Space-time evolution of wave groups in crossing seas with the Quasi-determinism theory

The space‐time evolution of wave groups in crossing seas is investigated. Profiles were calculated by applying Quasi‐determinism theory of Boccotti in its first formulation starting first from the laboratory data and then using the theoretical spectrum used for wave generation, given that a very high crest takes place at a fixed point in the basin. The analysis of the predictions shows that the group with the high crest is given by the superposition of two wave groups, associated one to the low‐frequency component of the spectrum and the other to the high‐frequency one. Different locations of high crest occurrence were considered in order to study the effect of the change in spectrum on the deterministic profiles. The comparison between the predictions obtained by the two modalities of application of the theory shows agreement when the spectrum at any point maintains almost the same characteristic of the spectrum measured in correspondence of the high crest occurrence location. Finally the analysis of the second‐order contribution revealed that the nonlinear effect gives higher and steeper crests and lower and flatter troughs than the linear ones whatever is the sea state considered being the greatest in presence of the wind wave dominated spectrum.