Experimental investigation on statistical properties of wave heights and crests in crossing sea conditions

Some theoretical and numerical studies highlighted that the occurrence of rogue waves could increase in the presence of crossing sea. This sea state is characterized by the coexistence of two wave systems with different directions of propagations and is considered one of the most common causes of ship accidents in bad weather conditions. In particular, the angle between the two interacting wavetrains, Δθ, was found to be an important parameter that could lead to an enhanced probability of extreme events. We present an experimental investigation on wave heights and crest for surface elevation mechanically generated in different crossing sea conditions (10° < Δθ < 40°). The results of statistical analysis confirm that the probability of extreme events increases with the angle between the two systems, but does not exceed the values of the unidirectional case, which also presents waves with greater heights. Moreover, the correlation between the heights, crests, and troughs of consecutive waves assumes higher values for the case of 40°, when compared to the unidirectional case: this could mean that it is easier to find waves of the same height within a packet in the conditions Δθ = 40° with respect to the unidirectional or other Δθ conditions considered.