Download or read book The Linear and Nonlinear Rheology of Multiscale Complex Fluids written by Aditya Jaishankar and published by . This book was released on 2014 with total page 337 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Rheology of Complex Fluids written by Abhijit P. Deshpande and published by Springer Science & Business Media. This book was released on 2010-09-20 with total page 259 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Complex Fluids in Biological Systems written by Saverio E. Spagnolie and published by Springer. This book was released on 2014-11-27 with total page 449 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Nonlinear Dynamics of Complex Fluids in Fragmentation and Fracture written by Bavand Keshavarz and published by . This book was released on 2017 with total page 337 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Multi scale Phenomena in Complex Fluids written by Thomas Y. Hou and published by World Scientific. This book was released on 2009 with total page 379 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multi-Scale Phenomena in Complex Fluids is a collection of lecture notes delivered during the ªrst two series of mini-courses from "Shanghai Summer School on Analysis and Numerics in Modern Sciences," which was held in 2004 and 2006 at Fudan University, Shanghai, China. This review volume of 5 chapters, covering various fields in complex fluids, places emphasis on multi-scale modeling, analyses and simulations. It will be of special interest to researchers and graduate students who want to work in the field of complex fluids.

Download or read book Nonlinear Rheological Characterization and Modeling of Complex Fluids Under Large Amplitude Oscillatory Shear LAOS written by Christopher Joseph Hershey and published by . This book was released on 2018 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Rheology of Complex Fluids written by Abhijit P. Deshpande and published by . This book was released on 2010-09-20 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Efficient Non stiff and Multiscale Methods for Complex Fluids written by George Owen Mohler and published by . This book was released on 2008 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work we focus on the connection of these two theories, drawing upon the strengths of each in order to couple polymer microstructure with the dynamics of the flow in a systematic way. We derive a model for an inhomogeneous melt of elastic dumbbell polymers, incorporating thermodynamic forces into a two-fluid model for the flow via field theory, and develop a corresponding efficient numerical methodology for the resulting system of equations. We illustrate the methodology with several examples of phase separation in an initially quiescent flow.

Download or read book Role of Viscoelasticity and Non linear Rheology in Flows of Complex Fluids at High Deformation Rates written by Thomas Joseph Ober and published by . This book was released on 2013 with total page 399 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Dynamics Of Complex Fluids Proceedings Of The Second Royal Society unilever Indo uk Forum In Materials Science And Engineering written by M J Adams and published by World Scientific. This book was released on 1998-08-08 with total page 513 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume records the presentations and discussions at the Second Royal Society-Unilever Indo-UK Forum on 'Dynamics of Complex Fluids' which was the culmination of the six-month programme on this topic organised at the Issac Newton Institute for Mathematical Sciences, Cambridge University.The authors of this important volume present an up-to-date, wide-ranging view on developments in the analysis of complex fluid behaviour. Emphasis is placed upon the relation between small-scale structure and large-scale response: this brings together the approaches of molecular physics and continuum mechanics.Experiments, constitutive models and computer simulations are combined to yield new insights into the flow behaviour of polymer melts and solutions, colloidal and neutral particle suspensions, and pastes and soils.

Download or read book Rheology Volume I written by Crispulo Gallegos and published by EOLSS Publications. This book was released on 2010-11-30 with total page 498 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book The Structure and Rheology of Complex Fluids written by and published by . This book was released on 2005* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fluid Flow Problems written by Farhad Ali and published by BoD – Books on Demand. This book was released on 2019-05-29 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids, liquids, and gases. It has several subdisciplines, including aerodynamics (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion). Fluid dynamics has a wide range of applications, including calculating forces and moments on aircraft, determining the mass flow rate of petroleum through pipelines, predicting weather patterns, understanding nebulae in interstellar space and modeling fission weapon detonation. In this book, we provide readers with the fundamentals of fluid flow problems. Specifically, Newtonian, non-Newtonian and nanofluids are discussed. Several methods exist to investigate such flow problems. This book introduces the applications of new, exact, numerical and semianalytical methods for such problems. The book also discusses different models for the simulation of fluid flow.

Download or read book Complex fluids written by Pierre Saramito and published by Springer. This book was released on 2016-10-26 with total page 287 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive overview of the modeling of complex fluids, including many common substances, such as toothpaste, hair gel, mayonnaise, liquid foam, cement and blood, which cannot be described by Navier-Stokes equations. It also offers an up-to-date mathematical and numerical analysis of the corresponding equations, as well as several practical numerical algorithms and software solutions for the approximation of the solutions. It discusses industrial (molten plastics, forming process), geophysical (mud flows, volcanic lava, glaciers and snow avalanches), and biological (blood flows, tissues) modeling applications. This book is a valuable resource for undergraduate students and researchers in applied mathematics, mechanical engineering and physics.

