Computer Simulation Study Of Collective Phenomena In Dense Suspensions Of Red Blood Cells Under Shear

The rheology of dense red blood cell suspensions is investigated via computer simulations based on the lattice Boltzmann, the immersed boundary, and the finite element methods. The red blood cells are treated as extended and deformable particles immersed in the ambient fluid. In the first part of the work, the numerical model and strategies for stress evaluation are discussed. In the second part, the behavior of the suspensions in simple shear flow is studied for different volume fractions, particle deformabilities, and shear rates. Shear thinning behavior is recovered. The existence of a shear-induced transition from a tumbling to a tank-treading motion is demonstrated. The transition can be parameterized by a single quantity, namely the effective capillary number. It is the ratio of the suspension stress and the characteristic particle membrane stress. At the transition point, a strong increase in the orientational order of the red blood cells and a significant decrease of the particle diffusivity are observed. However, the average cell deformation shows no signature of the transition.

Simulating blood cells for biomedical applications is a challenging goal. Whether you want to investigate blood flow behavior on the cell scale, or use a blood cell model for fast computational prototyping in microfluidics, Computational Blood Cell Mechanics will help you get started, and show you the path forward. The text presents a step-by-step approach to cell model building that can be adopted when developing and validating models for biomedical applications, such as filtering and sorting cells, or examining flow and deformations of individual cells under various conditions. It starts with basic building-blocks that, together, model the red blood cell membrane according to its physical properties, before moving on to discuss several issues that may pose problems along the way, and finally leads to suggestions on how to set up computational experiments. More details available at www.compbloodcell.eu

The five-volume set LNCS 11536, 11537, 11538, 11539, and 11540 constitutes the proceedings of the 19th International Conference on Computational Science, ICCS 2019, held in Faro, Portugal, in June 2019. The total of 65 full papers and 168 workshop papers presented in this book set were carefully reviewed and selected from 573 submissions (228 submissions to the main track and 345 submissions to the workshops). The papers were organized in topical sections named: Part I: ICCS Main Track Part II: ICCS Main Track; Track of Advances in High-Performance Computational Earth Sciences: Applications and Frameworks; Track of Agent-Based Simulations, Adaptive Algorithms and Solvers; Track of Applications of Matrix Methods in Artificial Intelligence and Machine Learning; Track of Architecture, Languages, Compilation and Hardware Support for Emerging and Heterogeneous Systems Part III: Track of Biomedical and Bioinformatics Challenges for Computer Science; Track of Classifier Learning from Difficult Data; Track of Computational Finance and Business Intelligence; Track of Computational Optimization, Modelling and Simulation; Track of Computational Science in IoT and Smart Systems Part IV: Track of Data-Driven Computational Sciences; Track of Machine Learning and Data Assimilation for Dynamical Systems; Track of Marine Computing in the Interconnected World for the Benefit of the Society; Track of Multiscale Modelling and Simulation; Track of Simulations of Flow and Transport: Modeling, Algorithms and Computation Part V: Track of Smart Systems: Computer Vision, Sensor Networks and Machine Learning; Track of Solving Problems with Uncertainties; Track of Teaching Computational Science; Poster Track ICCS 2019 Chapter “Comparing Domain-decomposition Methods for the Parallelization of Distributed Land Surface Models” is available open access under a Creative Commons Attribution 4.0 International License via link.springer.com.

This book presents the state-of-the-art in supercomputer simulation. It includes the latest findings from leading researchers using systems from the High Performance Computing Center Stuttgart (HLRS) in 2017. The reports cover all fields of computational science and engineering ranging from CFD to computational physics and from chemistry to computer science with a special emphasis on industrially relevant applications. Presenting findings of one of Europe’s leading systems, this volume covers a wide variety of applications that deliver a high level of sustained performance.The book covers the main methods in high-performance computing. Its outstanding results in achieving the best performance for production codes are of particular interest for both scientists and engineers. The book comes with a wealth of color illustrations and tables of results.

Recent advances witness the potential to employ nanomedicine and game-changing methods to deliver drug molecules directly to diseased sites. To optimize and then enhance the efficacy and specificity, the control and guidance of drug carriers in vasculature has become crucial. Current bottlenecks in the optimal design of drug carrying particles are the lack of knowledge about the transport of particles, adhesion on endothelium wall and subsequent internalization into diseased cells. To study the transport and adhesion of particle in vasculature, the authors have made great efforts to numerically investigate the dynamic and adhesive motions of particles in the blood flow. This book discusses the recent achievements from the establishment of fundamental physical problem to development of multiscale model, and finally large scale simulations for understanding transport of particle-based drug carriers in blood flow.

