Bulletin of the American Physical Society
71st Annual Meeting of the APS Division of Fluid Dynamics
Volume 63, Number 13
Sunday–Tuesday, November 18–20, 2018; Atlanta, Georgia
Session G17: Biological fluid dynamics: Biological Pumps |
Hide Abstracts |
Chair: Timothy Wei, University of Nebraska, Lincoln Room: Georgia World Congress Center B304 |
Monday, November 19, 2018 10:35AM - 10:48AM |
G17.00001: What is the best frequency for sniffing? Thomas Spencer, Adams Clark, David L Hu Mammals such as dogs are known for their keen sense of smell and have been relied upon for their ability to find odor sources. A key component to the mammalian sense of smell is the dynamic sniff cycle which increases in frequency when then animal is exposed to a new odor. Conversely, we find through oscillatory wind tunnel experiments and computational simulations that lower sniffing frequencies provide better odor collection in straight, rectangular channels. Lower sniffing frequencies reduce velocities near the channel walls, enabling a larger number of odor molecules to reach receptors via diffusion. We proceed from rectangular channels to investigating the effect of biological nasal cavity shapes helps to mitigate odor collection. We apply insights gleaned from our biological and experimental results to design an electronic nose pre-concentrator for improved chemical sensing. |
Monday, November 19, 2018 10:48AM - 11:01AM |
G17.00002: Ciliary Pumps Feng Ling, Hanliang Guo, David Stein, Janna C Nawroth, Michael John Shelley, Eva Kanso Motile cilia are microscopic hair-like structures that play important roles in fluid transport and pumping. However, the relationship between the pumping rates and the cilia organization in flow channels is not quantitatively understood. Here, we develop a computational model aimed at analyzing the transport rate and pumping efficiency of ciliated channels as a function of the cilia organization. Specifically, we use the Brinkman-Stokes equations to model flow through an oscillating porous medium that emulates the ciliary motion. We find a trade-off between the performance of cilia that line the channel walls and that of long cilia that cover the channel. The latter generate weaker flows at zero pressure gradients but outperform short cilia in the presence of adverse pressure gradients. This quantitative framework suggests that different cilia structures and organizations bring distinct advantages to the pumping organs depending on their surrounding and function. |
Monday, November 19, 2018 11:01AM - 11:14AM |
G17.00003: High-Throughput Transpiration Up a Large Synthetic Tree Ziad Rashed, Weiwei Shi, Ricky Dalrymple, Collin McKenny, David Morrow, Daniel Surinach, Jonathan Boreyko Over the past decade, advances in nanotechnology and micro-fabrication have enabled the development of sophisticated synthetic trees that mimic the transpiration cycle of natural trees. Current synthetic trees are scaled down for microfluidic applications, where water from a reservoir is pumped across a single micro-channel or even just held directly against the synthetic leaf material. Here, we demonstrate that synthetic trees can be made at the same scale as natural trees, ideal for water extraction applications. As many as 19 plastic tubes of millimetric diameter were fixed inside of a nanoporous ceramic disk on one end. After saturating the tree by boiling it underwater, the ceramic disk was elevated over 3 m into the air while the other end of the long tubes remained submerged in a water reservoir. A mass balance confirmed that water in the bottom reservoir was able to continuously flow up the tubes to replenish water evaporating from the ceramic disk. A model was developed to capture the transpiration rate by coupling the Laplace equation, Kelvin equation, Poiseuille’s law, and Darcy’s law. |
Monday, November 19, 2018 11:14AM - 11:27AM |
G17.00004: Experimental modeling of fluid homeostasis in the mammalian hearing organ Ruy Ibanez, Catherine A. Knox, Jong-Hoon Nam, Douglas H. Kelley The mammalian hearing organ (cochlea) contains a long microfluidic channel (channel width ≈ 50 μm and aspect ratio ≈ 700) where the ion concentration must be homogenized to ensure healthy hearing. We hypothesize that homeostasis is achieved not only through diffusion, but by advective mixing caused by peristaltic flow in the channel. By determining the relevant physical parameters in the channel and applying scaling laws, we designed an apparatus that replicates physical conditions in the channel. Our apparatus consists of a square channel with a flexible wall which can be deformed to induce a peristaltic flow in the channel. We seek to characterize the flow by using a particle imaging velocimetry system and calculating particle paths. Theory suggests that at the Reynolds number in the channel (Re ≈ 80) mixing will occur. We experimentally test a spectrum of parameters to verify theory predictions. The parameter region we study is also relevant for understanding other biophysical phenomena, as peristalsis is a common mechanism found in biological systems. Additionally, we compare experimental results with numerical simulations. |
Monday, November 19, 2018 11:27AM - 11:40AM |
G17.00005: Flow in a Microchannel with Propagative-Rhythmic Membrane Contraction: A Novel Insect-Inspired Micropumping Model Yasser Aboelkassem A newly derived micropumping mathematical model for the flow in a microchannel with propagative-rhythmic membrane contraction is given in this study. The model is inspired by the microscale flow transport phenomena in the network architecture of tracheal tubes found in most insect respiratory systems. The lubrication theory is used to approximate the induced flow field in a microchannel with a single membrane site at low Reynolds number flow regime. A well-posed expression for the wall profile is derived to describe the membrane propagative mode of rhythmic contractions. The model accounted for the coupling between the induced flow in the channel and propagative membrane deformation. We compare the pressure, axial pressure gradient, and axial and radial velocities in the channel, and the volumetric flow rate through the channel for propagative and non-propagative mode of membrane contractions. Unlike our previously derived pumping model "non-propagative" where at least two membranes that operate with time-lag are required to produce unidirectional flow, the present results demonstrate that an inelastic channel with a single membrane contraction that operates in a "propagative" mode can produce unidirectional flow and working as micropumping mechanism. |
