Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session X05: Physiological Fluid Mechanics IV: Large Vessels |
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Chair: Debanjan Mukherjee, University of Colorado, Boulder Room: Ballroom E |
Tuesday, November 26, 2024 8:00AM - 8:13AM |
X05.00001: A pipeline for deriving computational fluid models of the heart-to-brain pathway from standard-of-care clinical workup for stroke Ricardo Timothy Roopnarinesingh, Sreeparna Majee, Leon Rinkel, Jonathan Coutinho, Kelly Cao, Debanjan Mukherjee Embolic Stroke of Undetermined Source accounts for a significant fraction of all ischemic strokes, often with limited ability to disambiguate embolic stroke etiology - a critical step in improving treatment efficacy and reducing incidence of recurring stroke. In silico modeling of embolus transport can elucidate embolus source-destination dynamics but accurate hemodynamics modeling is needed to contextually simulate a stroke scenario. A common difficulty encountered when developing such computational models is integrating patient-specific physiology within the simulated hemodynamics that reflect each patient’s realistic condition. We will present a methodology for integrating patient-specific data derived from standard-of-care clinical workups from multi-modal imaging into data-rich computational fluid models of the heart-to-brain pathway. Specifically, we have used angiography, ultrasound, and perfusion imaging along with medical records data to derive arterial anastomosis, cerebral brain perfusion, systole and diastole cardiac timing, to inform in silico models. These efforts introduce a pipeline of transforming raw patient imaging from clinical workups into a patient-specific hemodynamic model that can further be used for digital twins of full embolic stroke scenarios. |
Tuesday, November 26, 2024 8:13AM - 8:26AM |
X05.00002: Super-resolution and denoising of vascular flow data by physics-informed machine learning Theophile Sautory, Shawn C Shadden We present the super-resolution and denoising of vascular flows using a deep learning model that does not require high resolution labels. The purpose of this model is to improve the resolution and fidelity of sparse and noisy flow measurements, as well as aid in the recovery of hidden quantities such as pressure or wall shear stress. The model is composed of 3 main components: a geometry autoencoder, a flow autoencoder and a phyics-informed neural network (PINN). A segmentation is performed on the noisy flow volume to identify the flow domain and a signed distance field to the flow boundary. Subsequently, a convolutional neural network (CNN) autoencoder is trained from signed-distance fields with a mean average error (MAE) loss on a noisy training dataset. Similarly a separate CNN is used for a flow autoencoder whose input is the 3-component, 3-dimensional fluid velocity field from the training dataset, again using a MAE loss. A PINN is developed to combine latent representations from the geometry and flow autoencoders to provide a pointwise estimate of the velocity and pressure at a given set of sample points. The PINN uses a multilayer perceptron and is trained using a reconstruction loss from the data and a PDE loss from evaluation of the Navier Stokes equations. The model was tested on stenotic and anuerysmal vascular flows computed from CFD and then downsampled and corrupted by noise to simulate measurements. We demonstrate model performance in comparison with a baseline CNN. In particular we demonstrate the ability of the proposed PINN to effectively denoise and super-resolve flow fields of different Reynolds numbers and for different geometries. In addition, demonstrate the ability of this model to recover well correlated pressure and wall shear stress fields. |
Tuesday, November 26, 2024 8:26AM - 8:39AM |
X05.00003: Dynamics of Physiological Blood Flow in Non-Planar Curved Artery Models Sepideh Salimi, Hamid Sadat The study of blood flow dynamics within arteries is crucial for understanding physiological functions and the development of various pathological conditions. In this research, high-fidelity simulations are used to analyze physiological flows in non-planar curved artery models using physiological flow rates under both pulsatile and steady flow conditions. Additional simulations are also conducted for planar models for comparison. The results are validated against available experimental data. The findings reveal that the combined effects of bending and curvature significantly impact the flow pattern, as well as the formation and evolution of vortical structures generated by secondary flows, for both steady flow at various Reynolds numbers and pulsatile flow, particularly during the acceleration and deceleration phases of the physiological waveform. The simulations also show that non-planar artery geometry may potentially reduce the risk of atherosclerosis by affecting wall shear stress distribution along the arterial wall. |
Tuesday, November 26, 2024 8:39AM - 8:52AM |
X05.00004: CFD simulation of non-Newtonian blood flow with radioisotope tracking for targeted cancer therapy Arpan Sircar, Zach Fox, Jayasai Rajagopal, Paul Inman, Zakaria Aboulbanine, Anuj Kapadia, Greeshma Agasthya Targeted radioisotope therapy (TRT) for cancer treatment has been the subject of many research studies in recent years. In this project we are developing a multi-scale modeling approach to study both the transport of radioisotopes from injection site to tumor and the consequent tumor dose. This approach constitutes (1) human body geometries (including internal organs and vasculature systems) from high resolution digital whole-body eXtended CArdio-Thoracic (XCAT) phantoms, (2) a physiologically-based pharmacokinetic (PBPK) model to track the amount and clearance of radioisotope within the human body, (3) a CFD model to obtain the spatio-temporal distribution of the isotope within the vasculature of the organ of interest, and (4) a radiation transport model to assess the resulting dose to the cancerous tumor. |
