Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session D16: Biofluids: Physiological II - Computational Blood Flow in Arteries |
Hide Abstracts |
Chair: Paolo Zunino, University of Pittsburgh Room: 304 |
Sunday, November 24, 2013 2:15PM - 2:28PM |
D16.00001: Modeling blood flow as a fluid- multilayered structure interaction problem consisting of poroelastic materials Martina Bukac, Paolo Zunino, Ivan Yotov We model arterial blood flow as an incompressible Newtonian fluid confined by a multilayered poroelastic wall. We consider a two layer model for the arterial wall, where the inner layers (the endothelium and the intima) behave as a thin structure modeled as a linearly elastic Koiter membrane, while the outer part of the artery (the media and adventitia) is described by the Biot model. The fluid, membrane, and poroelastic structure are two-way coupled via kinematic and dynamic coupling conditions. We propose and analyze a splitting strategy based on the Lie operator splitting method, which allows solving the Navier-Stokes and Biot equations separately. In this way, we uncouple the original problem into two problems defined on separate subregions, the lumen and the wall. We show that the proposed scheme is stable under mild restriction of the time approximation step. Numerically, we investigate the effects of porosity to the structure displacement. We distinguish a high storativity and a high permeability case in the Darcy equations, and compare them to the results obtained using a purely elastic model. Depending on the regime, we observe significantly different behaviors in response to perturbations of each parameter. [Preview Abstract] |
Sunday, November 24, 2013 2:28PM - 2:41PM |
D16.00002: Toward non-Newtonian effects on secondary flow structures in a 180 degree bent tube model for curved arteries Stevin van Wyk, Lisa Prahl Wittberg, Laszlo Fuchs, Kartik V. Bulusu, Michael W. Plesniak The purpose of this study is to investigate the development of vortical flow structures of blood like fluids in a 180 degree tube bend, analogous to the aortic arch. Cardiovascular diseases are localized to regions of curvature in the arterial tree. The pathology of atherogenesis is widely considered an inflammatory response, hypothesized to be modulated by the interplay between Wall Shear Stress (WSS) variations and particulate transport mechanisms from the bulk fluid core to the near wall. The WSS is determined by the local flow characteristics as well as the rheological properties of the blood, which in turn are dependent on the bulk secondary flows. In this work, the time dependent fluid flow under various physiological flow conditions are investigated both experimentally and numerically. A Newtonian blood analog fluid model is considered in both studies to validate both methods and thereby study flow structure development during steady as well as pulsatile conditions. Particle image velocimetry (2C -- 2D PIV) is used to acquire velocity field data from an acrylic tube bend. The numerical study is extended to consider the non-Newtonian properties of blood according to an empirical model to identify the relative importance of the non-Newtonian behavior. The studies show complex Dean and Lyne vortex interaction that are enhanced with increasing peak Reynolds numbers. [Preview Abstract] |
Sunday, November 24, 2013 2:41PM - 2:54PM |
D16.00003: Hydrodynamic Enhancements of Dissolution from Drug Particles: \textit{In vivo} vs. \textit{In vitro} James Brasseur, Yanxing Wang Absorption of drug molecules into the blood stream is generally limited by dissolution-rate in the intestines. Dissolution occurs via diffusion enhanced by a response to the hydrodynamic flow environment, a process that is very different in the human intestine than in a USP-II dissolution apparatus, commonly used by drug companies to validate new drug formulations. Whereas \textit{in vivo} hydrodynamics are driven by the motility of intestinal wall muscles, the USP-II apparatus is a rotating paddle to mix drug particles during dissolution testing. These differences are of current interest to agencies that regulate drug product development. Through lattice-Boltzmann-based computer simulation of point particles transported through human intestine, we analyze the hydrodynamic parameters associated with convection that quantify the extent to which \textit{in vitro} dissolution tests are or are not relevant to \textit{in vivo} hydrodynamics. . We show that for drug particles less that $\sim$100-200 microns, effects of convection are negligible in the intestines. However, we discover a previously unappreciated phenomenon that significantly enhances dissolution-rate and that distinguishes \textit{in vitro} from \textit{in vivo} dissolution: the fluid shear rate at the particle. \textit{Supported by NSF and AstraZeneca}. [Preview Abstract] |
