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 F20: Biological Fluid Dynamics: General II |
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Chair: Luciano Castillo, Purdue University Room: Georgia World Congress Center B308 |
Monday, November 19, 2018 8:00AM - 8:13AM |
F20.00001: Flow-based echolocation of silent prey Daisuke Takagi, J. Rudi Strickler We propose a theory for sensing a motionless particle suspended in a fluid. The principle is analogous to active sonar except with flow instead of sound; it relies on generating flow and detecting minor distortions induced by the particle. A simple analytical model shows that the size and location of the particle can be sensed remotely using pressure or hair sensors. This informs how some organisms, e.g. blind cavefish and copepods, may be able to actively hunt for prey without light or sound. |
Monday, November 19, 2018 8:13AM - 8:26AM |
F20.00002: Numerical Simulations of Pulsating Soft Corals Shilpa Khatri, Matea Alvarado, Diane Leal Delgado, Laura A Miller Soft corals of the family Xeniidae have a pulsating motion, a behavior not observed in many other sessile organisms. We are studying how this behavior may give these corals a competitive advantage. We will present computational simulations of the pulsations of the coral. Direct numerical simulations of the pulsating corals and the resulting fluid flow by solving the Navier-Stokes equations coupled with the immersed boundary method will be discussed. We will explore how the mixing created by the corals is modified as we vary parameters of the fluid flow and the pulsating motion. |
Monday, November 19, 2018 8:26AM - 8:39AM |
F20.00003: Physical constraints on mammalian suckling Emmanuel Virot, Erica Pack, Sunghwan Jung The feeding of infant mammals on milk, such as breastfeeding in humans, is a key characteristic of mammalian development. We report suckling data for 86 species of mammals extracted from the video-sharing website Youtube. Variations in the suckling rate of individual species suggest that there exists several physical constraints associated to fast muscular actuation and slow milk swallowing. In addition, we compare the suckling kinematics with the chewing of the same species of adult mammals. Our study provides a framework to detect pathologies in animal nursing and to improve the design of baby bottles in mammals including humans. |
Monday, November 19, 2018 8:39AM - 8:52AM |
F20.00004: Evasion strategies of zebrafish larvae Brendan Colvert, Yi Man, Sashank Pisupati, Jing Xuan Lim, Matthew McHenry, Eva Kanso Evasion maneuvers are primal behavioral responses that rely on fundamental neuro-sensory circuits. In fish, the sensory cues needed for prey to detect predators and initiate their escape are largely unclear, as are the details of the evasion response. Recent experiments on larval zebrafish indicate that evasion maneuvers vary between deterministically optimal and protean (random) strategies, depending on the predator location as perceived by the prey. Here, we propose several models of evasion and compare them to the empirical data. We find that the model derived from the classical notion that prey tend to maximize their distance of closest approach to the predator is not supported by experimental observations. Rather, the behavior is well-explained by parsimonious models requiring far less sensory effort than the classically optimal strategies. These results shed light on the neuro-sensory mechanisms underlying prey evasion, and, in particular, lay the groundwork for a further series of experiments uncovering the source of variation in larval zebrafish escape response. |
Monday, November 19, 2018 8:52AM - 9:05AM |
F20.00005: Parametric study of the hydrodynamics of a mangrove root model Humberto Bocanegra Evans, Amirkhosro Kazemi, Julio N Lebron Feliciano, Gerardo J Carbajal Benitez, Oscar M Curet, Luciano Castillo Mangrove trees can be found along (sub)tropical coastlines all over the world. Their roots act as obstacles for tidal currents, dissipating energy and providing coastal protection. Over the last century, a large portion of mangrove forests has been lost due to human activity, leading to remediation efforts that include man-made mangrove-like structures. Parametrization of the hydrodynamics of complex root networks is key to mimic a bio-inspired structure for coastal protection. In this study, we carried out a series of experiments on a simplified root patch, consisting of a symmetrical array of cylindrical rods in a radial arrangement, where we explore the effect of flow velocity, root size, porosity and stiffness on the drag experienced by the root patch. The patch models were fully submerged and tested at Reynolds numbers Re ∼ 103-104. Direct force and wake velocity measurements were performed on the patch. Dimensional analysis of the experimental results indicates that the root pitch and the effective patch diameter (obtained from the shedding frequency) are good indicators of the drag experienced by the patch. Our results will provide a baseline in the design and optimization of man-made structures used for coastal protection and potential energy harvesting. |
Monday, November 19, 2018 9:05AM - 9:18AM |