Tuesday, November 26, 2024 8:52AM - 9:05AM |
X05.00005: Enhancing Splenic Artery Embolization Outcomes with Patient-Specific Computational Fluid Dynamics Younes Tatari, Tyler A Smith, Jingjie Hu, Amirhossein Arzani Splenic artery embolization (SAE) has emerged as a minimally invasive solution for spleen injuries while maintaining organ function. Despite its growing popularity, the impact of hemodynamics during embolization is not fully understood. This study leverages patient-specific computational fluid dynamics (CFD) simulations to evaluate distal and proximal embolization techniques in SAE. We developed detailed 3D models encompassing the descending aorta, major visceral arteries, and iliac arteries. We then examined blood flow and pressure variations due to different coil placement strategies in proximal embolization, accounting for collateral vessels. Changes in pressure fields caused by coil placement were quantified and compared to baseline conditions, while flow stagnation was assessed using particle residence time. For distal embolization, we employed Lagrangian particle tracking to analyze the influence of particle size, release location, and timing on the embolization outcome. The findings emphasize the significant role of collateral vessels in preserving splenic blood supply post-proximal embolization. Coil placement affected distal pressure, and patient-specific CFD simulations can optimize coil positioning to achieve desired pressure reductions. Additionally, our results underscore the importance of particle size, release timing, and location in distal embolization. Our study represents an initial effort to use patient-specific modeling to refine SAE embolization. |
Tuesday, November 26, 2024 9:05AM - 9:18AM |
X05.00006: Guardians Against Atherosclerosis? Deciphering the Role of a Vortex in Carotid Artery Health Nora Caroline Wild, Kartik Venkat Bulusu, Michael W Plesniak Carotid artery diseases, such as atherosclerosis, are significant contributors to mortality in the United States. While it is recognized that low wall-shear-stresses trigger plaque formation, specifically in the internal carotid artery sinus, there is limited understanding of why only certain patients are predisposed to form plaques. Physiological pulsatile flow computational fluid dynamics simulations were performed on a ‘healthy’ and a ‘disease-prone’ carotid artery bifurcation model and a ‘hybrid’ model having a ‘healthy geometry with imposed disease-prone’ flow conditions’. The models were constructed from patient-averaged anatomical clinical data for a healthy population and one which is predisposed to develop stenotic plaques. |
Tuesday, November 26, 2024 9:18AM - 9:31AM |
X05.00007: On the study of fluid flow through a compliant tube with internal obstructions. Qianhong Wu, Siyu Chen, Bchara Sidnawi, Rungun Nathan, Qifu Wang Atherosclerosis often leads to severe pathological conditions, making it critical to understand the fluid-structure interaction (FSI) as blood flows through compliant blood vessels. Despite extensive computational studies, obtaining a comprehensive understanding of FSI remains challenging. This report presents a comprehensive investigation, combining theoretical analysis, experimental work, and simulation of flow through a compliant tube with an internal ball added to create obstruction. An elastic PDMS tube, horizontally submerged and fixed at both ends, was equipped with a fixed ball at the center and pressure transducers at each end. Pulsatile flow was induced through the compliant tube using a peristaltic pump, with uniform flow achieved by adding a flow stabilizer. The tube's shape was monitored with a high-speed camera, and the instantaneous profile was extracted by processing video frames offline using a Python program. The pressure data and contour of the compliant tube near the obstruction were analyzed to determine the impact of the obstacles on fluid flow and pressure drop. The main conclusions include the maximum deformation of the compliant tube and the presence of hysteresis in the position of the ball. Comparisons with rigid tube pressure data revealed that the deformation of the compliant tube effectively reduces the pressure drop. This study provides insights into the pressure drop characteristics and deformation behaviors of compliant tubes in the presence of obstructions, reflecting phenomena observed in conditions such as atherosclerosis and arterial stenosis. |
Tuesday, November 26, 2024 9:31AM - 9:44AM |
X05.00008: A novel flow-mediated dilation biophysical model for understanding vascular function changes of type 1 diabetes (T1D) patients BINGJIE ZHOU, Bchara Sidnawi, Ryan A Harris, Peter Kaufmann, Elizabeth Pantesco, Sridhar Santhanam, Qianhong Wu Atherosclerotic changes, such as arterial stiffening and endothelial dysfunction, begin early in individuals with Type 1 Diabetes (T1D), increasing cardiovascular risk. Endothelial function is widely assessed using the Flow-Mediated Dilation (FMD) test, which measures brachial artery diameter noninvasively during blood flow resurgence after brief ischemia. A novel model based on a recent FMD theory was developed to describe vascular function for 77 T1D and 38 healthy subjects from the Laboratory of Integrative Vascular and Exercise Physiology at Augusta University. After image preprocessing and data analysis, FMD percentage and new biophysics parameters were extracted. Diabetes patients exhibited a narrower, and lower distribution of B, indicating reduced artery sensitivity to wall shear stress (WSS), and a lower IQR of gamma, implying weaker mechanotransduction strength, compared to healthy individuals. Regression analysis showed that for diabetes patients, more changes in B and gamma are required for higher vasodilation. Moreover, clinical variables, including CRP, glucose, and HbA1c, correlate differently with FMD parameters in these two groups. Thus, the novel FMD model effectively differentiates between the arterial function of diabetes patients and that of healthy subjects. |
