A Study on Omnidirectional Ocean Wave Spectral Shape with Bimodal Index

Abstract

The wave spectrum defines the characteristics of a sea state, which can be used to determine the environmental load required to design marine structures. The wave spectral shape is related to the distribution of energy over wave frequency. This paper presents an analysis of the shape of the ocean wave spectrum based on eight years of wave records off the west coast of Korea's Jeju Island, which is located between the Yellow Sea and the East China Sea. The ocean wave spectral shape is classified according to the bimodal index (beta), which is a shape parameter based on spectral moments. The average shape of the classified ocean wave spectrum was compared with the bimodal Joint North Sea Wave Project (JONSWAP) spectrum, and the relationship between its five shape parameters and the bimodal index has been investigated in this study. It was confirmed by comparing with observation data that the ocean wave spectral shape can be represented by the bimodal index alone, including the energy concentration and distribution of both peaks.