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 G22: Biological Fluid Dynamics: Locomotion Swimming - Invertebrates |
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Chair: David Murphy, University of Southern Florida Room: Georgia World Congress Center B310 |
Monday, November 19, 2018 10:35AM - 10:48AM |
G22.00001: Metachronal Rowing by a Peacock Mantis Shrimp Kuvvat Garayev, David Murphy Metachronal rowing is a widely used swimming technique employed by animals which have multiple pairs of swimming legs such as shrimp and krill. In this locomotion technique, appendages are sequentially stroked in a back-to-front wave moving along the animal’s body, a pattern that is thought to increase swimming efficiency in comparison to front-to-back or synchronous stroke patterns. The fluid dynamics of metachronal rowing is not well understood. Experiments suggest that under some circumstances the flow pulses generated by each appendage may synergistically join together to form a coherent propulsive jet while in others the pulses remain separate, with unknown consequences for propulsive efficiency. Further, the swimming ability of mantis shrimp is not well investigated. Here we present time-resolved pleopod kinematics and planar particle image velocimetry measurements of the flow generated by a swimming peacock mantis shrimp (Odontodactylus scyllarus) with body and pleopod lengths of 114 mm and 15 mm, respectively. Illumination is provided by a near infrared laser. The flow generated by the metachronally stroking pleopods is captured in both hovering and fast forward swimming modes to examine the effect of varying advance ratio on the mantis shrimp’s flow signature. |
Monday, November 19, 2018 10:48AM - 11:01AM |
G22.00002: Underwater propulsion at intermediate Re: Multi-oar biomechanics of mysids M. Ruszczyk, D.R. Webster, J. Yen Appendage synchronization of free-swimming aquatic crustaceans can result in different styles of propulsion. Members of the order Mysida have a shrimp-like morphology, with females having oostegites acting as a brood pouch, which is unique to the order. Mysids move through the water by altering body orientation, angles between limb joints, and stroke frequency of their thoracopods (eight sets of limbs on the thorax) and their pleopods (five sets of limbs on their abdomen). Observations of swimming behavior in the mysid Americamysis bahia indicate that there are four different forms of swimming: hovering, slow forward swimming, fast forward swimming, and an inverted caridoid escape response. While hovering and slow forward swimming only require coordination of the thoracopods, fast forward swimming includes a metachronal thrust from the pleopods. For the inverted caridoid response, the mysid bends at its abdomen, bringing its carapace to its telson, and then unflexes to propel itself forward. Body orientation, thoracopod motion, and pleopod motion unique to each swimming mode are analyzed to quantify these differences. Understanding of biomechanics at this scale can be applied to mechanistic designs of robots that will operate in a similar regime. |
Monday, November 19, 2018 11:01AM - 11:14AM |
G22.00003: Using a Shell as a Wing: Fluid Dynamics and Kinematics of Atlantid Heteropod Swimming Ferhat Karakas, Daniel D’Oliveira, Amy E. Maas, David W Murphy Atlantid heteropods are a type of holoplanktonic marine snail with a single swimming fin and a coiled aragonite shell. Swimming is important for heteropod predation and diel vertical migration, but their mode of locomotion has not been well described or quantitatively studied. We used a high-speed stereophotogrammetry system to measure the 3D swimming kinematics of Atlanta selvagensis, a warm-water species collected off the coast of Bermuda. With a body length of 2.2 mm, an average beat frequency of 9 Hz, and mean swimming speed of 27 mm/s, the atlantid heteropod inhabits an intermediate Reynolds number regime (Re=50). We find that previous work incorrectly described atlantid heteropods as sculling through the water using only their swimming fin. Instead, the results show that this species uniquely synchronizes motion of its highly flexible swimming fin and of its rigid, flattened shell, both of which are used as wings, to propel itself through the water. Both the fin and shell flap through stroke angles of approximately 180º at high angles of attack and clap together at the end of each half-stroke. Time resolved 2D flow measurements with a micro-PIV system reveal the complex vortices generated by this motion and by the flow interaction between the two wings. |