In order to simulate cellular blood, a coarse-grained spectrin-link (SL) red blood cell (RBC) membrane model is coupled with a lattice-Boltzmann (LB) based suspension solver. The LB method resolves the hydrodynamics governed by the Navier--Stokes equations while the SL method accurately models the deformation of RBCs under numerous configurations. This method has been parallelized using Message Passing Interface (MPI) protocols for the simulation of dense suspensions of RBCs characteristic of whole blood on world-class computing resources. :Simulations were performed to study rheological effects in unbounded shear using the Lees-Edwards boundary condition with good agreement with rotational viscometer results from literature. The particle-phase normal-stress tensor was analyzed and demonstrated a change in sign of the particle-phase pressure from low to high shear rates due to RBCs transitioning from a compressive state to a tensile state in the flow direction. Non-Newtonian effects such as viscosity shear thinning were observed for shear rates ranging from 14-440 inverse seconds as well as the strong dependence on hematocrit at low shear rates. An increase in membrane bending energy was shown to be an important factor for determining the average orientation of RBCs, which ultimately affects the suspension viscosity. The shear stress on platelets was observed to be higher than the average shear stress in blood, which emphasizes the importance of modeling platelets as finite particles.

In this dissertation, we study Stokesian particulate flows. In particular, we are interested in the dynamics of vesicles and red blood cells (RBCs) suspended in Stokes flow. We aim to develop mathematical models and numerical techniques for accurate simulation of their dynamics in microcirculation. Vesicles are closed membranes made of a phospholipid bilayer and are filled with fluid. Red blood cells are highly deformable nucleus-free cells and have rich dynamics when subjected to viscous forcing. Understanding single RBC dynamics is a complex fluid-membrane interaction problem of fundamental importance in expanding our understanding of red blood cell suspensions. For example, one of the fundamental problems is the construction of phase diagrams for the red blood cell shapes as a function of the imposed flow and the mechanical properties of the cell. Accurate knowledge of their shape dynamics has also led to interesting approaches for cell sorting based on mechanical properties in lateral displacement devices. We model an RBC using two different models, namely, “vesicle" and “capsule". We use the term particle to refer to both of them. Vesicles are inextensible surfaces with bending resistance and serve as a good model for RBC in 2D. But in 3D, vesicles miss important features of RBC dynamics because they have zero shear resistance. In contrast, an inextensible capsule resists shear in addition to the bending and is a more accurate model of RBC in 3D. For both the particles, we use a boundary integral formulation to simulate their long time horizon dynamics using spherical harmonics based spectral singular quadratures, differentiation and reparameterization techniques. We demonstrate the full relevance of our simulations using quantitative comparisons with existing experimental results with RBCs and vesicles. Once we have verified and validated our code, we use it to study the bistability (two RBC equilibrium states depending on initial state of RBC) observed under same flow conditions in our simulations. We plot the phase diagrams of equilibrium shapes of vesicles and RBCs in confined and unconfined Poiseuille flow. Finally, we also develop a novel scheme for Stokesian particle simulation using regularized Stokes kernels and overset finite differences based on overlapping patchwise discretization of the surface. Our scheme has lower work complexity than the spherical harmonics based scheme and also exhibits a high order convergence (typically fourth order) than the quadratic convergence of the triangulation based schemes. Furthermore, the patchwise discretization approach allows for more local independent control over resolution of the different parts of the surface than the global spherical harmonics based scheme. We verify this new scheme for extensible capsule simulation by quantitative comparison with the previous results in the literature for extensible capsules. We also demonstrate easy acceleration of singular quadrature using all-pairs evaluation algorithm implemented for the GPU architecture. The GPU acceleration allows us to do long time horizon simulation of capsules of low reduced volume resulting in complex shapes. Our scheme is also easily accessible to further acceleration using the fast multipole methods (FMMs)

The first book to provide a physical perspective of blood microcirculation Draws attention to the potential of this physical approach for novel applications in medicine Edited by specialists in this field, with chapter contributions from subject area specialists

Red blood cells in humans—and most other mammals—have a tendency to form aggregates with a characteristic face-to-face morphology, similar to a stack of coins. Known as rouleaux, these aggregates are a normally occurring phenomenon and have a major impact on blood rheology. What is the underlying mechanism that produces this pattern? Does this really happen in blood circulation? And do these rouleaux formations have a useful function? The first book to offer a comprehensive review of the subject, Red Blood Cell Aggregation tackles these and other questions related to red blood cell (RBC) aggregates. The book covers basic, clinical, and physiological aspects of this important biophysical phenomenon and integrates these areas with concepts in bioengineering. It brings together state-of-the-art research on the determinants, mechanisms, and measurement and effects of RBC aggregation as well as on variations and comparative aspects. After an introductory overview, the book outlines factors and conditions that affect RBC aggregation. It presents the two hypotheses—the bridging model and the depletion model—that provide potential mechanisms for the adhesive forces that lead to the regular packing of the cells in rouleaux formations. The book also reviews the methods used to quantify RBC aggregation in vitro, focusing on their importance in clinical practice. Chapters discuss the effect of RBC aggregation on the in vitro rheology of blood as well as on tube flow. The book also looks at what happens in the circulation when red blood cells aggregate and examines variations due to physiological and pathophysiological challenges. The concluding chapter explores the formation of red blood cell aggregates in other mammals. Written by leading researchers in the field, this is an invaluable resource for basic science, medical, and clinical researchers; graduate students; and clinicians interested in mammalian red blood cells.