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Charles M. Schroeder - One of the best experts on this subject based on the ideXlab platform.
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dynamics and rheology of ring linear blend semidilute solutions in Extensional Flow single molecule experiments
Journal of Rheology, 2021Co-Authors: Yuecheng Zhou, Charles D Young, Megan Lee, Sourya Banik, Dejie Kong, Gregory B Mckenna, Rae M Robertsonanderson, Charles E Sing, Charles M. SchroederAbstract:Ring polymers exhibit unique Flow properties due to their closed chain topology. Despite recent progress, we have not yet achieved a full understanding of the nonequilibrium Flow behavior of rings in nondilute solutions where intermolecular interactions greatly influence chain dynamics. In this work, we directly observe the dynamics of DNA rings in semidilute ring-linear polymer blends using single molecule techniques. We systematically investigate ring polymer relaxation dynamics from high extension and transient and steady-state stretching dynamics in a planar Extensional Flow for a series of ring-linear blends with varying ring fraction. Our results show multiple molecular subpopulations for ring relaxation in ring-linear blends, as well as large conformational fluctuations for rings in a steady Extensional Flow, even long after the initial transient stretching process has subsided. We further quantify the magnitude and characteristic time scales of ring conformational fluctuations as a function of blend composition. Interestingly, we find that the magnitude of ring conformational fluctuations follows a nonmonotonic response with increasing ring fraction, first increasing at low ring fraction and then substantially decreasing at large ring fraction in ring-linear blends. A unique set of ring polymer conformations are observed during the transient stretching process, which highlights the prevalence of molecular individualism and supports the notion of complex intermolecular interactions in ring-linear polymer blends. In particular, our results suggest that transient intermolecular structures form in ring-linear blends due to a combination of direct forces due to linear chains threading through open rings and indirect forces due to hydrodynamic interactions; these combined effects lead to large conformational fluctuations of rings over distributed time scales. Taken together, our results provide a new molecular understanding of ring polymer dynamics in ring-linear blends in the nonequilibrium Flow.
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conformational dynamics and phase behavior of lipid vesicles in a precisely controlled Extensional Flow
Soft Matter, 2020Co-Authors: Dinesh Kumar, Channing M Richter, Charles M. SchroederAbstract:Lipid vesicles play a key role in fundamental biological processes. Despite recent progress, we lack a complete understanding of the non-equilibrium dynamics of vesicles due to challenges associated with long-time observation of shape fluctuations in strong Flows. In this work, we present a Flow-phase diagram for vesicle shape and conformational transitions in planar Extensional Flow using a Stokes trap, which enables control over the center-of-mass position of single or multiple vesicles in precisely defined Flows [A. Shenoy, C. V. Rao and C. M. Schroeder, Proc. Natl. Acad. Sci. U. S. A., 2016, 113(15), 3976-3981]. In this way, we directly observe the non-equilibrium conformations of lipid vesicles as a function of reduced volume ν, capillary number Ca, and viscosity contrast λ. Our results show that vesicle dynamics in Extensional Flow are characterized by the emergence of three distinct shape transitions, including a tubular to symmetric dumbbell transition, a spheroid to asymmetric dumbbell transition, and quasi-spherical to ellipsoid transition. The experimental phase diagram is in good agreement with recent predictions from simulations [V. Narsimhan, A. P. Spann and E. S. Shaqfeh, J. Fluid Mech., 2014, 750, 144]. We further show that the phase boundary of vesicle shape transitions is independent of the viscosity contrast. Taken together, our results demonstrate the utility of the Stokes trap for the precise quantification of vesicle stretching dynamics in precisely defined Flows.
