The ocean engineering vessels equipped with d mooring positioning system frequently should maintain their position in shallow waters with sea current. File restricted water depth and sea current affect wave parameters, hence- the exciting wave forces. Tile influence of shallow water and the current on the parameters In regular waves, especially on their amplitude is shown in the paper, because tile drift wave force depends of the wave quadratic amplitude. A sea current in the waved sea changes the encounter frequency for which the drift wave force was calculated. For drift wave force caused by the regular wave group with the current the second order transfer function was calculated and compared with the motions In the waves without current.


A moored vessel is frequently required to maintain position in shallow-waters under the action of a sea current. The restricted water depth and the current exert influence on wave parameters, hence on the wave-induced forces acting on the ship. In the paper was assumed that a regular wave is traveling from an area of deep-water and no current into an area of shallow depth and with a current when the vessel is moored. Influenced by the slowly-varying drift forces. the moored vessel performs low-frequency motions of velocity that have influence on drift force. This velocity also affects the slowly-varying drift forces. The joint action of the sea current and the slow motions on the wave drift force is considered in the form of linear coefficients of the wave-drift damping.

The propagation of regular waves in current

changes the encounter frequency. Waves are assumed to enter a sea current area with uniform over- the depth velocity Vc. For estimation of shallow-water wave parameters in current, two co-ordinate systems are used.

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