Nonlinear Rheological Characterization and Modeling of Complex Fluids Under Large Amplitude Oscillatory Shear (LAOS) PDF Download
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Author: Christopher Joseph Hershey
Publisher:
ISBN: 9780438329324
Category : Electronic dissertations
Languages : en
Pages : 116
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Book Description
Author: Christopher Joseph Hershey
Publisher:
ISBN: 9780438329324
Category : Electronic dissertations
Languages : en
Pages : 116
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Book Description
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: Joshua David John Rathinaraj
Publisher:
ISBN:
Category :
Languages : en
Pages : 177
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Book Description
Temporal changes in microstructure and relaxation dynamics are ubiquitously observed in materials such as hydrogels, food products and drilling fluids. These materials are in general known as mutating materials and the build-up or breakdown of microstructure is commonly both time- and shear-rate (or shear-stress)-dependent resulting in a range of complex phenomena collected under the term thixotropy. It is becoming increasingly im- portant to develop time-resolved rheometric techniques to quantify the behavior of mutating materials accurately. In the present study we first discuss the introduction of better time-resolved techniques in superposition rheometry. Conventional superposition rheometry consists of combining Small Amplitude Oscillatory Shear (SAOS) with a steady unidirectional shear rate to gain insight into the shear-induced changes to the viscoelastic properties of a complex fluid. Orthogonal superposition (OSP), in which the two modes of deformation are perpendicular, has been preferred over parallel superposition to avoid non-linear cross-coupling of the steady shear and oscillatory deformation fields. This cross coupling can lead to unphysi- cal sign changes in the measured material properties, and makes it difficult to interpret the flow-induced mechanical properties. Recently, orthogonal superposition has been used to investigate the shear-induced anisotropy taking place in colloidal gels by comparing the transient evolution of orthogonal moduli with the parallel moduli immediately after cessa- tion of shear. However, probing transient evolution using the OSP technique can be chal- lenging for rapidly mutating complex materials which evolve on time scales comparable to the time scale of the experiment. Using a weakly associated alginate gel, we demonstrate the potential of superimposing fast optimally windowed chirp (OWCh) deformations or- thogonally to the shear deformation which substantially reduces the measurement time. We evaluate the changes in the rate-dependent relaxation spectrum in the direction of applied unidirectional shear rate and in the orthogonal direction deduced from the damping function and orthogonal moduli data respectively. We measure systematic changes between the two spectra measured in orthogonal directions thus revealing and quantifying flow-induced anisotropy in the alginate gel. Secondly, we develop a signal processing technique to monitor accurate temporal evolution of the complex modulus for a specified deformation frequency. Oscillatory rheometric techniques such as Small Amplitude Oscillatory Shear (SAOS) and, more recently, Large Amplitude Oscillatory Shear (LAOS) are now quite widely used for rheological characterization of the viscoelastic properties of complex fluids. However, the conventional application of Fourier transforms for analyzing oscillatory data assume the signals are time- translation invariant, which constrains the rate of mutation of the material to be extremely small. This constraint makes it difficult to accurately study shear-induced microstructural changes in thixotropic and gelling materials. We explore applications of the Gabor transform (a Short Time Fourier Transform (STFT) combined with a Gaussian window), for providing optimal joint time-frequency resolution of a mutating material's viscoelastic properties. First, we show using simple analytic models that application of the STFT enables extraction of useful data from the initial transient response following the inception of oscillatory flow. Secondly, using measurements on a Bentonite clay we show that using a Gabor transform enables us to more accurately measure rapid changes in both the storage and loss modulus with time, and also extract a characteristic thixotropic/aging time scale for the material. Finally, we consider extension of the Gabor transform to non-linear oscillatory deformations using an amplitude-modulated input strain signal, in order to track the evolution of the Fourier-Chebyshev coefficients characterizing thixotropic fluids at a specified deformation frequency. We show that there is a trade-off between frequency and time resolution (effectively a rheological uncertainty principle). We refer to the resulting test proto col as Gaborheometry and construct an operability diagram in terms of the imposed ramp rate and the mutation time of the material. This unconventional, but easily implemented, rheometric approach facilitates both SAOS and LAOS studies of time-evolving materials, reducing the number of required experiments and the data post-processing time significantly. Finally, we use the time-resolved techniques developed in this thesis to understand the thixotropic aging behavior of bentonite dispersions. In soft glassy materials such as ben- tonite clays, the relaxation dynamics and the microstructure slowly but continuously evolve with time to progressively form more stable structures. We investigate and quantify this complex aging behavior of bentonite dispersions by measuring the evolution in the linear viscoelastic behavior at different age times and temperatures. We model the linear viscoelastic properties using a material time domain transformation and a fractional Maxwell gel model which allows us to develop a rheological master curve to quantify and predict the aging behavior of this soft glass over a range of temperatures and time scales. The time-resolved rheometric techniques and procedures for quantifying the rheology of rapidly mutating complex fluids can be extended to a wide range of soft materials and allows us to obtain insight into how microstructural changes drive the evolution in the bulk rheological behavior for thixotropic and aging materials.
