Analysis of Wave Energy Transfer Around Submerged Breakwaters Using Spectrograms of Observed Data

Abstract

Submerged breakwaters have been built in front of Songdo beach and Namhangjin beach on the east coast of Korea, where wave monitoring campaign had been carried out in front of and behind the submerged breakwaters. In this study, the transformation of Gravity Waves (GWs) and Infragravity Waves (IGWs) in the presence of submerged breakwaters was analyzed using the observation data collected at the two locations. Observed waves at various water depths around the submerged breakwaters were analyzed by comparing parameters of GWs and IGWs according to different wave conditions. In particular, the spatio-temporal variation of energy transfer and interaction between GWs and IGWs were investigated by using spectrograms of the significant wave height. The analysis results showed that spectral energies of both GWs and IGWs decreased as incoming waves pass through the submerged breakwater. In addition, some portion of energy corresponding to GWs is transferred to the frequency band of IGWs, especially under high wave conditions.