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A J Giacomin - One of the best experts on this subject based on the ideXlab platform.
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pattern method for higher harmonics from macromolecular orientation in oscillatory Shear Flow
Physics of Fluids, 2020Co-Authors: A J Giacomin, Chaimongkol Saengow, Layal M JbaraAbstract:For a suspension of rigid dumbbells, in any simple Shear Flow, we must first solve the diffusion equation for the orientation distribution function by a power series expansion in the Shear rate. Our recent work has uncovered the pattern in the coefficients of this power series [L. M. Jbara and A. J. Giacomin, “Orientation distribution function pattern for rigid dumbbell suspensions in any simple Shear Flow,” Macromol. Theory Simul. 28, 1800046-1–1800046-16 (2019)]. Specifically, we have here used this pattern on large-amplitude oscillatory Shear (LAOS) Flow, for which we have extended the orientation distribution function to the 6th power of the Shear rate. In this letter, we embed this extension into the Giesekus expression for the extra stress tensor to arrive at the alternant Shear stress response, up to and including the seventh harmonic. We thus demonstrate that the pattern method for macromolecular orientation now allows our harmonic analysis to penetrate the Shear stress response to oscillatory Shear Flow far more deeply than ever.For a suspension of rigid dumbbells, in any simple Shear Flow, we must first solve the diffusion equation for the orientation distribution function by a power series expansion in the Shear rate. Our recent work has uncovered the pattern in the coefficients of this power series [L. M. Jbara and A. J. Giacomin, “Orientation distribution function pattern for rigid dumbbell suspensions in any simple Shear Flow,” Macromol. Theory Simul. 28, 1800046-1–1800046-16 (2019)]. Specifically, we have here used this pattern on large-amplitude oscillatory Shear (LAOS) Flow, for which we have extended the orientation distribution function to the 6th power of the Shear rate. In this letter, we embed this extension into the Giesekus expression for the extra stress tensor to arrive at the alternant Shear stress response, up to and including the seventh harmonic. We thus demonstrate that the pattern method for macromolecular orientation now allows our harmonic analysis to penetrate the Shear stress response to oscillatory she...
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exact coefficients for rigid dumbbell suspensions for steady Shear Flow material function expansions
Physics of Fluids, 2019Co-Authors: Jourdain H Piette, Chaimongkol Saengow, Layal M Jbara, A J GiacominAbstract:From kinetic molecular theory, we can attribute the elasticity of polymeric liquids to macromolecular orientation. For a suspension of rigid dumbbells, subject to a particular Flow field, we must first solve the diffusion equation for the orientation distribution function. From this distribution, we then calculate physical properties such as the steady Shear Flow material functions. We thus arrive at power series expansions in the Shear rate for both the orientation distribution function and for the steady Shear Flow material functions. Analytical work on many viscoelastic material functions must be checked for consistency, in their steady Shear Flow limits, against these power series. For instance, for large-amplitude oscillatory Shear Flow, we recover the coefficients of these expansions in the limits of low test frequency. The coefficients of the steady Shear viscosity and the first normal stress coefficient functions are not known exactly beyond the fourth power. In this work, for both of these functions, we arrive at exact expressions for the first 20 coefficients. We close with five worked examples illustrating uses for our new coefficients.From kinetic molecular theory, we can attribute the elasticity of polymeric liquids to macromolecular orientation. For a suspension of rigid dumbbells, subject to a particular Flow field, we must first solve the diffusion equation for the orientation distribution function. From this distribution, we then calculate physical properties such as the steady Shear Flow material functions. We thus arrive at power series expansions in the Shear rate for both the orientation distribution function and for the steady Shear Flow material functions. Analytical work on many viscoelastic material functions must be checked for consistency, in their steady Shear Flow limits, against these power series. For instance, for large-amplitude oscillatory Shear Flow, we recover the coefficients of these expansions in the limits of low test frequency. The coefficients of the steady Shear viscosity and the first normal stress coeffic...
