Using time-stack overlooking images to separate incident and reflected waves in wave flume

Abstract

A time-stack wave image technique for separating incident and reflected waves in wave flumes is presented for normally incident waves propagating over a submerged breakwater with arbitrary 2D bathymetry. The wavenumber-frequency spectra from the time-stack wave image were used to determine the directions of incident and reflected waves, and the inverse Fourier transform method was used to derive the spatial variations and the time series of incident and reflected wave. The time series of separated incident and reflected wave and the wave reflection coefficients with the various wave phases between the incident waves and the reflected waves were fairly close to the values reported by Baldock and Simmonds, and the mean deviations in this study are slightly smaller than theirs. Furthermore, according to the profile of reflected wave heights, the reflection wave heights in this study case are not the constant, due to the incident waves encounter the various structures and sloping bathymetry. Additionally, existing 2D methods for separating incident and reflected waves over the sloping bathymetry; the water depths at the wave gauges must be known in order to calculate the linear shoaling coefficients. The present method, in contrast, does not require knowledge of the water depth, making it more practical than existing methods.