Effects of Swell on the Growth of Wind Waves and Extreme Wave Occurrence

Since ship captured accidents have been frequently occurred around Japan, it is sometimes regarded as freak wave as a cause of these accidents. Generally effects of swell are not well considered for wind wave modeling and their contributions to wave height statistics are unknown. A series of the wind-wave experiments was carried out using a wind-wave tunnel and numerical experiments using spectral wave model were also conducted. The energy growth of pure windsea and swell-windsea fields are analyzed in detail. The swell effects on the wave statistics, such as kurtosis and skewness are investigated. The effects of swell enhace the extreme waves if the windsea energy is close to the swell.