Vorticity transfer through rapid area change
Name
712141885-MIT.pdf
Description
Full printable version
Size
7.94 MB
Format
Adobe PDF
Checksum (MD5)
fd8fdaf3fb90a2c82052e137adbabad8
Author(s)
Wibawa, Martin Sulaiman
Advisor(s)
Michael S. Triantafyllou.
Date Issued
2010
Publisher
Massachusetts Institute of Technology
Abstract
Extensive studies have been conducted on the use of biomimetic foils for propulsion and maneuvering of vehicles. These studies, however, mostly focuses on the use of sinusoidal motion similar to bird flapping or fish swimming to generate the necessary forces. Few studies have been conducted to investigate the generation of maneuvering forces by using rapid vorticity transfer into the fluid through a rapid motion as observed in some animals. In this study a NACA 0012 foil was towed steadily at Reynolds number of 14000, then the foil is rapidly accelerated in the transverse direction. Two different cases were tested: One where the area decreases and one where it increases, referred to as vanishing foil and emerging foil, respectively. Various angle of attacks were tested, and in all the cases the circulation is conserved. The method of Particle Image Velocimetry and flow visualization were used to map out the three-dimensional vortical structure after the rapid motion. In the emerging foil experiment the flow structure is similar to the case of accelerating wing. From the vanishing foil experiment, however, we managed to discover a phenomenon called global separation, where separation happens instantaneously over the entire surface of the body. This global separation allows a more effective and rapid transfer of vorticity, at about one order of magnitude faster than vorticity transfer through conventional means.
Description
Thesis (S.M. in Naval Architecture and Marine Engineering)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 77-81).
Subjects
Mechanical Engineering.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
Terms of Use
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.
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.
Persistent DSpace Link
