Loading on a Vertical Cylinder in Multidirectional Waves

[+] Author and Article Information
J. R. Chaplin, K. Subbiah

Ocean Engineering Research Centre, Department of Civil Engineering, City University, London EC1V OHB, U.K

M. Irani

Institute for Marine Dynamics, National Research Council, Ottawa, Ontario, Canada

J. Offshore Mech. Arct. Eng 117(3), 151-158 (Aug 01, 1995) (8 pages) doi:10.1115/1.2827083 History: Received May 16, 1994; Revised December 21, 1994; Online December 17, 2007


This paper presents laboratory measurements of local and total loading on an isolated vertical cylinder in irregular unidirectional and multidirectional waves. Maximum Keulegan-Carpenter numbers in individual waves were about 16, and maximum Reynolds numbers about 3 × 104 . It is shown that in these conditions, existing theoretical and numerical models underestimate the reduction in loading on a cylinder due to wave spreading. Besides the changes that are predicted when Morison’s equation is used with constant coefficients, there are hydrodynamic influences that contribute further force reductions. Comparisons with Dean’s (1977) hybrid approach suggest that in the present conditions these reductions are in the region of 3 and 6 percent for a spreading function cos2s θ, with s = 8 and s = 2, respectively. Larger reductions can be expected at higher Keulegan-Carpenter numbers, though scale effects are likely to become more important in the drag-dominated regime.

Copyright © 1995 by The American Society of Mechanical Engineers
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