It is not always possible for ships to enter the harbors that are facing the open sea under severe wave conditions. There is a limit for entering. The dangerous ship motions that occur at entering under high waves are one of the problems in maritime transportation. The authors perform a field observation of the dangerous ship motions and develop the safety evaluation index. The authors consider that it would be possible to reduce such dangerous motions if the ships can avoid the encounter wave grouping phenomena around the harbor entrance, and review how to predict the encounter waves.
Many Japanese ports and harbors, where industrial and urban functions are concentrated, have been constructed in various places facing open seas aiming at the local promotion during the period of high economic growth. In most cases, these ports and harbors are located in the area under severe wave and wind conditions and it sometimes becomes impossible to offer the best of the switching function between land and sea transportation. The authors review the safety improvement of vessels entering a harbor, taking a fishing port as an example and conduct a hearing with the fishermen. The result shows that safety improvement of vessels entering a harbor under severe conditions is strongly expected. For this improvement, the evaluation of ship motions and forecast of dangerous encounter waves that the vessels may receive at the harbor entrance are required. And, for the purpose of evaluation, we consider that a field observation at a harbor under severe natural conditions is necessary. We develop a measurement system for the ship motions combining on-board and off-board units.
