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 M20: Biological Fluid Dynamics: Locomotion Swimming - Fishes I |
Hide Abstracts |
Chair: Alexandra Techet, Massachusetts Institute of Technology Room: Georgia World Congress Center B308 |
Tuesday, November 20, 2018 8:00AM - 8:13AM |
M20.00001: Big and slow: large-amplitude motions for highly efficient swimming Daniel Floryan, Tyler Van Buren, Clarence W. Rowley, Alexander J. Smits When a swimmer flaps its appendages, it adds momentum to the surrounding fluid, which, by action/reaction, propels the swimmer. When the propelling thrust balances the swimmer’s drag, the swimmer cruises at a constant speed. A swimmer can add a fixed amount of momentum to the fluid in two ways: by accelerating a small mass of fluid to a high speed, or by accelerating a large mass of fluid to a low speed. In other words, a swimmer can maintain a given speed using small and fast motions, or big and slow motions. A recent scaling theory suggests that big and slow motions are preferred for high propulsive efficiency. Here, we report experiments on large-amplitude heaving and pitching foils of high propulsive efficiency. Direct force and power measurements are understood in the context of the scaling theory, and we use flow visualization to further understand our findings. |
Tuesday, November 20, 2018 8:13AM - 8:26AM |
M20.00002: How aquatic animals leap out of water Brian Chang, Jihye Myeong, Emmanuel Virot, Christophe Clanet, Ho-Young Kim, Sunghwan Jung Many aquatic animals leap out of water to hunt, escape predators, or even recreationally. In this study, we investigate the physical conditions required for animals to leap out of water. By balancing power produced by the animal with drag-induced dissipation, we show that the normalized jumping height, H/L, scales with the Froude number as H/L∼Fr2. Simplified experiments were conducted by shooting axisymmetric bodies through the water surface. Here, we see a transition in which partial exits scale as H/L∼Fr and complete exits scale as H/L∼Fr2. Finally, a bio-inspired robot was built to jump out of water. We show that a large volume of water is entrained during the jump, which limits the maximum jumping height. Larger ratios of body mass to entrained fluid mass shows that the body will jump higher to a similar range as animals. |
Tuesday, November 20, 2018 8:26AM - 8:39AM |
M20.00003: How disc-shaped stingrays create sediment flow for effective burying Scott G Seamone, Douglas A Syme Disc-shaped stingrays are dorsoventrally flattened fishes with enlarged and flexible pectoral fins that are used to power locomotor behaviours along the floor of marine and freshwater ecosystems, making them an intriguing model system for advancing our understanding of aquatic movement along the substrate. These fishes commonly bury into the substrate, possibly to hide from predators and to station hold in high current flow. To bury, the animal displaces itself downwards and covers itself with sediment, yet we do not fully understand how the flows that move sediment are generated and propagated to affect burying. Burial events of the motoro stingray were analyzed via video. Rather than digging, stingrays functioned like a piston pump with flapping fins, whereby the head repeatedly pumped up and down to fluidize the sediment, and the fins folded up and over to direct a vortex of sediment onto the dorsal side of the fish. An increase in head pump and finbeat displacement and speed induced greater sediment coverage of the dorsal surface. Sediment coverage ranged from 60-97%, and the eyes and the barbed stinger at the tip of the tail always remained exposed. Accordingly, we argue that a disc shape can function to promote effective control of sediment displacement during burying.
|
Tuesday, November 20, 2018 8:39AM - 8:52AM |
M20.00004: Shark skin: three-dimensional structure and hydrodynamic function George V. Lauder, Dylan Wainwright, Mehdi Saadat, August Domel, James Weaver, Madeline Ankhelyi, Meagan Popp, Li Wen, Katia Bertoldi The skin of sharks consists of numerous tooth-like scales (denticles) that form a rough surface covering the body. Imaging this surface has mostly been accomplished using scanning electron microscopy. But in order to understand the hydrodynamic function of shark skin, it is critical to quantify surface roughness in three dimensions and measure fluid flow on both engineered models and living animals. We provide an overview of our recent work on three-dimensional surface imaging on a diversity of shark species and body locations using gel-based stereo profilometry, and summarize ongoing experiments on (1) denticle models mounted on airfoils to quantify their effect on lift and drag, (2) the propulsion of 3D-printed shark skin flexible foils, and (3) flow over the denticle surface in living sharks. Surface roughness in smooth dogfish varied from 9 to 42 µm and particularly interesting transitions in denticle shape and roughness were observed on the skin over the gills and on the fins. Denticles mounted on a NACA 0012 airfoil increased the lift-to-drag ratio by up to 323%. Experiments on the propulsion of flexible shark skin membranes show that denticle-containing surfaces are capable of both increasing self-propelled speed and reducing the cost of transport. |
Tuesday, November 20, 2018 8:52AM - 9:05AM |
M20.00005: Volumetric flow field analysis of freely swimming lamprey using SAPIV Andrea M. Lehn, Alexandra H. Techet Volumetric, time-resolved flow field analysis of freely swimming lamprey Petromyzon marinus will be presented from Synthetic Aperture Particle Image Velocimetry (SAPIV) experiments. Lamprey are slender-bodied, anguilliform swimmers that move by sending a traveling wave of increasing amplitude from head to tail, around Reynolds number order 105. Lamprey are a model biological organism for understanding locomotion control in vertebrates, thus inspiring this hydrodynamic investigation. The wakes considered herein are unconstrained in a quiescent tank, more than 15 body diameters deep, with a flat glass bottom; both forward swimming behaviors, as well as attempted burrowing behaviors, are observed. Kinematic body trajectory data and SAPIV results will be presented for several lamprey swimming cases. In general, lamprey swim by transferring momentum downstream via a traveling body wave to propel themselves forward, creating a thrust-like wake with downstream momentum flux. While 2D experiments with anguilliform swimmers have shown predominately lateral jets and a lack of downstream momentum flux, 3D SAPIV results show clear horizontal flows in the direction of fish swimming as well as lateral jets and flow around the top and bottom of body. |
