WAVE FORCE ON A VESSEL TIED AT OFFSHORE DOLPHINS

Yoshimi Goda, Tomotsuka Yoshimura

Abstract


The solution of wave scattering by a vertical elliptical cylinder is
applied to calculate the wave forces exerted upon it. The wave forces in
the directions of long and short axes of ellipsis are shown in nondimensional
forms as the functions of the angle of wave approach, the diameter-to-wavelength
ratio, and the aspect ratio of ellipsis. The results of wave force computed
are also shown in terms of the virtual mass coefficients associated with the
reference volume of the circular cylinder the diameter of which is approximately
equal to the apparent width of the elliptical cylinder observed from the direction
of wave approach.
Theory is further applied for the wave forces acting upon a vessel moored
tight at offshore dolphins and the forces transmitted to the dolphins through
the vessel. The vessel is approximated with the fixed elliptical cylinder
having the same width-to-length ratio. The computation with directional wave
spectra shows that a tanker of 200,000 D.W.T. may exert the force of about
1,400 tons at the one-third maximum amplitude to each breasting dolphin when
the tanker is exposed to the incident waves of H,/„=1.0m and T» / =10 sec from
the broadside.

Keywords


wave forces; vessel; dolphin; offshore dolphin

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