Author: Daniela Georgeta Coblaş
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
This paper was dedicated exclusively to the rheological characterization of simple and complex fluids and a detailed analyze of available rheometric testing procedures. Throughout this thesis the rheological behavior of both simple and complex fluids has been studied and modeled in both shear and the complex motions (shear tests and squeezing tests). By linking conventional experimental test methods with numerical simulations of real flows, this thesis introduces a new concept in rheology: Computational Rheometry. All experimental investigations carried out in this study for the squeezing flows were accompanied by numerical simulations. For the oscillatory squeezing flow the influence of initial film thikness, oscillatory amplitude and frequency, computational time step was investigated by comparison with the theoretical predictions of squeeze force and a Genrealized Reynolds Equation inclued in a finite element code in Fortran. A validity domain was established for the analitical formulation of squeezing force. The constant velocity squeeze flow was investigated also using a quasi-steady approximation of the motion, which brings a significant reduction of the computational time, and a very good correlation with the transient (deformable mesh) approximation and the analytical predictions. The investigation of free surface influence on the distribution of normal force in both constant velocity and oscillatory squeeze flow was analyzed. In the case of constant velocity squeeze flow, the numerical simulations coupled with the free surface evolution and measured normal force during experimental investigations are suggesting the presence of a partial slip during the experimen.
Author: Christopher J. Dimitriou
Publisher:
ISBN:
Category :
Languages : en
Pages : 320
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Book Description
Precipitate-containing crude oils are of increasing economic importance, due to diminishing oil reserves and the increased need to extract hydrate and wax-containing crude oil from ultra deep-water resources. Despite this need, the rheological behavior of these types of crude oil is often poorly understood. In this thesis, we investigate some of the underlying complexities associated with the rheology of waxy crude oils. These complex phenomena are often difficult to both quantify experimentally and capture with existing constitutive models. The contribution of this thesis is therefore to develop a detailed understanding of three of these particular phenomena, through the development and use of several new experimental and theoretical tools. A better understanding of waxy crude oil rheology is critical for developing flow assurance strategies, which can in turn ensure continuous production of precipitate-containing crude oils under adverse conditions. The three phenomena studied are, first: shear heterogeneities, i.e. the manifestation of wall slip, shear banding or other shear-localization events under imposed deformations that are assumed to be homogenous. For these purposes, flow visualization techniques capable of "Rheo-PIV" measurements are developed to detect these heterogeneities. Second: elasto-viscoplasticity, or the presence of an elastic response and a yield-like behavior in a non-Newtonian fluid. Constitutive modeling of this type of behavior is difficult to achieve using standard linear viscoelastic techniques, where the viscoelastic response is decomposed into a finite number of linear elements with a spectrum of relaxation times. For these reasons, additional concepts are adopted from plasticity models in order to describe this behavior. Finally: thixotropy, which refers to the ability of a fluid to continuously evolve, or age at rest and shear rejuvenate under a constant applied shear rate. A rigorous set of experimental tests is constructed which allow for the appropriate constitutive model parameters to be determined for a thixotropic fluid. Through quantitative study of these phenomena, we reach several conclusions about how to characterize and model the rheology of a precipitate-containing crude oil. First, measurements of shear heterogeneities are important in these fluids, so that rheological characterization may proceed with a knowledge of when these may arise and introduce artifacts into data. Second, new nonlinear rheometric techniques are necessary to develop quantitative data sets that describe the inherently nonlinear rheology of these fluids. The specific technique developed in this work is termed stress-controlled large amplitude oscillatory shear, or LAOStress. Finally, we show that the constitutive behavior of these materials is best prescribed using a framework which utilizes yielding and hardening mechanisms from plasticity theory. The resulting constitutive model for this nonlinear elasto-viscoplastic and thixotropic class of materials is expressed in a closed form that can be used in existing flow assurance simulation tools. The most relevant applications for this work are in the flow assurance challenges associated with crude oil production. Consequently, a large portion of the experimental work is carried out on a model waxy crude oil, containing a total wax content ranging from 5 to 10% by weight. However the phenomena studied here occur ubiquitously in a number of complex fluids. For this reason, the same rheological complexities are studied in the context of several other fluids, including a swollen microgel paste (Carbopol) and a shear-banding wormlike micellar solution.
