Due to the complexity of body-shape, the investigation of hydrodynamic forces on
mooring lines, especially those comprised of chain segments, has not been conducted to
a sufficient degree to properly characterize the hydrodynamic damping effect of mooring
lines on the global motions of a moored offshore platform. In the present study, an
experimental investigation of the hydrodynamic characteristics of various mooring
elements is implemented through free and forced oscillation tests. Since no direct
measurement capability for distributed hydrodynamic forces acting on mooring line
segments such as chain and wire rope is available yet, an indirect measurement
technique is introduced. The technique is based on the fact that hydrodynamic forces
acting on a body oscillating in still water and on a stationary body in an oscillatory flow
are equivalent except for the additional inertia force, the so-called Froude-Krylov force,
present in the latter condition. The time-dependent displacement of a slender body
moving in calm water is acquired through optical tracking with a high speed camera. The
distributed hydrodynamic measurements are then used to obtain the force by solving the
equation of motion with the boundary condition provided from tension measurements. Morison’s equation is employed along with Fourier analysis to separate the inertia and
drag components out of the total fluid force. Given the experimentally-derived
information on hydrodynamic behavior, the resistance provided by a mooring line to a
floating structure is briefly studied in terms of damping and restoring force in a coupled
dynamic system.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-3273 |
| Date | 15 May 2009 |
| Creators | Yang, Woo Seuk |
| Contributors | Mercier, Richard |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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