大岨度規則向波中における船首船橋船の船橋への海水打ち上げ速度 : 水槽実験による調査

抄録

The wheel house front glass of a fore-bridge-ship had been broken by the shipping of water in rough sea. It was an incredible accident because the ship had the bow freeboard about 2.5 times higher than that of ICLL Regulations, and because the front glass was positioned about 20m above the sea surface. In this study, we carried out the water tank experiment using a model ship and regular waves with high steepness (H/λ=1/15〜1/10), and examined ship motions and the water level overflowing the bow bulwark top by using video-cameras and a vertical wave probe put in the bow-end. And also the raising flow velocity at the position of the front glass was tried to measure. The results are summarized as follows : (1) We obtained a formula to estimate the raising flow velocity at arbitrary height above the deck. (2) From the analysis, the head velocity of the shipped water was about 1.3〜1.5 times as fast as that led from the dam breaking theory. (3) The asymmetric phenomena significantly appeared in the ship motion. In particular, the degree of the asymmetry of bow vertical acceleration and relative wave elevation at bow were about ±20% of the average amplitude.