Performance of biologically inspired flapping foils

Flapping foil propulsion is thought to provide AUVs with greater maneuverability than propellers. This thesis seeks to simplify the design process for this type of propulsion system by identifying thrust and wake characteristics for flapping foils and determining how these factors scale with certain parameters. First, the wake of a flapping NACA 0030 foil was studied qualitatively using fluorescent dye visualizations. The foil was heaved and pitched in a sinusoidal fashion. The effects of varying Reynolds number, Strouhal number, maximum pitch angle, and the phase shift between heave and pitch were studied. It was determined that at very low Strouhal numbers the wake was 'S' like and at moderate Strouhal numbers the wake contained discreet horseshoe-like vortices. Next, the wake was studied quantitatively using particle image velocimetry (PIV). Through this technique, numerical thrust coefficients and vorticity strengths were obtained as well as qualitative information regarding the morphology of the wake. The coefficient of thrust peaked at a different Strouhal number for each Reynolds number studied. This trend was compared to natural phenomenon.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2006

Author dc:creator

• Read, Melissa B. (Melissa Beth), 1982-

Advisor dc:contributor.advisor

• Alexandra H. Techet.

• 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/1721.1/35636

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/35636