Study Of Dynamics And Viscoelasticity In Entangled Solutions Of Semiflexible Polymers By Brownian Dynamics Simulations
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Study Of Dynamics And Viscoelasticity In Entangled Solutions Of Semiflexible Polymers By Brownian Dynamics Simulations
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Author : Shriram Ramanathan
language : en
Publisher:
Release Date : 2006
Study Of Dynamics And Viscoelasticity In Entangled Solutions Of Semiflexible Polymers By Brownian Dynamics Simulations written by Shriram Ramanathan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.
Polymer Dynamics In Dilute Media
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Author : Shikha Somani
language : en
Publisher: Stanford University
Release Date : 2011
Polymer Dynamics In Dilute Media written by Shikha Somani and has been published by Stanford University this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Polymers undergo a sharp coil to stretch conformational transition in extension dominated flows when the strain rate exceeds a critical value. Dramatic change in flow behavior is known to occur at the coil-stretch transition, making it useful for several commercial applications. Despite decades of study, this phenomenon remains surrounded with controversy as the effect of solvent properties and fluid flow elements on this transition is not fully understood. In this work, we present a study of the coil-stretch transition and related hysteresis phenomenon using stochastic computer simulations. We first investigate the effect of solvent quality on the coil-stretch transition using Brownian dynamics simulations. Unlike experiments, which are plagued with problems related to polydispersity of polymers and inaccurate control over flow profiles, simulations offer a powerful platform to systematically study the effect of solvent quality while keeping all other parameters in the system constant. The system consists of a polymer subjected to planar elongational flow in both theta solvents and good solvents. The polymer is represented by a bead-spring chain model undergoing elongational flow. Solvent-mediated effects such as fluctuating hydrodynamic interactions (HI) and excluded volume (EV) are included rigorously. Conformational hysteresis is understood in terms of a 1-D energy landscape theory with an activation energy barrier for transition. At steady state, depending upon the flow rate, the energy landscape can either have one or two energy wells. An energy landscape with one well corresponds to the coiled state at low flow rate and stretched state at high flowrate. The double welled landscape corresponds to the hysteretic regime where both coiled and stretched conformational states coexist across the ensemble population. A key factor in determining the effect of solvent quality is the use of a proper measure of solvent quality. In almost all earlier studies, the effect of molecular weight on solvent quality has been neglected, producing inconsistent results. Here, the solvent quality is quantified carefully such that the effect of molecular weight and temperature is taken into account. Contrary to earlier findings, it is observed that with improvement in solvent quality, the chains unravel faster and the critical strain rate at which the coil to stretch transition takes place decreases. Furthermore, the solvent quality has a profound effect on the scaling of the critical strain rate with molecular weight and on both the transient and steady state properties of the system. Universal functions are shown to exist for the observed dynamic and static properties, which will prove useful in determining the operating parameters for experiments. In particular, the ratio of the two different relaxation times (longest relaxation time and zero shear rate viscosity) is found to be a universal function of solvent quality independent of molecular weight. The relaxation times (both the longest relaxation time and the zero shear rate viscosity) increase while the critical strain rate is found to decrease with solvent quality. Next, the study of conformational hysteresis is extended to more complicated 3-D flows to understand the effect of flow vorticity on this phenomenon. Heretofore, there has been no systematic methodology for studying the dynamical interactions between polymer molecules and elementary flow patterns in three-dimensional flows. Such a framework is essential not just for gaining valuable insights into the physics of complex fluids at a fundamental level, but it is also crucial for various important applications like turbulent drag reduction where the underlying physical mechanisms involve dynamical interactions between polymers and turbulence fine scale flow features. Such a study is presented here to provide a framework to interpret complex fluid phenomenon in terms of elementary flow patterns. We investigate the conformational hysteresis using rigorous Brownian dynamics simulations and specifically explore the effect of flow vorticity on the lifetime and width of the hysteresis window in 3-D flows. A systematic procedure is developed with careful eigenvalue analysis to explore the sole effect of vorticity on polymer dynamics keeping the principal strain rate fixed. It is observed that the hysteresis width shrinks due to increase in flow vorticity irrespective of the flow type (bi-extensional, bi-compressional, spiral-inwards, spiral-outwards etc). This is further traced to the alignment of eigenvectors with the principal eigenvector direction leading to enhanced fluctuations. Vorticity is found to have a significant effect on both the transient and the steady state properties. Understanding the effect of vorticity on polymer conformational hysteresis can further help in understanding the fundamental processes in complex flows.
Predicting The Rheological Properties Of Dilute Polymer Solutions Using Bead Spring Models
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Author : Prabhakar Ranganathan
language : en
Publisher:
Release Date : 2005
Predicting The Rheological Properties Of Dilute Polymer Solutions Using Bead Spring Models written by Prabhakar Ranganathan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with Brownian motion processes categories.
Brownian Dynamics Simulations Of Dilute Polymer Solutions With Complex Hydrodynamics
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Author : Chih-Chen Hsieh
language : en
Publisher:
Release Date : 2005
Brownian Dynamics Simulations Of Dilute Polymer Solutions With Complex Hydrodynamics written by Chih-Chen Hsieh and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
A Brownian Dynamics Simulation Study Of Dilute Polymer Solutions In Exponential Shear And Polymer Brushes In Steady Shear
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Author : Thomas C. B. Kwan
language : en
Publisher:
Release Date : 2000
A Brownian Dynamics Simulation Study Of Dilute Polymer Solutions In Exponential Shear And Polymer Brushes In Steady Shear written by Thomas C. B. Kwan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2000 with categories.
