." In THMT-18. Turbulence Heat and Mass Transfer 9 Proceedings of the Ninth International Symposium On Turbulence Heat and Mass Transfer. Connecticut: Begellhouse, 2018. http://dx.doi.org/10.1615/thmt-18.530.

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Ding, Yi-Gang, Xia Lu, and Fu-Li Deng. "Numerical Simulation With a CFD-PBM Model of Hydrodynamics and Bubble Size Distribution of a Rectangle Bubble Column." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-64018.

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A coupled CFD-PBM (population balance mode) model is adopted to investigate complex behavior in a rectangle bubble column. In this work The Euler–Euler (E–E) model was adopted for the liquid phase and gas phase, while accounting for bubble coalescence and breakup a PBM discrete model was employed. The total gas holdup for a range of superficial gas velocities were studied and compared with the literature and modest agreement was found. The simulation result shows that the superficial gas velocity has great effect on bubble size distribution, and a wider bubble size distribution is found at higher superficial gas velocity. This indicates an increasing of the superficial gas velocity increases the bubble coalescence and break-up rate.

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Motin, Abdul, John M. Walsh, and André Bénard. "Modeling Droplets Shearing and Coalescence Using a Population Balance Method in Produced Water Treatment Systems." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-53097.

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Quantification of oil droplet shearing in produced water treatment facilities is a crucial aspect of operations for the oil and gas industry. In this paper, a detail mathematical modeling of droplet breakage and coalescence using a Population Balance Method (PBM) is addressed. The PBM models the dynamics of droplet size distribution due continuous interactions between individual droplets (such as coalescence and breakup). An understanding of the PBM in regards to the conservation of mass of dispersed droplets is also developed. A stand-alone PBM is used for calculating coalescence and breakage rates in a system having homogeneous mixture and constant turbulent energy dissipation. A coupled computational fluid dynamics-PBM approach is also implemented in a hydrocyclone to examine the local rates of droplet breakup and coalescence. Effects of the turbulent intensity and the interfacial tension of an oil-water mixture and the volume fraction of the dispersed phase on the time evolution of volume fraction distribution and Sauter mean diameter are examined. Results show that, for typical fluid properties associated with produced water, droplet-droplet coalescence is dominant over droplet breakage when the turbulent energy dissipation (ε) is small; the opposite is found for regions associated with high energy dissipation. In a hydrocyclone, the rate of droplets shearing is significant near the entry and at the inlet chamber; this rate decreases downstream. The research outcomes based on the stand-alone PBM and coupled CFD-PBM approaches allow us to identify and redesign the critical part of the water treating facilities to minimize shearing of dispersed droplets.

Звіти організацій з теми "Coalescence and breakup":

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Yao, Z. S., Y. Z. Li, and J. E. Mungall. Transport and deposition of sulphide liquid - vectors to ore accumulations. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328979.

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This project aims to model the kinetic controls on sulphide composition due to the extraction of chalcophile elements from silicate magmas, and use the numerical models to deepen our knowledge of the physical constraints that govern sulphide dynamic processes (e.g., breakup, coalescence, transport and deposition) in magmatic system. Based on the new understanding obtained from these forward models, we then take the textural and compositional features of sulphide globules from the field investigation at Raglan komatiite-associated deposits for instance, to better understand the control on entrainment, transport and deposition of sulphide liquids within the ore-forming processes.