Sunday, November 24, 2013 2:54PM - 3:07PM |
D16.00004: Analysis of perfusion, microcirculation and drug transport in tumors. A computational study. Paolo Zunino, Laura Cattaneo We address blood flow through a network of capillaries surrounded by a porous interstitium. We develop a computational model based on the Immersed Boundary method [C.~S. Peskin. Acta Numer. 2002.]. The advantage of such an approach relies in its efficiency, because it does not need a full description of the real geometry allowing for a large economy of memory and CPU time and it facilitates handling fully realistic vascular networks [L. Cattaneo and P. Zunino. Technical report, MOX, Department of Mathematics, Politecnico di Milano, 2013.]. The analysis of perfusion and drug release in vascularized tumors is a relevant application of such techniques. Blood vessels in tumors are substantially leakier than in healthy tissue and they are tortuous. These vascular abnormalities lead to an impaired blood supply and abnormal tumor microenvironment characterized by hypoxia and elevated interstitial fluid pressure that reduces the distribution of drugs through advection [L.T. Baxter and R.K. Jain. Microvascular Research, 1989]. Finally, we discuss the application of the model to deliver nanoparticles. In particular, transport of nanoparticles in the vessels network, their adhesion to the vessel wall and the drug release in the surrounding tissue will be addressed. [Preview Abstract] |
Sunday, November 24, 2013 3:07PM - 3:20PM |
D16.00005: Fractional-order viscoelasticity in one-dimensional blood flow models Paris Perdikaris, George Karniadakis In this work, we have integrated different integer, and for the first time, fractional order viscoelastic models in a one-dimensional blood flow solver, and we study their behavior by presenting an in-silico study on a patient-specific arterial network. Integer-order models are directly derived from the QLV (quasi linear viscoelasticity) theory and are comprised by simple combinations of springs and dashpots. Fractional-order models employ fractional derivatives and naturally introduce a new element, the so called ``spring-pot.'' We perform one-dimensional blood flow simulations in a large patient-specific cranial network using four different viscoelastic parameter data-sets. The results aim to quantify the effect of arterial wall viscoelasticity on pulse wave propagation, as well as reflect any sensitivity on the input parameters that define each model. To this end, we provide a comparison of several viscoelastic models, highlight the important role played by the fractional order, and carry out a detailed global sensitivity analysis study on a stochastic fractional order viscoelastic model. [Preview Abstract] |
Sunday, November 24, 2013 3:20PM - 3:33PM |
D16.00006: A Porous Media Model for Blood Flow within Reticulated Foam Jason Ortega A porous media model is developed for non-Newtonian blood flow through reticulated foam at Reynolds numbers ranging from 10$^{\mathrm{-8}}$ to 10. This empirical model effectively divides the pressure gradient versus flow speed curve into three regimes, in which either the non-Newtonian viscous forces, the Newtonian viscous forces, or the inertial fluid forces are most prevalent. When compared to simulation data of blood flow through two reticulated foam geometries, the model adequately captures the pressure gradient within all three regimes, especially that within the Newtonian regime where blood transitions from a power-law to a constant viscosity fluid. This work was supported by the National Institutes of Health/National Institute of Biomedical Imaging and Bioengineering Grant R01EB000462 and partially performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
Sunday, November 24, 2013 3:33PM - 3:46PM |
D16.00007: Vortex dynamics in ruptured and unruptured intracranial aneurysms Gabriel Trylesinski, Nicole Varble, Jianping Xiang, Hui Meng Intracranial aneurysms (IAs) are potentially devastating pathological dilations of arterial walls that affect 2-5{\%} of the population. In our previous CFD study of 119 IAs, we found that ruptured aneurysms were correlated with complex flow pattern and statistically predictable by low wall shear stress and high oscillatory shear index. To understand flow mechanisms that drive the pathophysiology of aneurysm wall leading to either stabilization or growth and rupture, we aim at exploring vortex dynamics of aneurysmal flow and provide insight into the correlation between the previous predictive morphological parameters and wall hemodynamic metrics. We adopt the Q-criterion definition of coherent structures (CS) and analyze the CS dynamics in aneurysmal flows for both ruptured and unruptured IA cases. For the first time, we draw relevant biological conclusions concerning aneurysm flow mechanisms and pathophysiological outcome. In pulsatile simulations, the coherent structures are analyzed in these 119 patient-specific geometries obtained using 3D angiograms. The images were reconstructed and CFD were performed. Upon conclusion of this work, better understanding of flow patterns of unstable aneurysms may lead to improved clinical outcome. [Preview Abstract] |
