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 M22: Biological Fluid Dynamics: Locomotion Swimming |
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Chair: Megan Leftwich, George Washington University Room: Georgia World Congress Center B310 |
Tuesday, November 20, 2018 8:00AM - 8:13AM |
M22.00001: Locomotion of flexible filaments Xuerui Mao, Jian Deng, Fazle Hussain Interaction of fluid and filaments is studied by means of three-dimensional Direct Numerical Simulation to reveal the locomotion ubiquitously exhibited by animals and vegetations. The filaments are assumed to be thin and flexible and are modelled using immersed boundary methods. A reduced integration scheme is adopted when computing the interaction forces between the fluid and filaments to improve the stability of the algorithm. After examining the vibration of a single filament in the fluid flow, multiple filaments with various initial layouts are tested. In the side-by-side arrangement, synchronization of filament motions via the oscillation of the fluid flow is observed and the deformation of the filaments are substantially suppressed by the neighbouring filaments. Such synchronization and suppression effects are much weaker in the tandem arrangement. As the rigidity of the filament increases, the synchronized motion changes from two-dimensional (in-plane) vibrations to three-dimensional (out-of-plane) rotations, during which the interactions between neighbouring filaments or sections of each individual filament become critical. |
Tuesday, November 20, 2018 8:13AM - 8:26AM |
M22.00002: Hydrodynamic significance of sea lion skin texture Gino M Perrotta, Michael Paul Schultz, Megan Leftwich An investigation of the influence of sea lion skin texture on skin friction was conducted by Laser Doppler Velocimetry measurements over small patches of extracted sea lion foreflipper skin. Sea lions are agile swimmers who propel and maneuver themselves using mainly their large foreflippers. The agility and amphibious capabilities of sea lions have inspired attempts to understand and model their methods of swimming. These studies have simplified flipper models by overlooking the skin and fur texture. Related studies on shark and dolphin skin have shown that small-scale skin texture can affect large-scale hydrodynamics. In the current work, 7 cm by 7 cm samples of sea lion foreflipper skin were extracted and mounted as a level insert in a flat plate for boundary layer testing at the United States Naval Academy. The measured boundary layer and its characteristics were compared between various skin samples, between forward and reverse flow over the samples, and between sea lion skin and sandpaper control samples. Preliminary results suggest minor hydrodynamic improvements are possible due to the sea lion’s skin and fur. |
Tuesday, November 20, 2018 8:26AM - 8:39AM |
M22.00003: The Robustness of Seal Whisker Morphology in Suppressing Flow-induced Oscillations Geng Liu, Qian Xue, Xudong Zheng Phocid seals are able to trace vibratile stimuli generated by prey fish in the ambient flow using only their whiskers. And the whiskers of most phocid seals exhibit wavy geometry along their spanwise directions, which is thought to be associated with the suppression of flow-induced oscillation (FIO). The current study uses computational fluid dynamics (CFD) simulations to investigate the relationship between seal whisker morphological properties and self-induced noises from FIO. We examine the lift force oscillation and flow structures of the whiskers in open steady flows over wide ranges of morphological and flow parameters. The preliminary results showed that the unique morphology of seal whisker generates stable three-dimensional vortex structures in the wake over the wide ranges of parameters which have important implication for the robustness of seal whisker morphology in suppressing FIO during swimming. The correlation between the morphological properties, vortex structures, and lift oscillations will be studied to uncover the underlying mechanism of the generation of vortex structures and suppression of FIO. Furthermore, the effect of the morphological properties on whisker-whisker interactions in a whisker array layout will be studied. |
Tuesday, November 20, 2018 8:39AM - 8:52AM |
M22.00004: Deployment of a Diver-Operated 3D Particle Tracking Imaging System Valerie Troutman, John O. Dabiri A SCUBA-diver operated imaging system to measure the 3D flow around organisms in their natural environment was developed and deployed. The suspended particulate surrounding the organism is tracked to investigate the animal-fluid interactions, allowing the study of organisms and biological processes in the water column. An ocean deployment and the measured flow fields around a gelatinous zooplankton will be presented. |
Tuesday, November 20, 2018 8:52AM - 9:05AM |
M22.00005: Swimming Freely Near the Ground Jackson Cochran-Carney, Melike Kurt, Qiang Zhong, Keith W Moored, Daniel Quinn A free-swimming potential flow analysis of unsteady ground effect is conducted for two-dimensional airfoils via a method of images. The foils undergo a pure pitching motion about their leading edge, and the positions of the body in the streamwise and cross-stream directions are determined by the equations of motion of the body. It is shown that the unconstrained swimmer is attracted to a time-averaged position that is mediated by the flow interaction with the ground. The location of this fluid-mediated equilibrium position is probed by varying the non-dimensional mass, initial conditions and kinematic parameters of motion. Comparisons to experimental data are also made to pinpoint the effects viscosity, leading edge separation, and unconstrained motion have on wake structures and the fluid-mediated forces. The benefits incurred from the solid boundary are extracted by normalizing propulsive metrics by performance data exhibited by isolated swimmers with identical kinematics. |
Tuesday, November 20, 2018 9:05AM - 9:18AM |
M22.00006: The relationship between torque and body shape of maneuvering swimmers Megan C. Leftwich, John O. Dabiri, Sean Colin, Bradford J. Gemmell, Kelsey N Lucas, John H Costello Animals in nature rarely swim in a straight, steady-state manner. Therefore, understanding how animals swim requires that we also understand how they maneuver. However, in a laboratory setting, it is challenging to capture and measure maneuvering animals, so limited data are available beyond steady forward swimming. To address this gap, we examined how two different species jellyfish (a primitive, non-vertebrate swimmer) and zebra fish (a higher order, vertebrate fish), complete turns ranging from 15 to 60 degrees. Using high-speed video and particle image velocimetry we quantified the kinematics and hydrodynamics of turning in multiple individuals from both species. We found that for the jellyfish the portion of the medusan bell located at the inside of the turn always initiates bell contraction. These asymmetric bell contractions set up pressure fields around the bell to generate imbalanced forces. Similarly, the zebra fish setup a pressure field that produces a turning torque before changing their body shape to minimize the moment of inertia and continue the turn passively. The temporal relationship between torque production and body shape have similar trends across turns, individuals and species.