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conformational dynamics and phase behavior of lipid vesicles in a precisely controlled Extensional Flow
arXiv: Biological Physics, 2019Co-Authors: Dinesh Kumar, Channing M Richter, Charles M. SchroederAbstract:Lipid vesicles play a key role in fundamental biological processes. Despite recent progress, we lack a complete understanding of the non-equilibrium dynamics of vesicles due to challenges associated with long-time observation of shape fluctuations in strong Flows. In this work, we present a Flow-phase diagram for vesicle shape and conformational transitions in planar Extensional Flow using a Stokes trap, which enables control over the center-of-mass position of single or multiple vesicles in precisely defined Flows [Shenoy, Rao, Schroeder, \textit{PNAS}, 113(15):3976-3981, 2016]. In this way, we directly observe the non-equilibrium conformations of lipid vesicles as a function of reduced volume $\nu$, capillary number $Ca$, and viscosity contrast $\lambda$. Our results show that vesicle dynamics in Extensional Flow are characterized by the emergence of three distinct shape transitions, including a tubular to symmetric dumbbell transition, a spheroid to asymmetric dumbbell transition, and quasi-spherical to ellipsoid transition. The experimental phase diagram is in good agreement with recent predictions from simulations [Narsimhan, Spann, Shaqfeh, \textit{J. Fluid Mech.}, 2014, \textbf{750}, 144]. We further show that the phase boundary of vesicle shape transitions is independent of the viscosity contrast. Taken together, our results demonstrate the utility of the Stokes trap for the precise quantification of vesicle stretching dynamics in precisely defined Flows.
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Stretching Dynamics of Single Comb Polymers in Extensional Flow
Macromolecules, 2018Co-Authors: Danielle J. Mai, Amir Saadat, Bamin Khomami, Charles M. SchroederAbstract:Molecular architecture plays a key role in determining the physical properties and emergent functional properties of polymeric materials. Despite recent progress in the synthesis of structurally defined polymers, we still lack a complete understanding of how the emergent properties of topologically complex polymers arise from molecular-scale phenomena. In this work, we study the nonequilibrium dynamics of DNA-based comb polymers in Extensional Flow using a combination of single molecule fluorescence microscopy and Brownian dynamics (BD) simulations. In this way, we directly observe the stretching dynamics of single DNA comb polymers in planar Extensional Flow. Transient stretching dynamics of isolated comb polymers is studied as a function of branch density and location, branch molecular weight, and Flow strength. High-fidelity BD simulations are used to provide a direct complement to single molecule experiments, providing key insights into the molecular stretching mechanisms for single combs in Flow. Our...
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direct observation of dna dynamics in semidilute solutions in Extensional Flow
Journal of Rheology, 2017Co-Authors: Kaiwen Hsiao, C Sasmal, Ravi J Prakash, Charles M. SchroederAbstract:The dynamic behavior of semidilute polymer solutions is governed by an interplay between solvent quality, concentration, molecular weight, and Flow type. Semidilute solutions are characterized by large fluctuations in polymer concentration, wherein polymer coils interpenetrate but may not be topologically entangled at equilibrium. In nonequilibrium Flows, it is generally thought that polymer chains can “self-entangle” in semidilute solutions, thereby leading to entanglements in solutions that are nominally unentangled at equilibrium. Despite recent progress in the field, we still lack a complete molecular-level understanding of the dynamics of polymer chains in semidilute solutions. In this work, we use single molecule techniques to investigate the dynamics of dilute and semidilute solutions of λ-phage deoxyribonucleic acid in planar Extensional Flow, including polymer relaxation from high stretch, transient stretching dynamics in step-strain experiments, and steady-state stretching in Flow. Our results a...
Eric S. G. Shaqfeh - One of the best experts on this subject based on the ideXlab platform.
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a theory for the coexistence of coiled and stretched configurational phases in the Extensional Flow of entangled polymer melts
Journal of Chemical Physics, 2021Co-Authors: Mohammad Hadi Nafar Sefiddashti, Bamin Khomami, Brian J Edwards, Eric S. G. ShaqfehAbstract:It has recently been demonstrated via nonequilibrium molecular dynamics (NEMD) simulation [M. H. Nafar Sefiddashti, B. J. Edwards, and B. Khomami, J. Chem. Phys. 148, 141103 (2018); Phys. Rev. Lett. 121, 247802 (2018)] that the Extensional Flow of entangled polymer melts can engender, within a definite strain-rate regime [expressed in terms of the Deborah number (De) based on the Rouse time], the coexistence of separate domains consisting primarily of either coiled or stretched chain-like macromolecules. This Flow-induced phase separation results in bimodal configurational distributions, where transitions of individual molecules between the coiled and stretched states occur very slowly by hopping over an apparent energy activation barrier. We demonstrate that the qualitative aspects of this phenomenon can be described via the single-mode Rolie-Poly model including Convective Constraint Release (CCR) and finite extensibility of the chain-like macromolecules. This analysis reveals the physical mechanism for the configurational coexistence, namely, the nonlinear rate of change of the average entropic restoring force of a given entangled chain with extension. Under conditions of significant Flow-induced disentanglement, the rate of change of the effective restoring force initially decreases with extension (effective spring softening) and then increases (hardens) as the maximum chain length is approached. When balanced by Flow-induced chain stretching, we find that there can be two configuration states within the same De regime, as covered by the NEMD simulations; therefore, a region of conformational coexistence can indeed exist. However, we demonstrate that this coexistence of configurational microstates is only possible when the magnitude of the CCR parameters is consistent with the rate of Flow-induced disentanglement, as observed in the NEMD simulations.