Polymer Dynamics In Dilute Media
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Author : Shikha Somani
language : en
Publisher:
Release Date : 2011
Polymer Dynamics In Dilute Media written by Shikha Somani and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Polymers undergo a sharp coil to stretch conformational transition in extension dominated flows when the strain rate exceeds a critical value. Dramatic change in flow behavior is known to occur at the coil-stretch transition, making it useful for several commercial applications. Despite decades of study, this phenomenon remains surrounded with controversy as the effect of solvent properties and fluid flow elements on this transition is not fully understood. In this work, we present a study of the coil-stretch transition and related hysteresis phenomenon using stochastic computer simulations. We first investigate the effect of solvent quality on the coil-stretch transition using Brownian dynamics simulations. Unlike experiments, which are plagued with problems related to polydispersity of polymers and inaccurate control over flow profiles, simulations offer a powerful platform to systematically study the effect of solvent quality while keeping all other parameters in the system constant. The system consists of a polymer subjected to planar elongational flow in both theta solvents and good solvents. The polymer is represented by a bead-spring chain model undergoing elongational flow. Solvent-mediated effects such as fluctuating hydrodynamic interactions (HI) and excluded volume (EV) are included rigorously. Conformational hysteresis is understood in terms of a 1-D energy landscape theory with an activation energy barrier for transition. At steady state, depending upon the flow rate, the energy landscape can either have one or two energy wells. An energy landscape with one well corresponds to the coiled state at low flow rate and stretched state at high flowrate. The double welled landscape corresponds to the hysteretic regime where both coiled and stretched conformational states coexist across the ensemble population. A key factor in determining the effect of solvent quality is the use of a proper measure of solvent quality. In almost all earlier studies, the effect of molecular weight on solvent quality has been neglected, producing inconsistent results. Here, the solvent quality is quantified carefully such that the effect of molecular weight and temperature is taken into account. Contrary to earlier findings, it is observed that with improvement in solvent quality, the chains unravel faster and the critical strain rate at which the coil to stretch transition takes place decreases. Furthermore, the solvent quality has a profound effect on the scaling of the critical strain rate with molecular weight and on both the transient and steady state properties of the system. Universal functions are shown to exist for the observed dynamic and static properties, which will prove useful in determining the operating parameters for experiments. In particular, the ratio of the two different relaxation times (longest relaxation time and zero shear rate viscosity) is found to be a universal function of solvent quality independent of molecular weight. The relaxation times (both the longest relaxation time and the zero shear rate viscosity) increase while the critical strain rate is found to decrease with solvent quality. Next, the study of conformational hysteresis is extended to more complicated 3-D flows to understand the effect of flow vorticity on this phenomenon. Heretofore, there has been no systematic methodology for studying the dynamical interactions between polymer molecules and elementary flow patterns in three-dimensional flows. Such a framework is essential not just for gaining valuable insights into the physics of complex fluids at a fundamental level, but it is also crucial for various important applications like turbulent drag reduction where the underlying physical mechanisms involve dynamical interactions between polymers and turbulence fine scale flow features. Such a study is presented here to provide a framework to interpret complex fluid phenomenon in terms of elementary flow patterns. We investigate the conformational hysteresis using rigorous Brownian dynamics simulations and specifically explore the effect of flow vorticity on the lifetime and width of the hysteresis window in 3-D flows. A systematic procedure is developed with careful eigenvalue analysis to explore the sole effect of vorticity on polymer dynamics keeping the principal strain rate fixed. It is observed that the hysteresis width shrinks due to increase in flow vorticity irrespective of the flow type (bi-extensional, bi-compressional, spiral-inwards, spiral-outwards etc). This is further traced to the alignment of eigenvectors with the principal eigenvector direction leading to enhanced fluctuations. Vorticity is found to have a significant effect on both the transient and the steady state properties. Understanding the effect of vorticity on polymer conformational hysteresis can further help in understanding the fundamental processes in complex flows.
Polymer Dynamics In Confined And Concentrated Media
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Author : Ajey Krishnamurty Dambal
language : en
Publisher:
Release Date : 2009
Polymer Dynamics In Confined And Concentrated Media written by Ajey Krishnamurty Dambal and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
Dissertation Abstracts International
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Author :
language : en
Publisher:
Release Date : 2006
Dissertation Abstracts International written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with Dissertations, Academic categories.
Brownian Dynamics Simulations Of Planar Mixed Flows Of Polymer Solutions At Finite Concentrations
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Author :
language : en
Publisher:
Release Date : 2015
Brownian Dynamics Simulations Of Planar Mixed Flows Of Polymer Solutions At Finite Concentrations written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
Brownian Dynamics Simulation For The Study Of Polymeric Liquids
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Author : Seong Jae Lee
language : en
Publisher:
Release Date : 1992
Brownian Dynamics Simulation For The Study Of Polymeric Liquids written by Seong Jae Lee and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1992 with Fluid dynamics categories.