On The Origin of Wave Induced Motions of Mooring Buoys

In the present paper the hydrodynamic loads working on buoys which are used as single point mooring terminals, are dealt with. A proper insight in these loads is a necessary basis for estimating the motions of a buoy system installed in waves. Such an estimate can be very helpful both for optimization purposes in the design stage of a new system or to explain observed phenomena of existing systems.
To obtain insight in the oscillatory hydrodynamic loads working on a buoy, the loads are split up into a number of parts. For each part an attempt is made to give a proper estimate, demonstrating the influence of the main parameters of the buoy. The thus obtained estimated loads are compared with the results of exact computer calculations and with the results of model -tests when available. The results presented are mainly related to cylindrical buoys used for Catenary Anchor Leg Mooring systems (CALM), but the described procedures can be used for other types of buoy systems too, such as SALM (Single Anchor Leg Mooring) systems or systems with stiff vertical legs. The effect of a skirt, with which most CALM buoys are fitted, is shown.
Finally-an example is given, how the motions of a CALM buoy in a not too severe sea state might be estimated when there is no tanker moored to the buoy, using the computed hydrodynamic loads. The results are compared with the results of some model tests.

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