38 results on '"Safa Jamali"'
Search Results
2. Rheology-Informed Neural Networks (RhINNs) for forward and inverse metamodelling of complex fluids
- Author
-
Mohammadamin Mahmoudabadbozchelou and Safa Jamali
- Subjects
Medicine ,Science - Abstract
Abstract Reliable and accurate prediction of complex fluids’ response under flow is of great interest across many disciplines, from biological systems to virtually all soft materials. The challenge is to solve non-trivial time and rate dependent constitutive equations to describe these structured fluids under various flow protocols. We present Rheology-Informed Neural Networks (RhINNs) for solving systems of Ordinary Differential Equations (ODEs) adopted for complex fluids. The proposed RhINNs are employed to solve the constitutive models with multiple ODEs by benefiting from Automatic Differentiation in neural networks. In a direct solution, the RhINNs platform accurately predicts the fully resolved solution of constitutive equations for a Thixotropic-Elasto-Visco-Plastic (TEVP) complex fluid for a series of flow protocols. From a practical perspective, an exhaustive list of experiments are required to identify model parameters for a multi-variant constitutive TEVP model. RhINNs are found to learn these non-trivial model parameters for a complex material using a single flow protocol, enabling accurate modeling with limited number of experiments and at an unprecedented rate. We also show the RhINNs are not limited to a specific model and can be extended to include various models and recover complex manifestations of kinematic heterogeneities and transient shear banding of thixotropic fluids.
- Published
- 2021
- Full Text
- View/download PDF
3. Time-rate-transformation framework for targeted assembly of short-range attractive colloidal suspensions
- Author
-
Safa Jamali, Robert C. Armstrong, and Gareth H. McKinley
- Subjects
Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
The aggregation of attractive colloids has been extensively studied from both theoretical and experimental perspectives as the fraction of solid particles is changed, and the range, type, and strength of attractive or repulsive forces between particles varies. The resulting gels, consisting of disordered assemblies of attractive colloidal particles, have also been investigated with regards to percolation, phase separation, and the mechanical characteristics of the resulting fractal networks. Despite tremendous progress in our understanding of the gelation process, and the exploration of different routes for arresting the dynamics of attractive colloids, the complex interplay between convective transport processes and many-body effects in such systems has limited our ability to drive the system toward a specific configuration. Here, we study a model attractive colloidal system over a wide range of particle characteristics and flow conditions undergoing aggregation far from equilibrium. The complex multiscale dynamics of the system can be understood using a time-rate-transformation diagram adapted from understanding of materials processing in block copolymers, supercooled liquids, and much stiffer glassy metals to direct targeted assembly of attractive colloidal particles. Keywords: Colloidal gels, Directed assembly, Rheology, Attractive colloids, Targeted-design of colloids
- Published
- 2020
- Full Text
- View/download PDF
4. UniFIDES: Universal Fractional Integro-Differential Equation Solvers.
- Author
-
Milad Saadat, Deepak Mangal, and Safa Jamali
- Published
- 2024
- Full Text
- View/download PDF
5. Solvation Thermodynamics of Solutes in Water and Ionic Liquids Using the Multiscale Solvation-Layer Interface Condition Continuum Model
- Author
-
Ali Mehdizadeh Rahimi, Safa Jamali, Jaydeep P. Bardhan, and Steven R. Lustig
- Subjects
Solutions ,Solvents ,Ionic Liquids ,Thermodynamics ,Water ,Physical and Theoretical Chemistry ,Computer Science Applications - Abstract
Molecular assembly processes are generally driven by thermodynamic properties in solutions. Atomistic modeling can be very helpful in designing and understanding complex systems, except that bulk solvent is very inefficient to treat explicitly as discrete molecules. In this work, we develop and assess two multiscale solvation models for computing solvation thermodynamic properties. The new SLIC/CDC model combines continuum solvent electrostatics based on the solvent layer interface condition (SLIC) with new statistical thermodynamic models for hydrogen bonding and nonpolar modes: cavity formation, dispersion interactions, combinatorial mixing (CDC). Given the structures of 500 solutes, the SLIC/CDC model predicts Gibbs energies of solvation in water with an average accuracy better than 1 kcal/mol, when compared to experimental measurements, and better than 0.8 kcal/mol, when compared to explicit-solvent molecular dynamics simulations. The individual SLIC/CDC energy mode values agree quantitatively with those computed from explicit-solvent molecular dynamics. The previously published SLIC/SASA multiscale model combines the SLIC continuum electrostatic model with the solvent-accessible surface area (SASA) nonpolar energy mode. With our new, improved parametrization method, the SLIC/SASA model now predicts Gibbs energies of solvation with better than 1.4 kcal/mol average accuracy in aqueous systems, compared to experimental and explicit-solvent molecular dynamics, and better than 1.6 kcal/mol average accuracy in ionic liquids, compared to explicit-solvent molecular dynamics. Both models predict solvation entropies, and are the first implicit-solvation models capable of predicting solvation heat capacities.
- Published
- 2022
- Full Text
- View/download PDF
6. Data-driven selection of constitutive models via rheology-informed neural networks (RhINNs)
- Author
-
Milad Saadat, Mohammadamin Mahmoudabadbozchelou, and Safa Jamali
- Subjects
General Materials Science ,Condensed Matter Physics - Published
- 2022
- Full Text
- View/download PDF
7. Increasing efficiency and accuracy of magnetic interaction calculations in colloidal simulation through machine learning
- Author
-
Chunzhou Pan, Mohammadamin Mahmoudabadbozchelou, Xiaoli Duan, James C. Benneyan, Safa Jamali, and Randall M. Erb
- Subjects
Machine Learning ,Biomaterials ,Colloid and Surface Chemistry ,Magnetic Phenomena ,Computer Simulation ,Neural Networks, Computer ,Algorithms ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
Calculating the magnetic interaction between magnetic particles that are positioned in close proximity to one another is a surprisingly challenging task. Exact solutions for this interaction exist either through numerical expansion of multipolar interactions or through solving Maxwell's equations with a finite element solver. These approaches can take hours for simple configurations of three particles. Meanwhile, across a range of scientific and engineering problems, machine learning approaches have been developed as fast computational platforms for solving complex systems of interest when large data sets are available. In this paper, we bring the touted benefits of recent advances in science-based machine learning algorithms to bear on the problem of modeling the magnetic interaction between three particles. We investigate this approach using diverse machine learning systems including physics informed neural networks. We find that once the training data has been collected and the model has been initiated, simulation times are reduced from hours to mere seconds while maintaining remarkable accuracy. Despite this promise, we also try to lay bare the current challenges of applying machine learning to these and more complex colloidal systems.