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experimental observation of the asymmetric instability of intermediate reduced volume vesicles in Extensional Flow
Soft Matter, 2016Co-Authors: Joanna Bechtel Dahl, Eric S. G. Shaqfeh, Vivek Narsimhan, Bernardo Gouveia, Sanjay Kumar, Susan J MullerAbstract:Vesicles provide an attractive model system to understand the deformation of living cells in response to mechanical forces. These simple, enclosed lipid bilayer membranes are suitable for complementary theoretical, numerical, and experimental analysis. A recent study [Narsimhan, Spann, Shaqfeh, J. Fluid Mech., 2014, 750, 144] predicted that intermediate-aspect-ratio vesicles extend asymmetrically in Extensional Flow. Upon infinitesimal perturbation to the vesicle shape, the vesicle stretches into an asymmetric dumbbell with a cylindrical thread separating the two ends. While the symmetric stretching of high-aspect-ratio vesicles in Extensional Flow has been observed and characterized [Kantsler, Segre, Steinberg, Phys. Rev. Lett., 2008, 101, 048101] as well as recapitulated in numerical simulations by Narsimhan et al., experimental observation of the asymmetric stretching has not been reported. In this work, we present results from microfluidic cross-slot experiments observing this instability, along with careful characterization of the Flow field, vesicle shape, and vesicle bending modulus. The onset of this shape transition depends on two non-dimensional parameters: reduced volume (a measure of vesicle asphericity) and capillary number (ratio of viscous to bending forces). We observed that every intermediate-reduced-volume vesicle that extends forms a dumbbell shape that is indeed asymmetric. For the subset of the intermediate-reduced-volume regime we could capture experimentally, we present an experimental phase diagram for asymmetric vesicle stretching that is consistent with the predictions of Narsimhan et al.
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the mechanism of shape instability for a vesicle in Extensional Flow
Journal of Fluid Mechanics, 2014Co-Authors: Vivek Narsimhan, Andrew Spann, Eric S. G. ShaqfehAbstract:When a flexible vesicle is placed in an Extensional Flow (planar or uniaxial), it undergoes two unique sets of shape transitions that to the best of the authors’ knowledge have not been observed for droplets. At intermediate reduced volumes (i.e. intermediate particle aspect ratio) and high extension rates, the vesicle stretches into an asymmetric dumbbell separated by a long, cylindrical thread. At low reduced volumes (i.e. high particle aspect ratio), the vesicle extends symmetrically without bound, in a manner similar to the breakup of liquid droplets. During this ‘burst’ phase, ‘pearling’ occasionally occurs, where the vesicle develops a series of periodic beads in its central neck. In this paper, we describe the physical mechanisms behind these seemingly unrelated instabilities by solving the Stokes Flow equations around a single, fluid-filled particle whose interfacial dynamics is governed by a Helfrich energy (i.e. the membranes are inextensible with bending resistance). By examining the linear stability of the steady-state shapes, we determine that vesicles are destabilized by curvature changes on its interface, similar to the Rayleigh–Plateau phenomenon. This result suggests that the vesicle’s initial geometry plays a large role in its shape transitions under tension. The stability criteria calculated by our simulations and scaling analyses agree well with available experiments. We hope that this work will lend insight into the stretching dynamics of other types of biological particles with nearly incompressible membranes, such as cells.
