Mechanism of Inclination of Spar-Buoy with Ring-Fin Motion Stabilizer in Shallow Sea Caused by Tidal Currents and Waves and Avoidance of the Inclination

Abstract

The main topics of this paper are the motion characteristics of a spar-buoy. Motion measurements for the spar-buoy with and without a ring-fin motion stabilizer in currents and waves were carried out at the circular water channel and the towing tank of Osaka Prefecture University, to investigate the characteristics of its motion. Motion amplitude of the spar-buoy with the stabilizer is much smaller than the spar-buoy without the stabilizer, however, the spar-buoy with the stabilizer causes the inclination that means a time average value of motion and the inclination becomes larger according to increase in wave height. On the other hand, from the results in currents, the inclination of the spar-buoy with the stabilizer is much smaller than the results of the spar-buoy without the stabilizer, however, it is found that there is clear possibility that it has multi-balanced-inclinations for higher current velocity than the designed current velocity. The mechanisms of these unexpected phenomena were investigated, and it is indicated that they can be avoided to optimize cross-section shape of the stabilizer to change its characteristics of hydrodynamics.