Bulletin of the American Physical Society
2005 58th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 20–22, 2005; Chicago, IL
Session KA: Bio-Fluid Dynamics: Cells and Capsules |
Hide Abstracts |
Chair: Prosenjit Bagchi, Rutgers University Room: Hilton Chicago International Ballroom South |
Monday, November 21, 2005 4:10PM - 4:23PM |
KA.00001: Simulation of Red Blood Cell Interaction with the Endothelial Cell Surface Cyrus Aidun, Xinli Jia, Jeff Morris, John McLaughlin It is hypothesized that the stress field on the EC surface felt through hydrodynamic interaction at the extracellular layer, known as the glycocalyx, is the pathophysiological link between the hemodynamics and the cell function. Simulations revealing the general stress distribution on the EC surface, and in particular the mechanical interactions of red blood cells (RBC's) with the EC's will be presented. The current focus is to investigate the drag force and the bending moment on the core proteins in the EC glycocalyx. The glycocalyx has been modeled as a quasiperiodic array of cylinders (Weinbaum et al., PNAS \textbf{100}, 1988-7995, 2003). The height and diameter of the cylinders were assumed to be 150 nm and 6 nm, respectively, and the gap between cylinders was 8 nm. Weinbaum et al. computed the average velocity profile by treating the glycocalyx as a porous medium. The focus of the work to be presented is on the effects upon the EC by close encounters with RBC's over a long period of time. We will present results for the flow in and above a model glycocalyx caused by the motion of a nearby surface. The flow was computed using the lattice Boltzmann method (LBM). The results of the LBM for the mean flow and the bending moment and drag on a model protein fiber will be compared with the predictions obtained from the model of Weinbaum. [Preview Abstract] |
Monday, November 21, 2005 4:23PM - 4:36PM |
KA.00002: Noninvasive Visualization of Human Capillary Vessel Blood Flow Masao Watanabe, Toshiyuki Sanada, Yoshinori Sawae, Masutaka Furue Human blood flows are highly susceptible to physical and health conditions. Hence quantitative evaluation of Blood flow is a useful parameter in the physical check up of individuals. However, the most convenient method is taking a blood sample, which can only examine ex vivo Blood condition. We turn our attention to the observation of the capillary loops of blood vessels in the finger skin nail fold, in which blood flow can be easily visualized without using complicated specialized tools other than capillaroscopy. We modified both the spatial and temporal resolution in capillaroscopy. A deep-focus high magnification zoom lens and a high speed video camera of 1000 fps allowed us to observe the motion of red blood cells, white blood cells and plasmas. Quantitative analysis of blood flow allowed us to observe the motion of red blood cells in capillary vessels with a diameter of about 10 micro meters. We discuss the quantitative evaluation of blood flow velocity in artery capillary vessels. We also conducted shape analysis of the capillary vessel, by using the level set method. By analyzing the obtained level set function, quantitative evaluation of the capillary blood shape, such as characteristic diameters and curvatures, are carried out. [Preview Abstract] |
Monday, November 21, 2005 4:36PM - 4:49PM |
KA.00003: The effects of non-Newtonian viscosity on the deformation of red blood cells in a shear flow Juldeh Sesay, Foluso Ladeinde The analyses of the effects of non-Newtonian viscosity on the membrane of red blood cells (RBCs) suspended in a shear flow are presented. The specific objective is to investigate the mechanical deformation on the surfaces of an ellipsoidal particle model. The hydrodynamic stresses and other forces on the surface of the particle are used to determine the cell deformation. We extended previous works, which were based on the Newtonian fluid models, to the non-Newtonian case, and focus on imposed shear rate values between 1 and 100 per second. Two viscosity models are investigated, which respectively correspond to a normal person and a patient with cerebrovascular accident (CVA). The results are compared with those obtained assuming a Newtonian model. We observed that the orientation of the cell influences the deformation and the imposed shear rate drives the local shear rate distribution along the particle surface. The integral particle deformation for the non-Newtonian models in the given shear rate regime is higher than that for the Newtonian reference model. Finally, the deformation of the cell surface decreases as the dissipation ratio increases. [Preview Abstract] |
Monday, November 21, 2005 4:49PM - 5:02PM |
KA.00004: An Experimental Study of a Giant Vesicle in a Simple Shear Flow Ryuta Hatakenaka, Takeshi Yamada, Shu Takagi, Yoichiro Matsumoto Deformation and motion of lipid bilayer vesicles with the diameter of 10-50$\mu $m (giant vesicle, GV) in a simple-shear-flow have been observed using phase contrast microscopy. We developed a simple-shear-flow apparatus, which consists of two cylinders with the diameter of 50mm separated by a narrow gap of 0.5mm. A linear shear is created in the gap and GVs prepared by the gentle hydration method are transferred there. Their behaviors in the flow are observed with microscope from the direction of the axis of the cylinders. In our observation, GVs are deformed to steady ellipsoidal shapes and show constant orientations of \textit{$\theta $}, which is the angle between the major axis and the flow direction. It is also observed that \textit{$\theta $} becomes smaller with decrease of swelling ratio \textit{$\tau $ }, which indicates the degree of deflation. Our experimental result shows good agreement with those of the previous theory [Keller and Skalak, \textit{J. Fluid. Mech}. \textbf{120}, 27-47 (1982)] and numerical simulations. [Preview Abstract] |
