Bulletin of the American Physical Society
74th Annual Meeting of the APS Division of Fluid Dynamics
Volume 66, Number 17
Sunday–Tuesday, November 21–23, 2021; Phoenix Convention Center, Phoenix, Arizona
Session Q02: Biological Fluid Dynamics: Physiological Large Vessels II |
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Chair: Rana Zakerzadeh, Duquesne University Room: North 120 CD |
Tuesday, November 23, 2021 8:00AM - 8:13AM |
Q02.00001: Particle Tracking Velocimetry as a Tool to Quantify Platelet Residence Times in Intracranial Aneurysms Treated with Flow Diverting Stents Nazanin Maani, Xinzhi Xue, Laurel M Marsh, David Bass, Michael Levitt, Alberto Aliseda Rupture of an Intracranial Aneurysm (IA) causes hemorrhagic stroke, with high mortality and morbidity. Success of endovascular stent treatment of IA relies on changes in hemodynamics, and specifically in the platelet biomechanical environment to form a stable thrombus in the IA sac post-treatment. PTV experiments are performed on in vitro models with patient-specific data, and Lagrangian analysis of platelet trajectories quantify residence times and hemodynamics. The particles are tracked in 3D for various cardiac cycles, in a novel experimental technique applied to neurovascular flows, and this data is used to characterize the platelet residence time and thrombotic shear exposure along their trajectories in the whole IA sac. |
Tuesday, November 23, 2021 8:13AM - 8:26AM |
Q02.00002: A Multiscale Framework for Simulation of Individual Red Blood Cells in Macroscale Flows with Relevance to Hemolysis Grant J Rydquist, Mahdi Esmaily
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Tuesday, November 23, 2021 8:26AM - 8:39AM |
Q02.00003: Investigation of viscosity effects in Womersley flows with Newtonian blood analog fluids Kartik V Bulusu, Michael W Plesniak
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Tuesday, November 23, 2021 8:39AM - 8:52AM |
Q02.00004: 4D flow MRI Velocity Gradient Correction Using Bias Error Estimates Sean M Rothenberger, Jiacheng Zhang, Pavlos P Vlachos, Vitaliy L Rayz 4D flow MRI provides time-resolved, 3-directional measurements of cardiovascular flow. Limited spatial resolution and partial volume (PV) effects introduce bias error in MRI-measured velocity fields, in turn, reducing the accuracy of velocity gradients derived from 4D flow data. We developed a model to estimate the instantaneous bias error distribution due to insufficient spatial resolution and PV effects, which was validated with synthetic, in vitro, and in vivo 4D flow MRI measurements. Herein, we investigated the improvement in the accuracy of near-wall velocity gradients derived from 4D flow data corrected for bias error. Synthetic 4D flow datasets were generated for Womersley flow in a 1 cm vessel with varying Womersley number, voxel size, and saturation ratio. Velocity gradients at the wall calculated from the 4D flow data with and without the bias error correction were compared to those from the analytical Womersley solution. Across all cases, removing the velocity bias error reduced the error of the near-wall velocity gradients, with the RMS gradient errors being 20.0% and 7.6% for the uncorrected and corrected 4D flow data, respectively, relative to the true gradient at the wall. Efforts are ongoing to apply the bias error correction to in vitro and in vivo 4D flow data. |
Tuesday, November 23, 2021 8:52AM - 9:05AM |
Q02.00005: Fluid-Structure Interaction (FSI) Modeling of Hemodynamics and Biomechanics in Patients with Multiple Cerebral Aneurysms Tanmay C Shidhore, Vitaliy L Rayz, Aaron A Cohen-Gadol, Ivan C Christov Growth and rupture of cerebral aneurysms - abnormal dilations of cerebral arteries - are attributed to a complex interplay between biomechanical, morphological and clinical risk factors. Previous patient-specific modeling studies have obtained correlations between hemodynamic factors and aneurysm progression across different patients. However, observed growth or stability could also be attributed to differences in clinical factors. Patients with multiple aneurysms, where growth is observed in one aneurysm while the other remains stable between baseline and follow-up imaging, act as self-controls, i.e., clinical factors are expected to affect each aneurysm in a similar manner. To this end, we perform a computational study investigating differences in hemodynamics and vascular mechanics between growing and stable aneurysms in the same subject. Patient-specific FSI simulations are performed for two patients with multiple aneurysms using the open-source solver SimVascular/svFSI. Relevant biomechanical parameters are compared between aneurysms in the same patient, indicating qualitative and quantitative differences in wall shear stress, oscillatory shear index, principal arterial stresses and their orientation, thus warranting further investigation on a larger patient cohort. |
Tuesday, November 23, 2021 9:05AM - 9:18AM |