Monday, November 19, 2018 11:40AM - 11:53AM |
G17.00006: Hydrodynamic functionality of the lorica in choanoflagellates Jens Honore Walther, Sayed Saeed Asadzadeh, Lasse Tor Nielsen, Anders Andersen, Julia Dolger, Thomas Kiørboe, Poul Scheel Larsen Choanoflagellates are unicellular microswimmers that are ubiquitous in aquatic habitats. They have a single flagellum that creates a flow toward the collar, the filtration apparatus composed of closely spaced filter strands. Loricate choanoflagellates have evolved a basket-like “skeleton” around the cell, the lorica, the function of which remains unknown. Here, we use Computational Fluid Dynamics (CFD) to explore the possible hydrodynamic function of the lorica by studying the choanoflagellate Diaphaoneca grandis, with and without its lorica. We study the flow rate, the flow recirculation, and the resulting clearance rate for the capture of motile and non-motile prey by the freely swimming choanoflagellate. We find no support for several previous hypotheses regarding the effects of the lorica. Rather, our simulations suggest that the main function of the lorica is to enhance the capture efficiency, but this happens at the cost of lower encounter rate with motile prey. |
Monday, November 19, 2018 11:53AM - 12:06PM |
G17.00007: Investigation of Dynamic Operation of Lymphatic Valve via Computational Modeling Ki Tae Wolf, Matthew S Ballard, Zhanna Nepiyushchikh, J. Brandon Dixon, Alexander Alexeev The lymphatic system is vital to the circulatory and immune systems with important functions such as transport of interstitial fluid, fatty acid, and immune cells. However, the lymphatic system, especially the influence of lymphatic valve and vessel to the lymphatic dysfunction, is not well understood. We present a fully-coupled fluid-solid, three-dimensional computational model to investigate lymphatic vessel and valve parameters and their effects on the lymphatic system performance. The simulations evaluate lymphatic system effectiveness under varied valve geometries and material properties, pinpointing to the optimal valve parameters maximizing pumping performance. Analysis of the valve function under dynamic loading reveals a hysteresis in the valve response consistent with experimental observations. The model is useful in providing insights in the relationship between lymphatic pathologies like valve defect and lymphatic dysfunction. |
Monday, November 19, 2018 12:06PM - 12:19PM |
G17.00008: Augment high-resolution-impedance-manometry using biophysical analysis and model Wenjun Kou, Shashank Acharya, Peter J. Kahrilas, Neelesh Ashok Patankar, John Erik Pandolfino Using biophysical analysis, we first evolved high-resolution-impedance-manometry (HRIM) into a 4 dimensional construct that allows one to assess the relationship between esophageal wall shape and bolus transit during swallowing. This provides 3D lumen morphology concurrent with pressure and signifies how the bolus transit pattern is modulated by contraction waves. It also extends previous bolus-retention analysis based on impedance change to direct visualization of evolution of bolus volume. Related results from normal and abnormal cases were compared. Furthermore, using our previously developed constraint-based immersed-boundary method, we developed a bio-mechanical model that augments the morphology data of HRIM. This augmented model enabled us to predict esophageal wall properties and flow characteristics. Results on the flow field and wall tension based on this augmented model were presented and discussed. |
Monday, November 19, 2018 12:19PM - 12:32PM |
G17.00009: Analysis of esophageal transport on reconstructed models from medical images Sourav Halder, Shashank Acharya, Wenjun Kou, John Erik Pandolfino, Peter J. Kahrilas, Neelesh Ashok Patankar The dynamics of esophageal bolus transport involves a complex interaction between muscle activation, esophageal wall material properties and the bolus. A better understanding of the physiologic biomechanics of esophageal transport will potentially improve patient diagnosis and treatment. This is an extension of the previous work on esophageal transport based on continuum mechanics where the simulations were performed on a simple cylindrical geometry. In this work, we have developed 3D models of the esophagus from medical scan image sequences. These images can be from various sources like Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) or Barium Swallow Test. This process mainly involves image segmentation to visualize the anatomy of the esophagus, generation of surface meshes and, finally, generate solid models for analysis. Immersed Boundary Finite Element method is used to develop a fully resolved model of the esophagus. Though the shape of the esophagus varies from patient to patient, this analysis gives more realistic insights of esophageal transport that could be more clinically relevant. |
Monday, November 19, 2018 12:32PM - 12:45PM |
G17.00010: A multiphasic, fluid-structure interaction-based model of peristalsis in the Upper Gastrointestinal tract Shashank Acharya, Wenjun Kou, John Erik Pandolfino, Peter J. Kahrilas, Neelesh Ashok Patankar In previous gastrointestinal (GI) models developed by our group, we’ve studied the phenomena of bolus transport in the esophagus and peristalsis in the stomach. The two organs were modeled in isolation and the gastric contents were limited to a single phase. The development of a new multiphase solver by our group for the open-source FSI framework IBAMR has enabled us to now model the gastric contents as a multiphase mixture. The goal of this work is to study the effects of gastric peristalsis on the gas-liquid contents in the entire Upper GI tract. The combined model allows for transfer of fluid between the stomach and esophagus. This enables the model to simulate 'acid reflux' which affects a large percentage of the adult population. With the help of this model, we aim to study the volume of acid reflux and its composition as a function of stomach contents and intensity of gastric peristalsis. A detailed numerical model that simulates acid reflux will also help us understand how the geometry at the Esophagogastric Junction (EGJ) affects the mechanism of reflux. This knowledge can assist in developing new medical techniques for treating GERD (Gastroesophageal Reflux Disease). |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700