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Slow drift of a floating cylinder in narrow-banded beam seas

Published online by Cambridge University Press:  21 April 2006

Yehuda Agnon ,
Hang S. Choi  and
Chiang C. Mei
Yehuda Agnon
Affiliation:
Woods Hole Oceanographic Institution, MA 02543, USA
Hang S. Choi
Affiliation:
Seoul National University, Seoul 131 Korea
Chiang C. Mei
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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Abstract

For a long cylinder floating on the sea surface, incident sea waves with a narrow frequency band excite body oscillations of short and long periods. Depending on the stiffness of the mooring system, the body displacement of the long-period motion can be comparable with, or even greater than that of the short-period oscillations. By combining the asymptotic methods of multiple scales and inner and outer expansions, we describe an essentially analytical theory for slow sway of both small and large amplitudes. Besides showing results for various quasi-steady and transient incident waves for a rectangular cylinder, we examine the effect of the gap between the keel of the body and the sea bottom. It is found in particular that a small gap can enhance moderate resonance by blocking the flow due to long waves and increase the apparent mass of the cylinder. Real-fluid effects are not included.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 190 , May 1988 , pp. 141 - 163
Copyright
© 1988 Cambridge University Press

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