Q02.00006: Pulse Wave 1D Algorithms: 21st Century Database for Modeling the Hemodynamic Responses to Acute Cardiovascular Stress Joseph C Muskat, Vitaliy L Rayz, Craig J Goergen, Charles F Babbs We simulated blood flow in the major vasculature of the trunk, limbs, and head to investigate the hemodynamic effects of acute cardiovascular stress (i.e., fear and aerobic exercise). Vessel dimensions were based on modern high-resolution medical imaging data with a focus on active young adult humans. Utilizing a network of reduced-order transmission line elements (0.5 cm or smaller arterial segments), together with peripheral three-element Windkessel models, we solved for instantaneous changes in flow rates and pressures in response to stress-adjusted cardiac output, peripheral resistance, and arterial compliance. Wave propagation was initiated by applying an external force mimicking the myocardial contraction of the left ventricle. We characterized the effects of fear and exercise on systemic arterial wall shear stress (WSS). Compared to the resting state, time-averaged WSS increased by 50% in the brachial arteries (BAs) and by 60% in the femoral arteries (FAs) in response to fear; likewise, WSS increased by 110% in the BAs and by 430% in the FAs during moderate aerobic exercise. Our updated anatomical database is publicly available (DOI: 10.5281/zenodo.4630326) and allows for location-specific assessment of hemodynamics under active physiologic conditions. |
Tuesday, November 23, 2021 9:18AM - 9:31AM |
Q02.00007: GPU-based scale-resolving simulations of the chaotic cardiovascular flows Hadi Zolfaghari, Mervyn Andiapen, Andreas Baumbach, Anthony Mathur, Rich R Kerswell Blood flow in the heart and large vessels presents a complex vortical character which involves a rich cascade of spatial and temporal scales. For instance, ejection of oxygenated blood out of the left ventricle results in a relatively high Reynolds number flow (Re=5000-10000) which is prone to a turbulence signature through interaction with the complex aortic geometry. Besides vessel curvature and subtle surface features, turbulence in the aorta may further be enhanced by a disease scenario e.g. atherosclerosis, and/or a present medical device. Scale-resolving computational fluid dynamics (CFD) simulations can be used to provide a detailed view of this turbulent flow. We present a GPU-based incompressible Navier-Stokes solver for scale-resolving simulations of blood flow in patient-specific aortic geometries. The flow solver leverages an optimised MPI-CUDA implementation and dedicated numerics, to coup with grid sizes beyond one billion. The geometric features are extracted from computed tomography (CT) angiograms and are integrated into the solver using a sharp-interface immersed boundary method. Using the present GPU-based solver, we show that intensive simulations matching O(100M) voxels which often require O(10K) CPU cores can now be performed with only O(10) P100 GPUs. |
Tuesday, November 23, 2021 9:31AM - 9:44AM |
Q02.00008: Towards an integrated platform for hemodynamics investigation in thoracic aorta: UQ in simulations and experiments Alessandro Mariotti, Emanuele Vignali, Emanuele Gasparotti, Simona Celi, Maria V Salvetti Techniques based on Computational Fluid Dynamics have been extensively used in the last few years to investigate hemodynamics inside arteries. Our aim is to develop an efficient platform in which in-vivo measurements are integrated into hemodynamic simulations to obtain detailed and accurate predictions on a patient-specific level. We consider real geometries of thoracic aorta and focus on the use of clinical information to impose accurate boundary conditions at the inlet/outlets of the computational model. |
Tuesday, November 23, 2021 9:44AM - 9:57AM |
Q02.00009: Black Blood MRI within Intracranial Aneurysms: Can Eulerian and Lagrangian Characteristics of the Flow Elucidate Signal Intensity? Laurel M Marsh, Jana E Korte, Franziska Gaidzik, Mariya S Pravdivtseva, Naomi Larsen, Alberto Aliseda, Philipp Berg Previous studies have shown that the signal intensity (SI) of black blood magnetic resonance imaging (BBMRI) in the lumen of intracranial aneurysms is influenced by fluid velocity. However, in-depth analysis of hemodynamic characteristics (WSS, etc.) in direct comparison to BBMRI SI has not been performed. To determine what further fluid mechanics variables can be linked to BBMRI SI, we employ computational fluid dynamics (CFD) simulations of 3 patient-specific aneurysms at a low and high pulsatile inlet flowrate, thereby providing a large range of hemodynamic and morphological parameters, for comparison to the in-vitro MRI experiments. Vorticity, circulation, and residence time are tracked in a Lagrangian-perspective. Point-to-point comparison of BBMRI SI and the computed hemodynamics show no correlation. However, when breaking down the signal into regions based on intensity, a correlation between both vorticity magnitude and vortex circulation is found. The analysis, thus, shows that BBMRI SI does relate to multiple Eulerian parameters. |
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