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exact analytical solution for large amplitude oscillatory Shear Flow
Macromolecular Theory and Simulations, 2015Co-Authors: Chaimongkol Saengow, A J Giacomin, Chanyut KolitawongAbstract:When polymeric liquids undergo large-amplitude Shearing oscillations, the Shear stress responds as a Fourier series, the higher harmonics of which are caused by fluid nonlinearity. Previous work on large-amplitude oscillatory Shear Flow has produced analytical solutions for the first few harmonics of a Fourier series for the Shear stress response (none beyond the fifth) or for the normal stress difference responses (none beyond the fourth) [JNNFM, 166, 1081 (2011)], but this growing subdiscipline of macromolecular physics has yet to produce an exact solution. Here, we derive what we believe to be the first exact analytical solution for the response of the extra stress tensor in large-amplitude oscillatory Shear Flow. Our solution, unique and in closed form, includes both the normal stress differences and the Shear stress for both startup and alternance. We solve the corotational Maxwell model as a pair of nonlinear-coupled ordinary differential equations, simultaneously. We choose the corotational Maxwell model because this two-parameter model (η0 and λ) is the simplest constitutive model relevant to large-amplitude oscillatory Shear Flow, and because it has previously been found to be accurate for molten plastics (when multiple relaxation times are used). By relevant we mean that the model predicts higher harmonics. We find good agreement between the first few harmonics of our exact solution, and of our previous approximate expressions (obtained using the Goddard integral transform). Our exact solution agrees closely with the measured behavior for molten plastics, not only at alternance, but also in startup.
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fourier decomposition of polymer orientation in large amplitude oscillatory Shear Flow
Structural Dynamics, 2015Co-Authors: A J Giacomin, P H Gilbert, A. M. SchmalzerAbstract:In our previous work, we explored the dynamics of a dilute suspension of rigid dumbbells as a model for polymeric liquids in large-amplitude oscillatory Shear Flow, a Flow experiment that has gained a significant following in recent years. We chose rigid dumbbells since these are the simplest molecular model to give higher harmonics in the components of the stress response. We derived the expression for the dumbbell orientation distribution, and then we used this function to calculate the Shear stress response, and normal stress difference responses in large-amplitude oscillatory Shear Flow. In this paper, we deepen our understanding of the polymer motion underlying large-amplitude oscillatory Shear Flow by decomposing the orientation distribution function into its first five Fourier components (the zeroth, first, second, third, and fourth harmonics). We use three-dimensional images to explore each harmonic of the polymer motion. Our analysis includes the three most important cases: (i) nonlinear steady s...
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fourier decomposition of polymer orientation in large amplitude oscillatory Shear Flow
Structural Dynamics, 2015Co-Authors: A J Giacomin, P H Gilbert, A. M. SchmalzerAbstract:In our previous work, we explored the dynamics of a dilute suspension of rigid dumbbells as a model for polymeric liquids in large-amplitude oscillatory Shear Flow, a Flow experiment that has gained a significant following in recent years. We chose rigid dumbbells since these are the simplest molecular model to give higher harmonics in the components of the stress response. We derived the expression for the dumbbell orientation distribution, and then we used this function to calculate the Shear stress response, and normal stress difference responses in large-amplitude oscillatory Shear Flow. In this paper, we deepen our understanding of the polymer motion underlying large-amplitude oscillatory Shear Flow by decomposing the orientation distribution function into its first five Fourier components (the zeroth, first, second, third, and fourth harmonics). We use three-dimensional images to explore each harmonic of the polymer motion. Our analysis includes the three most important cases: (i) nonlinear steady Shear Flow (where the Deborah number [Formula: see text] is zero and the Weissenberg number [Formula: see text] is above unity), (ii) nonlinear viscoelasticity (where both [Formula: see text] and [Formula: see text] exceed unity), and (iii) linear viscoelasticity (where [Formula: see text] exceeds unity and where [Formula: see text] approaches zero). We learn that the polymer orientation distribution is spherical in the linear viscoelastic regime, and otherwise tilted and peanut-shaped. We find that the peanut-shaping is mainly caused by the zeroth harmonic, and the tilting, by the second. The first, third, and fourth harmonics of the orientation distribution make only slight contributions to the overall polymer motion.
