Spectral Analysis and non-linear high wave groups in wind generated sea states

4 Introduction Engineering works are varied and complex. Particularly, maritime and ocean structures can be of different types: breakwaters for ports and harbors, seawalls for shore protection, platform for exploitation of oil beneath the seabed are some examples. Earthquakes, currents, effects of wind, waves are just some of the actions generated in the natural environmental subjected to the listed structures must perform their functions. In order to ensure their designated performance, deep investigation must be carried out, to be able to correctly understand the environmental conditions. Moving in the specific, waves are the most important phenomenon to be considered among the environmental conditions affecting maritime structures; since they exercise the greatest influence the presence of waves makes the design procedure for maritime structures quite different from that of structures on land. In this view, description and assessment of wind generated ocean waves provide vital information for the design and operation of marine systems such as ships and ocean and coastal structures. However, it must be said that waves are one of the most complex and changeable phenomena in nature and it is not easy to achieve a full understanding of their fundamental character and behavior. Wind-generated seas continuously vary over a wide range of severity depending on geographical location, season, presence of tropical cyclones etc. Furthermore, the wave profile in a given sea state is extremely irregular in time and space and thus any sense of apparent regularity is totally absent. Having said this, the random wave behavior of sea waves can be interpreted by mean of stochastic prediction approach that allows to estimate the response of marine systems with reasonable accuracy. Such probabilistic approach has become an integrated part of modern design technology in naval, ocean and coastal engineering. In this view, the main objective of this work is to investigate the random behavior of the wave motion by means of stochastic approach in order to interpret the nature