We obtain height of waves overtopping on a porous breakwater using both the one-layer and two-layer Boussinesq equations. The one-layer Boussinesq equations of Lee et al. (2014) are used and the two-layer Boussinesq equations are derived following Cruz et al. (1997). For solitary waves overtopping on a porous breakwater, we find through numerical experiments that the height of waves overtopping on a low-crested breakwater (obtained by the Navier-Stokes equations) are smaller than the height of waves passing through a highcrest breakwater (obtained by the one-layer Boussinesq equations) and larger than the height of waves passing through a submerged breakwater (obtained by the two-layer Boussinesq equations). As the wave nonlinearity becomes smaller or the porous breakwater width becomes narrower, the heights of transmitting waves obtained by the one-layer and two-layer Boussinesq equations become closer to the height of overtopping waves obtained by the Navier-Stokes equations.

In this study, we develop an algorithm to predict swell-like high waves on the east coast of Korea using the directional wave gauge which was installed near Sokcho. Using the numerical wave model SWAN, we estimate wave data in open sea from the wave data collected by using the directional wave gauge. Then, using the wave ray method and SWAN model with the open-sea wave data as offshore boundary conditions, we predict the swell-like high waves at several major points on the east coast of Korea. We verify the prediction methods with the SWAN and wave ray methods by comparing predicted data against measured one at Wangdolcho. We can improve the prediction of the swell-like high waves in the east sea of Korea using both the real-time wave measurement system and the present prediction algorithm.

We approximately obtain heights of cnoidal waves overtopping on a porous breakwater using both the one-layer Boussinesq equations (Vu et al., 2018) and the two-layer Boussinesq equations (Huynh et al., 2017). For cnoidal waves overtopping on a porous breakwater, we find through numerical experiments that the heights of cnoidal waves overtopping on a low-crested breakwater (obtained by the Navier-Stokes equations) are smaller than the heights of waves passing through a high-crested breakwater (obtained by the one-layer Boussinesq equations) and larger than the heights of waves passing through a submerged breakwater (obtained by the two-layer Boussinesq equations). As the cnoidal wave nonlinearity becomes smaller or the porous breakwater width becomes narrower, the heights of transmitting waves obtained by the one-layer and two-layer Boussinesq equations become closer to the height of overtopping waves obtained by the Navier-Stokes equations.

 Every 20 minutes, the station sends the measured data to the control office. These data include directional wave spectrum, peak wave period, direction and significant wave height, etc.  Analysis of measured data  Data were recorded from October 2012 to October 2013 at Sokcho and Whangdolcho stations.  The data were recorded 5 times when the wave height was higher than 3 m and the wave period was longer than 9 sec at Sokcho.  Observed wave directions at Sokcho are N ~ E, period is 8 ~ 12 sec.  Recently, long-period big waves have occurred continuously in the east coast of Korea seasonally, from October to February.  Estimation of deep water wave  Estimation of arrival time  Such big waves caused human deaths as well as damages to coastal structures.  These big waves were generated due to an atmospherically great valley in the north area of the East Sea.  Korea Hydrographic & Oceanographic Administration installed a real-time wave measurement station near Sokcho which is located at the north end of the east coast of Korea.

Regular waves were generated in a wave flume under perfect reflection condition to evaluate performance of three CFD models of CADMAS-SURF, olaFlow, and KIOSTFOAM. The experiments and numerical simulations were carried out for three different conditions of non-breaking, breaking of standing waves, and breaking of incident waves. Among the three CFD models, KIOSTFOAM showed best performance in reproducing the experimental results. Although the run time was reduced by using CADMAS-SURF, its computational accuracy was worse than KIOSTFOAM. olaFlow was the fastest model, but active wave absorption at the wave generation boundary was not satisfactory. In addition, the model excessively dissipated wave energy when wave breaking occurred.