波浪による平均水面の変化(第2報) : 2成分有限水深波

抄録

Succeeding to the first report, this paper deals with the mean water level in progressive waves with bichromatic elements in finite water depth by use of the theory of transient waves. The second order velocity potential contains a new term which corresponds to the depression of the mean water level and the uniform flow. They make the amount of the depression of the mean water level ("Set-Down") larger than the one predicted by the usual theory. Hence, in most cases, the local mean water level is "Set-down" everywhere. In a few cases, however, it is "Set-up" in the smaller amplitude of bichromatic group waves due to slowly varried water level. Therefore, the terminology "Set-down" for the local water level of group waves in the report of the Ocean Engineering Committee in 16th and 17th ITTC is not adequate, and the terminology "Group-induced long wave" should be used.