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 X17: Medical Flow and Devices II |
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Chair: Yan Zhang, North Dakota State University Room: 250 A |
Tuesday, November 26, 2024 8:00AM - 8:13AM |
X17.00001: In Vitro and In Silico Engineering of Cardiopulmonary Bypass Models Yunpeng Tu, Yi-Ting Yeh, Vishal Nigam, Christina L Greene, Juan Carlos del Alamo Pediatric patients undergoing open-heart surgery are supported by cardiopulmonary bypass (CPB), in which the artificial heart-lung machine pumps and oxygenates blood. CPB exposes blood to non-physiological stimuli, including high shear stress, which can cause acute postoperative systemic inflammation. We hypothesize that pro-inflammatory shear stresses can be mitigated by a data-driven optimization of CPB operation parameters and by introducing crystalloid fluid hemodilution. |
Tuesday, November 26, 2024 8:13AM - 8:26AM |
X17.00002: Quantitative comparisons of pulmonary artery hemodynamics before and after Pulsta valve implantation in patients with Tetralogy of Fallot using computational fluid dynamics Jongmin Seo, Seung Min Baek, Kieun Choi, Sang Yun Lee, Gi Beom Kim The evaluation of percutaneous pulmonary valve implantation (PPVI) performance has been predominantly confined to assessing changes in the right ventricular volume using magnetic resonance imaging (MRI). This study aimed to evaluate the hemodynamic changes in the pulmonary arteries following PPVI using computational fluid dynamics (CFD) in patients with Tetralogy of Fallot. We conducted CFD analysis based on MRI scans performed before and after PPVI using Pulsta valve in nine patients who underwent PPVI between 2016 to 2021. We constructed patient-specific anatomic models of the pulmonary arteries, prescribed inflow boundary conditions obatined from MRI measurements, and used Windkessel boundary conditions at the outlet of the pulmonary arteries. From CFD data, we measured hemodynamics metrics including energy dissipation and backward velocities at the main, right, left pulmonary artery regions. Statistical analysis, including Wilcoxon rank-sum tests and multivariable linear regression, was performed to examine the associations between CFD data and non-CFD factors, as well as changes in these parameters after PPVI. Before PPVI, the flow velocity in the right pulmonary artery was significantly higher than that in the left pulmonary artery and main pulmonary artery in both the forward and backward directions. Forward and backward velocities decreased after PPVI, leading to an attenuation of the velocity differences among the pulmonary arteries. After PPVI, the vorticity and energy dissipation decreased significantly, whereas changes in the Womersley and Reynolds numbers were not statistically significant. A deeper understanding of the hemodynamics of pulmonary arteries using CFD can aid in evaluating the effectiveness of PPVI and refining its indications in patients with Tetralogy of Fallot. |
Tuesday, November 26, 2024 8:26AM - 8:39AM |
X17.00003: The effect of trapping dynamics of metastatic and mon-metastatic circulating tumor cells on fluid flow in a heterogeneous network Ankur Deep Bordoloi, Dieke Gabriels, Tim Winkel, Pouyan E Boukany Metastasis is the foremost cause of cancer-related deaths that involves the intricate multistep process of transporting cancer cells through the vascular network. Despite ongoing research efforts, the mechanisms by which cancer cells navigate this complex and heterogeneous network are still not fully understood. This study focuses on investigating the impact of the migration and trapping behaviour of both metastatic and non-metastatic circulating tumour cells (CTCs) on fluid flow in a heterogeneous constriction network, mimicking the vascular capillaries. The study uses both poorly aggressive and non-invasive MCF-7 and aggressive and invasive MDA-MB-231 breast cancer cells. Using a microfluidic model featuring heterogeneous constriction network, we explore how complex velocity fields within the network impacts the migration, trapping, and viability of the two cell types. Simultaneously, we assess how the trapping of cells subsequently affects fluid velocity within these systems. Our results indicate that the migration and trapping behaviour of the more aggressive MDA-MB-231 cells have a lesser impact on fluid flow compared to the behaviour of poorly aggressive MCF-7 cells. In this talk, we will present our analysis on cell trapping profiles, the coupled effect between CTC migration and the fluid flow and viability trends for the referred two cell lines. |
Tuesday, November 26, 2024 8:39AM - 8:52AM |
