Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session L03: Focus Session: Fish Swimming Kinematics and Hydrodynamics II |
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Chair: Iman Borazjani Room: 201 |
Monday, November 25, 2019 1:45PM - 1:58PM |
L03.00001: Rainbow trout gait synchronisation with pitching aerofoil vortex shedding Valentine Muhawenimana, Sam Tucker Harvey, Stephanie Mueller, Petr Denissenko, Catherine Wilson The swimming kinematics of rainbow trout (\textit{Oncorhynchus mykiss}) were linked to the wake dynamics of a pitching aerofoil using motion tracking and Particle Image Velocimetry (PIV). A traveling wave equation was used to describe the fish's centreline deflection, while the fish's centre of volume was located in two dimensions. PIV measurements and dye visualisation of the aerofoil wake structures illustrated varied vortex shedding modes and vortex patterns, which were governed by the amplitude and frequency of aerofoil pitching, as well as the chord length based Reynolds number. Fish tuned their body dynamics to the aerofoil vortex street as indicated by changes in the fish Strouhal number, velocity and acceleration direction, yaw angle, and tailbeat frequency when comparing swimming in the wake of a stationary aerofoil to a flapping aerofoil. Due to the presence of turbulent structures shed from the pitching aerofoil, an additional oscillation of the fish body that was synchronised with the aerofoil vortex shedding occurred in the yaw behaviour, with clear peaks in the power spectrum of yaw angles. These experimental observations provide new evidence on the quick adaptation of fish to effectively swim in regions of coherent vortex structures by adjusting their swimming kinematics. [Preview Abstract] |
(Author Not Attending)
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L03.00002: In-phase vs. out-of-phase synchronization in side-by-side swimmers Ramiro Godoy-Diana, J\'er\^ome Vacher, Veronica Raspa, Benjamin Thiria In-phase and out-of-phase synchronization of neighboring swimmers is examined experimentally using two self-propelled independent flexible foils swimming side-by-side in a water tank. The foils are actuated by pitching oscillations at one extremity---the head of the swimmers---and the flow engendered by their undulations is analyzed using two-dimensional particle image velocimetry in their frontal symmetry plane. Following recent observations on the behavior of real fish, we focus on the comparison between in-phase and out-of-phase actuation by fixing all other geometric and kinematic parameters. We show that the advantage of out-of-phase synchronization in terms of swimming performance for the two-foil ``school'' results from the emergence of a periodic coherent jet between the two swimmers. We quantify the associated increase in impulse transfer to the fluid and the minimization of transverse mixing. [Preview Abstract] |
Monday, November 25, 2019 2:11PM - 2:24PM |
L03.00003: Trailing edge geometry and angular pitching amplitude effects on the propulsive performance of bio-inspired pitching panels Justin King, Melissa Green Many of the aquatic swimmers found in nature propel themselves through the water by oscillating a caudal fin or fluke. Among various species, these propulsive appendages display a wide diversity of planform geometries, including those with different trailing edge shapes. In the current work, the effects of systematically varying the trailing edge shape and angular pitching amplitude on the propulsive performance of pitching panels are studied using time-resolved force measurements collected in a water tunnel experiment. Results focus on the thrust production, propulsive efficiency, and power consumption of pitching panels with straight, forked, and pointed trailing edges. In total, five distinct panel geometries were pitched about their leading edge in a constant free stream flow through multiple angular pitching amplitudes. Experimental results are discussed in the context of changes to the Strouhal number, $St$, which ranged between 0.09 and 0.66, and the three-dimensional wake structure, which was measured and presented previously. The current work also focuses on the implications of the performance measurements on the design of bio-inspired, underwater vehicles and the effects that propulsor geometry and kinematics may have on the swimming characteristics of aquatic animals. [Preview Abstract] |
Monday, November 25, 2019 2:24PM - 2:37PM |
