A new predictor of extreme events in irregular waves considering interactions of adjacent wave groups

Abstract

An extreme wave may evolve from a wave group in random wave trains. In deep and intermediate water, coalescence and interaction of adjacent wave groups are common due to strong dispersive effects of waves, although this phenomenon is sometimes omitted in the prediction of extreme waves. In the present work, a new prediction method that considers coalescence and interaction of adjacent preliminary wave groups is proposed. This method can identify wave groups that may interact rapidly over short downstream distances and then uses these groups as the initial condition for the prediction of large events. The maximum of the scaled non-uniformity wavelet power of preliminary wave groups, and the summation of the maximum of the scaled non-uniformity wavelet power of coalesced wave groups are used as precursors to predict extreme waves generated due to nonlinear self-focusing of independent wave groups and interaction of adjacent wave groups, respectively. Then three theories (linear theory; an enhanced second-order solution; and the third-order solution) are adopted to predict when and where an extreme wave will occur. After testing a large number of cases, it is found that the enhanced second-order method predicts most extreme waves effectively within 40 peak wave lengths.