Modeling of Seabed Interaction of Oceanographic Moorings in the Frequency Domain
Publication: Journal of Waterway, Port, Coastal, and Ocean Engineering
Volume 132, Issue 6
Abstract
A simple empirical model for the interaction of a catenary mooring with the seabed is investigated in the frequency domain. The moorings that are considered here are low-pretension moorings often used in shallow waters. In these moorings, the catenary stiffness is more important than the elastic stiffness. The lower portion of the mooring is replaced by a mass–spring–damper system to include the effects of inertia, damping, and stiffness whereas the inertia and damping terms often have been neglected in previous studies. In this paper, the definitions of low-pretension and high-pretension moorings are clarified, and the parameters that determine whether the catenary or elastic stiffness is dominant are identified. The paper discusses the determination of the equivalent mass, stiffness, and damping as functions of static variables in these moorings, and the contribution of these terms toward the dynamic tension. It is shown that without the inertia term, the quadratic trend of the dynamic tension amplitude with the forcing frequency cannot be reproduced. It is also found that the aspect ratio, the ratio of the horizontal to the vertical dimension of the suspended portion of the mooring, is the critical parameter that determines whether the mooring behaves as a low-pretension or high-pretension mooring. In addition, it is found that, in low-pretension shallow water moorings, the equivalent mass, damping, and stiffness are also functions of the aspect ratio only.
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Acknowledgments
The writers gratefully acknowledge the support of the Office of Naval Research (Ocean Engineering and Marine Systems) under Grant No. ONRN00014-92-J-1269 and the Deep Ocean Exploration Institute of Woods Hole Oceanographic Institution. Additional support for the first writer was provided by a Woods Hole Oceanographic Institution postdoctoral fellowship.
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Information
Published In
Journal of Waterway, Port, Coastal, and Ocean Engineering
Volume 132 • Issue 6 • November 2006
Pages: 450 - 456
Copyright
© 2006 ASCE.
History
Received: Jan 31, 2005
Accepted: Nov 1, 2005
Published online: Nov 1, 2006
Published in print: Nov 2006
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