Bulletin of the American Physical Society
75th Annual Meeting of the Division of Fluid Dynamics
Volume 67, Number 19
Sunday–Tuesday, November 20–22, 2022; Indiana Convention Center, Indianapolis, Indiana.
Session Z07: Biological Fluid Dynamics: Physiological II |
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Chair: Jared Barber, Indiana University - Purdue University Room: 134 |
Tuesday, November 22, 2022 12:50PM - 1:03PM |
Z07.00001: Nutrient transport in biomimetic tissue engineering scaffolds George Booth, Hua Ye, Pierre-Alexis Mouthuy, Mohit Dalwadi, Sarah L Waters To engineer functional tissue, appropriate biomechanical and biochemical cues must be provided to cells to promote growth. Our collaborators have developed a deformable porous hollow fibre membrane scaffold that mimics the mechanical properties of human vasculature. Cells are seeded on the outer surface of these fibres which are then cultured in a bioreactor. Nutrients and growth factors are delivered to the system via flow into the fibre lumen, and they transport to the cells by advection and diffusion through the porous membrane wall. |
Tuesday, November 22, 2022 1:03PM - 1:16PM |
Z07.00002: A new solution for the deformations of an elastic-walled tube Danny Netherwood, Robert Whittaker We investigate the small-amplitude deformations of a long, thin-walled elastic tube |
Tuesday, November 22, 2022 1:16PM - 1:29PM |
Z07.00003: Fluid-structure interactions suppress flow in self-overlapping soft tubes Magnus V Paludan, Matthew D Biviano, Tomas Bohr, Kaare Hartvig Jensen Fluid flow in flexible pipes is ubiquitous in nature. It is well-established that the deformation of individual soft channels impacts flow quantity and quality in, e.g., the human cardiovascular system. In some critical cases, however, flow occurs in a self-overlapping channel that loops back onto itself. This is the case, for instance, in an animal placenta, kidney, finger, lung, or in the coupled xylem-phloem vascular tissue in plants. However, the effects of self-interactions on fluid transport capacity remains poorly understood. Inspired by the Quake valve, we study the pressure drop versus flow rate relationship in a multilayer microfluidic device that contains two linked channels separated by an elastic sheet. The application of pressure modifies both channel geometries and the total flow capacity. We show that fluid-structure interactions suppress flow and examine the dependence on geometric and material parameters. Surprisingly, short self-overlapping channels are particularly vulnerable to this effect. Finally, potential implications for small organs, limbs, and tissue protrusions are discussed. |
Tuesday, November 22, 2022 1:29PM - 1:42PM |
Z07.00004: Biofluid dynamics of digestion in the stomach: Insights from computational modeling Sharun Kuhar, Jae H Lee, Jung-Hee Seo, Jay Pasricha, Rajat Mittal The stomach is responsible for mixing, grinding, sieving, and chemically breaking down food. The peristaltic motion of the stomach walls combines with the secreted gastric enzymes to physically and chemically breakdown the ingested food. However, experimental investigation of these phenomenon is very challenging and cost intensive. In this study, we present a computational model of the stomach to simulate the digestion of a meal with solid and liquid components. The enzyme pepsin is secreted from the stomach walls and acts on the dissolved protein. The solid food particles move and dissolve under the action of the surrounding fluid motion, gravity, and drag forces. The mixing of the contents, the hydrolysis of the meal, and the emptying from the stomach are quantified for a healthy stomach, as well as for conditions with reduced stomach motility. The findings demonstrate the potential of computational approach in this field. They generate new insights into gastric digestion and show its effect under variations in wall motion caused by disease and dysfunction. |
Tuesday, November 22, 2022 1:42PM - 1:55PM |
Z07.00005: Neuromechanical model of esophageal transport Guy Elisha, Sourav Halder, John E Pandolfino, Peter J Kahrilas, Neelesh A Patankar Esophageal transport involves the recruitment of a large-scale distributed neural network as neurophysiological activity regulates the contraction of the esophageal muscle fibers. Some esophageal disorders are suspected to be directly related to neurological dysfunction. Hence, to achieve a better understanding of esophageal pathophysiology, one must incorporate quantitative neuromechanical models. The goal of this work is to develop such a model, which has not been developed before. To do so, we develop a 1D model of peristaltic flow in an elastic tube, where the traveling contraction is implemented by varying the rest cross-sectional area (CSA) of the tube. The rest CSA is computed based on a neuronal feedback model, triggered by stretch receptors and cell-to-cell communication. Unlike prior neuromechanical models, our mathematical model accounts for the gradient of increasing inhibitory innervation distally along the esophagus – an important feature implicated in key aspects of neural activation patterns of the esophagus. Thus, we can investigate the effect of gradient pattern, stretch receptors, and bolus size on the resulting peristaltic motion. By producing such model, we can understand the emergent peristaltic behavior of the esophagus, and the associated pathophysiology. |