- Published
- 2022
- Full Text
- View/download PDF
8. nn-PINNs: Non-Newtonian physics-informed neural networks for complex fluid modeling
- Author
-
Safa Jamali, Mohammadamin Mahmoudabadbozchelou, and George Em Karniadakis
- Subjects
Physics::Fluid Dynamics ,Partial differential equation ,Flow (mathematics) ,Mesh generation ,Constitutive equation ,Newtonian fluid ,Applied mathematics ,General Chemistry ,Boundary value problem ,Condensed Matter Physics ,Non-Newtonian fluid ,Complex fluid - Abstract
Time- and rate-dependent material functions in non-Newtonian fluids in response to different deformation fields pose a challenge in integrating different constitutive models into conventional computational fluid dynamic platforms. Considering their relevance in many industrial and natural settings alike, robust data-driven frameworks that enable accurate modeling of these complex fluids are of great interest. The main goal is to solve the coupled Partial Differential Equations (PDEs) consisting of the constitutive equations that relate the shear stress to the deformation and fully capture the behavior of the fluid under various flow protocols with different boundary conditions. In this work, we present non-Newtonian physics-informed neural networks (nn-PINNs) for solving systems of coupled PDEs adopted for complex fluid flow modeling. The proposed nn-PINN method is employed to solve the constitutive models in conjunction with conservation of mass and momentum by benefiting from Automatic Differentiation (AD) in neural networks, hence avoiding the mesh generation step. nn-PINNs are tested for a number of different complex fluids with different constitutive models and for several flow protocols. These include a range of Generalized Newtonian Fluid (GNF) empirical constitutive models, as well as some phenomenological models with memory effects and thixotropic timescales. nn-PINNs are found to obtain the correct solution of complex fluids in spatiotemporal domains with good accuracy compared to the ground truth solution. We also present applications of nn-PINNs for complex fluid modeling problems with unknown boundary conditions on the surface, and show that our approach can successfully recover the velocity and stress fields across the domain, including the boundaries, given some sparse velocity measurements.
- Published
- 2022
- Full Text
- View/download PDF
9. Viscosity measurement techniques in Dissipative Particle Dynamics.
- Author
-
Arman Boromand, Safa Jamali, and Joao M. Maia
- Published
- 2015
- Full Text
- View/download PDF
10. Gaussian-inspired auxiliary non-equilibrium thermostat (GIANT) for Dissipative Particle Dynamics simulations.
- Author
-
Safa Jamali, Arman Boromand, Shaghayegh Khani, and Joao M. Maia
- Published
- 2015
- Full Text
- View/download PDF
11. Structure and Dynamics of Force Clusters and Networks in Shear Thickening Suspensions
- Author
-
Mohammad Nabizadeh, Abhinendra Singh, and Safa Jamali
- Subjects
General Physics and Astronomy - Abstract
Dense suspensions can exhibit shear thickening in response to large deformation. A consensus has emerged over the past few years on the formation of force networks, that span the entire system size, that lead to increased resistance to motion. Nonetheless, the characteristics of these networks are to a large extent poorly understood. Here, force networks formed in continuous and discontinuous shear thickening dense suspensions (CST and DST, respectively) are studied. We first show the evolution of the network formation and its topological heterogeneities as the applied stress increases. Subsequently, we identify force communities and coarse grain the suspension into a cluster network, and show that cluster-level dynamics are responsible for stark differences between the CST and DST behavior. Our results suggest that the force clusters formed in the DST regime are considerably more constrained in their motion, while CST clusters are loosely connected to their surrounding clusters.
- Published
- 2022
- Full Text
- View/download PDF
12. In silico biophysics and hemorheology of blood hyperviscosity syndrome
- Author
-
Yixiang Deng, George Em Karniadakis, Elahe Javadi, and Safa Jamali
- Subjects
0303 health sciences ,medicine.diagnostic_test ,Chemistry ,Blood viscosity ,Biophysics ,Articles ,Hematocrit ,Blood Viscosity ,medicine.disease ,Blood proteins ,Cell aggregation ,03 medical and health sciences ,Viscosity ,0302 clinical medicine ,Hemorheology ,Hyperviscosity syndrome ,Circulatory system ,medicine ,Computer Simulation ,030217 neurology & neurosurgery ,030304 developmental biology - Abstract
Hyperviscosity syndrome (HVS) is characterized by an increase of the blood viscosity by up to seven times the normal blood viscosity, resulting in disturbances to the circulation in the vasculature system. HVS is commonly associated with an increase of large plasma proteins and abnormalities in the properties of red blood cells, such as cell interactions, cell stiffness, and increased hematocrit. Here, we perform a systematic study of the effect of each biophysical factor on the viscosity of blood by employing the dissipative particle dynamic method. Our in silico platform enables manipulation of each parameter in isolation, providing a unique scheme to quantify and accurately investigate the role of each factor in increasing the blood viscosity. To study the effect of these four factors independently, each factor was elevated more than its values for a healthy blood while the other factors remained constant, and viscosity measurement was performed for different hematocrits and flow rates. Although all four factors were found to increase the overall blood viscosity, these increases were highly dependent on the hematocrit and the flow rates imposed. The effect of cell aggregation and cell concentration on blood viscosity were predominantly observed at low shear rates, in contrast to the more magnified role of cell rigidity and plasma viscosity at high shear rates. Additionally, cell-related factors increase the whole blood viscosity at high hematocrits compared with the relative role of plasma-related factors at lower hematocrits. Our results, mapped onto the flow rates and hematocrits along the circulatory system, provide a correlation to underpinning mechanisms for HVS findings in different blood vessels.
