Research on the Offshore Structures for Deep Seas

本研究是日本和巴西为评估深海浮式海洋结构物的性能而组织的联合研究，涉及海洋开发，特别是深海油田的开发。第一年的研究中，我们讨论了进行联合研究的方式，并考察了巴西海岸外的油田。第二年，建立了考虑风、浪、流和系泊缆共同作用的深海海洋结构物动力性能计算模型。为了检验数值计算的正确性，我们还进行了水池试验，并增加了方向谱波的模型试验。最后一年，我们继续进行了长峰不规则波的数值计算，并进行了方向谱波的试验。在方向谱波试验的基础上，研究了方向响应函数的估计方法。(1)深海海洋结构物在波浪中的性能评估是可能的。(2)根据方向谱波中运动的实测结果，可以估计出方向响应函数。(3)方向谱波中的运动响应随方向扩展的增大而减小。

This joint research was organized between Japan and Brasil for the estimation of performance of floating offshore structures for deep seas, concerning to the development of ocean, especially for development of oil field in deep seas.For the first year study, we discussed on the way of conducting joint research, and inspected into the oil field off Brasilian coast.For the second year, we developed calculation model for estimating dynamic performance of offshore structures for deep sea considering the combined effect of wind, wave, current and mooring lines. We also conducted tank experiment for examining numerical calculation, and added model experiments in directional spectrum waves.For the final year, we continued the numerical calculation in long crested irregular waves and conducted experiments in directional spectrum waves.From the experiments in directional spectrum waves, estimation method of directional response function was studied.Summarizing the three years joint research, we obtained following main results.(1) Estimation of performance in waves of offshore structures for deep seas is possible.(2) Directional response function can be estimated from the measured results on motion in directional spectrum waves.(3) Motion responses in directional spectrum waves have a tendency to be decreased as the directional spreading become large.