Numerical prediction of Normal and Extreme Waves at Fukushima Offshore Site

Abstract

In this study, wave hindcasting was performed at Fukushima floating offshore wind turbine demonstration site by using Wave Watch III, and the simulation results were validated by using measurement data. Following results were obtained. It was found that the use of the computational domain which covers whole the Pacific Ocean improves the prediction accuracy of significant wave height and wave period. By applying correction factors to the extreme value of the significant wave height results in the accurate estimation of the average value and the frequency distribution of the significant wave height. The long-term variations of the annual average significant wave height and period as well as the extreme value distribution of the annual maxium wave height are estimated from 10 years of hindcasting data. Gumbel fitting can be used for the estimation of the extreme wave height in tropical cyclone prone region. The relationship between extreme wave height and period is consistent with IEC61400-3. However, when all the event is included, the effect of the swell cannot be neglected and a model proposed by Goda should be used. A model to describe the joint probability distribution of wind speed, wave height and wave period is proposed. Predicted joint probability distribution based on this model shows good agreement with measurement.