Slowly Varying Oscillations of Moored Vessels in Beam Seas (Part I)

Abstract

This paper is mainly aimed to study the phenomena of slowly varying oscillations of moored vessels and to state the procedures for predicting their values in wind and waves.
Model tests were conducted at IHI's ship model basin on the motions of a floating vessel moored by coil springs in regular and transient water waves, and theoretical calculations of dynamic behaviors of a moored vessel including slowly varying transient sway motions were also carried out. As a result of the studies, the following conclusions were reached;
1. Slowly varying oscillations of moored vessels exist as transient sway motions for a long period in regular beam seas, which are directly propotional to the steady-state displacement due to the wave drifting forces.
2. The calculation and the test results are in fairly good agreement showing the procedures for predicting slowly varying transient sway motions in regular beam seas.
3. Slowly varying transient sway motions also exist in transient water waves after the time when the transient water waves pass through.