- Published
- 2021
- Full Text
- View/download PDF
13. Rheology-Informed Neural Networks (RhINNs) for forward and inverse metamodelling of complex fluids
- Author
-
Safa Jamali and Mohammadamin Mahmoudabadbozchelou
- Subjects
Automatic differentiation ,Science ,Constitutive equation ,01 natural sciences ,Article ,Physics::Fluid Dynamics ,Engineering ,Chemical engineering ,0103 physical sciences ,Applied mathematics ,010306 general physics ,Complex fluid ,Theory and computation ,Multidisciplinary ,010304 chemical physics ,Artificial neural network ,Soft materials ,Ode ,Mechanical engineering ,Materials science ,Metamodeling ,Flow (mathematics) ,Ordinary differential equation ,Medicine - Abstract
Reliable and accurate prediction of complex fluids’ response under flow is of great interest across many disciplines, from biological systems to virtually all soft materials. The challenge is to solve non-trivial time and rate dependent constitutive equations to describe these structured fluids under various flow protocols. We present Rheology-Informed Neural Networks (RhINNs) for solving systems of Ordinary Differential Equations (ODEs) adopted for complex fluids. The proposed RhINNs are employed to solve the constitutive models with multiple ODEs by benefiting from Automatic Differentiation in neural networks. In a direct solution, the RhINNs platform accurately predicts the fully resolved solution of constitutive equations for a Thixotropic-Elasto-Visco-Plastic (TEVP) complex fluid for a series of flow protocols. From a practical perspective, an exhaustive list of experiments are required to identify model parameters for a multi-variant constitutive TEVP model. RhINNs are found to learn these non-trivial model parameters for a complex material using a single flow protocol, enabling accurate modeling with limited number of experiments and at an unprecedented rate. We also show the RhINNs are not limited to a specific model and can be extended to include various models and recover complex manifestations of kinematic heterogeneities and transient shear banding of thixotropic fluids.
- Published
- 2021
14. Digital rheometer twins: Learning the hidden rheology of complex fluids through rheology-informed graph neural networks
- Author
-
Mohammadamin Mahmoudabadbozchelou, Krutarth M. Kamani, Simon A. Rogers, and Safa Jamali
- Subjects
Multidisciplinary - Abstract
Significance Science-based data-driven methods that can describe the rheological behavior of complex fluids can be transformative across many disciplines. Digital rheometer twins, which are developed here, can significantly reduce the cost, time, and energy required to characterize complex fluids and predict their future behavior. This is made possible by combining two different methods of informing neural networks with the rheological underpinnings of a system, resulting in quantitative recovery of a gel’s response to different flow protocols. The platform developed here is general enough that it can be extended to areas well beyond complex fluids modeling.
- Published
- 2022
- Full Text
- View/download PDF
15. Rheology discussions: The physics of dense suspensions
- Author
-
Jeffrey F. Morris, Emanuela Del Gado, and Safa Jamali
- Subjects
Physics ,Polymer science ,Rheology ,Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2020
- Full Text
- View/download PDF
16. A hydrodynamic model for discontinuous shear-thickening in dense suspensions
- Author
-
Safa Jamali, Mu Wang, and John F. Brady
- Subjects
Dilatant ,Work (thermodynamics) ,Materials science ,010304 chemical physics ,Deformation (mechanics) ,Stokesian dynamics ,Mechanical Engineering ,Rotation around a fixed axis ,Mechanics ,Condensed Matter Physics ,01 natural sciences ,Condensed Matter::Soft Condensed Matter ,Mechanics of Materials ,0103 physical sciences ,Surface roughness ,Particle ,General Materials Science ,010306 general physics ,Magnetosphere particle motion - Abstract
Restricted sliding or rotational motion of colloidal particles plays a key role in the emergence of discontinuous shear thickening (DST). From viscometric functions to the number of contacting neighbors under an applied deformation, a hindrance to sliding motion significantly changes the behavior of dense suspensions on all scales. In this work, implicitly by using a modified hydrodynamic model based on Stokesian dynamics and explicitly by solving for the hydrodynamics of nonsmooth colloids, we show that lubrication forces that arise from surface asperities effectively provide such constraints to tangential particle motion. A transition from continuous shear thickening to DST is observed as the surface roughness of the particles is systematically increased. In this hydrodynamic model for DST, normal stress differences remain negative in the shear-thickened state (STS). Study of the spatial stress distribution indicates the onset of DST to be a highly localized event; however, particle self-diffusivity and the microstructural network suggest a rather uniform structure in the STS.
- Published
- 2020
- Full Text
- View/download PDF
17. Thixotropy and rheological hysteresis in blood flow
- Author
-
Elahe Javadi and Safa Jamali
- Subjects
General Physics and Astronomy ,Physical and Theoretical Chemistry ,Rheology - Abstract
Hemorheology is known to be a major diagnostic tool for many blood-altering diseases. While hemorheological measures of blood, such as the general flow curve, shear-thinning behavior, and its yield stress, are much more studied in detail, thixotropic behavior and thermokinematic memory formation in blood are less understood. Here, we study the thermokinematic memory formation in blood, resulting in a clear sensitivity to the flow history, i.e., thixotropic behavior. We also measure the thixotropic timescale for blood flow using a well-defined flow protocol. Employing a series of in silico flow loops in which the blood is subject to a sweep down/up flow, we measure and discuss the dependence of the thixotropic timescale to the concentration of fibrinogen in the plasma as the main driver of structural evolution under flow.
- Published
- 2022
18. A fully physiologically-informed time- and rate-dependent hemorheological constitutive model
- Author
-
Elahe Javadi, Matthew J. Armstrong, and Safa Jamali
- Subjects
Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Abstract
From a mechanical perspective, blood is a complex fluid with a rate- and time-dependent response to an applied deformation. At small deformation rates, cell aggregations owing to the bridging of fibrinogen proteins result in the formation of rouleaux structures manifesting in a large increase in the overall viscosity of the blood viscosity and the emergence of measurable yield stress. At elevated deformation rates, these internal aggregated mesostructures are broken down in a dynamical fashion, giving rise to a thermokinematic memory and thixotropic behavior of the blood. These rich and complex rheological features of blood are primarily governed by the interactions between different cells as well as the fraction of red blood cells (RBCs). Here, using a series of detailed computational tools and benchmarking experimental measurements, we present a constitutive model that accurately describes the rate- and time-dependent rheology of blood based on two physiological metrics of the blood: the hematocrit and fibrinogen concentration. We show that the model is capable of accurately predicting blood flow, not only under simple steady flows but also under different flow protocols relevant to a real circulatory system.
