Bulletin of the American Physical Society
63rd Annual Meeting of the APS Division of Fluid Dynamics
Volume 55, Number 16
Sunday–Tuesday, November 21–23, 2010; Long Beach, California
Session QT: Biolocomotion XII: Macro-Swimming II |
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Chair: Jeff Eldredge, University of California, Los Angeles Room: Long Beach Convention Center Grand Ballroom B |
Tuesday, November 23, 2010 12:50PM - 1:03PM |
QT.00001: Maneuver of juvenile chinook salmon during feeding in streams Jifeng Peng Before they head to the ocean, juvenile chinook salmon O. tshawytscha habitat in freshwater rivers and feed on small invertebrates drifting in streams. During drift-feeding, these fish hold fairly steady positions in the flow facing upstream, and maneuver to intercept drifting prey as it passes. They have a large arsenal of maneuver modes, which presumably enable them to maximize prey encounter while keeping energy expense low. Moreover, because these fish often gather in schools, they utilize their maneuvers so that they do not invade others' territories. In this study, we measured three-dimensional motion of juvenile chinook salmon in situ during feeding. The kinematics of some of the widely-used maneuvers, including slow lateral motion, sharp U-shaped turn and fast S-shaped turn, were analyzed. A computational model based on ideal fluid theory was developed to estimate the dynamics of these maneuvers. Energetics of the maneuvers was evaluated, together with effects on prey encounter, in order to compare and explain the choices of maneuvers in different situations. The effects of neighbors in a fish school on individual maneuvers were also studied. [Preview Abstract] |
Tuesday, November 23, 2010 1:03PM - 1:16PM |
QT.00002: Numerical investigation of the 3D flow field generated by a self-propelling manta ray Jean-Noel Pederzani, Hossein Haj-Hariri A mixed Lagrangian-Eulerian approach is used to solve the three dimensional Navier-Stokes equation around a self-propelling manta ray. The motion of the manta ray is prescribed using a kinematic model fitted to actual biological data. The dependence of thrust production mechanism on Strouhal and Reynolds numbers is investigated. The vortex core structures are accurately plotted using the $\lambda _{2}$ criteria; and a correlation between wake structures and propulsive performance is established. This insight is critical in understanding the key flow features that a bio-inspired autonomous vehicle should reproduce in order to swim efficiently. The solution method is implemented on a block-structured Cartesian grid using a volume of fluid approach. To enhance the computational efficiency, a parallel adaptive mesh refinement technique is used. The present method is validated for the flow around a sphere. A basic station keeping control problem for a pitching and lagging wing is also analyzed to show the capability of the code to aid in controller design and stability analysis. [Preview Abstract] |
Tuesday, November 23, 2010 1:16PM - 1:29PM |
QT.00003: Vortex Formation in the Starting Flow of Rotating Low-Aspect-Ratio Plates Adam DeVoria, Matthew Ringuette We investigate the unsteady flow of fish fin-like plates accelerating from rest through various angular velocity profiles. The objective is to gain an understanding of the connection among the prescribed kinematics and resulting vortex formation; a relationship which has not currently been thoroughly explored. The root-to-tip flow that is induced by the plate motion is expected to have significant effects on the vortex formation. Additionally, different plate shapes are studied to compare the effects of geometrical changes. The experiments are conducted in a water tank, and the plates have a fixed axis of rotation. Digital particle image velocimetry (DPIV) is used to measure the flow velocity in a symmetry plane through the plates. Vorticity and circulation are subsequently computed and vortices are distinguished from surrounding flow structures using vortex identification schemes. Carefully incorporating these techniques will aid the development of scaling laws to characterize the vortex formation with maximum attainable vortex strength. [Preview Abstract] |
Tuesday, November 23, 2010 1:29PM - 1:42PM |
QT.00004: Vortical structures in the wake of an undulating fin Peter A. Dewey, Antoine Carriou, Alexander J. Smits Batoid fish such as the manta ray propel themselves through the water by producing a traveling wave motion along the chord of their pectoral fin. Such a motion produces thrust through the development of an unsteady vortex street that results in a jet-like average flow. Digital particle image velocimetry (DPIV) is used to characterize the vortical patterns and structures developed in the wake of a manta ray-like fin. A DC servo motor powers a gear train to produce the traveling wave motion; whose frequency and wave length can be varied. The amplitude of the traveling wave motion linearly increases along the span of the fin. Wake morphologies for a wide spectrum of oscillation frequencies and traveling wave wavelengths are identified. A bifurcation from a 2S wake structure to a 2P wake structure is observed as the traveling wave wavelength is decreased, which corresponds to a decrease in efficiency as reported by Clark and Smits (2006). Alteration of the oscillation frequency, and thus Strouhal number, affects vortex interaction and is found to significantly modify the resulting velocity profiles in the wake of the fin. Notably, increasing the Strouhal number beyond optimal conditions, reported by Clark and Smits, corresponds to a reduction in the extent that the jet-like average flow is observed downstream of the fin. [Preview Abstract] |
Tuesday, November 23, 2010 1:42PM - 1:55PM |
