Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session E16: Biofluids: Cardiovascular Simulations and Devices |
Hide Abstracts |
Chair: Patrick McGah, University of Washington Room: 28B |
Sunday, November 18, 2012 4:45PM - 4:58PM |
E16.00001: Experimental Flow Characterization of a Flow Diverting Device Eph Sparrow, Ricky Chow, Gary Campbell, Afshin Divani, Jian Sheng Flow diverters, such as the Pipeline Embolization Device, are a new class of endovascular devices for the treatment of intracranial aneurysms. While clinical studies have demonstrated safety and efficacy, their impact on intra-aneurysmal flow is not confirmed experimentally. As such, optimization of the flow diversion behavior is not currently possible. A quasi-3D PIV technique was developed and applied in various glass models at Re = 275 and 550 to determine the changes to flow characteristics due to the deployment of a flow diverter across the aneurysm neck. Outcomes such as mean velocity, wall shear stress, and others metrics will be presented. Glass models with varying radii of curvature and aneurysm locations will be examined. Experiments were performed in a fully index-matched flow facility using $\sim $10$\mu $m diameter polystyrene particles doped with Rhodium 6G dye. The particles were illuminated with a 532nm laser sheet and observed with a CCD camera and a 592nm +/- 43nm bandpass filter. A quasi 3D flow field was reconstructed from multiple orthogonal planes (spaced 0.4mm apart) encompassing the entire glass model. Wall stresses were evaluated from the near-wall flow viscous stresses. [Preview Abstract] |
Sunday, November 18, 2012 4:58PM - 5:11PM |
E16.00002: Transitional Flow in an Arteriovenous Fistula: Effect of Wall Distensibility Patrick McGah, Daniel Leotta, Kirk Beach, Alberto Aliseda Arteriovenous fistulae are created surgically to provide adequate access for dialysis in patients with end-stage renal disease. Transitional flow and the subsequent pressure and shear stress fluctuations are thought to be causative in the fistula failure. Since 50\% of fistulae require surgical intervention before year one, understanding the altered hemodynamic stresses is an important step toward improving clinical outcomes. We perform numerical simulations of a patient-specific model of a functioning fistula reconstructed from 3D ultrasound scans. Rigid wall simulations and fluid-structure interaction simulations using an in-house finite element solver for the wall deformations were performed and compared. In both the rigid and distensible wall cases, transitional flow is computed in fistula as evidenced by aperiodic high frequency velocity and pressure fluctuations. The spectrum of the fluctuations is much more narrow-banded in the distensible case, however, suggesting a partial stabilizing effect by the vessel elasticity. As a result, the distensible wall simulations predict shear stresses that are systematically 10-30\% lower than the rigid cases. We propose a possible mechanism for stabilization involving the phase lag in the fluid work needed to deform the vessel wall. [Preview Abstract] |
Sunday, November 18, 2012 5:11PM - 5:24PM |
E16.00003: A CFD study of steady flow of a Newtonian and non-Newtonian fluid through a mildly curved tube with stent-like wall protrusions patterns Chekema Prince, Sean D. Peterson Early stent designs caused vessel straightening post-implantation and motivated the exploration of flow in the stent vicinity using straight pipe models with stent-like protrusion patterns. Recent advancements in stent design allow the device to better conform to the native vessel curvature. The present study focuses on the investigation of steady flow through mildly curved pipes with protrusion patterns that emulate current stent designs using computational fluid dynamics (CFD). The modeled geometries include various protrusion frequencies, heights, and widths with flow behavior within the range of physiologically relevant Dean numbers. The results are compared to smooth wall curved pipe models as well as straight pipe protrusion studies. Differences in flow behavior pre/post stent implantation will be discussed. Particular attention will be paid to flow characteristics, such as wall shear stress (WSS) magnitude and WSS gradients, indicative of potential stent failure. Newtonian and non-Newtonian fluid models will be utilized to discuss their impact on flow patterns. The study findings can be used to optimize stent design to mitigate flow conditions associated with stent failure. [Preview Abstract] |
Sunday, November 18, 2012 5:24PM - 5:37PM |
E16.00004: In vitro characterization of the technique of portal vein embolization by injection of a surgical glue Anne-Virginie Salsac, Mihai-Cristinel Sandulache, Oceane Lancon, Khadija El Kadri Benkara Partial embolization of the portal trunk by glue injection is a minimally invasive technique used in the case of malignant liver tumors. It is conducted few weeks prior to partial liver ablation, when the volume of the remnant liver section is too small to allow hepatectomy. The limitation of glue embolotherapy is that its clinical practice is based on empirical knowledge. The present objective is to study glue injection in a confined blood flow and investigate how the injection dynamics is coupled with glue polymerization. We first characterize polymerization under static conditions for various glue concentrations and then consider the influence of injection. An experimental setup reproduces the co-flow of two immiscible fluids. The glue mixture is injected through a capillary tube into a saline solution with the same ionic concentration, pH and viscosity as blood, flowing steadily in a straight cylindrical tube. The injected phase is visualized with a high-speed imaging system and results are compared with those obtained for non-reacting fluids. These experiments have enabled us to characterize the characteristic times of polymerization of the glue mixtures under static and dynamic conditions and understand how they affect the flow topology of the glue once injected. [Preview Abstract] |
Sunday, November 18, 2012 5:37PM - 5:50PM |
E16.00005: Endovascular Treatment of Thoracic Aortic Dissection: Hemodynamic Shear Stress Study Yik Sau Tang, Siu Kai Lai, Stephen Wing Keung Cheng, Kwok Wing Chow Thoracic Aortic Dissection (TAD), a life threatening cardiovascular disease, occurs when blood intrudes into the layers of the aortic wall, creating a new artificial channel (the false lumen) beside the original true lumen. The weakened false lumen wall may expand, enhancing the risk of rupture and resulting in high mortality. Endovascular treatment involves the deployment of a stent graft into the aorta, thus blocking blood from entering the false lumen. Due to the irregular geometry of the aorta, the stent graft, however, may fail to conform to the vessel curvature, and would create a ``bird-beak'' configuration, a wedge-shaped domain between the graft and the vessel wall. Computational fluid dynamics analysis is employed to study the hemodynamics of this pathological condition. With the `beaking' configuration, the local hemodynamic shear stress will drop below the threshold of safety reported earlier in the literature. The oscillating behavior of the shear stress might lead to local inflammation, atherosclerosis and other undesirable consequences. [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