Monday, November 21, 2005 5:02PM - 5:15PM |
KA.00005: The dynamics of a deflated giant Vesicle in a simple shear flow Takeshi Yamada, Shu Takagi, Yoichiro Matsumoto Giant vesicle (GV) is an artificial capsule which is composed of lipid bilayer and which has the size of several tens microns. In the present study, 3-D numerical simulation for the dynamics of a GV in a simple shear flow was conducted. Immersed-Boundary method was used to simulate a deformation of GV. We expressed a GV model with the fluidity of membrane taken into account and with its volume and surface area kept constant. At first, we calculated the deflated GV as an equilibrium shape. And a long stick-like shape called a prolate shape was obtained. Then we investigated the dynamics of a prolate GV in a simple shear flow for various values of viscosity inside the GV (\textit{$\mu $}$_{in})$ and swelling ratio, Sw. Sw denotes the degree of deflation of a GV. Depending on \textit{$\mu $}$_{in }$, GV showed two kinds of motions. When \textit{$\mu $}$_{in}$ is not large enough, a GV settled down a steady shape with its major axis at a certain angle \textit{$\theta $}. This motion is called tank-treading motion. We investigated the angle \textit{$\theta $} for various values of Sw. And our results are in good agreement with the results by Kraus (1996). Then we investigated the relationship between the angle \textit{$\theta $} and \textit{$\mu $}$_{in}$. As the value of \textit{$\mu $}$_{in}$ becomes larger, the angle \textit{$\theta $} becomes smaller. When \textit{$\mu $}$_{in}$ exceeded the threshold value, a GV started tumbling its major axis in clockwise direction. The transition between a prolate shape and a disc shape was observed during tumbling motion. [Preview Abstract] |
Monday, November 21, 2005 5:15PM - 5:28PM |
KA.00006: Hydrodynamic interaction of two capsules in simple shear flow Etienne Lac, Dominique Barthes-Biesel We present a numerical model of the hydrodynamic interactions between two capsules freely suspended in a simple shear flow (SSF). The capsules are identical and consist of a liquid droplet enclosed by a thin hyper-elastic membrane. Such particles can be used in applications where encapsulation of living cells or of active agents in a protecting membrane is necessary. We assume a Stokes flow and use a boundary integral method to represent the fluid motion of the internal and suspending liquids. An isolated capsule subjected to SSF will interact with the two liquids until equilibrium is reached between the in-plane elastic stress and the viscous traction exerted on the membrane. The membrane may undergo very large deformations, thus making the problem non-linear. Monitoring the stress level in the membrane is important to predict burst. When two capsules interact in SSF, they eventually overlap and pass each other. During that process, the membranes are submitted to extra strain/stress which may lead to unexpected break-up. Pairwise interactions also cause an irreversible cross-flow trajectory shift, showing the self-diffusivity of the capsules. The comparison with a pair of droplets shows that the membranes have a strong effect on short range interactions. [Preview Abstract] |
Monday, November 21, 2005 5:28PM - 5:41PM |
KA.00007: Effect of membrane constitutive equation on the recovery of capsules from large deformations Andres Gonzalez-Mancera, Charles Eggleton The recovery of capsules after large deformations can be used to calculate its material properties. We focus our attention on the influence of varying the membrane constitutive model and the initial geometry of the capsule on the recovery process. An axisymmetric computational model based on the boundary element method (BEM) is used to simulate the recovery of capsules from small and large deformations. Comparison is made between capsules having: (1) constant cortical (surface) tension [CCT], (2) two-dimensional Hooke's law [H], (3) Mooney-Rivlin law [MR] and (4) Evans and Skalak [ES] membrane models. At small initial deformations similar behavior is observed for all models and appears independent of initial geometry. The recovery process is more sensitive to initial conditions for large deformations due to the non-linear behavior of the elastic membranes. The difference in the local strain distribution caused by variations in the initial geometry significantly affects the membrane stress field at large deformations, and thus the recovery process. [Preview Abstract] |
Monday, November 21, 2005 5:41PM - 5:54PM |