Tuesday, November 20, 2018 9:05AM - 9:18AM |
M20.00006: Limit cycle dynamics of a Chaplygin sleigh - a surrogate model for fish like swimming Vitaliy Fedonyuk, Beau P Pollard, Phanindra Tallapragada The Chaplygin sleigh is a canonical problem in the area of nonholonomic systems. In recent work the constraint which governs the motion of the Chaplygin sleigh was shown to be similar to the Kutta condition which models the vortex shedding past the trailing edge of a Joukowski foil. Inspired by this similarity we investigate the dynamics of a Chaplygin sleigh subjected to viscous dissipation and a periodic input torque. The Chaplygin sleigh's velocities converge to a limit cycle under such actuation. Experiments on a Joukowski foil shaped robot confirm the existence of a similar limit cycle in its velocity space. We discuss analytical approximations of this limit cycle and show that this approximation is useful to control the motion and Chaplygin sleigh. The limit cycle dynamics then serve as a useful approximation for the swimming motion of a Joukowski foil. |
Tuesday, November 20, 2018 9:18AM - 9:31AM |
M20.00007: The mechanics of fish evasion Yusheng Jiao, Yi Man, Brendan Colvert, Matthew McHenry, Eva Kanso Fish evade predators by employing a rapid ‘fast C-start’ escape response. Previous studies of fish evasion focus on either identifying optimal evasion strategies, or on the mechanics of the fast C-start response. However, the connection between the mechanics of the fast start and the resulting evasion strategy is not well understood. Here, we develop a reduced-order mechanical model of the fast C-start, in order to evaluate the constraints imposed by the fluid-body mechanics on the evasion strategy. We employ a 3-link fish model and account for the fluid forces in the context of the potential flow theory. The model will serve to understand and evaluate evasion maneuvers in fish, it will also have implications for setting fast-start actuation in underwater soft robotics. |
Tuesday, November 20, 2018 9:31AM - 9:44AM |
M20.00008: Flow Interactions and Performance Benefits in Fish Schools Melike Kurt, Keith W Moored In nature fish are known to aggregate into large schools or collectives. It has long been argued that these collectives are formed for social reasons, as a protection strategy against predators, and even to save energy. However, our knowledge of the fluid dynamic interactions that occur among individuals and their collective energetics is based mostly on two-dimensional analyses. Here, we examine the role of three-dimensionality in altering the flow interactions, the force generation, and the energetics of two interacting swimmers. We model our two swimmers as simple finite-span pitching propulsors. Additionally, the positions of the two propulsors are configured in mixtures of canonical side-by-side and in-line arrangements. The forces and moments are then measured as the two wings undergo sinusoidal pitching motions over a large range of synchrony and spacing. Our aim is to identify the flow mechanisms that improve or degrade propulsive performance of individuals within a collective as well as to identify flow mechanisms that give rise to fluid-mediated forces among individuals. |
Tuesday, November 20, 2018 9:44AM - 9:57AM |
M20.00009: Aim affects fin interactions and wake topology in jumping archer fish Leah Mendelson, Alexandra H. Techet Archer fish jumping for aerial prey rapidly accelerate from a stationary aiming position below the free surface. Herein we investigate how this aiming behavior affects propulsion during an archer fish jump. Using high-speed imaging, we find that the angle between the body and the free surface at jump onset varies with target prey height. Through volumetric synthetic aperture particle image velocimetry, we find that this posture considerably influences the upward contributions of the fish's initial propulsive tailbeats. Furthermore, we show that the orientation of the body causes different modes of interaction between the anal and caudal fins. These interactions are also found to differ between when the body has minimal upward velocity (i.e., jump onset) and when the body has a greater instantaneous velocity at later times during the jump. We find strong agreement between the cumulative effects of multiple propulsive motions, measured through wake impulse, and the instantaneous ballistic velocity of the fish. Our results highlight how discrete tailbeats and multi-fin propulsive strategies enable accurate jumping from a spatially- and visually-constrained environment. |
Tuesday, November 20, 2018 9:57AM - 10:10AM |
M20.00010: How dorsal fin sharpness affects swimming speed and efficiency Qiang Zhong, Haibo Dong, Daniel Quinn How well fish swim depends on complex hydrodynamic interactions between their multiple fins. It has been shown, for example, that the wakes of anal fins, dorsal fins, and finlets can boost the thrust produced by the caudal fin. What fin shapes and thicknesses maximize this boost are unknown. Here we show that dorsal/anal fins only increase caudal fin thrust when the tips of their cross sections are sufficiently sharp. We quantified fin tip sharpness by parameterizing fin shapes using Bezier curves. Particle Image Velocimetry reveals that beyond a critical fin sharpness, the wake of the dorsal/anal fin promotes flow attachment along the caudal fin, resulting in higher thrust. We show that under certain conditions, dorsal/anal fins function like leading edge slats and slots, redirecting and stabilizing the incoming flow as it continues on to the main lifting surface. Our results demonstrate that cross-sectional shape is a key parameter in determining whether a dorsal fin will indeed increase swimming performance. Specifically, we show that sharpness is a critical constraint for effective dorsal/anal fin design – both in fish and in fish-inspired Unmanned Underwater Vehicles. |
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