F20.00006: Modeling E coli. Motility through Viscoelastic Networks in Stokes Flow Mica Elizabeth Jarocki, David Ellis Clark, Orrin Shindell, Hoa Nguyen E. coli bacteria swim and maneuver through complex fluid environments such as porous media containing polymeric filaments called viscoelastic networks. Because such bacteria can impact humans by causing sickness or contaminating water sources, researchers are motivated to understand how moving through viscoelastic networks affects bacteria trajectory and velocity. Using the method of regularized Stokeslets we model an E. coli cell initially encapsulated in a viscoelastic network. We vary network parameters to see how an E. coli cell would be affected in terms of its trajectory, velocity, efficiency, and power. We quantify the effect of the cell on the network by measuring the network’s deformation and potential energy relative to equilibrium. We found that pore size and number of layers have a strong influence on the interaction between the cell and the network. For example, sometimes the network has a positive effect on the cell, increasing its velocity, and other times it has a negative effect on the cell, decreasing its velocity. Our model allows us to better understand cell-viscoelastic network-fluid interactions and suggests different possibilities to design experiments using viscoelastic fluids with tunable properties that bacteria could swim in. |
Monday, November 19, 2018 9:18AM - 9:31AM |
F20.00007: The (Anti) Gravity Machine: A Tracking Microscope to Study Biotic/Abiotic Systems in Gravitational Fields Deepak Krishnamurthy, Francois Benoit du Rey, Hongquan Li, Pierre Cambournac, Elgin Korkmazhan, Manu Prakash It is often desirable to observe freely moving microscale objects over macroscale length and time scales. For instance, microscale marine plankton exhibit vertical migrations over distances that are several orders greater than their individual size. Currently the problem of studying such objects at sub-cellular resolution while allowing free movement over macro-length scales is a fundamental challenge. We present a simple table-top solution to this problem for the case of an object with significant vertical movement due to the effects of motility, hydrodynamics and gravity. Our solution, a “hydrodynamic treadmill”, consists of an annular fluidic chamber with a horizontal rotation axis, which allows unrestricted vertical motion of the object. Object movements are compensated by rotation of the chamber using a closed-loop tracking system such that the object remains at a fixed point in the lab frame. We demonstrate this method by tracking the behavior of marine plankton swimming freely in the vertical direction over several hours and with displacements of tens of meters at high spatiotemporal resolution. We further use this method to observe abiotic systems such as sedimenting/rising microparticles and drops in an ambient fluid over long time scales. |
Monday, November 19, 2018 9:31AM - 9:44AM |
F20.00008: Optical Tweezers-based velocimetry: A method to measure microscale unsteady flows Parviz Ghoddoosi Dehnavi, Daniel Tam, Da Wei Motility and transport of fluids by micro-organisms relies on the generation of oscillatory flows generated by flagella or cilia at high frequencies. To understand the underlying physics governing the motility of ciliated microorganisms and ciliary synchronization, it is essential to accurately measure and characterize the unsteady flow fields they generate. Time resolved measurements of unsteady flows of small amplitudes and high frequencies are challenging with PIV or PTV, and measurements have often been limited to average flows. The limitation of particle based methods lies in the fact that, on these scales, the particle motion is indistinguishable from Brownian motion. Here, we present a velocimetry method based on optical tweezers that allow us to measure oscillatory flows with high accuracy and resolution. In this method, we measure the nanometer-scale displacements of a bead trapped inside the optical tweezers, and analyze the position measurements to extract the actual flow velocity. In addition, as an example, we measure the unsteady oscillatory flow around the bi-flagellated green alga Chlamydomonas reinhardtii, and compare with numerical predictions. |
Monday, November 19, 2018 9:44AM - 9:57AM |
F20.00009: Airflow between Animal Cages in Airborne Disease Transmission Experiments Sima Asadi, Ramya S. Barre, Manilyn J. Tupas, Nassima Gaaloul, Anthony S. Wexler, Nicole M. Bouvier, William D. Ristenpart The airborne transmissibility of pathogens is often assessed using animal models, in which one animal is purposely inoculated and a naïve animal is placed downstream in a separate cage to see if transmission occurs. Although this paradigm has been widely adopted, little is known about what is actually carrying the pathogens from one animal cage to the other, and how the airflow conditions affect the transmission rate. Here we characterize the particles emitted from cages containing guinea pigs. We find that awake and mobile guinea pigs generate an average of 1000 particles/min, while anesthetized guinea pigs emit about 2 particles/min. The results suggest that expiratory particles account for less than 1% of all aerosol particles transmitted between cages. Furthermore, we designed and tested an apparatus to test the effect of average airflow velocity on influenza transmission between guinea pigs, with preliminary results suggesting a weak dependence on velocity. |
Monday, November 19, 2018 9:57AM - 10:10AM |
F20.00010: Experimental Study of Transient Squeezing Film Flow Rungun Nathan, Ji Lang, Qianhong Wu In this study, we report a novel experimental approach to examine a transient |
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