Tuesday, November 26, 2024 9:44AM - 9:57AM |
X05.00009: Exploring Polymer Vascular Grafts to Match to Compliance of Human Vascular Arteries Huidan (Whitney) Yu, Weichen Hong, Vijay Vijay, Jun Chen, Alan P Sawchuk To address the critical compliance mismatch between native human arteries and prosthetic grafts, which can lead to anastomotic neointimal hyperplasia and reduced graft patency, we leverage 3D printing technology to create silicone polymer arteries that closely mimic human arteries. By constructing these vascular grafts from various commercial resins with different wall thicknesses, we aim to optimize compliance matching with native human arteries through comparative measurements of compliance among human aortoiliac artery, conventional polytetrafluoroethylene (PTFE) graft, and several 3D-printed arteries using a mock circulation loop designed to simulate human arterial conditions. Through measurements of pressure waveforms and key hemodynamic metrics (heart rate, systolic, diastolic, pulse pressures, and mean arterial pressure), we find that the wall thickness of the 3D-printed grafts significantly affects their compliance properties. Notably, some specific resin grafts exhibit compliance closer to that of human arteries, outperforming traditional PTFE materials in matching both mean and pulse pressures. These promising results suggest that tailored 3D-printed resins, adjustable in size and wall thickness, are a fruitful area of research for investigations to enhance graft integration and reduce vascular complications. This warrants further research into their biocompatibility, durability, and surgical suitability. |
Tuesday, November 26, 2024 9:57AM - 10:10AM |
X05.00010: Analysis of In-Vivo Coronary Flows from a Fluid Mechanics Perspective as the Cardiovascular System is Conceptualized as a Network of Pumps and Pipes , Khiem Ngo, Thach N NGUYEN, Michael Gibson, Thang N Nguyen, Tam Tran, Nga N Nguyen The cardiovascular system is conceptualized as a network of pumps and pipes. The distinct characteristics of flows and phenomena in pipes are used as key parameters to analyze analogous in vivo arterial phenomena. At first, antegrade coronary laminar flow in diastole and retrograde flow in systole are identified. As they flow in opposing directions, the retrograde systolic flow could clash against the antegrade diastolic flow similar to a water hammer event. This results in turbulence injuring the intima, starting atherosclerosis. Lesion will grow if LDL cholesterol is plentiful. The second phenomenon is the separation of flows after the blood turns around a curve. Here the layers at the center flows faster than at border. Once the gradient between the two velocities reaches a critical level, separation and rupture of peripheral flow layers occur. These separated layers could turn, twist and form vortex which degenerates into turbulent flow. This is the mechanism of lesion at the ostium of the left circumflex artery. The 3rd arterial phenomenon is the possible vibration of coronary artery due to cyclic pounding by the alternating systolic contraction and diastolic relaxation of the left ventricle. If the frequency of this vibration matches the natural frequency of coronary artery, resonance happens. This enhanced pressure surge could rupture an atheroslerotic plaque and precipitates acute coronary syndrome. This same mechanim may cause critical limb ischemia in peripheral artery, stroke in cerebral artery. |
Tuesday, November 26, 2024 10:10AM - 10:23AM |
X05.00011: Accelerating cardiovascular CFD simulations: solving the harmonics balance form of the Navier-Stokes equations Dongjie Jia, Mahdi Esmaily The finite element methods for the solution of the Navier-Stokes equation have found common use for simulating cardiovascular flows. These simulations typically use periodic boundary conditions for physiological relevance. This results in a solution that is unsteady and often periodic. To capture this behavior, a conventional finite element method uses time-stepping to resolve the unsteady behavior of the flow to obtain cycle-to-cycle convergence. As a result, for most cardiovascular CFD simulations, more than 90% of the computational cost is spent on numerical convergence. |
Tuesday, November 26, 2024 10:23AM - 10:36AM |
X05.00012: Synchronization and Fluid Transport in Heterogeneous Ciliary Carpets Kalyan Naik Banoth, Jingyi Liu, Eva Kanso Cilia are essential for transporting fluids across epithelial surfaces, serving a critical function in human respiratory, reproductive, and cerebrospinal health. Variations in ciliary length, beat frequency, and density can significantly affect fluid transport and synchronization. However, it remains unclear which of these variations maintain healthy function and which indicate diseased conditions. In this study, we develop a mathematical model of ciliated tissues represented as a 2D lattice of force monopoles in a 3D viscous fluid. Using the Blake-Oseen solution, we construct the flow field induced by this lattice and examine its effects on the coordination of the force monopoles. Particularly, we study how heterogeneities in ciliary properties that mimic those observed in biological tissues affect coordination and fluid transport. Our simulations reveal that non-uniform ciliary distributions could lead to significant changes in fluid transport and synchronization patterns and disruption of the coordinated wave-like motion of cilia. These findings provide systematic and quantitative maps from structure to function in ciliated tissues. |
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