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loop subdivision surface boundary integral method simulations of vesicles at low reduced volume ratio in shear and Extensional Flow
Physics of Fluids, 2014Co-Authors: Andrew Spann, Hong Zhao, Eric S. G. ShaqfehAbstract:Using an unstructured boundary integral method with curvature determination via Loop subdivision surfaces, we explore a region of moderate reduced volume vesicles in Flow that includes prolate, biconcave, and stomatocyte shapes. We validate our Loop subdivision code against previously published spectral method simulations. In shear Flow, we report dynamic phase diagrams at reduced volumes ranging from 0.65 to 0.95 and determine the critical viscosity ratio at which the vesicle moves away from tank treading. We examine biconcave shapes and find the elimination of the trembling regime and a tumbling that includes significant stretch in the vorticity direction, as well as a general reduction in shear and normal stresses versus a prolate shape. Finally, we re-examine over a wider range of reduced volume the shape instability originally reported by Zhao and Shaqfeh [“The shape stability of a lipid vesicle in a uniaxial Extensional Flow,” J. Fluid Mech. 719, 345–361 (2013)] of a vesicle placed in an Extensional Flow. At sufficiently low reduced volume and high capillary number, we find the steady elongated dumbbell shape is unstable to odd perturbations and the vesicle's dumbbell ends become unequal in size. We also find that the critical capillary number as a function of reduced volume is similar between uniaxial and planar Extensional Flow.
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the shape stability of a lipid vesicle in a uniaxial Extensional Flow
Journal of Fluid Mechanics, 2013Co-Authors: Hong Zhao, Eric S. G. ShaqfehAbstract:The dynamics of a lipid vesicle in a uniaxial Extensional Flow are investigated by using a spectral boundary integral equation method. The vesicle at its stationary state assumes an axisymmetric shape of mirror symmetry, with its surface velocity vanishing everywhere. When the reduced volume of the vesicle is less than 0.75, there exists a critical capillary number, beyond which the stationary shape is unstable. The most unstable mode breaks the mirror symmetry of the shape so that the vesicle deforms into a dumbbell shape with two unequally sized ends. This is followed by the formation of a thin tube bridging the two dumbbell ends, whose length increases with time. The numerical results are in qualitative agreement with experimental observations.
Zaisha Mao - One of the best experts on this subject based on the ideXlab platform.
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internal mass and heat transfer between a single deformable droplet and simple Extensional creeping Flow
International Journal of Heat and Mass Transfer, 2018Co-Authors: Anjun Liu, Zaisha Mao, Jie Chen, Zhenzhen Wang, Chao YangAbstract:Abstract This work studied numerically the internal mass/heat transfer of a deformable droplet immersed in a simple Extensional Flow. The droplet would deform gradually from prolate spheroid to ‘peanut’ in uniaxial Extensional Flow, or from oblate spheriod to ‘red-blood-cell’ in biaxial Extensional Flow. Based on the analytical solution of Stokes Flow over a deformable droplet, the convection-diffusion transport equation was numerically solved by the finite difference method. The results show that the heat/mass transfer behaviors of a deformable droplet were different when compared with that of a spherical one. The effects of Pe (1 ≤ Pe ≤ 10000), capillary number Ca (0 ≤ Ca ≤ 0.5), viscosity ratio λ (0.01 ≤ λ ≤ 100) and the Extensional Flow direction on the Sh and mean concentration were numerically investigated. It shows that the internal mass/heat transfer rate was always enhanced with the increased degree of drop deformation in the diffusion-dominated case in both uniaxial/biaxial Extensional Flows. However, in the convection-dominated case, the Flow direction has opposite influence on transport rates of mass/heat transfer with different deformation rates. The stabilized mass transfer rate decreased for droplets with different deformation in the order: 'red-blood-cell' shaped droplet, oblate droplet, prolate droplet and 'peanut' shaped droplet. At last, we proposed the empirical correlations to predict the internal mass/heat transfer rate of a deformable droplet (by adding the parameter Ca to represent the deformation of a droplet) in simple Extensional Flow.
