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 A5: Cardiovascular I: Large ScaleBio Fluids: Internal
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Chair: Ricardo Mejia-Alvarez, Michigan State University Room: 405 |
Sunday, November 19, 2017 8:00AM - 8:13AM |
A5.00001: Experimental Study of Flow Through Carotid Aneurysms Faezeh Masoomi, Ricardo Mejia-Alvarez There is evidence that traditional endovascular techniques like coiling are not effective for treatment of wide-neck cerebral aneurysms [1]. Flow Diverter Stents (FDS) have emerged as promising devices for treating complex aneurysms since they enable treatment of aneurysms that were considered untreatable before. Recent studies suggest a number of associated risks with FDS, including in-stent thrombosis, perianeurysmal edema, delayed hemorrhage, and perforator occlusions. Chong et. al. [2] simulated hemodynamic behavior using patient-specific data. From their study, it is possible to infer that the standard deviation of energy loss could be a good predictor for intervention success. The aim of this study is to investigate the flow in models of cerebral aneurysms before and after FDS insertion using PIV. These models will be based on actual clinical studies and will be fabricated with advanced additive manufacturing techniques. These data will then be used to explore flow parameters that could inform the likelihood of post-intervention aneurysm rupture, and help determine FDS designs that better suit any particular patient before its procedure. [1] T. Becske et al. J Neurosurg (2016): 1-8. [2] W. Chong et al. American J Neurorad 35.1 (2014): 136-142. [Preview Abstract] |
Sunday, November 19, 2017 8:13AM - 8:26AM |
A5.00002: Wall shear stress fixed points in blood flow Amirhossein Arzani, Shawn Shadden Patient-specific computational fluid dynamics produces large datasets, and wall shear stress (WSS) is one of the most important parameters due to its close connection with the biological processes at the wall. While some studies have investigated WSS vectorial features, the WSS fixed points have not received much attention. In this talk, we will discuss the importance of WSS fixed points from three viewpoints. First, we will review how WSS fixed points relate to the flow physics away from the wall. Second, we will discuss how certain types of WSS fixed points lead to high biochemical surface concentration in cardiovascular mass transport problems. Finally, we will introduce a new measure to track the exposure of endothelial cells to WSS fixed points. [Preview Abstract] |
Sunday, November 19, 2017 8:26AM - 8:39AM |
A5.00003: Coupled 0D-1D CFD Modeling of Right Heart and Pulmonary Artery Morphometry Tree Melody Dong, Weiguang Yang, Jeffrey A. Feinstein, Alison Marsden Pulmonary arterial hypertension (PAH) is characterized by elevated pulmonary artery (PA) pressure and remodeling of the distal PAs resulting in right ventricular (RV) dysfunction and failure. It is hypothesized that patients with untreated ventricular septal defects (VSD) may develop PAH due to elevated flows and pressures in the PAs. Wall shear stress (WSS), due to elevated flows, and circumferential stress, due to elevated pressures, are known to play a role in vascular mechanobiology. Thus, simulating VSD hemodynamics and wall mechanics may facilitate our understanding of mechanical stimuli leading to PAH initiation and progression. Although 3D CFD models can capture detailed hemodynamics in the proximal PAs, they cannot easily model hemodynamics and wave propagation in the distal PAs, where remodeling occurs. To improve current PA models, we will present a new method that couples distal PA hemodynamics with RV function. Our model couples a 0D lumped parameter model of the RV to a 1D model of the PA tree, based on human PA morphometry data, to characterize RV performance and WSS changes in the PA tree. We will compare a VSD 0D-1D model and a 0D-3D model coupled to a mathematical morphometry tree model to quantify WSS in the entire PA vascular tree. [Preview Abstract] |
Sunday, November 19, 2017 8:39AM - 8:52AM |
A5.00004: Hemodynamics of a Patient-Specific Aneurysm Model with Proper Orthogonal Decomposition. Suyue Han, Gary Han Chang, Yahya Modarres-Sadeghi Wall shear stress (WSS) and oscillatory shear index (OSI) are two of the most-widely studied hemodynamic quantities in cardiovascular systems that have been shown to have the ability to elicit biological responses of the arterial wall, which could be used to predict the aneurysm development and rupture. In this study, a reduced-order model (ROM) of the hemodynamics of a patient-specific cerebral aneurysm is studied. The snapshot Proper Orthogonal Decomposition (POD) is utilized to construct the reduced-order bases of the flow using a CFD training set with known inflow parameters. It was shown that the area of low WSS and high OSI is correlated to higher POD modes. The resulting ROM can reproduce both WSS and OSI computationally for future parametric studies with significantly less computational cost. Agreement was observed between the WSS and OSI values obtained using direct CFD results and ROM results. [Preview Abstract] |
Sunday, November 19, 2017 8:52AM - 9:05AM |
A5.00005: The role of intraluminal thrombus on oxygen transport in abdominal aortic aneurysms Sudharsan Madhavan, Erica Cherry Kemmerling Abdominal aortic aneurysm is ranked as the $13^{th}$ leading cause of death in the United States. The presence of intraluminal thrombus is thought to cause hypoxia in the vessel wall eventually aggravating the condition. Our work investigates oxygen transport and consumption in a patient-specific model of an abdominal aortic aneurysm. The model includes intraluminal thrombus and consists of the abdominal aorta, renal arteries, and iliac arteries. Oxygen transport to and within the aortic wall layer was modeled, accounting for oxygen consumption and diffusion. Flow and transport in the lumen layer were modeled using coupled Navier-Stokes and scalar transport equations. The thrombus layer was assumed to be biomechanically inactive but permeable to oxygen transport in accordance with previously-measured diffusion coefficients. Plots of oxygen concentration through the layers illustrating reduced oxygen supply to the vessel walls in parts of the model that include thrombus will be presented. [Preview Abstract] |
