This research investigates the statistics properties of directional wave fields in finite depth. Both, directional and finite depth effects have significant impact on wave statistics. The research is of practical engineering importance since waves are directional and since the majority of the engineering applications are located in finite water depth. Moreover, an improved determination of the probability of occurrence of extreme (and therefore unexpected) waves for certain sea conditions can result in improved warning criteria and therefore also to improved safety at sea.
It is now well accepted that modulational instability, known as one of the main mechanisms for the formation of rogue waves, induces strong departures from Gaussian statistics. However, whereas non-Gaussian properties are remarkable when wave fields follow one direction of propagation over an infinite water depth, wave statistics only weakly deviate from Gaussianity when waves spread over a range of different directions. Over finite water depth, furthermore, wave instability attenuates overall and eventually vanishes for relative water depths as low as kh=1.36 (where k is the wavenumber of the dominant waves and h the water depth). In this regard, the aim of this research is to understand whether the combined effect of directionality and finite water depth has a significant effect on wave statistics and particularly on the occurrence of extremes. For this purpose, numerical experiments have been performed solving the Euler equation of motion with the Higher Order Spectral Method (HOSM) and compared with both, data of short crested wave fields for different sea states observed at the Lake George, Australia, and experimental data obtained at the ocean wave basin in MARINTEK, Norway.
A comparative analysis of the statistical properties (i.e. wave crest and wave height distributions) between simulations, experimental and in-situ data provides a confrontation between the numerical developments and real observations in field conditions.
A recording of Leandro's talk can be found here.