Author: Aditya Jaishankar
Publisher:
ISBN:
Category :
Languages : en
Pages : 337
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Book Description
The microstructures of many complex fluids are typically characterized by a broad distribution of internal length scales. Examples of such multiscale materials include physically and chemically cross-linked gels, emulsions, soft colloidal glasses and concentrated suspensions. Due to the complex microstructure, these materials exhibit multiscale power law relaxation under externally imposed deformation. Compact constitutive frameworks that can accurately describe and predict both the linear as well as the nonlinear rheology of such complex fluids have remained elusive. Moreover, the rheological behavior of these materials under extensional deformations, which is important in applications such as spraying and fiber spinning, is relatively poorly understood. The primary contribution of this thesis is the development of a compact constitutive modeling framework to quantitatively describe the rheology of multiscale complex fluids. In the linear limit of small deformations, fractional constitutive equations in conjunction with the concept of quasi-properties have been shown to provide accurate physical descriptions of the broad power law relaxation dynamics exhibited by multiscale materials. In this thesis we very generally show how fractional constitutive equations enable the prediction of the rheological response of multiscale fluids under complex deformation profiles. As a specific example, we analyze the damped inertio-elastic oscillations exhibited at early times by viscoelastic interfacial layers upon the imposition of a constant stress, and the subsequent long time power law creep. We also analyze the small strain lubrication flow regime of a typical tack experiment performed on a crosslinked power law gel, where the extensional deformation of the complex material plays an important role. We extend these models to the large strain nonlinear regime using an integral K-BKZ framework coupled with a strain damping function. We demonstrate in a general manner that nonlinear rheological responses such as shear-thinning and positive first normal stress coefficients can be predicted a priori from linear viscoelastic data and a single additional nonlinear parameter introduced through the damping function. We also demonstrate that well-known empirical rheological models utilized to describe nonlinear behavior such as the Herschel-Bulkley, Cross and Carreau models can be derived using the K-BKZ framework by selecting a suitable fractional relaxation kernel and an appropriate damping function. Additionally, we derive expressions for linear viscometric functions as well as the first normal stress coefficient for materials that exhibit steady shear flow behavior predicted by the above empirical models. Our approach also quantifies the applicability of widely known empirical rheological rules for nonlinear rheology such as the Cox-Merz rule. The second contribution of this thesis is in increasing the understanding of the rheological behavior of multiscale complex fluids in extensional flow fields. For this purpose we utilize a variety of experimental extensional rheology techniques such as Capillary Breakup Extensional Rheometry (CaBER), Filament Stretching Extensional Rheometry (FiSER) and an Optimized Shape Cross-slot Extensional Rheometer (OSCER). Due to their ubiquity in industrial applications as well as in biologically relevant complex fluids, we primarily study aqueous polysaccharide systems (for example Mamaku gum). With the help of these detailed experiments, we investigate and quantify the strength of hydrogen-bonding interactions in this multiscale physically associated gel. We also investigate the extensional rheology of Hyaluronic acid, which has been shown to be an important factor in proper synovial fluid function. The findings of this thesis are widely applicable given the widespread use of multiscale complex fluids in industrial, and biological applications. The fractional constitutive framework derived here overcomes the limitations of current modeling approaches that invoke a large number of empirical constitutive parameters. Our simple models will be useful for quantitative material diagnostics and quality control comparisons as well as for computational simulations. Moreover, the experimental findings on the extensional rheology of multiscale polysaccharide systems will help in the formulation of biologically relevant complex fluids for the treatment of physiological conditions such as osteoarthritis and dysphagia.