- Published
- 2023
- Full Text
- View/download PDF
19. Predicting Solvation Thermodynamics in Water and Ionic Liquids using the Multi-Scale Solvation Layer Interface Condition (SLIC)
- Author
-
Jaydeep Bardhan, Steve R. Lustig, Ali Mehdizadeh Rahimi, and Safa Jamali
- Subjects
Materials science ,Scale (ratio) ,biology ,Solvation ,Thermodynamics ,Dielectric ,biology.organism_classification ,Electrostatics ,Entropy (classical thermodynamics) ,chemistry.chemical_compound ,chemistry ,Sasa ,Ionic liquid ,Root-mean-square deviation - Abstract
We highlight the most recent developments of the solvation-layer interface condition (SLIC) continuum dielectric model in predicting solvation thermodynamics of neutral small molecules in water and multiple ionic liquids. We demonstrate that a simple temperature-dependent solvent-accessible-surface-area (SASA) correlation and a cavity-dispersion-combinatorial (CDC) theory, combined with the SLIC electrostatics model, provide highly accurate predictions of Gibbs solvation energies, solvation entropies, and solvation heat capacities. The SLIC/SASA model parameters are temperature dependent, whereas the SLIC/CDC parameters are constant. To address the lack of experimental data pertaining to the accuracy of the models, we conducted an extensive literature search and data compilation to obtain credible experimental solvation data. This yielded 159 and 123 data points for hydration entropies and heat capacities of neutral small molecules, respectively. Compared to experimental data, the SLIC/SASA and SLIC/CDC models, respectively, achieve an RMS error 1.39 (1.24) and 1.15 (1.76) kcal/mol for hydration free energy (hydration entropy) predictions. Solvation heat capacities are predicted with RMS errors 24.42 and 46.17 cal/mol/K. Most remarkably, the SLIC/CDC predictions of solvation entropies and heat capacities are made without apriori knowledge of experimental solvation entropies. In addition, the SLIC/SASA predictions of Gibbs solvation energies (solvation entropies) of 12 amino acid side-chain analogs in seven (three) ionic liquids are compared to the available explicit-solvent simulation data from Paluch et al.~\cite{Paluch12} and Latif~\cite{Latif14} et al.
- Published
- 2021
- Full Text
- View/download PDF
20. Hemorheology: the critical role of flow type in blood viscosity measurements
- Author
-
Elahe Javadi and Safa Jamali
- Subjects
Materials science ,Erythrocytes ,medicine.diagnostic_test ,Blood viscosity ,Laminar flow ,General Chemistry ,Mechanics ,Hematocrit ,Condensed Matter Physics ,Blood Viscosity ,Volumetric flow rate ,Rheology ,Flow (mathematics) ,Drag ,Hemorheology ,medicine ,Computer Simulation - Abstract
The crucial role of the hemorheological characteristics of blood in a range of diagnoses, treatments and drug delivery mechanisms is widely accepted. Nonetheless, the literature on blood rheology remains inconclusive and sometimes even contradictory. This is in part due to natural variance of blood samples from one study to another, but also stems from fundamental differences in the consequences of the choice of rheometric flow employed. Here, and using a detailed and accurate computational scheme, we thoroughly study the role of flow type in measurement of blood viscosity. Performing these in silico measurements, we isolate the role of flow type and geometry at different hematocrit levels. We show that flow curves obtained in pressure-driven flows relevant to laminar circulatory flows deviate greatly from ones obtained in drag flow at the same hematocrit level. Our numerical platform also allows for the yield stress to be measured under quiescent conditions and without imposing any flow for different hematocrits. We discuss the scaling of the yield stress with the hematocrit level, and show that the differences in pressure vs. drag flows stem from the Red Blood Cell (RBC) orientation at different flow rates as well as the existence of a cell free layer close to the walls.
- Published
- 2021
21. Drag reduction and the Vogel exponent of a flexible beam in transient shear flows
- Author
-
Ali Mehdizadeh Rahimi, Steven R. Lustig, Jaydeep P. Bardhan, and Safa Jamali
- Subjects
Fluid Flow and Transfer Processes ,Mechanics of Materials ,Mechanical Engineering ,Computational Mechanics ,Condensed Matter Physics - Abstract
Interactions between a flexible beam and a fluid in a channel are of great relevance to biological hairy surfaces, aquatic vegetation, marine life (e.g., fish gills), and many industrial systems alike. While steady state response of a beam to such flows is fairly well-explored, their behavior in the transient regime is not fully understood. A series of numerical simulations are performed to study the laminar Couette flow of an incompressible viscous fluid past an elastic beam in a two-dimensional channel. The flexible beam is perpendicular to the direction of flow, and its base is fixed to the stationary bottom of the channel. We measure the evolution of the Vogel exponent, drag reduction, and reconfiguration number during the transient and steady-state response of the fluid–structure system for different geometrical and physical properties. Our benchmark shows a good agreement between numerical and experimental observations. Our results show that the system's steady-state response at different bulk-fluid velocities can be reproduced by investigating the shear flow response during the transient regime. We define a new variable that characterizes the evolution of the local velocity profile in the proximity of the free end of the beam and use that to characterize the transient-regime response. The analysis yields insight into the competing effects of elasticity of the beam and non-linear flow response.
- Published
- 2022
- Full Text
- View/download PDF
22. Integrating blood cell mechanics, platelet adhesive dynamics and coagulation cascade for modelling thrombus formation in normal and diabetic blood
- Author
-
Chensen Lin, Yixiang Deng, Safa Jamali, Alireza Yazdani, Zhen Li, Elahe Javadi, Christos S. Mantzoros, He Li, Jay D. Humphrey, and George Em Karniadakis
- Subjects
Blood Platelets ,Excessive Bleeding ,Biomedical Engineering ,Biophysics ,Bioengineering ,Biochemistry ,Biomaterials ,Blood cell ,Tissue factor ,Adhesives ,Diabetes Mellitus ,medicine ,Humans ,Platelet ,Platelet activation ,Thrombus ,Blood Coagulation ,Life Sciences–Engineering interface ,Chemistry ,Thrombosis ,Mechanics ,medicine.disease ,medicine.anatomical_structure ,Coagulation ,Biotechnology - Abstract
Normal haemostasis is an important physiological mechanism that prevents excessive bleeding during trauma, whereas the pathological thrombosis especially in diabetics leads to increased incidence of heart attacks and strokes as well as peripheral vascular events. In this work, we propose a new multiscale framework that integrates seamlessly four key components of blood clotting, namely transport of coagulation factors, coagulation kinetics, blood cell mechanics and platelet adhesive dynamics, to model the development of thrombi under physiological and pathological conditions. We implement this framework to simulate platelet adhesion due to the exposure of tissue factor in a three-dimensional microchannel. Our results show that our model can simulate thrombin-mediated platelet activation in the flowing blood, resulting in platelet adhesion to the injury site of the channel wall. Furthermore, we simulate platelet adhesion in diabetic blood, and our results show that both the pathological alterations in the biomechanics of blood cells and changes in the amount of coagulation factors contribute to the excessive platelet adhesion and aggregation in diabetic blood. Taken together, this new framework can be used to probe synergistic mechanisms of thrombus formation under physiological and pathological conditions, and open new directions in modelling complex biological problems that involve several multiscale processes.