QT.00005: Characterization of the interaction between a rough boundary layer and multiple cylinders wakes Aline Cotel, Olivier Eiff, Pratik Pradhan Among many ecologically important aspects of fish locomotion, turbulence is thought to create large stability challenges for fishes. Turbulence is a ubiquitous, highly variable feature of aquatic habitats (Denny 1988). Species that are more prevalent in ``energetic water'' (high flow, high turbulence) have more effective control systems and greater ability to generate propulsive power to maneuver. There are direct engineering applications of such work: the design of fishways, fish ladders, culverts, etc. No work to date has explored the interaction of a rough boundary layer (typical of natural environments), with wake flows in the context of fish responses to turbulent fluctuations. The research performed at IMFT under the umbrella of the NSF IREE grant used complimentary laboratory experimental studies to further apply the results from our previous field observations (Cotel et al. 2005) and current laboratory experiments by determining how a rough turbulent boundary layer interacts with the flow structures created by obstacles (cylinders arrays) in the channel. PIV data were acquired for a variety of flow regimes. The results show a strong interaction between the turbulent boundary layer created by the roughness elements and the wakes behind the cylinder arrays, having strong implications for fish behavior in such environments. [Preview Abstract] |
Tuesday, November 23, 2010 1:55PM - 2:08PM |
QT.00006: Hydrodynamics of jumping for prey capture in Archer fish A.H. Techet, A.M. Shih The prey capture behavior by jumping Archer fish (Toxotes microlepisis) was investigated using high speed imaging and particle imaging velocimetry (PIV). Archer fish are renowned for their ability to spit jets of water at insects and also to jump out of the water to capture their prey. Our investigations reveal that the fish typically fail to reach their prey by jumping when the bait is placed at a height above 3.5 body lengths. After jumping and failing, the fish do not typically jump again, only spit. For our experiments bait was placed between 0.5 and 3.5 body lengths (BL) above the free surface, within reach of jumping, and thus the fish rarely spit unless they missed first by jumping. It is observed that the fish typically position their bodies under the bait with a slight angle, hover momentarily, snap in their pectoral fins, and then flap their tail in an ``S-start''-type maneuver with a fixed number of cycles, which increases as a function of bait height. High speed imaging, including time-resolved PIV, was used to capture the kinematics of the jumping behavior and compare the fluid impulse generated during the fast start, jump maneuver with the total change in momentum of the fish body. Maximum acceleration was observed in the early stages of the jump maneuver and was often on the order of 5 to 15 times gravity. Correlations between the maximum energy, power in, number of tail beats, jump height and overall jumping kinematics will be discussed. [Preview Abstract] |
Tuesday, November 23, 2010 2:08PM - 2:21PM |
QT.00007: The effect of a variable diameter nozzle on starting jet formation and separation dynamics Mike Krieg, Kamran Mohseni As a jet is forced through a nozzle, the shear layer formed at the interface rolls back on itself forming a vortex ring. At a critical point the circulation of the leading vortex ring becomes saturated causing it to ``pinch-off'' from the trailing shear flow, which then forms a wake of trailing vortices. Jet separation occurs at a nearly universal formation time (Gharib et. al. 1998). Both squid and jellyfish utilize the large impulse transfer associated with vortex ring formation to propel. Both swimmers are also known to actively change the diameter of the fluid interface during jetting. It was predicted by Mohseni et. al. (2001) that changing the diameter of the shear layer during formation can delay the vortex ring separation. We fabricated a prototype vortex ring generator which controls the jet diameter and jet velocity independently. This device was configured to eject a jet through a nozzle which was both opened and closed at a constant rate. The fluid driving mechanism was configured to compensate for the nozzle deformation and maintain a constant jet velocity. The jet formation dynamics were captured using a high speed camera and commercial DPIV software. The temporal evolution of the invariants of motion (circulation, energy and impulse) was determined from the DPIV velocity field. The invariance principle demonstrated a high accuracy before ring saturation, with some losses due to viscosity. [Preview Abstract] |
Tuesday, November 23, 2010 2:21PM - 2:34PM |
QT.00008: Caltech's Fish-inspired Wind Farm: Results from the first summer John Dabiri Field tests are being conducted at the Caltech Field Laboratory for Optimized Wind Energy to study the aerodynamic interactions of vertical-axis wind turbines in closely-spaced arrays. A model of the wind farm performance---inspired by previous mathematical models of fish schooling---suggests that substantially higher power per unit land area can be extracted relative to existing wind farms of horizontal-axis wind turbines by tuning the spatial arrangement of the turbines. Results from the first summer of field testing support the conclusions of the model, while indicating opportunities for further refinements of the model. [Preview Abstract] |
Tuesday, November 23, 2010 2:34PM - 2:47PM |
QT.00009: Effect of Noise and Flow Field Resolution on the Evaluation of Fluid Dynamic Forces on Bodies Using only the Velocity Field and its Derivatives Maria Cecilia Breda, Paul S. Krueger Determining unsteady fluid dynamic forces on bodies using only measurements of the velocity field and its derivatives is essential in many investigations, including studies of freely swimming or flying animals. In this project, all terms in a control-volume force equation utilizing only the velocity field and its derivatives discussed by Noca et al. (J. Fluids Struct., 13, 551 - 578) will be analyzed with regard to the influence of flow field noise and resolution to determine which terms dominate the error in the computed force and which factor has the greatest effect on the error. Using analytical and computational flow fields for which the lift and drag forces are known, irregularities found in real experimental results including noise and reduced spatial/temporal resolution will be added to assess their effect on the computed forces. Results for several canonical flows will be presented. [Preview Abstract] |
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