Vol.28 No.3(5) [2006]

Statistics of Waveheights -Numerical Simulation with a Purely Stochastic Model and Laboratory Experiments in a Wind Flume-

Natsue FURUKAWA, Akira MASUDA and Michiyoshi ISHIBASHI


Statistics of waveheights is investigated in relation to freak waves. First, numerical simulation was made with a purely stochastic model that takes into account only low-order (rather artificial) nonlinearity of water waves. The model tends to yield abnormally large waveheights more frequently than the Rayleigh distribution predicts, in qualitative agreement with recent many papers. The result suggests the mechanism of frequent appearance of freak waves may be simple. Then, real wind-waves in a wind-flume were measured for a long time under the same wind condition. The distribution of waveheights thus obtained was deviated significantly from both the classical Rayleigh distribution and that due to the simulation with the stochastic model. The result shows that wind alters the statistics of water waves significantly, at least in the wind-flume.