• Ocean and Polar Research
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• v.40 no.2
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• pp.87-98
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• 2018

It is widely known that infragravity waves can exert significant influence on wave run-up over beaches. Large run-ups can lead to overwash, flooding and severe coastal erosion. In spite of the importance of infragravity waves in relation to wave run-up and coastal erosion, few studies have been carried out with regard to the impact of infragravity waves on nearshore morphodynamics with respect to eastern beaches in Korea. The purpose of this study is to investigate the importance of infragravity waves in nearshore numerical modelling. For the study, XBeach model was set up to analyze morphodynamics in December 2016, in Ilsan beach which is located in Ilsan-dong, Ulsan Metropolitan City. After validation of the XBeach model, numerical experiments were conducted by using various directional spreading coefficients. As the directional spreading coefficients are increased, the effect of infragravity waves is also enhanced by narrowband frequency. With the increasing effect of infragravity waves, the amount of sediment transport is also increased and an erosion dominant pattern is found in the south part of Ilsan beach and a deposition pattern in the north part of the beach mainly due to the wave incident direction of NNE.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.434-445
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• 2020

In this study, the minimization of harbor oscillation using permeable breakwater was applied to the actual harbor and investigated an effect of minimization by computer simulation in order to take into account the water quality problems and measures of harbor oscillation by infragravity waves at the same time. The study site is Mukho harbor located at East coast of Korea that harbor oscillation has been occurred frequently. The infragravity waves obtained by analyzing the observed field data for five years focused on the distribution between wave periods of 40 s and 70 s and wave heights in less than 0.1 m was 94% of analyzing data. The target wave periods was 68.0 s. The most effective method of minimization of harbor oscillation by infragravity waves was to install a detached permeable breakwater with transmission coefficient of 0.3 on the outside harbor and replace some area of the vertical wall in the harbor with wave energy dissipating structure to achieve a reflectivity of 0.9 or less. The amplitude reduction rate of this method shown in 27.4%. And the effect of the difference in transmission coefficient of permeable breakwater on the reduction rate of the amplitude was not significant.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.1
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• pp.17-27
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• 2019

We carry out the numerical simulation to test a hypothesis that freak waves can be triggered by the infragravity waves of bound mode underlying the ever-present swells and its constructive interaction with swells using the Tool Box called the ihFoam that has its roots on the OpenFoam, and Bi-spectrum. Numerical simulation is implemented for the SamChcuk LNG Plant where freak waves have been reported in front of the private wharf during its construction phase due to the uncompleted northern breakwater. Infra-gravity waves of bound mode is generated using the difference wave-wave interaction between the local wind waves of 7 s and a swell of 11.4 s based on the Bi-spectrum. For the sake of comparison, numerical simulation for infra-gravity waves of free mode is also carried out. Numerical results show that stem waves along the private wharf for SamChcuk LNG Plant can be triggered by the infra-gravity waves of bound mode coming from the north, which eventually leads to freak waves when encounters the reflected waves from the south jetty.