Motion Suppression Devices of Work Vessels

摘要

New devices to reduce roll and pitch motions by use of motkn suppression boanls have been developed, and theireffects are confirmed by experiment and calculation.Recently, upgrading constructions at port in front of open sea are increasing, so work vessels are often used in more severecondition than before. It is necessary to reduce not only roll motions but also pitch motions to improve operational rale ofwork vessels. Pitch motions, however, are affected by large damping forces essentially. So it is difficult to decrease pitchmotions because motion reduction method based on increasing damping force produces little effect.In tins paper, the new devices to reduce roll and pitch motions are introduced. These devices, referred to as "MSboard",consist of simple flat plates attached to edge of structure's bottom with a clearance gap between the board and main structure.If MSboard is attached vertically, it influences motion damping more than wave excitation. So vertical MSboard reduces rollmotions effectively. To attach the MSboard horizontally can make wave excitation of pitch reduce. Effects of vertical andhorizontal MSboards attached to a work vessel are confirmed experimentally by tank tests in various wave directions using ascale model of 1/40.Moreover, a case study with computer simulation is carried out for a typical work vessel of crane barge. Operational rate ofhandling hoisted load is calculated from the assumed limitation of hoisted load motions. So a major improvement in terms ofoperational rate can be obtained by applying the horizontal and vertical MSboard concept.