Propulsion through wake synchronization using a flapping foil

The design issues associated with underwater vehicles operating in the surf zone or other high-energy environments are likely to have viable biomimetic solutions. The flapping fin is capable of producing high instantaneous forces, giving fish the ability to turn and accelerate rapidly, and fish are capable of sensing the flow characteristics in their environment using the lateral line, aiding obstacle entrainment, schooling, rheotaxis, and prey detection. A highly maneuverable vehicle that is capable of sensing the changing flows in its environment would have a considerably higher survival rate in dangerous currents. As an initial foray into the sensory and control methods that could be used by a biomimetic vehicle, we studied energy extraction through synchronization with an incoming Karman wake for both fish and mechanical flapping foils. Rainbow trout (Oncorhynchus mykiss) swimming within a flow channel voluntarily positioned themselves 4D downstream from a 2" D-section cylinder, and synchronized with the cylinder wake in both frequency and phase. The phase of the trout's lateral position relative to the wake, described through a Wake Function W(x, t) defined as the lateral-sum of vorticity at a point downstream from the cylinder, was 100Ê» for the head, 160Ê» for the center-of-mass, and 240Ê» for the tail, implying that the trout's mass was moving laterally with the flow in a low-power swimming mode, but that its head and tail had flow across them. A euthanized trout passively synchronized with the wake and accelerated forward towards the cylinder, through fluid-excited motion only, proving that trout benefit not only from drafting in the velocity deficit behind the cylinder, but also through interaction with the vortices in the wake.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Beal, David Nelson, 1973-

Advisor dc:contributor.advisor

• Michael S. Triantafyllou.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/17599

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/17599