Sunday, November 19, 2017 9:05AM - 9:18AM |
A5.00006: Intracranial Vascular Disease Evaluation With Combined Vessel Wall Imaging And Patient Specific Hemodynamics Kurt Samson, Mahmud Mossa-Basha, Chun Yuan, Maria de Gador Canton, Alberto Aliseda Intracranial vascular pathologies are evaluated with angiography, conventional digital subtraction angiography or non-invasive (MRI, CT). Current techniques present limitations on the resolution with which the vessel wall characteristics can be measured, presenting a major challenge to differential diagnostic of cerebral vasculopathies. A new combined approach is presented that incorporates patient-specific image-based CFD models with intracranial vessel-wall MRI (VWMRI). Comparisons of the VWMRI measurements, evaluated for the presence of wall enhancement and thin-walled regions, against CFD metrics such as wall shear stress (WSS), and oscillatory shear index (OSI) are used to understand how the new imaging technique developed can predict the influence of hemodynamics on the deterioration of the aneurysmal wall, leading to rupture. Additionally, histology of each resected aneurysm, evaluated for inflammatory infiltration and wall thickness features, is used to validate the analysis from VWMRI and CFD. This data presents a solid foundation on which to build a new framework for combined VWMRI-CFD to predict unstable wall changes in unruptured intracranial aneurysms, and support clinical monitoring and intervention decisions. [Preview Abstract] |
Sunday, November 19, 2017 9:18AM - 9:31AM |
A5.00007: Flow-mediated transport around a macroscopic arterial thrombus. Debanjan Mukherjee, Jocelyn Garduno, Shawn Shadden Pathological blood clotting (thrombosis) is the acute cause of most major cardiovascular events including heart attack and stroke. Local blood and plasma transport in the neighborhood of a clot is thought to govern the thrombotic process (e.g. growth and consolidation), embolization, and the effectiveness of pharmacological treatments. To better understand the fluid mechanics near a clot it is necessary to resolve the dynamic interactions between a realistic thrombus with arbitrary shape and microstructure, and viscous, pulsatile flow. Here, we describe a computational technique to characterize flow-mediated transport phenomena in the vicinity of macro-scale arterial clots. The technique comprises (a) resolving unsteady flow around a thrombus model using a discrete particle fictitious domain finite element method; (b) identifying coherent transport features using finite time Lyapunov exponent fields, and (c) characterizing mixing using a particle-based approach. Numerical examples are discussed using realistic thrombus aggregates derived from experimental data, and pulsatile flow typical in human arteries. The results indicate the existence of local transport barriers and coherent regions in the vicinity of the clot with potential influence to local biochemical mechanics. [Preview Abstract] |
Sunday, November 19, 2017 9:31AM - 9:44AM |
A5.00008: Pulsatile flow-induced shear stress in large vessels affects VE-Cadherin and Neuregulin-1 expression in endothelial cells. Matthew Watson, Lauren Baugh, Lauren Black, Erica Kemmerling It is well known that endothelial cell behavior is modulated by flow-induced shear stress. In smaller vessels, where Reynolds and Womersley numbers are much less than one, vessel wall shear stress is close to steady; however, in the larger vessels, shear stress is pulsatile. We investigated the effect of realistic healthy and unhealthy large vessel shear stresses on the endothelial cells' expression of vascular endothelial cadherin (VE-Cad) and neuregulin-1 (NRG-1). Our model accounts for the shear thinning behavior of blood when determining the shear stress profiles. A motor-driven cone-plate shearing device was used to expose human umbilical vein endothelial cells (HUVECs) to desired shear waveforms for 24 hours. Immunohistochemistry was used to qualitatively show that HUVECs were expressing VE-Cad and NRG-1. Western blots were performed to quantify the amount of VE-Cad and NRG-1 expressed by HUVECs after exposure to flow-induced shear stress. [Preview Abstract] |
Sunday, November 19, 2017 9:44AM - 9:57AM |
A5.00009: Ultrasound SIV measurement of helical valvular flow behind the great saphenous vein Jun Hong Park, Jeong Ju Kim, Sang Joon Lee, Eunseop Yeom Dysfunction of venous valve and induced secondary abnormal flow are closely associated with venous diseases. Thus, detailed analysis of venous valvular flow is invaluable from biological and medical perspectives. However, most previous studies on venous perivalvular flows were based on qualitative analyses. On the contrary, quantitative analysis on the perivalvular flows has not been fully understood yet. In this study, 3D valvular flows under \textit{in vitro} and \textit{in vivo} conditions were experimentally investigated using ultrasound speckle image velocimetry (SIV) for analyzing their flow characteristics. The results for \textit{in vitro} model obtained by the SIV technique were compared with those derived by numerical simulation and color Doppler method to validate its measurement accuracy. Then blood flow in the human great saphenous vein was measured using the SIV with respect to the dimensionless index, helical intensity. The results obtained by the SIV method are well matched well with those obtained by the numerical simulation and color Doppler method. The hemodynamic characteristics of 3D valvular flows measured by the validated SIV method would be helpful in diagnosis of valve-related venous diseases. [Preview Abstract] |
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