Pages 145-151
It is very important to consider low-frequency motion, in designing moored systems for a floating structure. Many researches have been studied about them. Still there remain various problems left related to uncertainties which were simplified or assumed in both theoretical calculations and model tests. Here, we try to explain how directional waves affect on the behaviour of moored offshore structures. We developed a simulation program to calculate low-frequency motions of moored floating structures in directional waves using the time domain analysis. We investigate the effects of steady drift force due to viscous drag force on the low-frequency motions. The results of theoretical calculations are validated through the comparison with model tests carried out at a square basin which can generate bi-directional waves. There are good agreements between the numerical simulations and experiments. Thus, we can investigate the effect of the directionality of waves on low-frequency motions of moored floating structures by the present simulation program.