- Published
- 2021
- Full Text
- View/download PDF
23. Time-rate-transformation framework for targeted assembly of short-range attractive colloidal suspensions
- Author
-
Robert C. Armstrong, Safa Jamali, and Gareth H. McKinley
- Subjects
Range (particle radiation) ,Condensed Matter - Materials Science ,endocrine system ,Materials science ,Mechanical Engineering ,digestive, oral, and skin physiology ,Time rate ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Condensed Matter - Soft Condensed Matter ,complex mixtures ,body regions ,Condensed Matter::Soft Condensed Matter ,Colloid ,Fractal ,Transformation (function) ,Chemical physics ,Percolation ,lcsh:TA401-492 ,Particle ,Soft Condensed Matter (cond-mat.soft) ,General Materials Science ,lcsh:Materials of engineering and construction. Mechanics of materials ,Supercooling - Abstract
The aggregation of attractive colloids has been extensively studied from both theoretical and experimental perspectives as the fraction of solid particles is changed, and the range, type, and strength of attractive or repulsive forces between particles varies. The resulting gels, consisting of disordered assemblies of attractive colloidal particles, have also been investigated with regards to percolation, phase separation, and the mechanical characteristics of the resulting fractal networks. Despite tremendous progress in our understanding of the gelation process, and the exploration of different routes for arresting the dynamics of attractive colloids, the complex interplay between convective transport processes and many-body effects in such systems has limited our ability to drive the system toward a specific configuration. Here, we study a model attractive colloidal system over a wide range of particle characteristics and flow conditions undergoing aggregation far from equilibrium. The complex multiscale dynamics of the system can be understood using a time-rate-transformation diagram adapted from understanding of materials processing in block copolymers, supercooled liquids, and much stiffer glassy metals to direct targeted assembly of attractive colloidal particles. Keywords: Colloidal gels, Directed assembly, Rheology, Attractive colloids, Targeted-design of colloids
- Published
- 2020
24. A generalized frictional and hydrodynamic model of the dynamics and structure of dense colloidal suspensions
- Author
-
João M. Maia, Brandy Grove, Arman Boromand, and Safa Jamali
- Subjects
Dilatant ,Mesoscopic physics ,Materials science ,integumentary system ,Deformation (mechanics) ,Mechanical Engineering ,Nucleation ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,010305 fluids & plasmas ,body regions ,Condensed Matter::Soft Condensed Matter ,Rheology ,Mechanics of Materials ,Chemical physics ,Percolation ,0103 physical sciences ,General Materials Science ,0210 nano-technology ,Complex fluid - Abstract
Controlling the structure and the rheological properties of colloidal suspension is essential in numerous applications to control the phenomenon known as shear-thickening. Here, we report on the nontrivial interplay between hydrodynamic and frictional interactions using mesoscopic characterization of semidense, φ = 0.48, and dense, φ = 0.58, colloidal suspensions. Monitoring computationally both rheology and microstructure of these complex fluids under an external deformation, we show that in the semidense regime the interactions in colloidal suspensions are dominated by hydrodynamics while the fraction of frictional bonds remains negligible and consequently the size of frictional clusters remain small. For these systems, the normal stresses remain negative and large. For dense suspensions, frictional forces are necessary to capture discontinuous shear-thickening (DST); however, the microstructure and rheology are sensitive to the level of roughness of colloidal particles. Furthermore, we show that the frictional bonds in the dense and semidense regime follow the same statistics as random networks introduced by Erdős–Renyi where the presence of frictional bonds in dense suspensions promotes formation of a Giant percolated cluster. We show that for both semidense and dense regimes hydroclusters initially form, within which the frictional contacts nucleate. In the case of dense suspensions these nuclei grow and percolate and form a frictional network. We show that the presence of such a percolated cluster is also necessary for DST to occur.
- Published
- 2018
- Full Text
- View/download PDF
25. Jamming Distance Dictates Colloidal Shear Thickening
- Author
-
Safa Jamali, Alan R. Jacob, Lilian C. Hsiao, Mohammad Nabizadeh, and Shravan Pradeep
- Subjects
Dilatant ,Materials science ,Rheometry ,Condensed matter physics ,Dissipative particle dynamics ,digestive, oral, and skin physiology ,General Physics and Astronomy ,FOS: Physical sciences ,Jamming ,02 engineering and technology ,Surface finish ,Condensed Matter - Soft Condensed Matter ,021001 nanoscience & nanotechnology ,01 natural sciences ,Condensed Matter::Soft Condensed Matter ,Colloid ,Shear (geology) ,0103 physical sciences ,Surface roughness ,Soft Condensed Matter (cond-mat.soft) ,010306 general physics ,0210 nano-technology - Abstract
We report experimental and computational observations of dynamic contact networks for colloidal suspensions undergoing shear thickening. The dense suspensions are comprised of sterically stabilized poly(methyl methacrylate) hard sphere colloids that are spherically symmetric and have varied surface roughness. Confocal rheometry and dissipative particle dynamics simulations show that the shear thickening strength scales exponentially with the scaled deficit contact number and the scaled jamming distance. Rough colloids, which experience additional tangential and rolling constraints, require an average of 1.5 - 2 fewer particle contacts as compared to smooth colloids, in order to generate the same shear thickening strength. This is because the surface roughness enhances geometric friction in a way that the rough colloids do not experience a large change in the free volume near the jamming point. In contrast, smooth colloids must undergo significant reduction in the free volume to support an equivalent shear stress. The available free volume for different colloid roughness is related to the deficiency from the maximum number of nearest neighbors at jamming under shear. Our results further suggest that the force per contact is different for particles with different morphologies.
