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 S27: Biological Fluid Dynamics: High Re Propulsions - Jellyfish, Cephalopods, and Underwater Vehicles |
Hide Abstracts |
Chair: Oscar Curet, Florida Atlantic University Room: 609 |
Tuesday, November 26, 2019 10:31AM - 10:44AM |
S27.00001: Lagrangian description of the unsteady flow induced by a jellyfish Jin-Tae Kim, Leonardo P Chamorro The unsteady flow induced by a single pulse of \textit{Aurelia aurita} was quantified via 3D particle tracking velocimetry. Inspection of the flow included Lagrangian statistics, velocity and acceleration probability density functions (PDF), acceleration variance as well as pair dispersion. PDF of the Lagrangian velocity components indicated more intense mixing in the radial direction and revealed three stages dominated by flow acceleration, mixing, and dissipation. During the mixing phase, the flow shares characteristics of homogeneous isotropic turbulence. We show that a single pulse may induce rich dynamics, where pair dispersion exhibits a super-diffusive t$^{\mathrm{3}}$ regime during the accelerated flow due to large-scale flow inhomogeneity; this is followed by a coherent t$^{\mathrm{2}}$-Batchelor scaling in the mixed wake and then t$^{\mathrm{1}}$-Brownian motions in a late stage dominated by flow dissipation. Kolmogorov microscales during the fully mixed phase were obtained with three distinct approaches, namely, Heisenberg-Yaglom relation of the Lagrangian acceleration variance, the fluctuating rate of the strain tensor in the Eulerian frame and the Batchelor scaling in pair dispersion, which showed good agreement. [Preview Abstract] |
Tuesday, November 26, 2019 10:44AM - 10:57AM |
S27.00002: Metabolic costs of enhancing propulsion in artificially controlled live jellyfish Nicole Xu, John Dabiri Artificial control of animal locomotion has the potential to address previously inaccessible questions about the biology of swimming organisms and animal-fluid interactions, where we are otherwise limited to observations of natural behavior. This work presents a biohybrid robot that uses a self-contained microelectronic system to induce swimming in live jellyfish. By driving body contractions at an optimal frequency range faster than observed in natural behavior, swimming speed can increase nearly threefold, with only a twofold increase in cost of transport to the animal. Robotic control was also used to characterize the metabolic response of the jellyfish to swimming in the enhanced mode, and it was determined that the animals can sustainably support the associated metabolic costs. These experimental results are consistent with an adapted hydrodynamic model developed to characterize enhanced propulsion. This capability can potentially be leveraged in applications such as ocean monitoring, and to enable further studies of swimming organisms in more user-controlled, systematic experiments. [Preview Abstract] |
Tuesday, November 26, 2019 10:57AM - 11:10AM |
S27.00003: Swimming via size-change: High efficiency propulsion using resonant fluid-structure interactions Gabriel Weymouth Cephalopods use large-scale structural deformation to propel themselves underwater, changing their internal volume by 20-50{\%}. In this work, the hydroelastic response of a swimmer comprised of a fluid-filled elastic-membrane is studied via analytic, numerical, and experimental methods. The self-propelled soft-body fluid and solid dynamics are shown to benefit greatly from the jet flow, the internal added-mass variation, and the pulsation in tune with the swimmer's immersed fundamental frequency. It is shown that even a simplistic size-changing structure can utilize these physical mechanisms to achieve quasi-propulsive power ratios of greater than 100{\%}, i.e. self-propulsion for these swimmers requires less energy than towing at the same speed. [Preview Abstract] |
Tuesday, November 26, 2019 11:10AM - 11:23AM |
S27.00004: Validating Improved Efficiency of Bioinspired Unsteady Jetting Propulsion Michael Krieg, Kamran Mohseni Jetting propulsion has historically been considered inefficient, as the rate of momentum transfer for a continuous jet scales with the velocity squared; whereas, the rate of kinetic energy scales with the velocity cubed. For steady jets, efficiency decreases with the ratio of jet velocity to vehicle velocity. Several animals propel themselves with high velocity jets, but none jet continuously. They pause between jetting to refill, and expel the next jet starting from rest resulting in a leading vortex ring. Vortex ring formation induces a converging radial velocity increasing hydrodynamic impulse and increasing cavity pressure. Also, fluid acceleration generates propulsion without significant wake energy. This study validates improved propulsive efficiency on a freely swimming autonomous underwater vehicle (AUV). We have developed AUVs that use such thrusters for maneuvering, and previously validated propulsive efficiency measurement using motion capture position data and motor frequency data. But in a maneuvering configuration the thrusters have lower propulsive efficiency due to losses from vehicle drag. With a streamlined AUV, we demonstrate that propulsive efficiency of unsteady jetting rivals that of unducted propellers, and is nearly double the efficiency in a maneuvering configuration. [Preview Abstract] |
