Mining Smartness from Nature

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Authors: Meliha Bozkurttas, James Tangorra, George Lauder, Rajat Mittal
Abstract: The research effort described here is concerned with developing a maneuvering propulsor for an autonomous underwater vehicle (AUV’s) based on the mechanical design and performance of sunfish pectoral fin. Bluegill sunfish (Lepomis macrochirus) are highly maneuverable bony fishes that have been the subject of a number of experimental analyses of locomotor function [5, 6]. Although swimming generally involves the coordinated movement of many fin surfaces, the sunfish is capable of propulsion and maneuvering using almost exclusively the pectoral fins. They use pectoral fins exclusively for propulsion at speeds of less than 1.1 body length per second (BL/s). The curve in Fig. 1 depicts two peaks of body acceleration of bluegill sunfish during steady forward swimming. These abilities are the direct result of their pectoral fins being highly deformable control surfaces that can create vectored thrust. The motivation here is that by understanding these complex, highly controlled movements and by borrowing appropriately from pectoral fin design, a bio-robotic propulsor can be designed to provide vectored thrust and high levels of control to AUVs. This paper will focus on analyses of bluegill sunfish’s pectoral fin hydrodynamics which were carried out to guide the design of a flexible propulsor for AUV’s
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Authors: Stefan Kern, Philippe Chatelain, Petros Koumoutsakos
Abstract: Biological mimesis pertains usually to the translation of a natural form or mechanism into an engineering design. Mimesis however can also apply to the design process itself as one may employ the principles of natural evolution to the optimization of engineering problems. As an exemplary case study for this approach, we present the application of an Evolutionary Strategy to the optimization of anguilliform swimming. This investigation uses three-dimensional simulations of the flow past a self-propelled body. The motion of the body is not specified a priori but is instead the result of a reverse engineering process. This procedure helps us identify systematically the links between swimming kinematics and biological function. Three distinct objectives are considered: the swimming efficiency, the burst swimming speed, and the acoutic far field signature. We focus on the acoustic and dynamic features, and in particular, we extract phaseshift information for motion controllers..
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Authors: Jeff D. Eldredge, Megan Wilson, Daniel Hector
Abstract: Most aquatic creatures achieve motility through the dynamic interaction of their flexible body with the surrounding medium. This flexibility is used to provide a spectrum of active and passive control, allowing the creature to sometimes prescribe its shape changes and at other times extract energy from the fluid. This mix is particularly important in the moderate Reynolds number regime, in which wake vortices play an important energetic role. A well-devised control strategy for a bio-inspired vehicle should – perhaps must – exploit such flexion and energy exchange; as yet, we lack sufficient understanding to develop such a strategy. In this work, we present two canonical problems that distill fundamental modes of fluid/flexible body mechanics in biological systems, which are analyzed using high-fidelity numerical simulation. The first system consists of an articulated three-link swimmer considered in free-swimming. The second system involves an articulated jellyfish, in which the active/passive flexibility mix is explored by designation of the individual hinges.
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Authors: Motomu Nakashima
Abstract: Swimming movement of human being is quite distinctive compared to those of the other aquatic animals. Taking into account of such peculiarity, the authors recently have developed a simulation model “SWUM” to analyze the dynamics of the human swimming. The simulation model itself is firstly described. Next, examples of analysis, applications of the model, and its future are respectively described.
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Authors: Scott David Kelly
Abstract: The controlled shedding of vorticity and the resulting development of liftlike forces on control surfaces are fundamental to the hydrodynamics of macroscopic marine animals and underwater vehicles alike. Computational models can reproduce these phenomena with high fidelity, but such models are largely incompatible with analytical methods of model-based feedback control design. Problems in aquatic locomotion have recently attracted attention within the analytical mechanics community, leading to the framing of such problems in the context of Lagrangian systems and geometric nonlinear control, but efforts in this area have been limited to idealized problems in which vortex shedding is conspicuously absent. This paper describes preliminary work to extend the language of geometric mechanics to address the effects of vortex shedding implicitly by modeling the development of liftlike forces on self-propelling bodies.