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mass and heat transfer from or to a single sphere in simple Extensional creeping Flow
Aiche Journal, 2012Co-Authors: Jingsheng Zhang, Chao Yang, Zaisha MaoAbstract:The first detailed numerical investigation on the mass and heat transfer both outside and inside a solid or liquid sphere immersed in a simple Extensional Flow for a larger range of Peclet numbers (1100,000) is presented. By making use of the known Stokes velocity field at small Reynolds numbers, a finite difference method with the control volume formulation is adopted to solve the convection-diffusion transport equation. Simulation results show that the transport rate, which is represented by Sherwood number, is significantly affected by Peclet number and viscosity ratio. The Flow direction, no matter a uniaxial Extensional Flow or a biaxial Extensional Flow, has no effect on the total transport rate but affects the concentration distribution a lot. Some comparisons between present simulations and previous studies are made to validate each other and confirm the reliability and applicable scopes of reported correlations. A few new correlations are put forward to predict the transfer rate at finite Peclet numbers for various values of viscosity ratios. (c) 2011 American Institute of Chemical Engineers AIChE J, 58: 32143223, 2012
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unsteady conjugate mass transfer from a spherical drop in simple Extensional creeping Flow
Chemical Engineering Science, 2012Co-Authors: Jingsheng Zhang, Chao Yang, Zaisha MaoAbstract:This paper presents the detailed numerical investigation on the unsteady conjugate mass transfer from a spherical drop immersed in a simple Extensional Flow. By making use of the known Stokes velocity field at small Reynolds numbers, a finite difference method with the control volume formulation is adopted to solve the convection-diffusion transport equations. The interactive effects of Peclet number, viscosity ratio, diffusivity ratio and distribution coefficient, as well as Flow direction on the conjugate transport process are examined in terms of numerical simulation. Simulation results show that the conjugate mass transport is significantly influenced by these four parameters and it approaches some limit cases if viscosity ratio, diffusivity ratio and distribution coefficient become far larger or less than unity. The Flow direction, no matter uniaxial Extensional or biaxial Extensional Flow, has no influence on the total transport rate but affects a lot the distribution of solute concentration. (C) 2012 Elsevier Ltd. All rights reserved.
Jingsheng Zhang - One of the best experts on this subject based on the ideXlab platform.
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mass and heat transfer from or to a single sphere in simple Extensional creeping Flow
Aiche Journal, 2012Co-Authors: Jingsheng Zhang, Chao Yang, Zaisha MaoAbstract:The first detailed numerical investigation on the mass and heat transfer both outside and inside a solid or liquid sphere immersed in a simple Extensional Flow for a larger range of Peclet numbers (1100,000) is presented. By making use of the known Stokes velocity field at small Reynolds numbers, a finite difference method with the control volume formulation is adopted to solve the convection-diffusion transport equation. Simulation results show that the transport rate, which is represented by Sherwood number, is significantly affected by Peclet number and viscosity ratio. The Flow direction, no matter a uniaxial Extensional Flow or a biaxial Extensional Flow, has no effect on the total transport rate but affects the concentration distribution a lot. Some comparisons between present simulations and previous studies are made to validate each other and confirm the reliability and applicable scopes of reported correlations. A few new correlations are put forward to predict the transfer rate at finite Peclet numbers for various values of viscosity ratios. (c) 2011 American Institute of Chemical Engineers AIChE J, 58: 32143223, 2012
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unsteady conjugate mass transfer from a spherical drop in simple Extensional creeping Flow
Chemical Engineering Science, 2012Co-Authors: Jingsheng Zhang, Chao Yang, Zaisha MaoAbstract:This paper presents the detailed numerical investigation on the unsteady conjugate mass transfer from a spherical drop immersed in a simple Extensional Flow. By making use of the known Stokes velocity field at small Reynolds numbers, a finite difference method with the control volume formulation is adopted to solve the convection-diffusion transport equations. The interactive effects of Peclet number, viscosity ratio, diffusivity ratio and distribution coefficient, as well as Flow direction on the conjugate transport process are examined in terms of numerical simulation. Simulation results show that the conjugate mass transport is significantly influenced by these four parameters and it approaches some limit cases if viscosity ratio, diffusivity ratio and distribution coefficient become far larger or less than unity. The Flow direction, no matter uniaxial Extensional or biaxial Extensional Flow, has no influence on the total transport rate but affects a lot the distribution of solute concentration. (C) 2012 Elsevier Ltd. All rights reserved.