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Tuesday, November 20, 2018 9:18AM - 9:31AM |
M22.00007: Buckling of sperm flagella in an extensional flow Manish Kumar, Derek M. Walkama, Jeffrey S. Guasto, Arezoo M. Ardekani Swimming cells live in dynamic fluid environments. Here, we probe the buckling dynamics of sperm flagella in an extensional flow and show good agreement between microfluidic experiments and numerical simulations. The sperm number, representing the ratio of viscous force and elastic force, characterizes the buckling behavior of the sperm flagella. We quantify the phase diagram of flagella deformation and bucking behavior for different sperm numbers and normalized strain rates. At small sperm numbers and strain rates, flagella exhibit minor elastic deflection, whereas at high sperm numbers and strain rates, multiple buckling modes occur corresponding to large deformations at multiple locations along the flagellum. |
Tuesday, November 20, 2018 9:31AM - 9:44AM |
M22.00008: Swimming on limit cycles with nonholonomic constraints Beau P Pollard, Vitaliy Fedonyuk, Phanindra Tallapragada Reduced order mathematical models are particularly useful when designing real time control algorithms, which inherently need to be computationally efficient. The complexities of the fluid-body interaction between a swimming robot and its environment make finding a reduced order model crucial for the implementation of real time control. The Chaplygin sleigh, a well known nonholonomic system, serves as an inspiration for such a low dimensional model. We show through experiments that the steady state dynamics of a swimming fish shaped body propelled by a periodic torque are confined to a limit cycle that is topologically similar to the limit cycle in the dynamics of the dissipative Chaplygin Sleigh. Using an unsteady version of the panel method potential flow solver and the harmonic balance approach we obtain a surrogate model of a Chaplygin sleigh with equivalent dynamics. We demonstrate the utility of such a surrogate model by designing a control torque that steers the fish shaped body in a desired direction while simultaneously tracking a prescribed speed. |
(Author Not Attending)
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M22.00009: Development of Microfluidic Device Operated by Hydrostatic Pressure for Sorting Motile Sperm Afrouz Ataei, Andy W.C. Lau, Waseem Asghar The first step of in-vitro fertilization is to sort out the motile sperms from the non-motile ones.In this work, we construct a sorting device based on microfluidic principles and hydrostatic pressure and explore its efficiency in selecting highly motile sperm.The sperm sorting device consists of two chambers (top and bottom),separated by a polycarbonate filter with pores of a particular size (5-12μm).The top chamber is aligned and attached to the bottom chamber, where there are two small points.The hydrostatic pressure can generate the flow in the bottom chamber.The sperm sample is injected into the bottom chamber.After 45 minutes, a sample of sperm suspension collected from the top chamber is placed on a glass slide for visual observation.We observe that (1)the larger the pore size of the filter reduces the DNA fragmentation in the sperms.(2)Our data show that within a range of sperm density, the average motility can reach 90-95%.(3)The flow rate 27μL/min gives the highest concentration of motile sperm and the lowest DNA fragmentation.(4)Our design allows a much larger pressure difference which is easier to use in clinical laboratory.Taken together, the presented research may provide an efficient method to increase the selection of highly motile sperm, without centrifugation. |
Tuesday, November 20, 2018 9:57AM - 10:10AM |
M22.00010: Passive Propulsion of Anisotropic Objects in Turbulence Jia Yang, Nicolas Francois, Hua Xia, Horst Punzmann, Michael Shats Aquatic animals have evolved different strategies to swim through water effectively. These strategies combine both active (flapping, undulating or oscillating appendages) and passive (a non-smooth compliant skin, hair, feathers and other passive protrusions) mechanisms. Animals use passive mechanism to harvest the energy of an external flow directly so that they can propel themselves without spending energy. Passive mechanisms also offer clear advantages when swimming in unfavourable environmental condition, especially in the presence of strongly turbulent flows. However, identifying passive mechanism is challenging. Here we demonstrate that an anisotropic object can tap the energy from wave-driven two-dimensional turbulent flows to fuel its directed motion. The mechanism of the propulsion relies on (1) the underlying fabric of the turbulent flow and (2) the coupling between the translation and rotation of the object. This knowledge gives us the ability to switch the "swimming gait'' of the objects from a propulsion dominated regime to a random walk regime. Our experimental results yield insights into passive swimming in turbulence and suggest a new method of designing floating objects capable of converting energy of turbulence into deterministic, directional motion. |
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