BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Memento EPFL// BEGIN:VEVENT SUMMARY:MechE Colloquium: Development of Bio-inspired Platforms for Study of Fish Locomotion DTSTART:20190319T121500 DTEND:20190319T131500 DTSTAMP:20260925T101628Z UID:de55d7ea03b765799f2b57ba5adc3f0c7e02e1bcd7f468f378d49231 CATEGORIES:Conferences - Seminars DESCRIPTION:Prof. Hilary Bart-Smith\, Department of Mechanical and Aerospa ce Engineering\, University of Virginia\nAbstract:\nBiology has evolved ma ny unique solutions to the problem of locomotion.  In oceans\, rivers\, a nd lakes\, there are numerous fish and mammal examples that can be used fo r inspiration for next generation underwater vehicles.  These examples de monstrate capabilities—such as speed\, acceleration\, maneuverability\, stealth\, efficiencies\, operating in all environments—that far outperfo rm those of current man-made underwater vehicles.  The underlying complex ity of biological systems contribute to their superior performance and the bio-inspired studies that will be presented are focused on teasing out\, understanding\, and developing the key features of these systems that prod uce high performance. \nTo overcome the challenges of studying and quanti fying performance of swimming fish\, a bio-inspired platform that mimics i ts biological counterpart provides opportunities to study underlying physi cs of swimming. To this end\, two platforms have been developed to study t he influence of some key characteristics in fish locomotion.  The first p latform is the MantaBot\, which is inspired by biological design criteria in batoid rays: flattened rigid body and flexible actuators. The MantaBot body is rendered from a computer tomography scanning image of a cownose ra y. The flexible fins are made of elastomer in an airfoil cross-section sha pe. The fins are driven by active tensegrity structures. An additional rig id fin is attached to the rear of the body for pitch control. The vehicle is powered by a Li-ion battery pack and controlled by an Arduino microcont roller. A pressure sensor and a MEMS gyroscope/accelerometer device are us ed for depth feedback control and navigation.  Experiments were conducted in a water tank where the Mantabot was attached to a rail for rectilinear swimming. Optimal operation conditions (fin flapping amplitude and freque ncy) were determined for fastest swimming by surveying a wide range of par ameters. Free swimming tests were done in a swimming pool. Results show\, under optimal condition\, the MantaBot can swim faster than one body lengt h per second and cruise about 7 km per charge.\n \nThe second platform mi mics key characteristics of thunniform swimming\, including a fusiform bod y shape\, stiff crescent-shaped caudal fin\, narrowed peduncle and swimmin g mode.  Previous studies have shown that tunas are highly efficient swim mers.  This platform allowing us to study the underlying physics of each individual sub-systems as well as a whole system. The performance study of tuna swimming is focused on roles of (i) the peduncle structure\; (ii) th e flexibility of the caudal fin\, and (iii) flapping frequency. An artific ial peduncle was designed\, inspired on the biological counterpart. The sw imming performance of the artificial peduncle with a rigid caudal fin is c ompared with to the biological one on the same platform. Results showed th at the artificial peduncle with a rigid caudal fin swam at a speed about 8 0% of those with a biological one. Moreover\, the flexibility of the cauda l fin may contribute more than 20% of the overall speed performance. We al so designed 2D flexible panel structures inspired by fin-rays to study eff ects of isolated chordwise/spanwise flexibility on swimming performance. B y 3D printing panels with uneven thickness\, we can achieve anisotropic fl exural stiffness in artificial fin design. Our results showed that a purel y pitching rectangular panel with only chordwise flexibility has higher ef ficiency\, while one with only spanwise flexibility loses both thrust and efficiency. The 2D skeleton-enhanced structure makes it feasible to fine-t une flexibility of an artificial fin and make it perform better than biolo gy under certain circumstances.  With respect to flapping frequency\, the platform achieved a maximum tail beat frequency of 15 Hz which is compara ble to tuna fish\, and its maximum speed is 4.0 BL/s. High speed video cap tured the swimming mechanics of the platform from the ventral view at 1000 frames/s. Midline kinematics extracted from these videos were analyzed an d compared against corresponding biological data.  One key difference bet ween the two is the effective angle of attack of the main propulsor—biol ogy is able to maintain this angle within the optimal range for dynamic st all\, whereas the artificial rigid fin experiences effective angles of att ack beyond deep dynamic stall for most of the tail beat period. This diffe rence suggests the mackerel produced superior thrust by retaining the lead ing-edge vortex\, whereas the platform’s caudal fin quickly releases its leading-edge vortex.\n\nBio:\nProfessor Hilary Bart-Smith obtained her un dergraduate degree in Mechanical Engineering from the University of Glasgo w\, Scotland and her PhD degree in Engineering Sciences from Harvard Unive rsity. Dr. Bart-Smith was a post-doctoral fellow at Princeton University.   Since joining the Mechanical and Aerospace Engineering faculty at the U niversity of Virginia in 2002\, Bart-Smith has founded the Multifunctional Materials and Structures Laboratory and the Bio-inspired Engineering Rese arch Laboratory.   Bart-Smith is currently leading a research collaborat ion between UVA\, Harvard\, Princeton\, Lehigh\, and West Chester Universi ties to understand the physics of fast\, efficient bio-inspired swimming. LOCATION:MED 0 1418 https://plan.epfl.ch/?room==MED%200%201418 STATUS:CONFIRMED END:VEVENT END:VCALENDAR