L03.00004: Understanding the Effects and Limits of a Passive Tail on Escape Performance in a Robotic Fast-Start Fish Capable of Rapid Underwater Locomotion Todd Currier, Samuel Lheron, Yahya Modarres-Sadeghi An experimental study is conducted on a robotic fish designed to emulate the fast-start response. The fish body is constructed of 3D materials and a light spring steel spine. The body is actuated using pressurized pistons. A total of two pistons are supplied with pressure through lightweight high-pressure service lines. The source of pressure is carbon dioxide with a 4.82 MPa peak operating pressure resulting in a body response that can cycle a C-start maneuver in milliseconds. The motion of the fish is controlled using large bandwidth solenoids with a control signal produced by a programmable microprocessor. The buckling modes of a slender column in compression are used to produce organic movements in the body with only two sources of actuation. The interaction of the fluid with the underactuated structure results in a travelling wave in the body of the robotic fish that is kinematically comparable to the live fish. The classical question of which tail stiffness is optimal in the fast-start is explored in a complete free floating model of the fish. [Preview Abstract] |
Monday, November 25, 2019 2:37PM - 2:50PM |
L03.00005: A proprioceptive robotic swimmer. Mederic Argentina, Jesus Sanchez Roridguez, Christophe Raufaste In the context of fish locomotion, Lighthill proposed in 1971 his elongated body theory to predict the swimming gait [1]. Since his seminal article, the swimming velocity has been related to the fin kinematics (tail-beat amplitude and frequency) through the Strouhal number [2], which is found to be constant over 6 decades of Reynolds number for natural swimmers [3]. This result can be accounted for by a simple force balance, but the selection mechanism of the fin kinematics is still poorly understood. Here, we propose that the swimming locomotion might be driven by a proprioceptive feedback, which determines the tail-beat amplitude and frequency. A robotic fish has been built to test this mechanism and we will present our last results.\newline [1]Lighthill M. J. “Large-amplitude elongated-body theory of fish locomotion 179 Proc. R. Soc. Lond”. B, 1971\newline [2]Triantafyllou, M. S., G. S. Triantafyllou, and R. Gopalkrishnan. "Wake mechanics for thrust generation in oscillating foils." Physics of Fluids A: Fluid Dynamics 3, no. 12 (1991): 2835-2837.\newline [3]Gazzola, M., Argentina, M. and Mahadevan., L .”Scaling macroscopic aquatic locomotion." Nature Physics 10.10 (2014): 758. [Preview Abstract] |
Monday, November 25, 2019 2:50PM - 3:03PM |
L03.00006: Empirical generalized regressions for swim speed and endurance of sturgeon species Christos Katopodis, Lu Cai, Richard Gervais Swim performance data of various fish species ranging from prolonged (low) to burst (high) speeds are useful for both theoretical hydrodynamics and ecohydraulic applications, such as fish passage. Commonly such data are collected with experimental tests, are limited to fish speed and endurance for a small percentage of species, and are insufficient for variables such as tailbeat frequency. Limited data are available for the Sturgeon species, especially for burst speeds, and dimensionless variables use them more effectively. Robust regressions for several groups of species, as well as sturgeon, are obtained with a dimensionless fish speed, expressed in the form of a fish Froude number which does account for fish length. Regressions improve with dimensionless variables, including fish speed expressed as a fish Reynolds number, compared to traditional measures such as body lengths/s. Such regressions demonstrate swim performance similarity in sturgeon and other fish groups, offer empirical data generalizations, data collection strategies, and help validate biomimetic simulations. [Preview Abstract] |
Monday, November 25, 2019 3:03PM - 3:16PM |
L03.00007: Impact of hydrodynamics of porous and non-porous structures on upstream fish passage performance Stephanie Mueller, Elizabeth Follett, Catherine Wilson, Pablo Ouro, Jo Cable Flow visualization and velocity measurements using ADV were used to assess upstream and wake flow characteristics of non-porous and porous structures made of wooden dowels. Upstream of the structure, flow becomes diverted towards the bed with higher downwards vertical velocities for the non-porous case. A turbulent wall jet formed beneath, showing higher flow acceleration with decreasing porosity, leading to stronger turbulent momentum exchange along the shear layers in the wake. Behind the non-porous structure a larger recirculation area formed. At the downstream edge of the structure, turbulent kinetic energy (TKE) was larger for the non-porous case, with highest levels found approximately at mid-structure height. In the porous cases, two peaks in TKE occurred at the trailing edge of the lowest dowel, due to inter-dowel wake effects. Swimming behavior observations of rainbow trout (Oncorhynchus mykiss) revealed fish spent time beneath the structure, likely to avoid the high momentum jet. With increasing structure porosity, fish preferred to swim in the structure's wake due to reduced mean velocities and turbulent fluctuations near the bed. These observations indicate that porous and non-porous structures create heterogeneous habitats, influencing fish behavior. [Preview Abstract] |
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