- Published
- 2020
- Full Text
- View/download PDF
26. Alternative Frictional Model for Discontinuous Shear Thickening of Dense Suspensions: Hydrodynamics
- Author
-
John F. Brady and Safa Jamali
- Subjects
Dilatant ,Materials science ,General Physics and Astronomy ,Mechanics ,Contact model ,01 natural sciences ,Physics::Fluid Dynamics ,Condensed Matter::Soft Condensed Matter ,Shear (geology) ,0103 physical sciences ,Lubrication ,Surface roughness ,010306 general physics ,Magnetosphere particle motion - Abstract
A consensus has emerged that a constraint to rotational or sliding motion of particles in dense suspensions under flow is the genesis of the discontinuous shear thickening (DST) phenomenon. We show that tangential fluid lubrication interactions due to finite-sized asperities on particle surfaces effectively provide these constraints, changing the dynamics of particle motion. By explicitly resolving for the surface roughness of particles, we show that, while smooth particles exhibit continuous shear thickening, purely hydrodynamic interactions in rough particles result in DST. In contrast to the frictional contact model, the hydrodynamic model predicts negative first and second normal stress differences for dense suspensions in the shear thickened state.
- Published
- 2019
- Full Text
- View/download PDF
27. Multiscale Nature of Thixotropy and Rheological Hysteresis in Attractive Colloidal Suspensions under Shear
- Author
-
Gareth H. McKinley, Robert C. Armstrong, and Safa Jamali
- Subjects
Thixotropy ,Materials science ,Time constant ,Mesoscale meteorology ,General Physics and Astronomy ,Mechanics ,01 natural sciences ,Hysteresis ,Rheology ,Shear (geology) ,0103 physical sciences ,Shear stress ,010306 general physics ,Microscale chemistry - Abstract
Colloids with short range attractions self-assemble into sample-spanning structures, whose dynamic nature results in a thermokinematic memory of the deformation history, also referred to as "thixotropy." Here, we study the origins of the thixotropic effect in these time- and rate-dependent materials by investigating hysteresis across different length scales: from particle-level local measurements of coordination number (microscale), to the appearance of density and velocity fluctuations (mesoscale), and up to the shear stress response to an imposed deformation (macroscale). The characteristic time constants at each scale become progressively shorter, and hysteretic effects become more significant as we increase the strength of the interparticle attraction. There are also strong correlations between the thixotropic effects we observe at each scale.
- Published
- 2019
28. Structural fingerprints of yielding mechanisms in attractive colloidal gels
- Author
-
João M. Maia, Arman Boromand, and Safa Jamali
- Subjects
Chemistry ,Dissipative particle dynamics ,Compaction ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Dissociation (chemistry) ,Condensed Matter::Soft Condensed Matter ,Colloid ,Crystallography ,Rheology ,Chemical physics ,0103 physical sciences ,Volume fraction ,Shear stress ,010306 general physics ,0210 nano-technology ,Anisotropy - Abstract
Core-Modified Dissipative Particle Dynamics (CM-DPD) with a modified depletion potential and full hydrodynamics description is used to study non-equilibrium properties of colloidal gels with short range attraction potentials at an intermediate volume fraction (ϕ = 0.2) under start-up shear deformation. Full structural and rheological analysis using the stress fabric tensor complemented by bond number and bond distribution evolution under flow reveals that similarly to dilute colloidal gels, flow-induced anisotropy and strain-induced stretching of bonds are present during the first yielding transition. Unlike in low volume fraction depletion gels however, a small fraction of bond dissociation is required to facilitate bond rotation at intermediate volume fractions. The strain at which structural stretching and anisotropy in bond distribution emerge coincides with the first maximum in the shear stress (first yielding transition). At higher strains, depending on flow strength, a second peak in stress signal appears which is attributed to the compaction and melting of clusters. In this work, for the first time we provide evidence that multibody hydrodynamic interactions are essential to predict the correct dynamics of depletion gels under flow, namely two-step yielding process.
- Published
- 2017
- Full Text
- View/download PDF
29. Correction: Hemorheology: the critical role of flow type in blood viscosity measurements
- Author
-
Elahe Javadi and Safa Jamali
- Subjects
Materials science ,Blood viscosity ,Flow type ,Thermodynamics ,Hemorheology ,General Chemistry ,Soft matter ,Condensed Matter Physics - Abstract
Correction for ‘Hemorheology: the critical role of flow type in blood viscosity measurements’ by Elahe Javadi et al., Soft Matter, 2021, 17, 8446–8458, DOI: 10.1039/D1SM00856K.
- Published
- 2021
- Full Text
- View/download PDF
30. Entropy analysis and thermal optimization of nanofluid impinging jet using artificial neural network and genetic algorithm
- Author
-
Safa Jamali, Amirsaman Eghtesad, Mohammadamin Mahmoudabadbozchelou, and Hossein Afshin
- Subjects
Artificial neural network ,Turbulence ,020209 energy ,General Chemical Engineering ,Enhanced heat transfer ,Nanoparticle ,02 engineering and technology ,Mechanics ,Condensed Matter Physics ,01 natural sciences ,Nusselt number ,Atomic and Molecular Physics, and Optics ,010406 physical chemistry ,0104 chemical sciences ,Nanofluid ,Heat transfer ,Volume fraction ,0202 electrical engineering, electronic engineering, information engineering - Abstract
Optimized and informed design of impinging jets can effectively enhance their rate of heat transfer. One practical pathway for such designing is to add nanoparticles to a background fluid. Here, we determine the effects of nanoparticle chemistry, their size, and their total volume fraction in water on the rate of heat transfer. We perform a comprehensive optimization using artificial neural network (ANN) and genetic algorithm (GA) to systematically study the enhanced heat transfer in nanofluids compared to pure water in obtaining a uniform cooling on a constantly heated surface in a turbulent flow. Our results indicate that increasing the size and concentration of nanoparticles enhances the rate of heat transfer. Nanoparticles are found to improve the uniformity of Nusselt distribution in the range of Nu = 57.5–72.5, however, in the range of Nu = 20–35, air is found to be more uniform. Finally, we perform a Thermodynamic analysis to determine the contribution of heat transfer and the frictional forces of the system on the total entropy generation in the optimal point. Results show that the portion of the two sources on entropy generation virtually equal for air, but the effects of heat transfer dominates for water and Al2O3/water nanofluids.