X17.00004: Experimental Investigation of Immiscible Liquid Drop Dynamics in a Collapsible Tube Nafis S Resan, Yan Zhang The formation and transport of immiscible liquid drops in large, thin-walled vessels are crucial for cardiovascular flow phenomena, such as thrombus transport, and endovascular treatments like portal vein embolization. Physiologically, thin-walled vessels are highly flexible and can buckle or collapse when subjected to imbalances in transmural pressures, such as muscle and hydrostatic pressure changes. Despite extensive research on microfluidic droplet formation, the dynamics of large drops in collapsible vessels under naturally constricted or collapsed conditions remain underexplored. This study experimentally investigates the formation and transport dynamics of immiscible liquid drops in deformable thin-walled tubes. A co-flow liquid-in-liquid injection system generated immiscible silicone oil drops within a continuous phase of glycerin and water mixtures, ensuring neutral buoyancy as drops flowed through distended and constricted tube cross-sections. High-speed camera footage captured drop motion, while pressure and flow rates were monitored. Results indicate that drop size, spacing, and the transition from dripping to jetting regimes depend on both the external Capillary number (ratio of viscous force to surface tension) and the internal Weber number (ratio of inertial force to surface tension). Vessel deformation and collapse further constrict drop transport, altering drop geometry, average diameter, and transport efficiency. |
Tuesday, November 26, 2024 8:52AM - 9:05AM |
X17.00005: Enhanced VWF Cleavage in Turbulence: Mechanistic Insights through Taylor-Green Vortex Flows Larry C Willis, Rukiye Tuna, Alice Liu, David Bark, Leo Liu Mechanical circulatory assist devices, such as left ventricular assist devices (LVADs), often create non-laminar and turbulent flow conditions, leading to significant clinical challenges including increased risks of hemolysis, thrombosis, and bleeding. Recent studies suggest that device-generated turbulence can enhance the cleavage of the clotting-control biopolymer called von Willebrand Factor (VWF). However, the biophysical mechanisms underlying this turbulence-enhanced VWF cleavage remain unexplored. To address this gap, we develop a Taylor-Green vortex model coupled with the Langevin equation for VWF polymer suspension dynamics to investigate how turbulent flow eddies interact with VWF polymers in an idealized yet characteristically representative turbulent shear layer flow. Our study reveals that counter-rotating eddies, down to the Kolmogorov length scale, locally generate microscale elongational flow regions that significantly enhance the unfolding, tensile stretching, and subsequent cleavage of VWF in a molecular weight-dependent manner. Our work provides mechanistic insights into how turbulence enhances VWF cleavage and offers valuable hemodynamic considerations for optimizing the design of blood-contacting devices for improved hemocompatibility. |
Tuesday, November 26, 2024 9:05AM - 9:18AM |
X17.00006: Microfluidic principles for designing vascular-like supply networks for large three-dimensional human tissue models Venkata Satya Pramodt Srinivasula, Ulrike A Nuber, Steffen Hardt In vitro models of tissues are created by providing suitable microphysiological conditions to the cells. In larger human tissue models, a vascular-like supply network is required to ensure sufficient transport of metabolic species (such as oxygen, glucose, and carbon dioxide) to and from cells. In this work, the species transport in human tissue models with an artificial supply network of porous-wall microfluidic channels in Cartesian grid structure is analyzed numerically and analytically. The species diffusion and metabolic activity in the space occupied by the cellular matrix (outside the supply network) is considered in combination with the diffusive and advective transport of the species in the culture medium inside the supply network. Thereby, correlations between the dimensionless groups characterizing the transport processes and the biological parameters indicating the type of tissue cells are derived, as well as principles for designing the artificial supply network. In addition to metabolic aspects, the resilience of the network to clogging of channels and the ease of fabrication of the network using 3D printing are analyzed. In sum, this study addresses key microfluidic problems to be solved when creating the next generation of large three-dimensional tissue models. |
Tuesday, November 26, 2024 9:18AM - 9:31AM |
X17.00007: Abstract Withdrawn
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Tuesday, November 26, 2024 9:31AM - 9:44AM |
X17.00008: Mixing and transport driven by oscillatory waves of small intestine wall Yanxing Wang, Dafne Sotelo Andana, Ruben Gonzalez Pizarro, Hui Wan, Tie Wei, Fangjun Shu The mixing and transport of different substances in the intestinal contents are driven by patterned fluctuation waves in the intestinal wall, generated by the contractions of circular and longitudinal muscle fibers within the muscularis propria. The primary types of waves include peristaltic, segmental, and pendular waves. Through high-fidelity numerical simulations based on the lattice Boltzmann method, the mixing and transport induced by different types of waves under a wide range of parameter conditions have been thoroughly investigated. The results indicate that the fluctuation waves in the intestinal wall can create diverse flow patterns, shear distributions, and mixing modes within the intestine by altering the wave frequency and amplitude. Furthermore, the combination of different types of waves, as well as waves of the same type with varying parameters, can produce more complex flow patterns. This suggests that human body may actively regulate the mixing and transport processes within the small intestine by controlling intestinal motility. |
