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Author: Thomas Joseph Ober
Publisher:
ISBN:
Category :
Languages : en
Pages : 399
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Book Description
We combine pressure, velocimetry and birefringence measurements to study three phenomena for which the fluid rheology plays a dominant role: 1) shear banding in micellar fluids, 2) extension-dominated flows in microfluidic devices, and 3) flow-induced particle migration in microchannels. Firstly, worm-like micellar solutions are model non-Newtonian fluids having a single relaxation time [beta]. At shear rates larger than ... however, these systems exhibit shear banding and non-linear rheological behavior, whose importance is characterized by the Weissenberg number ... We develop a stability criterion for the onset of a purely viscoelastic instability for shear-banding fluids, to establish the limitations of conventional rheometric techniques for studying these fluids. A second challenge for conventional rheometers is inertially-driven secondary flows. The onset of these flows is governed by the Reynolds number ... where U is the velocity, D is the flow geometry length and v is the fluid kinematic viscosity. We develop microfluidic devices to impose shear and extensional deformation rates up to ...at low Re. These experiments combine pressure measurements, micro-particle image velocimetry ([mu]-PIV) and birefringence measurements. We develop a microfluidic chip that enables applied rheologists to quantitatively differentiate between fluid formulations intended for applications at high deformation rates. Finally, we study the interplay between fluid inertia and elasticity on particle migration. The inertially-dominated case is governed by the channel Reynolds number Re, and particle Reynolds number ... where a is the particle diameter. In a microfluidic device, the particle and channel size are on the same order, and hence migration occurs at ... in the so-called 'inertial focusing' regime which may have applications in clinical medicine. However, most physiological fluids are viscoelastic and therefore particle migration in these fluids occurs at high Reynolds and Weissenberg numbers, which is a mostly unstudied regime. We combine pressure measurements, streak imaging, [my]-PIV and particle trajectory analysis (PTA) to study the migration of polystyrene beads. Inertia drives particles toward the channel walls, whereas elasticity drives particles toward the channel centerline even at Re, ~ 2000.
Author: Thomas Joseph Ober
Publisher:
ISBN:
Category :
Languages : en
Pages : 399
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Book Description
We combine pressure, velocimetry and birefringence measurements to study three phenomena for which the fluid rheology plays a dominant role: 1) shear banding in micellar fluids, 2) extension-dominated flows in microfluidic devices, and 3) flow-induced particle migration in microchannels. Firstly, worm-like micellar solutions are model non-Newtonian fluids having a single relaxation time [beta]. At shear rates larger than ... however, these systems exhibit shear banding and non-linear rheological behavior, whose importance is characterized by the Weissenberg number ... We develop a stability criterion for the onset of a purely viscoelastic instability for shear-banding fluids, to establish the limitations of conventional rheometric techniques for studying these fluids. A second challenge for conventional rheometers is inertially-driven secondary flows. The onset of these flows is governed by the Reynolds number ... where U is the velocity, D is the flow geometry length and v is the fluid kinematic viscosity. We develop microfluidic devices to impose shear and extensional deformation rates up to ...at low Re. These experiments combine pressure measurements, micro-particle image velocimetry ([mu]-PIV) and birefringence measurements. We develop a microfluidic chip that enables applied rheologists to quantitatively differentiate between fluid formulations intended for applications at high deformation rates. Finally, we study the interplay between fluid inertia and elasticity on particle migration. The inertially-dominated case is governed by the channel Reynolds number Re, and particle Reynolds number ... where a is the particle diameter. In a microfluidic device, the particle and channel size are on the same order, and hence migration occurs at ... in the so-called 'inertial focusing' regime which may have applications in clinical medicine. However, most physiological fluids are viscoelastic and therefore particle migration in these fluids occurs at high Reynolds and Weissenberg numbers, which is a mostly unstudied regime. We combine pressure measurements, streak imaging, [my]-PIV and particle trajectory analysis (PTA) to study the migration of polystyrene beads. Inertia drives particles toward the channel walls, whereas elasticity drives particles toward the channel centerline even at Re, ~ 2000.
Author: Nhan Phan-Thien
Publisher: Springer
ISBN: 3319620002
Category : Science
Languages : en
Pages : 312
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Book Description
This book presents an introduction to viscoelasticity, in particular, to the theories of dilute polymer solutions and dilute suspensions of rigid particles in viscous and incompressible fluids. These theories are important, not just because they apply to practical problems of industrial interest, but because they form a solid theoretical base upon which mathematical techniques can be built, from which more complex theories can be constructed, to better mimic material behaviour. The emphasis of this book is not on the voluminous current topical research, but on the necessary tools to understand viscoelasticity. This is a compact book for a first year graduate course in viscoelasticity and modelling of viscoelastic multiphase fluids. The Dissipative Particle Dynamics (DPD) is introduced as a particle-based method, relevant in modelling of complex-structured fluids. All the basic ideas in DPD are reviewed. The third edition has been updated and expanded with new results in the meso-scale modelling, links between the fluid modelling to its physical parameters and new matlab programs illustrating the modelling. Particle-based modelling techniques for complex-structure fluids are added together with some sample programs. A solution manual to the problems is included.
