Kinetic and kinematic equations of a discus buoy are derived assuming large angles represented by Euler parameters. The three-dimensional coupled interaction of a floating discus and its mooring is studied. External loadings include hydrodynamic forces, tether tensions, wind loadings and system weight. Nonlinearities include large rotational and translational motions and non-conservative fluid loadings. At each instant in time, the twit boundary-value mooring problem is solved by direct integration using a successive iterative algorithm to satisfy boundary conditions. Coupling between the buoy and the mooring is enforced by matching of the velocities at the attachment point. A predictor-corrector coupling algorithm is developed with multiple sizes of time steps used to provide stability for the separate mooring and buoy models. Numerical results are compared to experimental responses of the discus buoy subjected to regular waves.


In the oceanic environment, mooring-buoy systems are used in various works as navigational aids, as ship and platform moorings, etc. Often, buoy systems float at the ocean surface and may be held to the bottom by mechanical devices that include mooring cables and anchors. Buoy systems come in various shapes, sizes, and mooring configurations, depending on their purpose and environmental constraints. The focus of this study is on discus buoys. In addition to hydrodynamic loading from ocean waves and currents, wind, installation or deployment loads may be applied to the discus buoy system. Systems with small characteristic lengths are analyzed by methods that include fluid viscosity effects, while relatively large-diameter structures are analyzed by methods based on potential flow theory. The problem of simulating the response of buoy systems is complicated by the fact that the motion of a tethered buoy is affected by its mooring cables. The mooring cables also experience nonlinear hydrodynamic loads.

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