- Published
- 2020
- Full Text
- View/download PDF
31. Microstructure and rheology of soft to rigid shear-thickening colloidal suspensions
- Author
-
Safa Jamali, João M. Maia, Norman J. Wagner, and Arman Boromand
- Subjects
Dilatant ,Materials science ,Mechanical Engineering ,Modulus ,Condensed Matter Physics ,Atomic packing factor ,Physics::Fluid Dynamics ,Condensed Matter::Soft Condensed Matter ,Colloid ,Rheology ,Shear (geology) ,Mechanics of Materials ,Shear stress ,General Materials Science ,Composite material ,Elastic modulus - Abstract
The shear rate-dependent rheological properties of soft to rigid colloidal suspensions are studied using computational models. We show that a contact force defined based on an elasto-hydrodynamic deformation theory captures an important rheological behavior of colloidal suspensions: While near hard-sphere particles exhibit a strong and continuous shear thickening the evolves to a constant viscosity state, soft suspensions undergo a second shear-thinning regime at high Peclet numbers when the hydrodynamic stresses become larger than the modulus of the colloidal particles. We measure N1 and N2 to be large and negative in the shear-thickening regime; however, for soft spheres at the onset of second shear-thinning N2 reduces in magnitude and eventually becomes positive. We show that for near hard-sphere suspensions, colloidal pressure, shear stress, and normal stress difference coefficients tend to diverge near the maximum packing fraction while P>σ>N1>N2.
- Published
- 2015
- Full Text
- View/download PDF
32. Polymer-mediated nanorod self-assembly predicted by dissipative particle dynamics simulations
- Author
-
Safa Jamali, João M. Maia, Michael J. A. Hore, Arman Boromand, and Shaghayegh Khani
- Subjects
chemistry.chemical_classification ,Quantitative Biology::Biomolecules ,Materials science ,Dissipative particle dynamics ,Nanotechnology ,General Chemistry ,Polymer ,Condensed Matter Physics ,Condensed Matter::Soft Condensed Matter ,Matrix (mathematics) ,chemistry ,Chemical physics ,Phase (matter) ,Nanorod ,Self-assembly ,Dispersion (chemistry) ,Phase diagram - Abstract
Self-assembly of nanoparticles in polymer matrices is an interesting and growing subject in the field of nanoscience and technology. We report herein on modelling studies of the self-assembly and phase behavior of nanorods in a homopolymer matrix, with the specific goal of evaluating the role of deterministic entropic and enthalpic factors that control the aggregation/dispersion in such systems. Grafting polymer brushes from the nanorods is one approach to control/impact their self-assembly capabilities within a polymer matrix. From an energetic point of view, miscible interactions between the brush and the matrix are required for achieving a better dispersibility; however, grafting density and brush length are the two important parameters in dictating the morphology. Unlike in previous computational studies, the present Dissipative Particle Dynamics (DPD) simulation framework is able to both predict dispersion or aggregation of nanorods and determine the self-assembled structure, allowing for the determination of a phase diagram, which takes all of these factors into account. Three types of morphologies are predicted: dispersion, aggregation and partial aggregation. Moreover, favorable enthalpic interactions between the brush and the matrix are found to be essential for expanding the window for achieving a well-dispersed morphology. A three-dimensional phase diagram is mapped on which all the afore-mentioned parameters are taken into account. Additionally, in the case of immiscibility between brushes and the matrix, simulations predict the formation of some new and tunable structures.
- Published
- 2015
- Full Text
- View/download PDF
33. Rheological State Diagrams for Rough Colloids in Shear Flow
- Author
-
Peter F. Green, Michael J. Solomon, Ronald G. Larson, Emmanouil Glynos, Lilian C. Hsiao, and Safa Jamali
- Subjects
Dilatant ,Condensed Matter - Materials Science ,Materials science ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,General Physics and Astronomy ,02 engineering and technology ,Mechanics ,Surface finish ,Condensed Matter - Soft Condensed Matter ,021001 nanoscience & nanotechnology ,Atomic packing factor ,01 natural sciences ,Physics::Fluid Dynamics ,Condensed Matter::Soft Condensed Matter ,Rheology ,0103 physical sciences ,Lubrication ,Shear stress ,Surface roughness ,Soft Condensed Matter (cond-mat.soft) ,010306 general physics ,0210 nano-technology ,Shear flow - Abstract
The flow of dense suspensions, glasses, and granular materials is heavily influenced by frictional interactions between constituent particles. However, neither hydrodynamics nor friction has successfully explained the full range of flow phenomena in concentrated suspensions. Particles with asperities represent a case in point. Lubrication hydrodynamics fail to completely capture two key rheological properties - namely, that the viscosity increases drastically and the first normal stress difference can switch signs as volume fraction increases. Yet, simulations that account for interparticle friction are also unable to fully predict these properties. Furthermore, experiments show that rheological behavior can vary depending on particle roughness and deformability. We seek to resolve these apparent contradictions by systematically tuning the roughness of model colloids, investigating their viscosity and first normal stress differences under steady shear, and finally generating a rheological state diagram that demonstrates how surface roughness influences the transition between shear thickening and dilatancy. Our simulations, which are in good agreement with the experiments, suggest that friction between rough particles is significant. In addition, we find that roughness progressively lowers the critical conditions required for the onset of shear thickening and dilatancy. Our results thus provides a major contribution in the field of suspension rheology with broad relevance to granular and particulate materials. For instance, particle geometry can be tuned to increase the efficacy of materials that turn solid-like on the application of stimuli. On the other hand, engineers who work with concentrated slurries can now use images of the constituent particles to estimate optimal flow processing conditions.
- Published
- 2017
- Full Text
- View/download PDF
34. Mechanism of ionic conduction in multi-layer polymeric films studied via electrochemical measurement and theoretical modelling
- Author
-
Sina S. Jamali, Douglas J Mills, Yue Zhao, Thomas F Suesse, and Safa Jamali
- Subjects
Materials science ,Plane (geometry) ,Scattering ,General Chemical Engineering ,Organic Chemistry ,Statistical model ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Thermal conduction ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Coating ,Chemical physics ,Phase (matter) ,Materials Chemistry ,Forensic engineering ,engineering ,Ionic conductivity ,0210 nano-technology - Abstract
Ionically permeable domains in polymeric protective coatings have been investigated empirically and theoretically. In the first part of the paper, results from recent experiments both complement and show agreement with received knowledge. This has allowed a physical model to be proposed for the mechanism of ionic conduction in polymeric coatings. This model assumes the random scattering of small regions with very different physical and chemical properties, akin almost to separate phase. Particularly the much higher rate of conduction is likely to have an impact on the coating’s anti-corrosion ability. Based on the superimposition of permeable and impermeable domains, the model can be applied to allow comparison of multi-layer systems with single coat films of the same thickness. Such a statistical model has practical corollaries and in the second part of the paper statistical methods are advanced to allow determination of the probability of having these permeable domains in two, three, four and more coats. This has been further refined by a virtual simulation process using the distribution of permeable domains on a two dimensional plane. The significance of the theoretical models is then discussed with respect to the experimental data and what they mean in terms of protective ability.