Tuesday, November 26, 2024 9:44AM - 9:57AM |
X17.00009: Development of High-Speed Birefringence Measurement System for Investigating Fluid-Structure Interaction in Hemodynamics Ryo Umezawa, Masakazu MUTO, Akihito SAWAI, Kazuya KOBAYASHI, Shinji TAMANO Elucidation of the stress interaction between blood and blood vessels is important for understanding the phenomena of cerebral vascular diseases. One of the factors contributing to the pathogenesis is wall shear stress (WSS) induced by hydrodynamic stress of blood flowing in blood vessels. Numerical analysis for investigating WSS has been performed mainly with computational fluid dynamics (CFD), such as fluid-structure interaction (FSI). However, it is difficult to reproduce the complex phenomena of blood and blood vessels exactly in CFD. Therefore, we have developed a birefringence measurement method with a high-speed polarization camera to experimentally understand the stress interaction between blood and blood vessels. Birefringence is the physical quantity of polarized light and is proportional to stress. In the present study, the stress fields of solid (elastic channel) and liquid (working fluid) which simulate the elasticity of blood vessels and shear-thinning characteristics of blood, respectively, were visualized. Moreover, the visualization of WSS interaction between the simulated blood and blood vessels based on the birefringence data was performed. |
Tuesday, November 26, 2024 9:57AM - 10:10AM |
X17.00010: Presence of red blood cells promotes tension-dependent cleavage of von Willebrand factor under high shear Rukiye Tuna, Alice Liu, David Bark, Z. Leonardo Liu Von Willebrand factor (VWF) is a mechanosensitive plasma glycoprotein that controls thrombosis and hemostasis. Once secreted from endothelial cells, VWV remains ultra-large in size and must be cleaved by ADAMTS13 in circulation to maintain healthy hemostasis. A recent study suggests that laminar high shear in a single-phase flow can only lead to moderate cleavage of high molecular weight VWF, suggesting additional mechanisms in circulation that regulate VWF cleavage. In this study, we investigate the effect of red blood cells (RBCs) on VWF cleavage under simple shear flows using computational and experimental rheometer techniques. Our experiments demonstrate that the presence of RBCs at physiological hematocrit (40%) can significantly enhance VWF cleavage under shear while elevating plasma viscosity to the whole blood level (4 cP) without adding RBCs does not enhance cleavage as much. Through the computational study of the VWF conformation in a sheared RBC suspension, we observe instantaneously elevated VWF tensile forces beyond ~10 pN required for VWF cleavage. The elevated tension levels are strongly correlated with the percentage of VWF cleavage. This study suggests a new RBC-enhanced tension-dependent VWF cleavage mechanism, highlighting the intricate interplay between hemorheology and human pathophysiology. |
Tuesday, November 26, 2024 10:10AM - 10:23AM |
X17.00011: Examining the backspatter of blood during bullet impacts using biological simulant materials Labiba Imtiaz Kaya, Dulce C Resendiz, Sarah A. Bentil, James B Michael Bloodstain pattern analysis is vital to criminal investigation and provides crucial forensic information. However, much of the existing literature on backspatter uses very simplified geometries consisting of blood soaked sponges or penetration into liquid cavities. To better simulate cranial geometries, experiments used three configurations of materials subjected to ballistic impacts, including the effects of a brain and tissue surrogate on the spray pattern. Optical diagnostics include simultaneous capture of the cavity formation in ballistic gels and the resulting spray pattern and digital inline holography on downstream droplets to infer their size and velocity from high-speed images. These images provide comprehensive information on the time scales of cavity collapse and backspatter events. Bloodstains were also collected on butcher paper downstream of the test targets. Size distribution from the blood stain patterns are analyzed, and different stain patterns are seen for various configurations of surrogate materials. These experiments aim to integrate a fluid dynamics component into the modeling used in pattern-based forensic studies to allow for improved trajectory models, and aim to provide sufficient datasets to the BPA forensics community to establish confidence in these models. |
Tuesday, November 26, 2024 10:23AM - 10:36AM |
X17.00012: Comparative Analysis of Arterial and Choroid Plexus Oscillations on CSF Dynamics in Hydrocephalic Ventricles Christopher Roberts, Elliot Widd, Adam Menkara, Carolyn Harris Objective Hydrocephalus treatment involves the implantation of a ventricular catheter (VC) into the ventricles to drain excess cerebrospinal fluid (CSF). This study compares the effects of CSF oscillations from arterial pulsations and choroid plexus secretions on CSF flow dynamics in shunted hydrocephalic ventricles of varying morphology. |
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