Sunday, November 24, 2013 3:46PM - 3:59PM |
D16.00008: Accuracy of Computational Cerebral Aneurysm Hemodynamics Using Patient-Specific Endovascular Measurements Patrick McGah, Michael Levitt, Michael Barbour, Pierre Mourad, Louis Kim, Alberto Aliseda We study the hemodynamic conditions in patients with cerebral aneurysms through endovascular measurements and computational fluid dynamics. Ten unruptured cerebral aneurysms were clinically assessed by three dimensional rotational angiography and an endovascular guidewire with dual Doppler ultrasound transducer and piezoresistive pressure sensor at multiple peri-aneurysmal locations. These measurements are used to define boundary conditions for flow simulations at and near the aneurysms. The additional in vivo measurements, which were not prescribed in the simulation, are used to assess the accuracy of the simulated flow velocity and pressure. We also performed simulations with stereotypical literature-derived boundary conditions. Simulated velocities using patient-specific boundary conditions showed good agreement with the guidewire measurements, with no systematic bias and a random scatter of about 25\%. Simulated velocities using the literature-derived values showed a systematic over-prediction in velocity by 30\% with a random scatter of about 40\%. Computational hemodynamics using endovascularly-derived patient-specific boundary conditions have the potential to improve treatment predictions as they provide more accurate and precise results of the aneurysmal hemodynamics. [Preview Abstract] |
Sunday, November 24, 2013 3:59PM - 4:12PM |
D16.00009: Effects of Aortic Irregularities on the Blood Flow Iris Gutmark-Little, Lisa Prahl-Wittberg, Stevin van Wyk, Mihai Mihaescu, Laszlo Fuchs, Philippe Backeljauw, Ephraim Gutmark Cardiovascular defects characterized by geometrical anomalies of the aorta and its effect on the blood flow are investigated. The flow characteristics change with the aorta geometry and the rheological properties of the blood. Flow characteristics such as wall shear stress often play an important role in the development of vascular disease. In the present study, blood is considered to be non-Newtonian and is modeled using the Quemada model, an empirical model that is valid for different red blood cell loading. Three patient-specific aortic geometries are studied using Large Eddy Simulations (LES). The three geometries represent malformations that are typical in patients populations having a genetic disorder called Turner syndrome. The results show a highly complex flow with regions of recirculation that are enhanced in two of the three aortas. Moreover, blood flow is diverted, due to the malformations, from the descending aorta to the three side branches of the arch. The geometry having an elongated transverse aorta has larger areas of strong oscillatory wall shear stress. [Preview Abstract] |
Sunday, November 24, 2013 4:12PM - 4:25PM |
D16.00010: A Computational Fluid Dynamic Study of Blood Flow Within the Coiled Umbilical Arteries David Wilke, James Denier, Trent Mattner, Yee Khong The umbilical cord is the lifeline of the fetus throughout gestation. In a normal pregnancy it facilitates the supply of oxygen and nutrients from the placenta via a single vein, in addition to the return of deoxygenated blood from the developing embryo or fetus via two umbilical arteries. Despite the major role it plays in the growth of the fetus, pathologies of the umbilical cord are poorly understood. In particular, variations in the cord geometry, which typically forms a helical arrangement, have been correlated with adverse outcomes in pregnancy. Cords exhibiting either abnormally low or high levels of coiling have been associated with pathological results including growth-restriction and fetal demise. Despite this, the methodology currently employed by clinicians to characterize umbilical pathologies can misdiagnose cords and is prone to error. In this talk a computational model of blood flow within rigid three-dimensional structures representative of the umbilical arteries will be presented. This study determined that the current characterization was unable to differentiate between cords which exhibited clinically distinguishable flow properties, including the cord pressure drop, which provides a measure of the loading on the fetal heart. [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