MechE Colloquium: Development of Bio-inspired Platforms for Study of Fish Locomotion
Event details
| Date | 19.03.2019 |
| Hour | 12:15 › 13:15 |
| Speaker | Prof. Hilary Bart-Smith, Department of Mechanical and Aerospace Engineering, University of Virginia |
| Location | |
| Category | Conferences - Seminars |
Abstract:
Biology has evolved many unique solutions to the problem of locomotion. In oceans, rivers, and lakes, there are numerous fish and mammal examples that can be used for inspiration for next generation underwater vehicles. These examples demonstrate capabilities—such as speed, acceleration, maneuverability, stealth, efficiencies, operating in all environments—that far outperform those of current man-made underwater vehicles. The underlying complexity 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 produce high performance.
To overcome the challenges of studying and quantifying performance of swimming fish, a bio-inspired platform that mimics its biological counterpart provides opportunities to study underlying physics of swimming. To this end, two platforms have been developed to study the influence of some key characteristics in fish locomotion. The first platform 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 ray. The flexible fins are made of elastomer in an airfoil cross-section shape. The fins are driven by active tensegrity structures. An additional rigid 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 microcontroller. A pressure sensor and a MEMS gyroscope/accelerometer device are used 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 frequency) were determined for fastest swimming by surveying a wide range of parameters. Free swimming tests were done in a swimming pool. Results show, under optimal condition, the MantaBot can swim faster than one body length per second and cruise about 7 km per charge.
The second platform mimics key characteristics of thunniform swimming, including a fusiform body shape, stiff crescent-shaped caudal fin, narrowed peduncle and swimming mode. Previous studies have shown that tunas are highly efficient swimmers. 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) the flexibility of the caudal fin, and (iii) flapping frequency. An artificial peduncle was designed, inspired on the biological counterpart. The swimming performance of the artificial peduncle with a rigid caudal fin is compared with to the biological one on the same platform. Results showed that the artificial peduncle with a rigid caudal fin swam at a speed about 80% of those with a biological one. Moreover, the flexibility of the caudal fin may contribute more than 20% of the overall speed performance. We also designed 2D flexible panel structures inspired by fin-rays to study effects of isolated chordwise/spanwise flexibility on swimming performance. By 3D printing panels with uneven thickness, we can achieve anisotropic flexural stiffness in artificial fin design. Our results showed that a purely pitching rectangular panel with only chordwise flexibility has higher efficiency, while one with only spanwise flexibility loses both thrust and efficiency. The 2D skeleton-enhanced structure makes it feasible to fine-tune flexibility of an artificial fin and make it perform better than biology under certain circumstances. With respect to flapping frequency, the platform achieved a maximum tail beat frequency of 15 Hz which is comparable to tuna fish, and its maximum speed is 4.0 BL/s. High speed video captured the swimming mechanics of the platform from the ventral view at 1000 frames/s. Midline kinematics extracted from these videos were analyzed and compared against corresponding biological data. One key difference between the two is the effective angle of attack of the main propulsor—biology is able to maintain this angle within the optimal range for dynamic stall, whereas the artificial rigid fin experiences effective angles of attack beyond deep dynamic stall for most of the tail beat period. This difference suggests the mackerel produced superior thrust by retaining the leading-edge vortex, whereas the platform’s caudal fin quickly releases its leading-edge vortex.
Bio:
Professor Hilary Bart-Smith obtained her undergraduate degree in Mechanical Engineering from the University of Glasgow, Scotland and her PhD degree in Engineering Sciences from Harvard University. Dr. Bart-Smith was a post-doctoral fellow at Princeton University. Since joining the Mechanical and Aerospace Engineering faculty at the University of Virginia in 2002, Bart-Smith has founded the Multifunctional Materials and Structures Laboratory and the Bio-inspired Engineering Research Laboratory. Bart-Smith is currently leading a research collaboration between UVA, Harvard, Princeton, Lehigh, and West Chester Universities to understand the physics of fast, efficient bio-inspired swimming.
Biology has evolved many unique solutions to the problem of locomotion. In oceans, rivers, and lakes, there are numerous fish and mammal examples that can be used for inspiration for next generation underwater vehicles. These examples demonstrate capabilities—such as speed, acceleration, maneuverability, stealth, efficiencies, operating in all environments—that far outperform those of current man-made underwater vehicles. The underlying complexity 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 produce high performance.
To overcome the challenges of studying and quantifying performance of swimming fish, a bio-inspired platform that mimics its biological counterpart provides opportunities to study underlying physics of swimming. To this end, two platforms have been developed to study the influence of some key characteristics in fish locomotion. The first platform 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 ray. The flexible fins are made of elastomer in an airfoil cross-section shape. The fins are driven by active tensegrity structures. An additional rigid 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 microcontroller. A pressure sensor and a MEMS gyroscope/accelerometer device are used 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 frequency) were determined for fastest swimming by surveying a wide range of parameters. Free swimming tests were done in a swimming pool. Results show, under optimal condition, the MantaBot can swim faster than one body length per second and cruise about 7 km per charge.
The second platform mimics key characteristics of thunniform swimming, including a fusiform body shape, stiff crescent-shaped caudal fin, narrowed peduncle and swimming mode. Previous studies have shown that tunas are highly efficient swimmers. 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) the flexibility of the caudal fin, and (iii) flapping frequency. An artificial peduncle was designed, inspired on the biological counterpart. The swimming performance of the artificial peduncle with a rigid caudal fin is compared with to the biological one on the same platform. Results showed that the artificial peduncle with a rigid caudal fin swam at a speed about 80% of those with a biological one. Moreover, the flexibility of the caudal fin may contribute more than 20% of the overall speed performance. We also designed 2D flexible panel structures inspired by fin-rays to study effects of isolated chordwise/spanwise flexibility on swimming performance. By 3D printing panels with uneven thickness, we can achieve anisotropic flexural stiffness in artificial fin design. Our results showed that a purely pitching rectangular panel with only chordwise flexibility has higher efficiency, while one with only spanwise flexibility loses both thrust and efficiency. The 2D skeleton-enhanced structure makes it feasible to fine-tune flexibility of an artificial fin and make it perform better than biology under certain circumstances. With respect to flapping frequency, the platform achieved a maximum tail beat frequency of 15 Hz which is comparable to tuna fish, and its maximum speed is 4.0 BL/s. High speed video captured the swimming mechanics of the platform from the ventral view at 1000 frames/s. Midline kinematics extracted from these videos were analyzed and compared against corresponding biological data. One key difference between the two is the effective angle of attack of the main propulsor—biology is able to maintain this angle within the optimal range for dynamic stall, whereas the artificial rigid fin experiences effective angles of attack beyond deep dynamic stall for most of the tail beat period. This difference suggests the mackerel produced superior thrust by retaining the leading-edge vortex, whereas the platform’s caudal fin quickly releases its leading-edge vortex.
Bio:
Professor Hilary Bart-Smith obtained her undergraduate degree in Mechanical Engineering from the University of Glasgow, Scotland and her PhD degree in Engineering Sciences from Harvard University. Dr. Bart-Smith was a post-doctoral fellow at Princeton University. Since joining the Mechanical and Aerospace Engineering faculty at the University of Virginia in 2002, Bart-Smith has founded the Multifunctional Materials and Structures Laboratory and the Bio-inspired Engineering Research Laboratory. Bart-Smith is currently leading a research collaboration between UVA, Harvard, Princeton, Lehigh, and West Chester Universities to understand the physics of fast, efficient bio-inspired swimming.
Practical information
- General public
- Free