This Thesis investigates the methods which are currently avail-
able for the dynamic analysis of Offshore Mooring Terminals, particular
regard being paid to Single Point Mooring (SPM) Terminals. Various
aspects of the problem are considered in turn, these being the random
vibration of non-linear systems, the analysis of catenary mooring
lines, buoy dynamics, ship motions, second order (or slow drift)
forces and motions, and low frequency motions caused by instabilities.
These various aspects are then applied to the dynamic analysis of a
Single Buoy Storage (SBS) System and the effect of the method of
analysis employed, the system dimensions and the environmental
conditions on the computed response is investigated.
A Time Domain investigation of the stability of the SBS System
in the presence of wind and current alone reveals that the system is
only unstable for combinations of wind and current which are unlikely
to occur in practise. A static offset position is then assumed and
the calculation of the three-dimensional first and second order
response to random waves is performed in the Frequency Domain, linear
wave theory being used. The first order wave forces are calculated by
using strip theory for the tanker and Morison's equation for the buoy.
The second order response in surge, sway and yaw is calculated by a
reflection coefficient method, these coefficients being obtained from
published literature. The non-linear mooring system and the drag
forces acting on the buoy are linearised using the equivalent
linearisation method, due account being taken of the coupling between
the first and second order response. The model developed for the first
order response of the system allows the use of a spreading function
in the incident wave spectrum.
The accuracy of linearisation techniques and the statistics of
the second order force and response are also investigated.
| Identifer | oai:union.ndltd.org:CRANFIELD1/oai:dspace.lib.cranfield.ac.uk:1826/3621 |
| Date | 02 1900 |
| Creators | Langley, R. S. |
| Contributors | Kirk, Colin L. |
| Publisher | Cranfield University |
| Source Sets | CRANFIELD1 |
| Language | English |
| Detected Language | English |
| Type | Thesis or dissertation, Doctoral, PhD |
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