Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session A31: Biological Fluid Dynamics: General I |
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Chair: Jin Liu, Washington State University Room: 613 |
Saturday, November 23, 2019 3:00PM - 3:13PM |
A31.00001: Machine learning in cardiovascular flows modeling: Predicting pulse wave propagation from non-invasive clinical measurements using physics-informed deep learning Georgios Kissas, Yibo Yang, Eileen Hwuang, Walter Witschey, John Detre, Paris Perdikaris Advances in computational science offer a principled pipeline for predictive modeling of cardiovascular flows and aspire to provide a valuable tool for monitoring, diagnostics \& surgical planning. Such models can nowadays be deployed on large patient-specific topologies of systemic arterial networks; but their success heavily relies on tedious pre-processing and calibration procedures that typically induce a significant computational cost. In this work we put forth a machine learning framework that enables the seamless synthesis of non-invasive in-vivo measurement techniques \& computational flow dynamics models derived from first physical principles. We illustrate this new paradigm by showing how one-dimensional models of pulsatile flow can be used to constrain the output of deep neural networks such that their predictions satisfy the conservation of mass and momentum principles. Once trained on noisy and scattered clinical data of flow and wall displacement, these networks can return physically consistent predictions for velocity, pressure and wall displacement pulse wave propagation, and calculate the Windkessel model parameters as a post-processing step. [Preview Abstract] |
Saturday, November 23, 2019 3:13PM - 3:26PM |
A31.00002: A Simplified Model for the Motion of the Brain Matter in Response to Translational Impacts to the Head Ji Lang, Qianhong Wu A simplified mathematical model is developed to simulate the motion of the brain matter as our head is exposed to sudden external impacts. During the process, the cerebrospinal fluid in the subarachnoid space behaves as a squeeze damper to provide protection to the brain matter. The problem involves a solid object bathed in a liquid environment and enclosed in a container. The relative motion of the object to the container causes a squeezing flow on one side of the object, and a reverse squeezing flow on the other side. A simplified theoretical model is developed in which both the inner object and the outer container are modeled as cylinders of different sizes. A constant acceleration is imposed on the container. The pressurization of the fluid and the resultant motion of the inner object is analytically predicted and validated using Ansys CFX. The result shows that the relative motion of the inner object is very sensitive to the gap thickness and the density difference between the object and the surrounding liquid. The squeezing damping effect can effectively prevent the direct contact between the solid object and the container. [Preview Abstract] |
Saturday, November 23, 2019 3:26PM - 3:39PM |
A31.00003: Kinetics of Lactoferrin-Mediated Iron Transport through Blood-Brain Barrier Endothelial Cells. Prashanta Dutta, Aminul Khan, Jin Liu Abnormally high levels of iron have been confirmed in the brain cells during several neuro-diseases such as Parkinson's, Alzheimer's etc. Although transferrin-mediated transcytosis is the leading mechanism for iron transport to brain, it has been found that the excessive brain irons are not resulted from transferrin. Instead, lactoferrin (Lf) is a prime suspect because of its abundant availability in the affected regions of brain. However, the kinetics of Lf-mediated iron transport is still unknown. In this paper, a mass-action based kinetic model has been presented to address the transport of Lf-mediated irons through the blood-brain barrier. The kinetic rate parameters of the model are estimated by Bayesian inference method. The robustness of the model is verified by perturbing the estimated parameters. Our results show that an increase in high affinity, but not low affinity, receptors results in higher lactoferrin as well as irons in the brain. The Lf contributes free as well as bound irons to the brain. The absence of a feedback loop such as iron regulatory proteins allows continuous transport of Lf and iron through Lf-mediated pathway, which might raise brain irons and contribute to the neurodegeneration. [Preview Abstract] |
Saturday, November 23, 2019 3:39PM - 3:52PM |
