Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session G4: Cardiovascular V: Small ScaleBio Fluids: Internal
|
Hide Abstracts |
Chair: Joseph Bull, Tulane University Room: 404 |
Monday, November 20, 2017 10:35AM - 10:48AM |
G4.00001: Predicting Insulin Absorption and Glucose Uptake during Exercise in Type 1 Diabetes Spencer Frank, Ling Hinshaw, Rita Basu, Andrew Szeri, Ananda Basu A dose of insulin infused into subcutaneous tissue has been shown to absorb more quickly during exercise, potentially causing hypoglycemia in persons with type 1 diabetes. We develop a model that relates exercise-induced physiological changes to enhanced insulin-absorption($k)$ and glucose uptake(GU). Drawing on concepts of the microcirculation we derive a relationship that reveals that $k$ and GU are mainly determined by two physiological parameters that characterize the tissue: the tissue perfusion rate($Q)$ and the capillary permeability surface area (\textit{PS}). Independently measured values of $Q$ and \textit{PS }from the literature are used in the model to make predictions of $k$ and GU. We compare these predictions to experimental observations of healthy and diabetic patients that are given a meal followed by rest or exercise. The experiments show that during exercise insulin concentrations significantly increase and that glucose levels fall rapidly. The model predictions are consistent with the experiments and show that increases in $Q$ and \textit{PS }directly increase $k$ and GU. This mechanistic understanding provides a basis for handling exercise in control algorithms for an artificial pancreas. [Preview Abstract] |
Monday, November 20, 2017 10:48AM - 11:01AM |
G4.00002: Direct numerical simulation of cellular-scale blood flow in microvascular networks Peter Balogh, Prosenjit Bagchi A direct numerical simulation method is developed to study cellular-scale blood flow in physiologically realistic microvascular networks that are constructed in silico following published in vivo images and data, and are comprised of bifurcating, merging, and winding vessels. The model resolves large deformation of individual red blood cells (RBC) flowing in such complex networks. The vascular walls and deformable interfaces of the RBCs are modeled using the immersed-boundary methods. Time-averaged hemodynamic quantities obtained from the simulations agree quite well with published in vivo data. Our simulations reveal that in several vessels the flow rates and pressure drops could be negatively correlated. The flow resistance and hematocrit are also found to be negatively correlated in some vessels. These observations suggest a deviation from the classical Poiseuille’s law in such vessels. The cells are observed to frequently jam at vascular bifurcations resulting in reductions in hematocrit and flow rate in the daughter and mother vessels. We find that RBC jamming results in several orders of magnitude increase in hemodynamic resistance, and thus provides an additional mechanism of increased in vivo blood viscosity as compared to that determined in vitro. [Preview Abstract] |
Monday, November 20, 2017 11:01AM - 11:14AM |
G4.00003: Microscopic Measurements of Axial Accumulation of Red Blood Cells in Capillary Flows Effects of Deformability Takahiro Sasaki, Junji Seki, Tomoaki Itano, Masako Sugihara-Seki In the microcirculation, red blood cells (RBCs) are known to accumulate in the region near the central axis of microvessels, which is called the "axial accumulation". Although this behavior of RBCs is considered to originate from high deformability of RBCs, there have been few experimental studies on the mechanism. In order to elucidate the effect of RBC deformability on the axial accumulation, we measured the cross-sectional distributions of RBCs flowing through capillary tubes with a high spatial resolution by a newly devised observation system for intact and softened RBCs as well as hardened RBCs to various degrees. It was found that the intact and softened RBCs are concentrated in the small area centered on the tube axis, whereas the hardened RBCs are dispersed widely over the tube cross section dependent on the degree of hardness. These results demonstrate clearly the essential role of the deformability of RBCs in the "axial accumulation" of RBCs. [Preview Abstract] |
Monday, November 20, 2017 11:14AM - 11:27AM |
