Hydrodynamic performance and vortex shedding of a biologically inspired three-dimensional flapping foil

The dynamics of flapping remains a subject a great theoretical and practical interest. Propulsion and maneuvering by flapping, optimized through years of evolution, is ubiquitous in nature, yet marine pulsars inspired by examples of highly maneuverable marine life or aquatic birds remain unheard of. The motivation of this research stems from the notion that better propulsive strategies could be obtained from flapping foils; presenting superior alternatives to the conventional propeller for waterborne propulsion. The propulsive properties of a Nasa 0012 linearly tapered rigid foil, with a .5.5 cm average chord and 24.6 cm span performing a combined roll and pitch motion are investigated. The mean planform area thrust coefficient and efficiency are recorded over a paramtetric space that included three roll amplitudes, with induced heave (at 0.7 span) to chord ratio, ḣ₀.₇ / c = 1.0, 1.5 and 2.0; Strouhal numbers ranging from 0.2 to 0.6 and maximum angle of attack varying from 15 to 45 degrees. Results show that a maximum planform area thrust coefficient of 2.09 is achieved at h₀.₇ / c = 1.5, St = 0.6 and ,[alpha][max] = 30⁰. The thrust and efficiency data also reveal a useful performance trend where at low [alpha][max], high thrust and efficiency can be gained at sufficiently high Strouhal numbers.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Ocean Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Lim, Keith, K. L

Advisor dc:contributor.advisor

• Alexandra H. Techet.

• Ocean 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/1721.1/33570

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/33570