• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.3
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• pp.119-127
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• 1990

Wave directional spectrum estimation methods for irregular waves were considered in this study. Until now, the Longuet-Higgins Method (LHM) initiated by Longuet-Higgins et al. (1963) has been widely used, but resolutions of the estimation were found to be low. Kobune's Maximum Entropy Method (MEM) for the estimation of wave directional spectrum, bas-ed on the entropy Principle showed higher resolutions comparing with the LHM . If the wave directional spectrum is of Delta functions, the MEM is exact in its estimation. It was also found that for a unimodal spectrum, if the Mitsuyasu's spreading coefficient is above 5, the estimation resolutions were high. In bimodal spectrum, as the angle difference between the two peaks increased, the resolution improved. The energy seems to transfer to the smoother peak in the smoothing of peak's peakedness. LHM has a tendency to estimate bimodal spectrum as a unimodal spectrum ； thus, except for its computational speed, the resolution of LHM falls far below that of MEM.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.2
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• pp.154-163
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• 2009

Incident wave angles are conventionally estimated by the directional spectrum analysis of wave data collected from in-situ sensors. The in-situ measurements are limited in monitoring incident wave angles in the wide surf zone, since the techniques are typically expensive, labor-intensive, and point-measuring. In this study, estimation of incident wave angles using wave crest features captured in digital video imagery is proposed to observe incident wave directions over the surf zone. Line signatures of wave crests having high image pixel intensities are extracted by moving an interrogation window to identify high intensity pixels in sequential video images. Wave angles are computed by taking the first derivative of the extracted crest signatures, i.e. local slope of the crest signatures in the two-dimensional physical plane. Compared to the wave angle estimates obtained by the directional spectrum analysis, video-based wave angle estimates show good agreements in general.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.12 no.2
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• pp.87-95
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• 2000

Spectral wave models are applied to the area of Kyung-gi bay with two different combinations. One combination assumes a constant tidal elevation over the whole region when applying the wave model to the area. In this case no tidal currents exist in any place. The other combination employs tide model as well as wave model so that tidal condition is defined at every computation time when wave modelling is carried out. Significant wave heights and wave directions are shown for these two cases. With these two different constraints of tidal variation, the results are checked and compared with each other. Both results are found significantly different from each other.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1992.08a
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• pp.99-99
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• 1992

해운항만청은 1986년 파랑관측업무 개선 방안을 마련하여 표준 파랑관측망과 국지 파랑 모니터링 시스템으로 구분하여 표준파랑관측망은 1987년부터 시작하여 단계적으로 설치하여 1991년에 거의 완성 단계에 이르렀다. 이 표준파랑관측 시스템은 넓은 해역을 대표할 수 있는 곳에서 원칙적으로 파향스펙트럼을 실시간으로 모니터링하는 시스템으로 현장관측 기기와 실시간 자료전달 시스템과 중앙자료센타로 구성되어 그 자료는 해운항만청, 기상청, 수산청, 해양경찰청, 해군, 내무부, 대하 및 연구기관과 해양산업체에서 다목적으로 활용하고 있다.(중략)

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2009.10a
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• pp.81-84
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• 2009

• Journal of the Society of Naval Architects of Korea
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• v.39 no.1
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• pp.38-48
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• 2002

Theoretical development to generate the directional extreme waves in model basin is established based on wave focusing method. The effects of associated parameters, such as the directional range, frequency width, and center frequency, are investigated in terms of wave focusing efficiency. The two different spectral models of constant wave amplitude and constant wave slope are applied to control the wave characteristics. The wave packets simulated by theory are compared with numerical results based on Boussinesq equation and FEM. Both controls of direction and frequency spectrum are essential to focus directional waves effectively. It is noticed that wave focusing ability depends on the frequency bandwidth of spectrum rather than center frequency, and both spectral models with same parameters result in the equivalent efficiency of wave focusing.

• Journal of Korea Water Resources Association
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• v.56 no.8
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• pp.521-528
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• 2023

An approach for producing a rip current risk index using the rip current likelihood distribution obtained through the FUNWAVE simulations was applied to a rip current forecast system. The approach originally developed for an observation-based real-time rip current warning system was utilized with wave forecast data instead of observations for the rip current forecast system. The availability of the present approach was checked by comparing the observation-based rip current risk index and the wave forecast-based rip current risk index of the Haeundae Beach in 2021.

• Journal of Ocean Engineering and Technology
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• v.32 no.2
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• pp.123-130
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• 2018

The present study investigated the validity of an equilibrium shoreline empirical formula for real phenomena. Among three types of equilibrium shoreline formulas, Hsu's parabolic type static formula was employed, which is well-known and the most practical for shoreline estimation after coastal or harbor structure construction. The wave data observed at Maengbang beach and the CERC formula on longshore sediment transport were used in the present investigation. A comparison study was only conducted for the case of a shoreline change after the construction of a groyne. Reasonable agreement was seen between the observed wave data and the data obtained under a wave angle spreading function S = 3.5. However, significant changes were observed when S increased. Thus, careful application is required when using Hsu's formula.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1992.08a
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• pp.83-83
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• 1992

풍파가 수심이 불규칙하고 조류 및 해류 등의 흐름이 존재하는 연안역을 전파해 갈 때 파고 및 파향이 굴절ㆍ회절 및 천수, 에너지 감쇠 효과 등에 의해 크게 변형된다. 이러한 현상은 연안역의 파랑변형 계산 및 퇴적물이동현상 분석에 매우 중요하다. 불규칙파의 스펙트럼 형태와 에너지의 방향 분산 정도에 따라 단순 규칙파 모델과의 계산치가 50-100%에 이르기도 한다.(중략)

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2003.05a
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• pp.166-167
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• 2003

파랑ㆍ흐름의 공존장에서 그 간섭작용은 Tidal inlet 와 하구부근와 같은 천해영역에서 중요한 물리적 현상이다. 이러한 파ㆍ흐름간섭현상은 파랑의 파고, 스펙트럼과 파향등을 현저하게 변화시키고, 하구와 inlet부근에 출현하는 사주(砂洲)등의 발생기구 및 해빈 안정화에 관계하는 중요한 요인이기 때문에 이에 대한 적절한 해석이 필요하다. 본 보고에서는 확장형 부시네스크방정식을 토대로 한 수치모델을 통하여 파ㆍ흐름 공존장에서의 적용성을 검토하고자 한다. (중략)