Download or read book The Craft of Fractional Modelling in Science and Engineering written by Jordan Hristov and published by MDPI. This book was released on 2018-06-22 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a printed edition of the Special Issue "The Craft of Fractional Modelling in Science and Engineering" that was published in Fractal Fract

Download or read book Time resolved Linear and Non linear Rheology of Thixotropic and Aging Complex Fluids written by Joshua David John Rathinaraj and published by . This book was released on 2021 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Multiscale Investigation of Fundamental Rheological Phenomena in Particulate Suspensions Based on Flow microstructure Interactions written by P. Masafu Mwasame and published by . This book was released on 2018 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: Suspensions and dispersions are an important class of complex fluids frequently encountered in a variety of industrial processes and are prominent in many consumer products such as beauty creams and food dressing. The extensive use of suspensions can be partly attributed to their unique rheological properties such as shear-induced normal stresses, yield stress, time-dependent viscosity and shear thinning. These rheological properties are a direct result of the interplay between the suspension microstructure and flow and have consequences for material processing. The quantitative understanding of suspension rheology so far has been dominated by empirical models. However, such models are either very specialized to particular flows, involve numerous/unphysical parameters, or are inadequate to describe rheological phenomena such as normal stresses. Alternatively, microscopic approaches have primarily been successful in addressing idealized cases and/or small length/time scales. Therefore, the goal of this thesis is to develop new and improved classes of continuum models that clearly connect the suspension microstructure under flow to the observed macroscopic rheology. ☐ In this thesis, new, generally multiscale methods are applied towards developing robust constitutive models for suspension rheology. Two primary modeling approaches are employed to advance the modeling of suspension rheology in this thesis. First is a bottom-up approach that starts from a microscopic description of the suspension microstructure (e.g., the evolving aggregate size distribution) that is then coupled to an empirical/phenomenological equation to allow for the evaluation of the shear stress. The shortcoming of using a phenomenological stress expression is counterbalanced by the accurate microstructure picture provided by a microscopic framework. The second technique is a top-down approach that starts from a macroscopic description of the system through the use of state variables whose dynamic equations are developed within the Hamiltonian-enhanced Non-Equilibrium Thermodynamics framework. The key benefit of this latter approach is that the expressions for the stress tensor and microstructure, with the latter represented by a second rank tensor, emerge self-consistently from the framework. Moreover, the generated equations are applicable to general flows. The multiscale nature of suspension microstructure implies that depending on the phenomena of interest, one or the other or a combination of the two approaches may be favored. Regardless of the approach taken, a recurrent theme in this work is the clear association of the observed macroscopic rheological behavior with an underlying microscopic picture. Finally, for all the suspensions emphasized in this thesis i.e., thixotropic, polydisperse, noncolloidal and emulsions, the corresponding rheological models developed are validated against experimental/simulation data revealing their predictive capability. ☐ A number of important specific accomplishments are achieved in this thesis. To begin with, a population balance-based constitutive model for thixotropic suspensions is developed. Unlike alternative phenomenological models currently in use, a population balance-based model incorporates parameters with clear physical meaning. As a result, the resultant model holds promise for inverse design of thixotropic materials such as pastes that are used in many industrial processes. Next, the use of a conformation tensor as an internal variable to represent changes in suspension microstructure during material deformation is also demonstrated. For the first time, a comprehensive conformation tensor-based framework for suspensions, with a rigor approaching that performed previously for polymeric system, is realized. When applied to dilute emulsions, the conformation tensor-based rheological model that results is in exact agreement with existing asymptotic microscopic theory. In the same emulsion system, effects of microinertia and Ostwald ripening have also been included within a conformation tensor-based model for the first time. In concentrated suspensions, the conformation based theory has been shown to be capable of describing emerging secondary structure in the particle configuration leading to first and second normal stress differences that are both negative. Additional advances have also been made to develop self-consistent approximations for polydisperse suspension viscosity and testing them against prototype experiments. On a broader level, this work provides a number of methodologies for systematic constitutive model development in complex fluids. From an engineering perspective, the results of this thesis can be used to improve upon existing numerical tools, e.g., computational fluid dynamics, to allow for accurate simulation of industrial processes such as extrusion and screen printing of thixotropic pastes, suspensions and emulsions.