Tuesday, November 26, 2019 11:23AM - 11:36AM |
S27.00005: Yaw Turning Experiments of a Bio-Inspired Vessel with Undulating Fin Propulsion Mohammad I Uddin, Gonzalo A. Garcia, Oscar M. Curet Navigation of autonomous underwater vehicles (AUVs) in tight spaces, coastal zones and close to submerge structures remains a challenge. One of the problems preventing AUVs to navigate in these complex environments is an adequate propulsion system that allows the vessel to move in multiple directions and/or perform precise station-keeping. We present an underwater vehicle equipped with a bio-inspired fin propulsion. The propulsion system is a single flexible undulating fin that runs along the length of the robot which control forward and directional maneuvers. We establish a dynamic and control model relating different fin kinematics to performance in yaw turning maneuvers. Turning performance were tested during free-swimming experiments and compared with a numerical model. In particular, fin kinematics for two turning characteristic were considered: heading change or correction and minimum radius turns. In addition, the flow generated by the fin for turning kinematics were measured using particle image velocimetry. These experiments will be useful to establish optimal combination of the yaw turning parameters of undulating fin propulsion. [Preview Abstract] |
Tuesday, November 26, 2019 11:36AM - 11:49AM |
S27.00006: Maneuver Control of an Undulating-Fin Underwater Vessel with a Central Pattern Generator Albert Espinoza, Gonzalo Garcia, Oscar Curet Undulating fin propulsion for underwater vehicles provides key advantages over traditional propeller-based methods, including increased maneuverability and high efficiency at low speed. However, some of the challenges of controlling the motion of the vessel using an undulating fin propulsion are the high coupling of the propulsive forces and torques, and the extensive parameter space of the propulsive surface. In this work, we implemented a Central Pattern Generator (CPG) to control the fin and provide a smooth transition between rapidly-changing fin wave control commands. We developed a numerical model of an underwater vehicle propelled by a single undulating fin equipped with a central pattern generator to control the swimming motion and perform different maneuvers. The model includes a 6 degree-of-freedom motion of the vessel and a discretized hydrodynamic model of the fin. This model was used to study the effects of CPG dynamics on vessel response for different swimming modes, including straight line and forward-reverse motion. The results were compared to experiments using a robotic underwater vessel. [Preview Abstract] |
Tuesday, November 26, 2019 11:49AM - 12:02PM |
S27.00007: Reinforcement Learning for a Bio-Inspired Vehicle with Undulating Fin Propulsion. Gonzalo Garcia, Mohammad Uddin, Siddhartha Verma, Oscar Curet Undulating fins provide natural swimmers with fascinating locomotion capabilities. However, the use of undulating fin propulsion for underwater vessel to perform specific maneuvers is non-trivial. Currently, researchers implement ad-hoc fin kinematics such as sinusoidal traveling waves due to ease of implementation, or use kinematics based on live animals. In the proposed work, we integrate reinforcement learning with simulations and underwater robotic experiments to determine optimal undulating fin kinematics for a variety of swimming performance. A six degree-of-freedom numerical model is used to simulate the motion of a vessel with an undulating fin. The swimmer is modeled as a rigid body with a single fin running along the length of the body. A reinforcement learning algorithm was developed to determine the optimal kinematics of the fin for basic locomotion, including straight swimming and turning. We find that a model-free self-learning approach can be used to generate more complex actuation combination for improved performance. The simulation results are compared to the performance of a bio-inspired vehicle with an undulating fin propulsion. The results indicate that the use of reinforcement learning could be particularly useful for unsupervised decision-making, especially in the presence of unpredictable disturbances or flow conditions. [Preview Abstract] |
(Author Not Attending)
|
S27.00008: Experiments with Impulsive Motion of a Foil to Generate Large Lift and Thrust Forces Miranda Kotidis, Michael Triantafyllou As underwater vehicles become increasingly versatile and capable, bio-inspired propulsion systems are becoming a viable possibility for future vehicles. In particular, flapping foil actuators are promising in their abilities for propulsion and maneuvering. Current underwater vehicles rely on propellers, which form a jet wake to produce propulsion forces, and as such, experience an inherent delay between the movement of the propeller and the vehicle feeling a propulsive force. To mitigate this shortcoming, flapping foils were moved in swift, one-time strokes to produce large, transient forces in still water. These strokes take advantage of added mass/inertial effects to produce propulsive forces almost instantaneously. Various combinations of heave and pitch motions were tested and dye visualization was performed with a custom wing to elucidate the wake and vortical structures produced by these strokes. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700