- Published
- 2017
35. Dispersion and re-agglomeration phenomena during melt mixing of polypropylene with multi-wall carbon nanotubes
- Author
-
Safa Jamali, José A. Covas, Maria C. Paiva, and Universidade do Minho
- Subjects
Nanotube ,Materials science ,Polymers and Plastics ,Composite number ,Carbon nanotubes ,02 engineering and technology ,Carbon nanotube ,010402 general chemistry ,01 natural sciences ,Nanocomposites ,law.invention ,Nanocomposites Carbon nanotubes Polypropylene Dispersion ,chemistry.chemical_compound ,Electrical resistivity and conductivity ,law ,Composite material ,Polypropylene ,Science & Technology ,Nanocomposite ,Organic Chemistry ,Dispersion ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Shear (sheet metal) ,chemistry ,0210 nano-technology ,Dispersion (chemistry) - Abstract
The present work reports study of the dispersion and re-agglomeration of carbon nanotubes in a polymer melt using a prototype mixer that enables precise control over the processing parameters. Since dispersion of CNT in polymer matrices has been comprehensively studied in the literature, the focus here is to understand the spatial or temporal evolution of the process. Dispersion showed a far from gradual evolution and good correlation with the composite electrical resistivity. The effect of composite reprocessing on nanotube re-agglomeration and subsequent dispersion was also investigated. A large nanotube re-agglomeration was detected on composite re-melting, matching an increase in electrical resistivity. However, the efficiency of reprocessing in terms of rate and level of dispersion depends on the thermo-mechanical stresses created during the initial processing stage, as shown by data obtained for processing at two shear rates, and reprocessing performed at lower, identical and higher shear rates.
- Published
- 2013
- Full Text
- View/download PDF
36. Microstructural Rearrangements and their Rheological Implications in a Model Thixotropic Elastoviscoplastic Fluid
- Author
-
Robert C. Armstrong, Gareth H. McKinley, and Safa Jamali
- Subjects
Thixotropy ,Materials science ,FOS: Physical sciences ,General Physics and Astronomy ,02 engineering and technology ,Condensed Matter - Soft Condensed Matter ,01 natural sciences ,Physics::Fluid Dynamics ,Rheology ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Shear stress ,010306 general physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Isotropy ,Dissipative particle dynamics ,Fluid Dynamics (physics.flu-dyn) ,Physics - Fluid Dynamics ,Mechanics ,Vorticity ,021001 nanoscience & nanotechnology ,Condensed Matter::Soft Condensed Matter ,Shear rate ,Shear (geology) ,Soft Condensed Matter (cond-mat.soft) ,0210 nano-technology - Abstract
We identify the sequence of microstructural changes that characterize the evolution of an attractive particulate gel under flow and discuss their implications on macroscopic rheology. Dissipative Particle Dynamics (DPD) is used to monitor shear-driven evolution of a fabric tensor constructed from the ensemble spatial configuration of individual attractive constituents within the gel. By decomposing this tensor into isotropic and non-isotropic components we show that the average coordination number correlates directly with the flow curve of the shear stress vs. shear rate, consistent with theoretical predictions for attractive systems. We show that the evolution in non-isotropic local particle rearrangements are primarily responsible for stress overshoots (strain-hardening) at the inception of steady shear flow and also lead, at larger times and longer scales, to microstructural localization phenomena such as shear banding flow-induced structure formation in the vorticity direction., 15 pages, 4 figures
- Published
- 2017
- Full Text
- View/download PDF
37. Bridging the gap between microstructure and macroscopic behavior of monodisperse and bimodal colloidal suspensions
- Author
-
João M. Maia, Mikio Yamanoi, and Safa Jamali
- Subjects
Materials science ,Dispersity ,Dissipative particle dynamics ,Nanotechnology ,General Chemistry ,Condensed Matter Physics ,Microstructure ,Physics::Fluid Dynamics ,Condensed Matter::Soft Condensed Matter ,Shear rate ,Colloid ,Shear (geology) ,Rheology ,Chemical physics ,Particle size - Abstract
Colloidal suspensions exhibit a transition from shear-thinning to shear-thickening behavior as the shear rate increases. Despite all the experimental and computational studies, an understanding of the structure of suspensions in different flow regimes remains controversial. In this work, a dissipative particle dynamics model was employed to perform a comprehensive study of the rheological and morphological behaviors of monodisperse and bimodal suspensions over a wide range of shear rates. The interplay between rheology and structure indicates that hydroclusters are formed in the shear-thickening regime, whereas interparticle interaction is responsible for the shear-thinning response at low stresses. The effect of particle size, ratio, and combination in bimodal systems have also been investigated and quantitative agreement with existing experimental data was found. Thus, it was possible for the first time to perform a comprehensive study on different aspects of the bimodal dispersions and correlate the macroscopic behavior with the microstructure in different flow regimes.
- Published
- 2013
- Full Text
- View/download PDF
38. Generalized mapping of multi-body dissipative particle dynamics onto fluid compressibility and the Flory-Huggins theory
- Author
-
Arman Boromand, Shaghayegh Khani, João M. Maia, Mikio Yamanoi, Jacob W. Wagner, and Safa Jamali
- Subjects
Work (thermodynamics) ,Equation of state ,Chemistry ,Dissipative particle dynamics ,General Physics and Astronomy ,Thermodynamics ,Flory–Huggins solution theory ,Condensed Matter::Soft Condensed Matter ,Viscosity ,Incompressible flow ,Compressibility ,Radius of gyration ,Statistical physics ,Physical and Theoretical Chemistry - Abstract
In this work, a generalized relation between the fluid compressibility, the Flory-Huggins interaction parameter (χ), and the simulation parameters in multi-body dissipative particle dynamics (MDPD) is established. This required revisiting the MDPD equation of state previously reported in the literature and developing general relationships between the parameters used in the MDPD model. We derive a relationship to the Flory-Huggins χ parameter for incompressible fluids similar to the work previously done in dissipative particle dynamics by Groot and Warren. The accuracy of this relationship is evaluated using phase separation in small molecules and the solubility of polymers in dilute solvent solutions via monitoring the scaling of the radius of gyration (Rg) for different solvent qualities. Finally, the dynamics of the MDPD fluid is studied with respect to the diffusion coefficient and the zero shear viscosity.
- Published
- 2015
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.