Author: Ronald G. Larson
Publisher: OUP USA
ISBN: 9780195121971
Category : Mathematics
Languages : en
Pages : 688
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Book Description
The Structure and Rheology of Complex Fluids describes the microstructures of polymeric, colloidal, amphiphilic, and liquid crystalline liquids, and the relationship between microstructure and mechanical and flow properties. It provides illustrations, practical examples, and worked problems. This book can serve as both a textbook for a graduate course and a research monograph.
Author: Abhijit P. Deshpande
Publisher: Springer Science & Business Media
ISBN: 1441964940
Category : Technology & Engineering
Languages : en
Pages : 259
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Book Description
The aim of the School on Rheology of Complex fluids is to bring together young researchers and teachers from educational and R&D institutions, and expose them to the basic concepts and research techniques used in the study of rheological behavior of complex fluids. The lectures will be delivered by well-recognized experts. The book contents will be based on the lecture notes of the school.
Author: Bavand Keshavarz
Publisher:
ISBN:
Category :
Languages : en
Pages : 337
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Book Description
The fragmentation and breakup of complex fluids are fundamental elements of many industrial and biological processes. The fracture of food gels, atomization of paints, combustion of fuels containing anti-misting agents and application of pharmaceutical and agricultural sprays, as well as involuntary physiological processes such as sneezing, are common examples in which the atomized/fractured material contains synthetic or biological macromolecules that result in viscoelastic fluid characteristics. For many of these processes the effects of varying the rheological properties on the dynamics of fragmentation or fracture are still poorly understood. In this thesis, we investigate some of the underlying complexities associated with varying the rheology of such materials in both shear and elongation. The complex nonlinear rheology of these complex fluids under representative conditions of large strain and deformation rate is difficult to quantify experimentally and is a known challenge for existing constitutive models. The contribution of this thesis is therefore to develop and exploit several new experimental tools that enable precise rheological measurements under appropriate test conditions. A better experimental understanding of the dynamics of fragmentation/fracture in complex fluids will also help guide the development of new theoretical models that can quantitatively predict the mechanical response of complex fluids in such flows. Two distinct classes of model fluids/gels are studied in this thesis. First, a series of model viscoelastic solutions composed of a flexible homopolymer, poly(ethylene oxide) or PEO, dissolved in a water/glycerol mixture. These dilute solutions are known to behave very similarly to their Newtonian solvent in shearing deformations but exhibit markedly different extensional rheological properties due to the onset of a coil-stretch transition in the solvated microstructure at high elongation rates. Secondly we also consider a family of biopolymer networks: acid-induced casein gels. These canonical protein gels display a multiscale microstructure that is responsible for their gel-like viscoelastic properties. Upon external deformation, these soft viscoelastic solids exhibit a generic power-law rheological response followed by pronounced stress- or strain-stiffening prior to irreversible damage and failure, most often through macroscopic fractures. We study the dynamics of fragmentation for the dilute PEO solutions in different canonical flows: air-assisted atomization, drop impact on a small target, jet impact atomization and rotary spraying. We also study the fracture of the casein protein gels under conditions of both constant applied stress and constant applied shear rate. Through quantitative study of these high strain and high deformation rate phenomena, we reach several conclusions about how the rheological properties of these materials can affect their mechanical behavior in fragmentation/fracture. First, for dilute viscoelastic solutions, the breakup and atomization of these fluids is markedly different than the analogous processes in a simple Newtonian fluid. The average droplet diameter shows a monotonic increase with added viscoelasticity, which is precisely monitored by accurate measurements of elongational relaxation times through a novel characterization method we have developed; Rayleigh Ohnesorge Jet Elongational Rheometry (ROJER). Based on our measurements of the material relaxation time scale a new theoretical model for the evolution in the average droplet diameter is developed for viscoelastic sprays. Second, the size distributions measured in each viscoelastic fragmentation process show a systematic broadening from the Newtonian solvent. In each case the droplet sizes are well described by Gamma distributions that correspond to an underlying fragmentation/coalescence scenario. We show that this broadening results from the pronounced change in the corrugated shape of viscoelastic ligaments as they separate from the liquid core. These corrugations saturate in amplitude and the measured distributions for viscoelastic liquids in each process are given by a universal probability density function, corresponding to a Gamma distribution with nmin = 4. The breadth of this size distribution for viscoelastic filaments is shown to be constrained by a geometrical limit, which can not be exceeded in ligament-mediated fragmentation phenomena. Third, in the fracture of the model acid-induced protein gels, we show that the fractal network of the underlying microstructure leads to a very broad power-law behavior in their linear viscoelastic response that can be precisely modeled by a simple model based on fractional calculus. We show that specific geometric properties of the microstructure set the value of the parameters that are used in the fractional model. The nonlinear viscoelastic properties of the gel can be described in terms of a 'damping function' that enables quantitative prediction of the gel mechanical response up to the onset of macroscopic failure. Using a nonlinear integral constitutive equation - built upon the experimentally-measured damping function in conjunction with power-law linear viscoelastic response - we derive the form of the stress growth in the gel following the start up of steady shear. We also couple the shear stress response with Bailey's durability criteria for brittle solids in order to predict the critical values of the stress and strain for failure of the gel, and show how they scale with the applied shear rate. This provides a generalized failure criterion for biopolymer gels across a range of different deformation histories. Results from this work are of relevance to many processes that involve breakup and rupture of complex fluids such as failure of viscoelastic gels, emulsification, spray painting and even biological processes such as pathogen transfer resulting from violent expiration. By investigating the linear and nonlinear behavior of two distinct classes of soft matter that lie on two ends of the viscoelasticity spectrum, one close to Newtonian liquids and one close to elastic solids, we provide key physical insights that can be generalized to broad classes of different complex fluids that undergo fracture and fragmentation processes.