Monday, November 19, 2018 11:14AM - 11:27AM |
G22.00004: Robokrill: a metachronal robotic swimmer Yair Sanchez, Pedro Ávila, Francisco Cuenca Jiménez, Valentina Di Santo, Monica M Wilhelmus Metachronal swimming, in which an organism beats adjacent appendages in sequence to propel forward, is a common locomotion mechanism among species of crustaceans that undergo diel vertical migrations (DVM). While recent experimental studies have demonstrated large-scale transport during lab-induced DVM, the hydrodynamic effects of morphology and stroke kinematics within this context are not yet well understood. In this talk, we present a newly developed metachronal robotic swimmer designed to mimic the swimming gait of the Antarctic krill E. superba during forward propulsion with the aim to analyze aspects of metachrony that are challenging to isolate in natural systems. More broadly, our goal is to understand which design parameters can be leveraged to maximize transport. We present preliminary particle image velocimetry measurements during vertical migration of a single swimmer and compare its hydrodynamic signature to flow fields of real organisms presented in the literature. We discuss the feasibility of leveraging this system to engineer new self-propelled robots that maximize transport in a transitional Reynolds regime. |
Monday, November 19, 2018 11:27AM - 11:40AM |
G22.00005: Examining behavior of a cruise swimming copepod in a Burgers' vortex D. Elmi, S. Soumya, D.R. Webster, D.M. Fields Copepods continuously encounter small-scale turbulent fluid motions in their habitat, which can be conceptualized as a random size and orientation distribution of stretching vortices. Any change in the turbulence intensity affects the copepod’s vertical distribution in the water column, and the response is species specific. The purpose of this study is to examine the interaction of individual copepods (Temora longicornis) with small-scale turbulent fluid motions, which are ideally described by Burgers’ vortex model. The vortex is generated in the laboratory with its axis aligned in either the horizontal and vertical directions to examine the directional swimming response of T. longicornis, which depends on its mechanosensory setae architecture and its orientation with respect to gravity. The turbulence intensity is classified into 4 levels, corresponding to target turbulent dissipation rates of 0.002 (level 1) to 0.25 (level 4) cm2/s3 in the coastal environments. The swimming behavior of T. longicornis is assessed in the presence of the vortex treatment and compared to the control level (no flow). The results show that T. longicornis exhibited a minimal response to level 1 and level 2 intensities, but significantly changed its swimming behavior in higher turbulent intensities. |
Monday, November 19, 2018 11:40AM - 11:53AM |
G22.00006: Improved Understanding of Biological Cavity-Jet Flows Using a Circulation Based Theoretical Pressure Model Michael Krieg, Kamran Mohseni A novel technique for determining pressure inside deformable jetting cavities was recently derived (Krieg & Mohseni 2015) with respect to circulation dynamics. The use of such a model lies in the fact that circulation is an invariant for inviscid flows, hence circulation can be modeled as a series of sources and sinks. Therefore, this model allows high accuracy pressure calculation without solving for the full flow field, as long as the sources of vorticity are known. In this talk, the model’s usefulness is illuminated through analysis of complex biological systems including swimming of jellyfish, squid, and other animals. The accuracy of internal pressure calculated in these examples validates the model for low Reynolds number flows and complex body geometries, provided that the circulation generation is determined using inviscid models. Furthermore, the model also allows us to isolate different aspects of body deformation, identify the relationship to system circulation, and determine their contribution to the total propulsive output. Specifically, velar flap deformation is explained in terms of jet thrust and efficiency; as is the differences in squid and jellyfish internal geometry with respect to increases in propulsion vs respiration, respectively. |
Monday, November 19, 2018 11:53AM - 12:06PM |