A31.00004: Microfluidics modeling of interstitial flow through a tumor Benjamin Tay, Marcos Marcos, David Gonzalez-Rodriguez 90{\%} of cancer-related mortalities are due to metastasis. Interstitial pressure and flow within tumor microenvironment have been identified to influence biological and biochemical aspects of metastasis. However, little is known on the biophysical effect. This study focuses on the effect of interstitial pressure and flow on the detachment of tumor cells from primary tumor. Interstitial flow through a tumor generates tensile force in the direction of flow which might contribute to detachment of tumor cells from primary tumor. Here, flow is introduced into a microfluidic device to measure pressure difference across MCF-7 aggregates with different adhesions. Aggregates with different adhesions mimic in-vivo heterogenous tumor. Initially, fluid seeps through the porous aggregate. As pressure builds up at the afferent end, pressure-driven flow through the aggregate increases. At critical pressure difference, fracture occurs and hydraulic permeability increases. Cell masses dislodge from aggregate. Fractures occur at different critical pressure for aggregates with different adhesions. This mimic the detachment of tumor cells from primary tumor. These findings will provide better understanding about the biophysical effects of interstitial pressure and flow. [Preview Abstract] |
Saturday, November 23, 2019 3:52PM - 4:05PM |
A31.00005: Fluid exchange dynamics during respiratory-type flows Erin Connor, Aaron True, Melanie Holland, John Crimaldi Respiratory-type flows occur across a large range of scales in natural and engineered environments. These flows, characterized by the cyclic inhale and exhale of a fixed fluid volume through an orifice, result in dynamic spatiotemporal flow interactions even in quiescent surroundings. We use numerical and experimental approaches to investigate simple respiratory-type flows at scales relevant to biological sensory and metabolic processes. Organisms successfully gain access to scalars in the flow when the amount of exhaled fluid that is subsequently re-inhaled (exchange ratio, r$_{\mathrm{E}})$ is small. This study focuses on this exchange of fluid, whereas studies of other similar flows with `net-zero mass flux' (e.g. synthetic jets) often emphasize the transport of momentum. Using time-resolved flow fields to map the Lagrangian histories of inhale and exhale cycles, we demonstrate that r$_{\mathrm{E}}$ is sensitive to small changes in Reynolds number (Re). We show that this sensitivity is due to asymmetries in the inhale and exhale flow structures; these asymmetries vanish only in the limit as Re approaches zero. We also demonstrate that r$_{\mathrm{E}}$ is sensitive to the I:E ratio, defined as the ratio of inhalation time to exhalation time. Our results suggest that organisms could optimize the exchange of fluids with their environment by modulating Re or I:E ratio. [Preview Abstract] |
Saturday, November 23, 2019 4:05PM - 4:18PM |
A31.00006: Starting jet formation through eversion of flexible plates Cheolgyun Jung, Daegyoum Kim A starting jet found in nature, such as flow through heart valves or jet propulsion of aquatic animals, is generated by the interaction of pressurized fluid with deformable membranes. The starting jet can also be formed by the interaction with everted flexible structure. For example, the nematocysts of the \textit{Cnidarian}, the fastest stinging organelles that penetrate the skin of a prey or a predator, inject toxin through a structure that is everted by flow from a high-pressure chamber. Most studies on the everted structure have been limited to its structural properties or focused on the manufacturing of medical devices or soft robots, but the interaction with compressed fluid still remains unclear. Here, inspired by the discharge mechanism of the nematocysts, we investigate experimentally the formation of a starting jet flow through eversion process using a simplified model that represents an everted structure. The ends of two everted flexible plates with a large aspect ratio are clamped at both sides of a rectangular channel, and the other ends of them are in contact with each other in the middle of the channel to model the everted structure. With this configuration, we study the eversion dynamics of the flexible plates and the formation of jet flow at the exit of the channel. [Preview Abstract] |
Saturday, November 23, 2019 4:18PM - 4:31PM |
A31.00007: Acceleration-induced water ejection in the human ear canal Anuj Baskota, Seungho Kim, Hosung Kang, Sunghwan Jung Water entering the ear canal is a common problem during swimming, showering or other water sports. The trapped water can lead to an ear infection as well as damage to the ear canal. A common strategy for emptying water from the ear canal is to shake the head, where the force created due to the head jerk helps push the water out. One-end closed hydrophobic glass tubes of varying diameters were used as a simplified model of the ear canal. Then, the tube is dropped onto a spring to mimic the shaking strategy. Results revealed that the critical acceleration to remove the water from the ear canal strongly depends on the volume and the position of trapped liquid inside the tube. We found that the critical acceleration is on the order of 10 g, which may cause serious damage to the human brain. The critical acceleration tends to be much higher in smaller sized tubes which indicates that shaking heads for water removal can be more laborious to children due to their small size of the ear canal, compared to adults. [Preview Abstract] |
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