On Statistical Properties of Artificial Irregular Water Waves : Part3 : On Extreme Steepness

Abstract

The previous report (KSR No.198) dealt mainly with the wave slope characteristics and wave steepness statistics of irregular deep water waves. This paper investigates in details the saturation shape of frequency spectrum of wave elevation and wave slope etc. by the experiments of artificial irregular water waves. Moreover, extreme high steepness irregular waves including many breaking individual waves are generated in the long tank, and the statistical characteristics and the limiting frequency spectrum etc. are researched. The Half-Cycle Counting Method (HACYM), recently suggested to use in the analysis of irregular phenomena, was applied to clarify the details of statistical character on nonlinear irregular water waves with large wave slope. Consequently, non-dimensional value 0.8 x 10^<-2> given by Longuet-Higgins as the saturation range constant of frequency spectrum is best fit for our experiment. Furthermore, non-dimensional value 3.0 x 10^<-2> is obtained as an example of the extra-ordinary unstable constant of rapidly growing high steepness irregular water waves. Those extreme high irregular waves can be artificially generated only in the near field of the wave-maker.