Chao Yang - One of the best experts on this subject based on the ideXlab platform.
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internal mass and heat transfer between a single deformable droplet and simple Extensional creeping Flow
International Journal of Heat and Mass Transfer, 2018Co-Authors: Anjun Liu, Zaisha Mao, Jie Chen, Zhenzhen Wang, Chao YangAbstract:Abstract This work studied numerically the internal mass/heat transfer of a deformable droplet immersed in a simple Extensional Flow. The droplet would deform gradually from prolate spheroid to ‘peanut’ in uniaxial Extensional Flow, or from oblate spheriod to ‘red-blood-cell’ in biaxial Extensional Flow. Based on the analytical solution of Stokes Flow over a deformable droplet, the convection-diffusion transport equation was numerically solved by the finite difference method. The results show that the heat/mass transfer behaviors of a deformable droplet were different when compared with that of a spherical one. The effects of Pe (1 ≤ Pe ≤ 10000), capillary number Ca (0 ≤ Ca ≤ 0.5), viscosity ratio λ (0.01 ≤ λ ≤ 100) and the Extensional Flow direction on the Sh and mean concentration were numerically investigated. It shows that the internal mass/heat transfer rate was always enhanced with the increased degree of drop deformation in the diffusion-dominated case in both uniaxial/biaxial Extensional Flows. However, in the convection-dominated case, the Flow direction has opposite influence on transport rates of mass/heat transfer with different deformation rates. The stabilized mass transfer rate decreased for droplets with different deformation in the order: 'red-blood-cell' shaped droplet, oblate droplet, prolate droplet and 'peanut' shaped droplet. At last, we proposed the empirical correlations to predict the internal mass/heat transfer rate of a deformable droplet (by adding the parameter Ca to represent the deformation of a droplet) in simple Extensional Flow.
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mass and heat transfer from or to a single sphere in simple Extensional creeping Flow
Aiche Journal, 2012Co-Authors: Jingsheng Zhang, Chao Yang, Zaisha MaoAbstract:The first detailed numerical investigation on the mass and heat transfer both outside and inside a solid or liquid sphere immersed in a simple Extensional Flow for a larger range of Peclet numbers (1100,000) is presented. By making use of the known Stokes velocity field at small Reynolds numbers, a finite difference method with the control volume formulation is adopted to solve the convection-diffusion transport equation. Simulation results show that the transport rate, which is represented by Sherwood number, is significantly affected by Peclet number and viscosity ratio. The Flow direction, no matter a uniaxial Extensional Flow or a biaxial Extensional Flow, has no effect on the total transport rate but affects the concentration distribution a lot. Some comparisons between present simulations and previous studies are made to validate each other and confirm the reliability and applicable scopes of reported correlations. A few new correlations are put forward to predict the transfer rate at finite Peclet numbers for various values of viscosity ratios. (c) 2011 American Institute of Chemical Engineers AIChE J, 58: 32143223, 2012
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unsteady conjugate mass transfer from a spherical drop in simple Extensional creeping Flow
Chemical Engineering Science, 2012Co-Authors: Jingsheng Zhang, Chao Yang, Zaisha MaoAbstract:This paper presents the detailed numerical investigation on the unsteady conjugate mass transfer from a spherical drop immersed in a simple Extensional Flow. By making use of the known Stokes velocity field at small Reynolds numbers, a finite difference method with the control volume formulation is adopted to solve the convection-diffusion transport equations. The interactive effects of Peclet number, viscosity ratio, diffusivity ratio and distribution coefficient, as well as Flow direction on the conjugate transport process are examined in terms of numerical simulation. Simulation results show that the conjugate mass transport is significantly influenced by these four parameters and it approaches some limit cases if viscosity ratio, diffusivity ratio and distribution coefficient become far larger or less than unity. The Flow direction, no matter uniaxial Extensional or biaxial Extensional Flow, has no influence on the total transport rate but affects a lot the distribution of solute concentration. (C) 2012 Elsevier Ltd. All rights reserved.
