Spatial Modulation of Nonlinear Waves due to Bragg Reflection

J. Ocean Eng. Technol. 2010;24(6):34-40.

Choi Ka-Ram,Koo Weon-Cheol

School of Naval Architecture and Ocean Engineering University of Ulsan,School of Naval Architecture and Ocean Engineering University of Ulsan

Bragg 반사에 의한 비선형파의 공간적 파형변조해석

최가람,구원철

울산대학교 조선해양공학부,울산대학교 조선해양공학부

Keywords: Numerical wave tank, Fully nonlinear, Bragg reflection Bragg, Boundary element method, Nonlinear waves, Spatial modulation

핵심용어: 수치 파동 수조, 완전 비선형, 반사, 경계요소법, 비선형파, 공간적 변조

Abstract

Bragg reflection of nonlinear waves is simulated by a 2D fully nonlinear numerical wave tank (NWT). The developed NWT was based on the Boundary Element Method (BEM) with potential theory and the mixed Eulerian-Lagrangian (MEL) time marching scheme with Runge-Kutta 4th-order time integration. A spatial variation of wave elevations and their Fourier amplitudes of each component are compared to investigate the effect of sea bottom ripples and their relative heights. The incident waves over an undulated sea bottom are partially reflected and changed to partial standing waves due to Bragg reflection. The present results are verified with linear calculations and experimental data. It is found that the 1st-order wave component is mainly affected by Bragg reflection and its spatial modulation is significant in front of the bottom ripples.