KA.00008: \textsc{Numerical simulations of cell interactions under shear flows in complex geometries} Gaozhu Peng, Norman Zabusky, Prosenjit Bagchi The receptor-mediated leukocyte adhesion and rolling on endothelium under shear flows are of crucial importance in governing a range of cell functions: inflammatory response, lymphocyte homing, and sickle cell vascular occlusion. In vivo, an endothelium-lined blood vessel lumen has a non-flat irregular complex geometry presented to blood flows, and adherent leukocytes can lead to further geometry complexity. This geometry factor can have a prominent impact on the mechanics and hemodynamics of cell interactions and adhesions in high endothelial venules, non-uniform capillaries and post-capillary expansions to name a few. In this work, a ghost-cell immerse boundary/front tracking method is presented to examine the physiological role of the blood vessel geometry in microcirculation. Motions of deformable blood cells are computed via a multiphase front tracking method. Boundary conditions for arbitrary geometries are enforced through a high-order ghost cell immersed boundary method. The current method is validated and used to explore the potential roles of vessel geometry in modulating hemodynamics and kinetics of 2d/3d cell interactions, in particular leukocyte adhesion and accumulation. [Preview Abstract] |
Monday, November 21, 2005 5:54PM - 6:07PM |
KA.00009: Numerical evaluation of stress contribution by model red blood cells in shear flow Jeffrey Morris, Jon Clausen, Cyrus Aidun, John McLaughlin Contributions to the stress of a dilute suspension of biconcave disks in simple shear flow are reported. The disks are a geometric but nondeformable model of red blood cells (RBCs), with biconcave disk geometry. Motion of disks and an equal density suspending liquid is computed using a lattice-Boltzmann equation technique. The disks, unless oriented with the normal to their ``flat'' side oriented along the vorticity direction of the shear flow, are found to tumble in a motion which becomes periodic after an initial transient. The stress contribution of the RBCs thus undergoes a periodic variation, and we report results of the instantaneous and averaged stress contributions of these particles in the dilute limit where computations of a single body motion suffice. The symmetric first moment of the surface force distribution, or stresslet is the primary contribution at low Reynolds number, and its shear and normal stress components are determined. The role of weak inertia, requiring integration over the volume of the fluid to capture the Reynolds stress contribution resulting from velocity fluctuations induced by the model RBC, will be discussed. [Preview Abstract] |
Monday, November 21, 2005 6:07PM - 6:20PM |
KA.00010: Hydrodynamic interaction among blood cells in microcirculation Prosenjit Bagchi, Sai Doddi, Gaozhu Peng Particulate nature of blood plays an important role in many hemodynamic events in small vessels. One example is the Fahraeus-Lindqvist effect which arises due to the flow-induced deformation and lateral migration of red blood cells away from the vessel wall. The lateral migration creates a region of cell- free layer which has a reduced local viscosity, and thus a pronounced effect on the blood rheology and many physiological events. The formation of the cell-free layer also plays an important role in the wall-bounded motion (margination) and vascular adhesion of white blood cells, which are critical steps in the body's immune response. To explore hydrodynamic interactions among various blood cells, under normal and disease conditions, we are developing 2D/3D numerical simulations of multiple deformable cells using front tracking/immersed boundary method. In this talk, we will describe some numerical results on the effect of neighboring particles on the lateral migration, and the development of the cell-free layer. We will also explore the effect of flowing red blood cells on the wall-bounded rolling motion and adhesion of white blood cells, as well as the effect of the white blood cells on the dispersion of the red blood cells. [Preview Abstract] |
Monday, November 21, 2005 6:20PM - 6:33PM |
KA.00011: Three-dimensional numerical simulation of cell deformation Sai Doddi, Prosenjit Bagchi Blood is a multiphase suspension of various deformable cells. The particulate nature of blood is absent in large blood vessels making a numerical/theoretical analysis somewhat easier. The analysis is also simplified for the flow through small capillaries, where blood cells flow in an ordered, `single-file' fashion. The main difficulty arises for the vessels of $\sim$10--500 micron diameter, where the cells move in a 'multi-file' fashion. The Casson fluid model, used to describe blood flow in such vessels, often fails to elucidate many microrheological events. In order to perform accurate and detailed numerical simulations of blood flow at microscales, we are developing 3D simulation techniques for multiple deformable cells using immersed boundary method. In this method, the cells are modeled as capsules, that is, liquid drops surrounded by elastic membranes. The model allows us to include various constitutive laws for the cell membrane, as well as the rheological properties of the liquid inside the cell. It also allows inclusion of the cell nucleus, as in case of a white blood cell or a neonatal red blood cell. In this talk we will describe the numerical techniques, and then explore the deformation dynamics of a nucleated/non-nucleated cell in a shear flow. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700