Numerical Study on Frequency Downshift due to Nonlinear Energy Transfer

Abstract

Coastal and maritime structures around Japan have been occasionally damaged by the long period waves ranging from 15 to over 20 seconds. The mechanism of their generation and development has not been clarified yet. Hence, their predictability and reproducibility accuracy of the existing wave models have been hardly discussed so far. In this paper, we therefore numerically investigate the characteristics of frequency downshift of directional spectrum caused by the nonlinear energy transfer considered to be one of their generation and development mechanisms. Numerical simulations are carried out with an improved WAM implemented with SRIAM proposed by Komatsu (1996). The characteristics of the nonlinear energy transfer were discussed in relation to the various shapes of directional spectra.