Tuesday, November 22, 2022 1:55PM - 2:08PM |
Z07.00006: Urination, defecation, flatulence, and diarrhea: the four seasons of toilet acoustics David Ancalle, Maia Gatlin, Cade Tyler, Anthony Popa, Ashima Taneja, David Meyer, David L Hu, Alexis Noel Diarrheal diseases are a leading cause of death among children under five years old, killing over 500,000 annually. Rapid detection of diarrheal diseases is necessary for treatment and prevention of outbreaks. We hypothesize that the acoustic characteristics of excretion events (urination, flatulence, solid defecation, and diarrhea) are unique and identifiable, and can be used to detect outbreaks of diarrhea in public restrooms. To test this hypothesis, we design and construct a Synthetic Human Acoustic Reproduction Testing (S.H.A.R.T.) Machine to generate toilet sound variations. In this talk, we present both experimental spectrograms of the sound and theoretical predictions for the frequency and duration. |
Tuesday, November 22, 2022 2:08PM - 2:21PM |
Z07.00007: Coronavirus Pleomorphism Mona Kanso, Alan Jeffrey Giacomin The coronavirus is always idealized as a spherical capsid with radially protruding |
Tuesday, November 22, 2022 2:21PM - 2:34PM |
Z07.00008: Mechanics-informed MRI (MRI-MECH) for estimating esophageal health Sourav Halder, Ethan M Johnson, Jun Yamasaki, Peter J Kahrilas, Michael Markl, John E Pandolfino, Neelesh A Patankar Dynamic magnetic resonance imaging (MRI) is a technique used extensively for imaging flow through blood vessels, but its application to bolus transport in the esophagus has been limited due to the lack of a framework that quantifies the state and functioning of the esophagus. We present a framework called mechanics-informed MRI (MRI-MECH) that uses MRI measurements of esophageal bolus transport to provide quantitative prediction of esophageal mechanical health, thus enhancing the capability of MRI to diagnose esophageal disorders. MRI-MECH models the esophagus as a flexible 1D tube that follows a 1D tube-law with the flow through it governed by 1D mass and momentum conservation equations. These equations are solved using a physics-informed neural network (PINN) which minimizes the difference between the measurements from the MRI and the solutions of the governing equations. MRI-MECH works well with missing data or poor image resolution, and we demonstrate that by predicting missing information about the lower esophageal sphincter (LES) during the esophageal emptying process. Finally, the MRI-MECH estimates the mechanical health of the esophagus by calculating the esophageal wall stiffness and active relaxation. |
Tuesday, November 22, 2022 2:34PM - 2:47PM |
Z07.00009: Understanding esophageal pressure-area loop patterns in different diagnostic devices Xinyi Liu, Guy Elisha, Sourav Halder, Dustin A Carlson, Peter J Kahrilas, John E Pandolfino, Neelesh A Patankar The esophagogastric junction (EGJ) acts as a valve allowing swallowed materials to enter the stomach and prevent acid reflux. The relationship between the changes in area and intraluminal pressure, during opening and closing, have been used to quantify EGJ function. Previous studies in our group have identified pressure-area loops with positive slope using the clinical data from FLIP (an endoscopic device). This indicated that the EGJ opening involves both pressurization and active tone relaxation. However, High Resolution Impedance Manometry (HRIM) clinical data revealed loops with an 'L'-shaped pattern. In this case, the area increases initially (lumen opening) while pressure remains unchanged (static) and then pressure increases (contracting) while area decreases (lumen closing). This pattern distinguishes the loops from the ones using the FLIP data. This study aims to explain this apparent discrepancy. We developed a 1D model for an elastic tube. We simulated the two scenarios with the different boundary conditions. These results provide insights into how the loop patterns differ based on problem setup and should be an important consideration in diagnostics. |
Tuesday, November 22, 2022 2:47PM - 3:00PM |
Z07.00010: A mechanistic continuum model for the blood protein VWF and its role in arterial blood clotting Edwina F Yeo, Netanel Korin, James M Oliver, Sarah L Waters Arterial blood clot formation (thrombosis) is the leading cause of both stroke and heart attack. Accurate prediction of clotting dynamics under high shear is a key part of developing safe and effective treatments. Thrombosis under pathologically high shear stresses relies on the protein Von Willebrand Factor (VWF). At high shear, VWF unfolds, which exposes binding sites, and facilitates rapid platelet deposition from the blood to the vessel walls. |
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