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Authors: Paul S. Krueger, Ali A. Moslemi, J. Tyler Nichols, Ian K. Bartol, William J. Stewart
Abstract: Pulsed-jets are commonly used for aquatic propulsion, such as squid and jellyfish locomotion. The sudden ejection of a jet with each pulse engenders the formation of a vortex ring through the roll-up of the jet shear layer. If the pulse is too long, the vortex ring will stop forming and the remainder of the pulse is ejected as a trailing jet. Recent results from mechanical pulsedjets have demonstrated that vortex rings lead to thrust augmentation through the acceleration of additional ambient fluid. This benefit is most pronounced for short pulses without trailing jets. Simulating vehicle motion by introducing background co-flow surrounding the jet has shown that vortex ring formation can be interrupted, but only if the co-flow is sufficiently fast. Recent in situ measurements on squid have captured vortical flows similar to those observed in the laboratory, suggesting thrust augmentation may play a role in their swimming performance. Likewise, recent measurements with a mechanical self-propelled pulsed-jet vehicle (“robosquid”) have shown a cruise-speed advantage obtained by pulsing.
237
Authors: Mathias Paschen, Hans Joachim Winkel, Henning Knuths
Abstract: To study the phenomenon of fluid-net-structure interaction of a trawl the authors investigated effects of hydro-elasticity of stiff net panels (grids) by means of special experiments in a wind tunnel. The analyses were especially focused on how the grids affect the current. One of the targets was to observe the correlation between the actual distribution of velocity distant and close to the grid and the respective hydrodynamic load distribution namely under consideration of prevailing geometrical and kinematical parameters. Another aim of the tests was to get an idea of the fluid-dynamic interactions between neighbouring mesh bars which is implicitly expressed in the well known nomographic diagram by Koritzky (1973). And last but not least the third target was to analyse the impact of the grid on the fluid parameters in correlation with further investigations regarding the understanding of the phenomenon of selectivity of fishing gears. In context of these objectives the hydrodynamic loads as well as the current distributions close to and far from the grid surface were measured by a six-component balance, by hot-wire anemometers as well as by a 2d-PIV-system. The tests were focused on small angles of attack. To control the motion of fluid two end plates and a base plate were used. The consequences of a fluid blockage at the end of a grid were analysed. Results are presented and discussed.
247
Authors: Robert L. Allwood
Abstract: This paper describes the culmination of two separate programmes of work undertaken at the Offshore Technology Centre at Cranfield University. The problems of underwater vision in dark turbid water have been of interest to us over a number of years and a technique employing laser illumination has been developed to partially overcome them. The system incorporates a solid state frequency doubled cw diode pumped Nd:YAG laser emitting light at 532nm as a source of illumination. Using an oscillating mirror to form a stripe of illumination on the target, image processing techniques have been used on standard CCTV outputs to reduce backscattered light thus improving image quality and range of vision. Also, an Autonomous Underwater Vehicle (Hammerhead) has been developed for the purpose of investigating control and guidance strategies. This paper describes the implementation of the above-mentioned viewing system onto the vehicle and how data extracted from the sensor has been used in the control and guidance of the AUV. In addition, the use of image tracking software, that can be trained to recognise an object, has enabled the AUV to detect and follow a predetermined target, such as an underwater pipeline or subsea telecommunications cable – a truly bio-inspired operational technique.
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Authors: Naomi Kato, Hiroyoshi Suzuki
Abstract: This paper describes the utility of a suite of oscillating fins designed to optimize the hovering and low-speed maneuvering performance of an underwater vehicle from the viewpoints of guidance and control of an underwater vehicle equipped with 2 pairs of oscillating fins in water currents, development of CFD-based motion simulator and design test of flexible fins including fluid-structure interaction.
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