Chaimongkol Saengow - One of the best experts on this subject based on the ideXlab platform.
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pattern method for higher harmonics from macromolecular orientation in oscillatory Shear Flow
Physics of Fluids, 2020Co-Authors: A J Giacomin, Chaimongkol Saengow, Layal M JbaraAbstract:For a suspension of rigid dumbbells, in any simple Shear Flow, we must first solve the diffusion equation for the orientation distribution function by a power series expansion in the Shear rate. Our recent work has uncovered the pattern in the coefficients of this power series [L. M. Jbara and A. J. Giacomin, “Orientation distribution function pattern for rigid dumbbell suspensions in any simple Shear Flow,” Macromol. Theory Simul. 28, 1800046-1–1800046-16 (2019)]. Specifically, we have here used this pattern on large-amplitude oscillatory Shear (LAOS) Flow, for which we have extended the orientation distribution function to the 6th power of the Shear rate. In this letter, we embed this extension into the Giesekus expression for the extra stress tensor to arrive at the alternant Shear stress response, up to and including the seventh harmonic. We thus demonstrate that the pattern method for macromolecular orientation now allows our harmonic analysis to penetrate the Shear stress response to oscillatory Shear Flow far more deeply than ever.For a suspension of rigid dumbbells, in any simple Shear Flow, we must first solve the diffusion equation for the orientation distribution function by a power series expansion in the Shear rate. Our recent work has uncovered the pattern in the coefficients of this power series [L. M. Jbara and A. J. Giacomin, “Orientation distribution function pattern for rigid dumbbell suspensions in any simple Shear Flow,” Macromol. Theory Simul. 28, 1800046-1–1800046-16 (2019)]. Specifically, we have here used this pattern on large-amplitude oscillatory Shear (LAOS) Flow, for which we have extended the orientation distribution function to the 6th power of the Shear rate. In this letter, we embed this extension into the Giesekus expression for the extra stress tensor to arrive at the alternant Shear stress response, up to and including the seventh harmonic. We thus demonstrate that the pattern method for macromolecular orientation now allows our harmonic analysis to penetrate the Shear stress response to oscillatory she...
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hydrodynamic interaction for rigid dumbbell suspensions in steady Shear Flow
Physics of Fluids, 2019Co-Authors: Jourdain H Piette, Chaimongkol Saengow, Jeffrey A GiacominAbstract:From kinetic molecular theory, we can attribute the rheological behaviors of polymeric liquids to macromolecular orientation. The simplest model to capture the orientation of macromolecules is the rigid dumbbell. For a suspension of rigid dumbbells, subject to any Shear Flow, for instance, we must first solve the diffusion equation for the orientation distribution function. From this distribution, we then calculate the first and second normal stress differences. To get reasonable results for the normal stress differences in steady Shear Flow, one must account for hydrodynamic interaction between the dumbbell beads. However, for the power series expansions for these normal stress differences, three series arise. The coefficients for two of these series, (ck, dk), are not known, not even approximately, beyond the second power of the Shear rate. Analytical work on many viscoelastic material functions in Shear Flow must be checked for consistency, in their steady Shear Flow limits, against these normal stress difference power series expansions. For instance, for large-amplitude oscillatory Shear Flow, we must recover the power series expansions in the limits of low frequency. In this work, for (ck, dk), we arrive at the exact expressions for the first 18 of these coefficients.From kinetic molecular theory, we can attribute the rheological behaviors of polymeric liquids to macromolecular orientation. The simplest model to capture the orientation of macromolecules is the rigid dumbbell. For a suspension of rigid dumbbells, subject to any Shear Flow, for instance, we must first solve the diffusion equation for the orientation distribution function. From this distribution, we then calculate the first and second normal stress differences. To get reasonable results for the normal stress differences in steady Shear Flow, one must account for hydrodynamic interaction between the dumbbell beads. However, for the power series expansions for these normal stress differences, three series arise. The coefficients for two of these series, (ck, dk), are not known, not even approximately, beyond the second power of the Shear rate. Analytical work on many viscoelastic material functions in Shear Flow must be checked for consistency, in their steady Shear Flow limits, against these normal stress...