G4.00004: Observation of Bright Ring Phenomenon for Red Blood Cells by Lattice Boltzmann Method Young Woo Kim, Ji Young Moon, Joon Sang Lee RBC (Red Blood Cell) aggregation is one of interests for various biomechanical fields such as cell chip or visualization. The unique phenomenon called “bright ring” is due to RBC aggregation in pulsatile flow of blood. Shear rate and flow acceleration on RBC causes them to repeat aggregating and scattering from center of the channel. The reason that this phenomenon is called bright ring is because that when observed by ultrasound imaging, the bright ring occurs periodically (Paeng DG et al., 2004). Many studies tried to observe this bright ring phenomenon experimentally (Paeng DG et al., 2009). However, there are yet not many studies trying to make use of this phenomenon for practical purposes. Bright ring phenomenon has high potential when used for cell separation or other microchip devices (Mehmet T et al., 2005). In this paper, the Lattice Boltzmann method is used to control this bright ring phenomenon. The purpose of this paper is to find conditions when bright ring phenomenon occurs, and to control the aggregating-scattering frequency and degree. Deformability of RBC is calculated following the work of Moon JY et al (2016). The result of this paper could be further extended to the optimization of cell-separating microchips. [Preview Abstract] |
Monday, November 20, 2017 11:27AM - 11:40AM |
G4.00005: A biphasic model for bleeding in soft tissue Yi-Jui Chang, Kwitae Chong, Jeff D. Eldredge, Joseph Teran, Peyman Benharash, Erik Dutson The modeling of blood passing through soft tissues in the body is important for medical applications. The current study aims to capture the effect of tissue swelling and the transport of blood under bleeding or hemorrhaging conditions. The soft tissue is considered as a non-static poro-hyperelastic material with liquid-filled voids. A biphasic formulation—effectively, a generalization of Darcy’s law---is utilized, treating the phases as occupying fractions of the same volume. The interaction between phases is captured through a Stokes-like friction force on their relative velocities and a pressure that penalizes deviations from volume fractions summing to unity. The soft tissue is modeled as a hyperelastic material with a typical J-shaped stress-strain curve, while blood is considered as a Newtonian fluid. The method of Smoothed Particle Hydrodynamics is used to discretize the conservation equations based on the ease of treating free surfaces in the liquid. Simulations of swelling under acute hemorrhage and of draining under gravity and compression will be demonstrated. Ongoing progress in modeling of organ tissues under injuries and surgical conditions will be discussed. [Preview Abstract] |
Monday, November 20, 2017 11:40AM - 11:53AM |
G4.00006: Bubble transport in bifurcations Joseph Bull, Adnan Qamar Motivated by a developmental gas embolotherapy technique for cancer treatment, we examine the transport of bubbles entrained in liquid. In gas embolotherapy, infarction of tumors is induced by selectively formed vascular gas bubbles that originate from acoustic vaporization of vascular droplets. In the case of non-functionalized droplets with the objective of vessel occlusion, the bubbles are transported by flow through vessel bifurcations, where they may split prior to eventually reach vessels small enough that they become lodged. This splitting behavior affects the distribution of bubbles and the efficacy of flow occlusion and the treatment. In these studies, we investigated bubble transport in bifurcations using computational and theoretical modeling. The model reproduces the variety of experimentally observed splitting behaviors. Splitting homogeneity and maximum shear stress along the vessel walls is predicted over a variety of physical parameters. Maximum shear stresses were found to decrease with increasing Reynolds number. The initial bubble length was found to affect the splitting behavior in the presence of gravitational asymmetry. This work was supported by NIH grant R01EB006476. [Preview Abstract] |
Monday, November 20, 2017 11:53AM - 12:06PM |
