NUMERICAL STUDY ON FREQUENCY DOWNSHIFT OF GRAVITY WAVE SPECTRA IN DEEP AND INTERMEDIATE WATER DEPTHS DUE TO NONLINEAR ENERGY TRANSFER

Noriaki Hashimoto,Fitri Suciaty,Masaru Yamashiro,Mitsuyoshi Kodama,Masaki Yokota

doi:10.9753/icce.v34.waves.14

Noriaki Hashimoto, Fitri Suciaty + Show 3 more

Open Access

https://doi.org/10.9753/icce.v34.waves.14

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Journal: Coastal Engineering Proceedings	Publication Date: Oct 26, 2014
Citations: 7	License type: cc-by

Affiliation: Kyushu University

Abstract

Frequency downshift of gravity wave spectra in deep and finite water depths due to the nonlinear energy transfer are discussed. In deep water depths, numerical computations of the nonlinear energy transfer are performed with DIA (Hasselmann et al., 1985), RIAM (Komatsu et al., 1993) and SRIAM (Komatsu et al., 1996). Then, differences in temporal changes of directional spectra computed with a modified WAM implemented with RIAM and SRIAM are compared with those computed with the original WAM implemented with DIA. In finite water depth, numerical computations are performed with a modified WAM implemented with FD-RIAM (Hashimoto, et al., 2002), an exact method, which was upgraded from an earlier version (Hashimoto et al., 1998) based on Komatsu et al., (2001). Differences in frequency downshift of gravity wave spectra in deep and finite water depths are discussed based on the numerical results for various directional spectra in various water depths.

Highlights

Long period waves ranging from 15 to over 25 seconds occasionally cause damage to coastal structures
This study evaluates the frequency downshift of directional spectra computed by a third generation wave model, WAM, with several computation methods of the nonlinear energy transfer such as Discrete Interaction Approximation (DIA), RIAM (Komatsu et al, 1993) and Simplified RIAM (SRIAM) (Komatsu et al, 1996) in deep water waves
We evaluate the frequency downshift of directional spectra computed with a modified WAM implemented with FD-RIAM (Hashimoto, et al, 2002) in deep water waves, where FD-RIAM is an accurate method for computing the nonlinear energy transfer in finite water depth, which was upgraded from an earlier version (Hashimoto et al, 1998) based on Komatsu et al, (2001)

Summary

Introduction

Long period waves ranging from 15 to over 25 seconds occasionally cause damage to coastal structures. This study evaluates the frequency downshift of directional spectra computed by a third generation wave model, WAM, with several computation methods of the nonlinear energy transfer such as DIA, RIAM (Komatsu et al, 1993) and SRIAM (Komatsu et al, 1996) in deep water waves.

Results

Conclusion