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exact coefficients for rigid dumbbell suspensions for steady Shear Flow material function expansions
Physics of Fluids, 2019Co-Authors: Jourdain H Piette, Chaimongkol Saengow, Layal M Jbara, A J GiacominAbstract:From kinetic molecular theory, we can attribute the elasticity of polymeric liquids to macromolecular orientation. For a suspension of rigid dumbbells, subject to a particular Flow field, we must first solve the diffusion equation for the orientation distribution function. From this distribution, we then calculate physical properties such as the steady Shear Flow material functions. We thus arrive at power series expansions in the Shear rate for both the orientation distribution function and for the steady Shear Flow material functions. Analytical work on many viscoelastic material functions must be checked for consistency, in their steady Shear Flow limits, against these power series. For instance, for large-amplitude oscillatory Shear Flow, we recover the coefficients of these expansions in the limits of low test frequency. The coefficients of the steady Shear viscosity and the first normal stress coefficient functions are not known exactly beyond the fourth power. In this work, for both of these functions, we arrive at exact expressions for the first 20 coefficients. We close with five worked examples illustrating uses for our new coefficients.From kinetic molecular theory, we can attribute the elasticity of polymeric liquids to macromolecular orientation. For a suspension of rigid dumbbells, subject to a particular Flow field, we must first solve the diffusion equation for the orientation distribution function. From this distribution, we then calculate physical properties such as the steady Shear Flow material functions. We thus arrive at power series expansions in the Shear rate for both the orientation distribution function and for the steady Shear Flow material functions. Analytical work on many viscoelastic material functions must be checked for consistency, in their steady Shear Flow limits, against these power series. For instance, for large-amplitude oscillatory Shear Flow, we recover the coefficients of these expansions in the limits of low test frequency. The coefficients of the steady Shear viscosity and the first normal stress coeffic...
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pade approximant for normal stress differences in large amplitude oscillatory Shear Flow
Physics of Fluids, 2018Co-Authors: A. Jeffrey Giacomin, P Poungthong, Chaimongkol Saengow, Chanyut Kolitawong, Dimitri Merger, Manfred WilhelmAbstract:Analytical solutions for the normal stress differences in large-amplitude oscillatory Shear Flow (LAOS), for continuum or molecular models, normally take the inexact form of the first few terms of a series expansion in the Shear rate amplitude. Here, we improve the accuracy of these truncated expansions by replacing them with rational functions called Pade approximants. The recent advent of exact solutions in LAOS presents an opportunity to identify accurate and useful Pade approximants. For this identification, we replace the truncated expansion for the corotational Jeffreys fluid with its Pade approximants for the normal stress differences. We uncover the most accurate and useful approximant, the [3,4] approximant, and then test its accuracy against the exact solution [C. Saengow and A. J. Giacomin, “Normal stress differences from Oldroyd 8-constant framework: Exact analytical solution for large-amplitude oscillatory Shear Flow,” Phys. Fluids 29, 121601 (2017)]. We use Ewoldt grids to show the stunning ...
