An improved technique to generate rogue waves in random sea

Abstract

This paper presents an improved technique to generate rogue (freak) waves embedded in random sea based on the approach proposed by Kribel and Alsina (2000). In this method, a part of the wave energy is focused using the temporal-spatial focusing approach to generate an extreme transient wave and the rest behaves randomly. By introducing a correction term, the improved technique removes the numerical.ly spurious fluctuations of the spectra in the existing approach. Various effects of the correction are investigated numerically by using the second-order wave theory and two existing numerical. methods based on the fully nonlinear potential theory (FNPT), including the improved Spectral Boundary Integral (SBI) method and the Quasi Arbitrary Lagrangian-Eulerian Finite Element Method (QALE-FEM). The discussions are mainly focused on (1) the effectiveness of the correction on retaining the features of the specified wave spectrum; and (2) the effects of the correction on the probability of the maximum wave heights.