Measurements of freak waves in Norway and related ship accidents

This paper describes establisment of a world data bank related to ship and platform accidents caused by freak waves and rogue waves. It was found that many of these accidents follow a certain pattern. It was not the highest waves but violent breaking waves that gave the largest responses on the structures. Force models that predict drag- lift- and impact forces on superstructures of ships and platforms are developed. Some of the coefficients used in the force models are obtained from measurements on platforms at sea. Here impact forces were measured in asymmetric wind waves. Others are obtained from laboratory experiments some of them performed in a wind-wave flume with asymmetric wind waves. Thus a large data bank was established, and valuable information might be available for future designs. Accidents related to freak waves are not randomly distributed but are concentrated in 21 specific sea areas worldwide. Further a forecast of freak waves were established in one of these exposed areas.