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 T06: Physiological Fluid Mechanics II: Small Vessels and Microcirculation |
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Chair: Peter Balogh, New Jersey Institute of Technology Room: Ballroom F |
Monday, November 25, 2024 4:45PM - 4:58PM |
T06.00001: Deep representation and unsupervised learning for the experimental analysis of rigid particle margination in red blood cell flows Gonçalo Coutinho, Philipp Warlitz, Ana Moita, Jochen Kriegseis, António Moreira, Massimiliano Rossi In continuation of recent experimental efforts by Coutinho et al. (2023, Phys. Rev. Fluids), we provide further evidence on the margination mechanism of rigid particles (RPs) in microcirculation, which is in contrast to predictions from previous numerical works (Crowl and Fogelson, 2011, J. Fluid. Mech.; Závodszky et al., 2019, Phys. Fluids). We depart from single particle trajectories (SPT) of the RPs in red blood cell (RBC) flows obtained from defocus particle tracking (DPT) measurements in straight microchannels and employ an unsupervised learning pipeline for the analysis of SPT data patterns. The combination of feature extraction, dimensionality reduction, and HDBSCAN clustering allows an analysis of physical quantities beyond traditional approaches while minimizing user influence on hidden structures in the SPT data. The optimal clustering solution in RBC flows showed the presence of two clusters: one located in the core flow region and another sitting closer to the cell-free layer (CFL). The RPs in the latter region exhibited a wavy pattern, with those moving close to the CFL being re-directed towards the center of the flow. The absence of external forces acting on the system points to the RBCs flowing at the boundary with the CFL as key elements in delaying margination. |
Monday, November 25, 2024 4:58PM - 5:11PM |
T06.00002: Revisiting the Relevance of Platelet Margination in Arteries: a Computational Investigation Arnav Garcha, Noelia Grande Gutiérrez Platelet margination (PM) refers to the migration of platelets toward the endothelial wall. Hence, it may influence platelet wall adhesion and thrombosis formation. PM has been experimentally observed in coronary-sized tubes (mm diameter) [1], [2] between 10 and 25 cm of tube length. These values surpass the typical axial locations of epicardial coronary arterial segments with atherosclerotic plaques [3]. This observation questions the need to consider PM in thrombosis simulations of the epicardial coronary arteries. |
Monday, November 25, 2024 5:11PM - 5:24PM |
T06.00003: Network analysis of flow in glomeruli Anton Glazkov, Peter J Schmid, Dominik Obrist Blood filtration in the kidneys is performed in tufts of narrow blood vessels called glomeruli that serve as the functional units of the organ. At these small scales, blood plasma behaves as Stokes fluid, and the flow rates through a piecewise-1D network are easily recovered by a linear Kirchhoff flow analysis. The introduction of red blood cells (RBCs), however, renders the flow highly nonlinear, and leads to a heterogeneous distribution of RBCs. Recent imaging efforts have unlocked rich datasets, enabling us to study these glomeruli through the lenses of graph theory and flow physics. This talk will explore these complex networks and present a quantitative analysis of flow through them, which will form the foundation of a statistical study of flow behaviour through an entire network of glomeruli. |
Monday, November 25, 2024 5:24PM - 5:37PM |
T06.00004: Abstract Withdrawn
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Monday, November 25, 2024 5:37PM - 5:50PM |
T06.00005: New Blood Vessel Sprouts and the Unique Hemodynamics Within Mir Md Nasim Hossain, Ali Kazempour, Nien-Wen Hu, Walter L Murfee, Peter Balogh The growth of new blood vessels off existing vessels, or angiogenesis, is ubiquitous at all stages of animal life and in both health and disease. New blood vessels commonly form as blind-ended sprouts off of a host vessel through which red blood cells (RBCs) flow. Endothelial cells (ECs) comprising sprout walls are not perfectly sealed to one another, leading to plasma leakage into tissue and facilitating sprout growth. While it is known that hemodynamics influence sprout growth, current knowledge is based on reduced-order approaches which neglect 3D details and RBC-resolved fluid dynamics that are present in vivo. In the current work, we model in vivo microvessel sprouts off host vessels through which RBCs flow using high-fidelity simulations. 3D surface shapes of ECs comprising the sprout walls as well as gaps permitting leakage into surrounding tissue are fully resolved. We consider a range physiological conditions and quantify key hemodynamic features including wall shear stress (WSS), velocity distribution, and heterogeneous 3D wall permeability. 3D WSS patterns are revealed with peaks reaching an order of magnitude higher than the host vessel. Relationships between EC gap geometry and leakage are identified, enabling quantification of permeability that is difficult to measure in vivo. We also quantify the influence of RBCs which can enter sprouts on observed characteristics. Altogether, this work provides new and novel insights into the microenvironment likely experienced by sprouts in vivo. |
Monday, November 25, 2024 5:50PM - 6:03PM |