Author: Saverio E. Spagnolie
Publisher: Springer
ISBN: 1493920650
Category : Science
Languages : en
Pages : 449
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Book Description
This book serves as an introduction to the continuum mechanics and mathematical modeling of complex fluids in living systems. The form and function of living systems are intimately tied to the nature of surrounding fluid environments, which commonly exhibit nonlinear and history dependent responses to forces and displacements. With ever-increasing capabilities in the visualization and manipulation of biological systems, research on the fundamental phenomena, models, measurements, and analysis of complex fluids has taken a number of exciting directions. In this book, many of the world’s foremost experts explore key topics such as: Macro- and micro-rheological techniques for measuring the material properties of complex biofluids and the subtleties of data interpretation Experimental observations and rheology of complex biological materials, including mucus, cell membranes, the cytoskeleton, and blood The motility of microorganisms in complex fluids and the dynamics of active suspensions Challenges and solutions in the numerical simulation of biologically relevant complex fluid flows This volume will be accessible to advanced undergraduate and beginning graduate students in engineering, mathematics, biology, and the physical sciences, but will appeal to anyone interested in the intricate and beautiful nature of complex fluids in the context of living systems.
Author: Dennis R. Heldman
Publisher: CRC Press
ISBN: 0429831560
Category : Science
Languages : en
Pages : 1244
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Book Description
As the complexity of the food supply system increases, the focus on processes used to convert raw food materials and ingredients into consumer food products becomes more important. The Handbook of Food Engineering, Third Edition, continues to provide students and food engineering professionals with the latest information needed to improve the efficiency of the food supply system. As with the previous editions, this book contains the latest information on the thermophysical properties of foods and kinetic constants needed to estimate changes in key components of foods during manufacturing and distribution. Illustrations are used to demonstrate the applications of the information to process design. Researchers should be able to use the information to pursue new directions in process development and design, and to identify future directions for research on the physical properties of foods and kinetics of changes in the food throughout the supply system. Features Covers basic concepts of transport and storage of liquids and solids, heating and cooling of foods, and food ingredients New chapter covers nanoscale science in food systems Includes chapters on mass transfer in foods and membrane processes for liquid concentration and other applications Discusses specific unit operations on freezing, concentration, dehydration, thermal processing, and extrusion The first four chapters of the Third Edition focus primarily on the properties of foods and food ingredients with a new chapter on nanoscale applications in foods. Each of the eleven chapters that follow has a focus on one of the more traditional unit operations used throughout the food supply system. Major revisions and/or updates have been incorporated into chapters on heating and cooling processes, membrane processes, extrusion processes, and cleaning operations.
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: Alberto Fernandez-Nieves
Publisher: John Wiley & Sons
ISBN: 111806562X
Category : Technology & Engineering
Languages : en
Pages : 444
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Book Description
This book presents a compilation of self-contained chapters covering a wide range of topics within the broad field of soft condensed matter. Each chapter starts with basic definitions to bring the reader up-to-date on the topic at hand, describing how to use fluid flows to generate soft materials of high value either for applications or for basic research. Coverage includes topics related to colloidal suspensions and soft materials and how they differ in behavior, along with a roadmap for researchers on how to use soft materials to study relevant physics questions related to geometrical frustration.
