ESTIMATING FREAK WAVE OCCURRENCE IN THE AGHULHAS CURRENT WITH SWAN

摘要

The third-generation wave model SWAN, which accounts for current-induced refraction, requency shifting, wave-current energy transfer, wind generation, white-capping and non-linear wave-wave interactions, has been experimentally extended to compute the Benjamin-Feir Index as an indicator for the occurrence of freak waves. This index is defined as the ratio of the wave steepness over the width of the frequency spectrum. Computations in the coastal jet and a ring Of the Agulhas current under conditions of strong currents and (locally) moderate wind and waves, show an increase of a factor two of the probability of encountering individual waves that are higher than twice the significant wave height and an additional factor three due to wind generation.