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exact analytical solution for large amplitude oscillatory Shear Flow
Macromolecular Theory and Simulations, 2015Co-Authors: Chaimongkol Saengow, A J Giacomin, Chanyut KolitawongAbstract:When polymeric liquids undergo large-amplitude Shearing oscillations, the Shear stress responds as a Fourier series, the higher harmonics of which are caused by fluid nonlinearity. Previous work on large-amplitude oscillatory Shear Flow has produced analytical solutions for the first few harmonics of a Fourier series for the Shear stress response (none beyond the fifth) or for the normal stress difference responses (none beyond the fourth) [JNNFM, 166, 1081 (2011)], but this growing subdiscipline of macromolecular physics has yet to produce an exact solution. Here, we derive what we believe to be the first exact analytical solution for the response of the extra stress tensor in large-amplitude oscillatory Shear Flow. Our solution, unique and in closed form, includes both the normal stress differences and the Shear stress for both startup and alternance. We solve the corotational Maxwell model as a pair of nonlinear-coupled ordinary differential equations, simultaneously. We choose the corotational Maxwell model because this two-parameter model (η0 and λ) is the simplest constitutive model relevant to large-amplitude oscillatory Shear Flow, and because it has previously been found to be accurate for molten plastics (when multiple relaxation times are used). By relevant we mean that the model predicts higher harmonics. We find good agreement between the first few harmonics of our exact solution, and of our previous approximate expressions (obtained using the Goddard integral transform). Our exact solution agrees closely with the measured behavior for molten plastics, not only at alternance, but also in startup.
A. M. Schmalzer - One of the best experts on this subject based on the ideXlab platform.
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normal stress differences in large amplitude oscillatory Shear Flow for dilute rigid dumbbell suspensions
Journal of Non-newtonian Fluid Mechanics, 2015Co-Authors: A. M. Schmalzer, R B Bird, A. Jeffrey GiacominAbstract:Abstract We examine the simplest relevant molecular model for large-amplitude oscillatory Shear (LAOS) Flow of a polymeric liquid: the suspension of rigid dumbbells in a Newtonian solvent. We find explicit analytical expressions for the Shear rate amplitude and frequency dependences of the zeroth, second and fourth harmonics of the first and second normal stress difference responses. We include a detailed comparison of these predictions with the corresponding results for the simplest relevant continuum model: the corotational Maxwell model. We find that the responses of both models are qualitatively alike. The rigid dumbbell model relies entirely on the dumbbell orientation to explain the viscoelastic response of the polymeric liquid, including the higher harmonics in large-amplitude oscillatory Shear Flow. Our analysis employs the general method of Bird and Armstrong (1972) for analyzing the behavior of the rigid dumbbell model in any unsteady Shear Flow. We derive the first three terms of the deviation of the orientational distribution function from the equilibrium state. Then, after getting the “paren functions,” we use these for evaluating the normal stress differences for large amplitude oscillatory Shear Flow. We find the shapes of the first normal stress difference versus Shear rate loops predicted to be reasonable [see Fig. 1 (a)]. We find that the second normal stress difference is not proportional to the first, and that its shape differs markedly from that of the first [cf. Fig. 1 (a) and (b)]. We discover the same remarkable qualitative similarity between the predictions of the rigid dumbbell model and the corotational Maxwell model for the first normal stress difference. We find no qualitative similarities between the dumbbell and the continuum models for any of the predicted coefficients of the second normal stress differences in large-amplitude oscillatory Shear Flow.
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fourier decomposition of polymer orientation in large amplitude oscillatory Shear Flow
Structural Dynamics, 2015Co-Authors: A J Giacomin, P H Gilbert, A. M. SchmalzerAbstract:In our previous work, we explored the dynamics of a dilute suspension of rigid dumbbells as a model for polymeric liquids in large-amplitude oscillatory Shear Flow, a Flow experiment that has gained a significant following in recent years. We chose rigid dumbbells since these are the simplest molecular model to give higher harmonics in the components of the stress response. We derived the expression for the dumbbell orientation distribution, and then we used this function to calculate the Shear stress response, and normal stress difference responses in large-amplitude oscillatory Shear Flow. In this paper, we deepen our understanding of the polymer motion underlying large-amplitude oscillatory Shear Flow by decomposing the orientation distribution function into its first five Fourier components (the zeroth, first, second, third, and fourth harmonics). We use three-dimensional images to explore each harmonic of the polymer motion. Our analysis includes the three most important cases: (i) nonlinear steady s...