G4.00007: Stretching Behavior of Red Blood Cells at High Strain Rates Jordan E. Mancuso, William D. Ristenpart Most work on the mechanical behavior of red blood cells (RBCs) in flow has focused on simple shear flows. Relatively little work has examined RBC deformations in the physiologically important extensional flow that occurs at the entrance to a constriction. In particular, previous work suggests that RBCs rapidly stretch out and then retract upon entering the constriction, but to date no model predicts this behavior for the extremely high strain rates typically experienced there. In this work, we use high speed video to perform systematic measurements of the dynamic stretching behavior of RBCs as they enter a microfluidic constriction. We demonstrate that both the Kelvin-Voigt and Skalak viscoelastic models capture the observed stretching dynamics, up to strain rates as high as 2000 s$^{-1}$. The results indicate that the effective elastic modulus of the RBC membrane at these strain rates is an order of magnitude larger than moduli measured by micropipette aspiration or other low strain rate techniques. [Preview Abstract] |
Monday, November 20, 2017 12:06PM - 12:19PM |
G4.00008: Simulation of Red Blood Cells by the Lubricated Immersed Boundary Method in 2D Thomas Fai, Chris Rycroft The flow of red cells through capillaries involves near-contact between structures, including both cell-cell and cell-wall interactions. The thin fluid layers that arise during near-contact are difficult to resolve by standard computational fluid dynamics methods based on uniform fluid grids. Motivated by this fluid-structure interaction problem, we have developed an immersed boundary method that uses elements of lubrication theory as a subgrid model to resolve the thin fluid layers between immersed boundaries. In contrast to methods based on adaptive mesh refinement, our approach does not impose additional restrictions on the timestep. We have applied this lubricated immersed boundary method to 2D flows of increasing complexity, including a single red cell near a wall in shear flow and a suspension of red cells. We find that our method gives accurate results and reduces numerical artifacts. [Preview Abstract] |
Monday, November 20, 2017 12:19PM - 12:32PM |
G4.00009: Capture of microparticles by bolus flow in capillaries. Naoki Takeishi, Yohsuke Imai Previous studies have concluded that microparticles (MPs) can more effectively approach the microvessel wall than nanoparticles because of margination. In this study, however, we show that MPs are not marginated in capillaries where the vessel diameter is comparable to that of red blood cells (RBCs). We numerically investigated the behavior of MPs with a diameter of 1 \textmu m in various microvessel sizes, including capillaries. In capillaries, the flow mode of RBCs shifted from multi-file flow to bolus flow, and MPs were captured by the bolus flow of the RBCs instead of being marginated. Once MPs were captured, they rarely escaped from the vortex-like flow structures between RBCs. These capture events were enhanced when the hematocrit was decreased, and reduced when the shear rate was increased. Our results suggest that microparticles may be rather inefficient drug carriers when targeting capillaries because of capture events, but nanoparticles, which are more randomly distributed in capillaries, may be more effective carriers. [Preview Abstract] |
Monday, November 20, 2017 12:32PM - 12:45PM |
G4.00010: Mechanical Dissociation of Platelet Aggregates in Blood Stream Masoud Hoore, Dmitry A. Fedosov, Gerhard Gompper von Willebrand factor (VWF) and platelet aggregation is a key phenomenon in blood clotting. These aggregates form critically in high shear rates and dissolve reversibly in low shear rates (Chen et al. Nat Comm 4 (2013): 1333). The emergence of a critical shear rate, beyond which aggregates form and below which they dissolve, has an interesting impact on aggregation in blood flow. As red blood cells (RBCs) migrate to the center of the vessel in blood flow, a RBC free layer (RBC-FL) is left close to the walls into which the platelets and VWFs are pushed back from the bulk flow (M{\"u}ller et al Sci Rep 4 (2014): 4871). This margination process provides maximal VWF-platelet aggregation probability in the RBC-FL. Using mesoscale hydrodynamic simulations of aggregate dynamics in blood flow, it is shown that the aggregates form and grow in RBC-FL wherein shear rate is high for VWF stretching. By growing, the aggregates penetrate to the bulk flow and get under order of magnitude lower shear rates. Consequently, they dissolve and get back into the RBC-FL. This mechanical limitation for aggregates prohibits undesired thrombosis and vessel blockage by aggregates, while letting the VWFs and platelets to aggregate close to the walls where they are actually needed. [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