T06.00006: Hemodynamic Characteristics of a Tortuous In Vivo Microvessel Using Red Blood Cell Resolved Simulations Ali Kazempour, Mir Md Nasim Hossain, Nien-Wen Hu, Walter L Murfee, Peter Balogh Tortuous microvessels are characteristic of microvascular remodeling associated with numerous physiological and pathological scenarios. These vessels have unique morphology compared to straight vessels, the latter being the subject of extensive flow modeling studies over the past few decades. Three-dimensional (3D) hemodynamics in tortuous microvessels influenced by red blood cells (RBCs), however, remain largely unknown and important questions remain. Is blood viscosity influenced by vessel tortuosity? Do RBC flow dynamics cause localized hematocrit variations in tortuous vessels? How do these dynamics affect wall shear stress (WSS) patterns and the near-wall cell-free layer (CFL)? Here we use high-fidelity 3D RBC-resolved simulations in a tortuous in vivo microvessel over a range of physiological flow conditions to elucidate novel hemodynamic characteristics unique to this vessel morphology. The findings show how curvature can increase apparent viscosity by upwards of 26% compared to a straight tube. Due to unique RBC flow patterns, curvature-dependent variations in the Fahraeus effect are quantified and observed. We further characterize dependencies of the CFL and WSS on flow conditions and demonstrate correlation patterns between these two quantities as influenced by tortuosity. Altogether, the results provide new information to better understand the role of vessel tortuosity in physiological and pathological processes, as well as help improve reduced-order models. |
Monday, November 25, 2024 6:03PM - 6:16PM |
T06.00007: Hemodynamic regulation allows stable growth of microvascular networks Yujia Qi, Marcus Roper, Shyr-Shea Chang, Yixuan Wang How do vessels find optimal radii? Capillaries are known to adapt their radii to maintain the shear stress of blood flow at the vessel wall at a set point, yet models of adaptation purely based on average shear stress have not been able to produce complex loopy networks that resemble real microvascular systems. For narrow vessels where red blood cells travel in a single file, the shear stress on vessel endothelium peaks sharply when a red blood cell passes through. We show that stable shear-stress-based adaptation is possible if vessel shear stress set points are cued to the stress peaks. Model networks that respond to peak stresses alone can quantitatively reproduce the observed zebrafish trunk microcirculation, including its adaptive trajectory when hematocrit changes or parts of the network are amputated. Our work reveals the potential for mechanotransduction alone to generate stable hydraulically tuned microvascular networks. |
Monday, November 25, 2024 6:16PM - 6:29PM |
T06.00008: Red blood cells transition from single-file to two-file induced by streamline curvature Yu Terada, Tomoaki Watamura, Satoshi Ii, Shu Takagi Red blood cells(RBCs) in narrow capillaries take parachute-like shape and flow in single-file. In wider vessels, RBCs take slipper-like shape and flow in two-file. Previous research on these phenomena is mainly focused on straight vessels, while actual flow in human body or microfluidic devices include curve or bifurcation. In this research, we investigated the effect of streamline curvature for blood flow by numerical simulation. The immersed boundary method was employed to calculate the motion of RBCs. Simulations were conducted in toroidal vessels and a straight vessel. Imposed pressure gradient and vessel radius were set to be the same. Initial distributions of RBCs were in single-file in both simulations. Transition from single-file to two-file was observed only in toroidal pipe. Additionally, the effective viscosity increased after the transition. In single-file flow, the gradient of angular velocity was small because flow rotates as if solid body. However, in two-file flow, the gradient of angular velocity increased because each RBCs can move separately. The effective viscosity increase is caused by the difference of red blood cells motions and energy dissipation between single-file flow and two-file flow. |
Monday, November 25, 2024 6:29PM - 6:42PM |
T06.00009: Direct comparison between dissipative particle dynamics simulation of blood flow and live imaging in zebrafish vasculature Shun Tomizawa, Vivek Kumar, Hiroyuki Nakajima, Zhen Li, Yosuke Hasegawa Hemodynamic factors play crucial roles in various biological and medical phenomena, suggesting the significance of mechanical information. However, in-vivo measurement of local hemodynamic factors such as the blood flow velocity, the wall shear stress (WSS) and the blood pressure is still quite challenging. Therefore, a blood flow simulation can be a powerful alternative tool to obtain the hemodynamic parameters in real vasculatures. So far, large amount of studies on blood flow simulations and analyses in microcirculatory systems have been reported, while the thorough validation of the simulation results with experimental data is still lacking. In the present study, we develop and validate a framework to simulate the blood flow inside complex vascular structures of zebrafish based on dissipative particle dynamics (DPD) combined with the live imaging data. First, we construct a three-dimensional vascular network structure from a series of two-dimensional images. Then, the complex interaction between plasma and red blood cells is explicitly taken into account in DPD simulation. It is demonstrated that the present approach successfully reproduces the complex interactions between red blood cells and plasma inside the real vascular network of zebrafish. |
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