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fourier decomposition of polymer orientation in large amplitude oscillatory Shear Flow
Structural Dynamics, 2015Co-Authors: A J Giacomin, P H Gilbert, A. M. SchmalzerAbstract:In our previous work, we explored the dynamics of a dilute suspension of rigid dumbbells as a model for polymeric liquids in large-amplitude oscillatory Shear Flow, a Flow experiment that has gained a significant following in recent years. We chose rigid dumbbells since these are the simplest molecular model to give higher harmonics in the components of the stress response. We derived the expression for the dumbbell orientation distribution, and then we used this function to calculate the Shear stress response, and normal stress difference responses in large-amplitude oscillatory Shear Flow. In this paper, we deepen our understanding of the polymer motion underlying large-amplitude oscillatory Shear Flow by decomposing the orientation distribution function into its first five Fourier components (the zeroth, first, second, third, and fourth harmonics). We use three-dimensional images to explore each harmonic of the polymer motion. Our analysis includes the three most important cases: (i) nonlinear steady Shear Flow (where the Deborah number [Formula: see text] is zero and the Weissenberg number [Formula: see text] is above unity), (ii) nonlinear viscoelasticity (where both [Formula: see text] and [Formula: see text] exceed unity), and (iii) linear viscoelasticity (where [Formula: see text] exceeds unity and where [Formula: see text] approaches zero). We learn that the polymer orientation distribution is spherical in the linear viscoelastic regime, and otherwise tilted and peanut-shaped. We find that the peanut-shaping is mainly caused by the zeroth harmonic, and the tilting, by the second. The first, third, and fourth harmonics of the orientation distribution make only slight contributions to the overall polymer motion.
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viscous heating in large amplitude oscillatory Shear Flow
Physics of Fluids, 2012Co-Authors: A. Jeffrey Giacomin, R B Bird, Chuanchom Aumnate, A M Mertz, A. M. SchmalzerAbstract:When measuring rheological properties in oscillatory Shear Flow, one worries about experimental error due to the temperature rise in the sample that is caused by viscous heating. For polymeric liquids, for example, this temperature rise causes the measured values of the components of the complex viscosity to be systematically low. For such linear viscoelastic property measurements, we use an analytical solution by Ding et al. [J. Non-Newtonian Fluid Mech. 86, 359 (1999)10.1016/S0377-0257(99)00004-X] to estimate the temperature rise. However, for large-amplitude oscillatory Shear Flow, no such analytical solution is available. Here we derive an analytical solution for the temperature rise in a corotational Maxwell fluid (a model with just two parameters: η0 and λ) subject to large-amplitude oscillatory Shear Flow. This result can then be generalized to a superposition of corotational Maxwell models for a quantitative estimate of the temperature rise. We chose the corotational Maxwell model because, when ge...
G R Tynan - One of the best experts on this subject based on the ideXlab platform.
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observation of turbulent driven Shear Flow in a cylindrical laboratory plasma device
Physical Review Letters, 2006Co-Authors: C Holland, A N James, D Nishijima, Masashi Shimada, N Taheri, G R TynanAbstract:An azimuthally symmetric radially Sheared plasma fluid Flow is observed to spontaneously form in a cylindrical magnetized helicon plasma device with no external sources of momentum input. A turbulent momentum conservation analysis shows that this Shear Flow is sustained by the Reynolds stress generated by collisional drift turbulence in the device. The results provide direct experimental support for the basic theoretical picture of drift-wave-Shear-Flow interactions.
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observation of turbulent driven Shear Flow in a cylindrical laboratory plasma device
Plasma Physics and Controlled Fusion, 2006Co-Authors: G R Tynan, C Holland, A N James, D Nishijima, Masashi Shimada, N TaheriAbstract:A turbulent-generated azimuthally symmetric radially Sheared plasma fluid Flow is observed in a cylindrical magnetized helicon plasma device with no external sources of momentum input. A turbulent momentum conservation analysis shows that this Shear Flow is sustained against dissipation by the turbulent Reynolds stress generated by collisional drift fluctuations in the device. In the wavenumber domain this process is manifested via a nonlinear transfer of energy from small scales to larger scales. Simulations of collisional drift turbulence in this device have also been carried out and clearly show the formation of a Shear Flow quantitatively similar to that observed experimentally. The results integrate experiment and first-principle simulations and validate the basic theoretical picture of drift-wave/Shear Flow interactions.