Author: Nhan Phan-Thien
Publisher: Springer Science & Business Media
ISBN: 366210704X
Category : Technology & Engineering
Languages : en
Pages : 154
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Book Description
In this book, the necessary background for understanding viscoelasticity is covered; both the continuum and microstructure approaches to modelling viscoelastic materials are discussed, since neither approach alone is sufficient.
Author: Arthur S. Lodge
Publisher: Academic Press
ISBN: 1483263355
Category : Technology & Engineering
Languages : en
Pages : 456
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Book Description
Viscoelasticity and Rheology covers the proceedings of a symposium by the same title, conducted by the Mathematics Research Center held at the University of Wisconsin-Madison on October 16-18, 1984. The contributions to the symposium are divided into four broad categories, namely, experimental results, constitutive theories, mathematical analysis, and computation. This 16-chapter work begins with experimental topics, including the motion of bubbles in viscoelastic fluids, wave propagation in viscoelastic solids, flows through contractions, and cold-drawing of polymers. The next chapters covering constitutive theories explore the molecular theories for polymer solutions and melts based on statistical mechanics, the use and limitations of approximate constitutive theories, a comparison of constitutive laws based on various molecular theories, network theories and some of their advantages in relation to experiments, and models for viscoplasticity. These topics are followed by discussions of the existence, regularity, and development of singularities, change of type, interface problems in viscoelasticity, existence for initial value problems and steady flows, and propagation and development of singularities. The remaining chapters deal with the numerical simulation of flow between eccentric cylinders, flow around spheres and bubbles, the hole pressure problem, and a review of computational problems related to various constitutive laws. This book will prove useful to chemical engineers, researchers, and students.
Author: D.A. Siginer
Publisher: Elsevier
ISBN: 0080540554
Category : Technology & Engineering
Languages : en
Pages : 895
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Book Description
These two volumes contain chapters written by experts in such areas as bio and food rheology, polymer rheology, flow of suspensions, flow in porous media, electrorheological fluids, etc. Computational as well as analytical mathematical descriptions, involving appropriate constitutive equations deal with complex flow situations of industrial importance. This work is unique in that it brings together state of the art reviews and recent advances in a variety of areas, involving viscoelastic materials, in a desirable and timely manner.
Author: Howard A. Barnes
Publisher: Elsevier
ISBN: 9780444871404
Category : Science
Languages : en
Pages : 214
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Book Description
This text introduces the subject of rheology in terms understandable to non-experts and describes the application of rheological principles to many industrial products and processes.
Author: Crispulo Gallegos
Publisher: EOLSS Publications
ISBN: 1848263198
Category : Economic development
Languages : en
Pages : 498
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Book Description
Rheology is a component of Encyclopedia of Chemical Sciences, Engineering and Technology Resources in the global Encyclopedia of Life Support Systems (EOLSS), which is an integrated compendium of twenty Encyclopedias. Rheology is the study of the flow of matter. It is classified as a physics discipline and focuses on substances that do not maintain a constant viscosity or state of flow. That can involve liquids, soft solids and solids that are under conditions that cause them to flow. It applies to substances which have a complex molecular structure, such as muds, sludges, suspensions, polymers and other glass formers, as well as many foods and additives, bodily fluids and other biological materials. The theme on Rheology focuses on five main areas, namely, basic concepts of rheology; rheometry; rheological materials, rheological processes and theoretical rheology. Of course, many of the chapters contain material from more than one general area. Rheology is an interdisciplinary subject which embraces many aspects of mathematics, physics, chemistry, engineering and biology. These two volumes are aimed at the following five major target audiences: University and College students Educators, Professional practitioners, Research personnel and Policy analysts, managers, and decision makers and NGOs.