G22.00007: Asymmetric kinematics and stiffness produce turning maneuvers in rowing jellyfish Gregory Krummel, Colin Stewart, Shashank Priya It was recently reported that oblate jellyfish modulate the local stiffness of their bell margins and the radial symmetry of their bell contractions while turning. Here, we investigate the individual contribution of these behaviors to turning performance using a free-swimming robot model of the jellyfish Cyanea capillata. We report angular turning rates calculated from planar motion tracking and explore the underlying fluid dynamics using DPIV measurements of the flow field. Increases in marginal stiffness, contraction timing asymmetry, and relaxation timing asymmetry each result in statistically significant increases in body turning rate. These behavioral changes create imbalances in momentum flux during contraction, as well as imbalances in jet impingement during refilling, which result in torque about the body center of mass. Graded control of each behavior allows for finely controlled turning maneuvers observed in nature. |
Monday, November 19, 2018 12:06PM - 12:19PM |
G22.00008: Stimulation of latent enhanced propulsion in freely swimming jellyfish Nicole W Xu, John O. Dabiri The external control of jellyfish swimming can potentially address basic science questions about animal-fluid interactions. To produce muscle contractions in free-swimming jellyfish, we use a wireless system of microelectronics embedded at the center of the animal, with electrodes embedded toward the bell margin. A symmetric two-electrode system is used to induce straight swimming downward in a 1.8-m vertical tank. Both experimental and model results show that we can enhance propulsion in freely swimming animals by increasing the external stimulation frequency above natural behavior, with a peak twofold increase in velocity. However, incomplete refilling of the subumbrellar volume at high frequencies can decrease swimming performance. By characterizing how the stimulation frequency affects swim velocity, this work constitutes an essential step toward user control of jellyfish locomotion for studies in basic science and engineering applications. |
Monday, November 19, 2018 12:19PM - 12:32PM |
G22.00009: Multi-jet propulsion kinematics, gaits, and scaling of a siphonophore colony Colin Stewart, Gregory Krummel, John H Costello, Shashank Priya Many animals swim by squeezing single fluid jets out of a body cavity, one pulse at a time (e.g. squid), but a few fascinating animals propel themselves by ejecting simultaneous jets from multiple cavities. One such animal is the physonect siphonophore, a colonial animal resembling a long chain of connected jellyfish. Here we detail the physonect Nanomia bijuga, which uses its multi-jet locomotion strategy to maneuver with surprising speed and agility. A theoretical fluid dynamics model reveals that the coordinated mechanics of Nanomia's individual jet propulsors result in a whole-colony swimming performance that is greater than the sum of its individuals. The natural kinematics of each propulsor and its flexible nozzle maximize both thrust and propulsive efficiency when compared to simpler kinematic options. Integration of propulsors into a closely packed, streamlined colony reduces cost of transport, gives functional redundancy, and allows for adjustable jetting gaits. The benefits of multi-jet locomotion help explain the wide success of siphonophores, and greater understanding of their biomechanics can guide the design of distributed propulsion vehicles. |
Monday, November 19, 2018 12:32PM - 12:45PM |
G22.00010: Hydrodynamics of ciliate swimming revealed by individual ciliary motions Hiroaki Ito Ciliate, such as Paramecium, can swim in surrounding liquid by beating thousands of cilia. In 1971, Blake introduced a mathematical model of swimming microorganism, called as squirmer, and it has been widely used in fluid mechanical researchers. In the original squirmer model, the tips of cilia formed a ciliary envelope, and the displacement and stretch of the envelope surface was modeled by surface squirming velocities. The model was successful in describing the flow field external to the envelope. However, it could not describe the flow field inside the envelope, i.e. between the cell surface and the ciliary envelope. In this study, therefore, we develop a model of ciliate with hundreds of cilia, and analyze its swimming using a boundary element method. We found that the swimming is strongly affected by the existence of cilia. Especially, the swimming efficiency was found to be much smaller in the present model compared to the original squirmer model. These findings provide a fundamental basis in modeling a swimming ciliate. |
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