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on the nonlinear turbulent dynamics of Shear Flow decorrelation and zonal Flow generation
Physics of Plasmas, 2001Co-Authors: G R Tynan, R A Moyer, M J Burin, C HollandAbstract:Sheared Flows, thought to be generated by turbulence in magnetized fusion plasmas, are predicted to mediate the transport of mass, momentum, and heat across the Shear Flow region. In this paper we show that an examination of three-wave coupling processes using the bispectrum and bicoherence of turbulent fields provides an experimentally accessible test of the turbulence-generated Shear Flow hypothesis. Results from the Continuous Current Tokamak (CCT), Princeton Beta Experiment–Modified (PBX–M), and DIII–D tokamaks indicate that the relative strength of three-wave coupling increases during low-mode to high-mode (L–H) transitions and that this increase is localized to the region of strong Flow and strong Flow Shear. These results appear to be qualitatively consistent with the turbulence-generated Shear Flow hypothesis.
Gerhard Gompper - One of the best experts on this subject based on the ideXlab platform.
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Active Brownian Filamentous Polymers under Shear Flow
MDPI AG, 2018Co-Authors: Aitor Martín-gómez, Gerhard Gompper, Roland G. WinklerAbstract:The conformational and rheological properties of active filaments/polymers exposed to Shear Flow are studied analytically. Using the continuous Gaussian semiflexible polymer model extended by the activity, we derive analytical expressions for the dependence of the deformation, orientation, relaxation times, and viscosity on the persistence length, Shear rate, and activity. The model yields a Weissenberg-number dependent Shear-induced deformation, alignment, and Shear thinning behavior, similarly to the passive counterpart. Thereby, the model shows an intimate coupling between activity and Shear Flow. As a consequence, activity enhances the Shear-induced polymer deformation for flexible polymers. For semiflexible polymers/filaments, a nonmonotonic deformation is obtained because of the activity-induced shrinkage at moderate and swelling at large activities. Independent of stiffness, activity-induced swelling facilitates and enhances alignment and Shear thinning compared to a passive polymer. In the asymptotic limit of large activities, a polymer length- and stiffness-independent behavior is obtained, with universal Shear-rate dependencies for the conformations, dynamics, and rheology
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semidilute polymer solutions at equilibrium and under Shear Flow
Macromolecules, 2010Co-Authors: Chiencheng Huang, Roland G. Winkler, Godehard Sutmann, Gerhard GompperAbstract:The properties of semidilute polymer solutions are investigated at equilibrium and under Shear Flow by mesoscale simulations, which combine molecular dynamics simulations and the multiparticle collision dynamics approach. In semidilute solution, intermolecular hydrodynamic and excluded volume interactions become increasingly important due to the presence of polymer overlap. At equilibrium, the dependence of the radius of gyration, the structure factor, and the zero-Shear viscosity on the polymer concentration is determined and found to be in good agreement with scaling predictions. In Shear Flow, the polymer alignment and deformation are calculated as a function of concentration. Shear thinning, which is related to Flow alignment and finite polymer extensibility, is characterized by the Shear viscosity and the normal stress coefficients.
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fluid vesicles with viscous membranes in Shear Flow
Physical Review Letters, 2004Co-Authors: Hiroshi Noguchi, Gerhard GompperAbstract:The effect of membrane viscosity on the dynamics of vesicles in Shear Flow is studied. We present a new simulation technique, which combines three-dimensional multiparticle collision dynamics for the solvent with a dynamically triangulated membrane model. Vesicles are found to transit from steady tank treading to unsteady tumbling motion with increasing membrane viscosity. Depending on the reduced volume and membrane viscosity, Shear can induce both discocyte-to-prolate and prolate-to-discocyte transformations. This behavior can be understood from a simplified model.
