• Journal of Korean Society of Coastal and Ocean Engineers
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• v.1 no.1
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• pp.15-21
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• 1989

A simple numerical refraction model is presented. The model takes into account refraction, shoaling and bottom dissipation. Eikonal equation and equation of energy conservation are discretized by an explicit finite-difference method, which provides wave angle and height at each grid point, respectively. Applications of the model were made to simple geometries as well as complex geometries, and some advantages on computing time and stability have been observed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.1
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• pp.11-20
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• 2003

In this paper we examine several methods tor calculating the reflection of irregular waves from a perforated-wall caisson breakwater using a regular wave model. The first method is to approximate the irregular waves as a regular wave whose height and period are the same as the root-mean-squared wave height and significant wave period, respectively, of the irregular waves. The second is to use the regular wave model, repeatedly, for each frequency component of the irregular wave spectrum. The wave period is determined according to the frequency of the component wave, and the root-mean-squared wave height is used for all the frequencies. The third method is the same as the second one except that the wave height corresponding to the energy of each component wave is used. Comparison with experimental data from previous authors shows the second method is the most adequate, giving reasonable agreement in both frequency-averaged reflection coefficients and reflected wave spectra.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.4
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• pp.197-203
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• 1998

An approach of decomposing the reflecting components is proposed by using the mild-slope equation of hyperbolic type which has the similar form to the shallow water equations. The approach is verified on Booij's problem and sinusoidally varying ripples. Inclusion of higher-order bottom effect given by chamberlain and Porter(1995) yields even more satisfactory results than the Berkhoff's mild-slope equation when compared with finite element solution or experiments.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.142-146
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• 2017

지진해일의 수리특성을 분석하기 위하여 유사한 파형특성을 가진 고립파를 많이 이용하고 있다. 그러나 고립파의 근사파형은 실제 지진해일에 비해 상당히 좁은 파형분포를 가지고 있다. 이에 수치모의에서는 기존의 고립파 근사식을 개량하여 고립파형의 지진해일을 수치적으로 생성하고 있다. 본 연구에서는 지진해일의 파형분포에 따른 월파특성을 수치적으로 조사하기 위하여 개량된 고립파 근사식을 2차원 N-S solver에서 적용하였다. 이것에 기초하여 수치파동수조에 직립호안과 그 배후에는 월파수조를 설치하고, 지진해일 월파량을 측정하였다. 수치해석결과로부터 직립호안 주변의 공간파형과 마루 위의 유속분포로부터 파형분포에 따른 월파현상을 분석할 수 있었다. 또한 기존 고립파 근사이론 대비 개량된 고립파의 체적비에 따른 월파량 변화를 정량적으로 조사하였다. 그 결과 지진해일의 체적비가 증가할수록 월파량이 거의 선형적으로 증가하는 경향을 나타내었다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.1
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• pp.116-125
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• 1995

Higher order nonlinear transfer functions are applied to model the nonlinear responses obtained Inn dynamic analysis of single degree of freedom systems (SDOF) subjected to wave and current loadings. The structural systems are subjected to single harmonic, two wave combination and irregular wave loading. Three different sources of nonlinearities are examined for each of the wave loading condition and it is shown that the nonlinear response appear at the resonance frequencies of the SDOF even when virtually no wave energy exists at those resonance frequencies. Higher order nonlinear transfer functions based on Volterra series representation are used to model the nonlinear responses mainly f3r the flexible systems and clearly shows the degrees of nonlinearity either as quadratic or cubic.

• Proceedings of the Acoustical Society of Korea Conference
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• 1996.06a
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• pp.33-36
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• 1996

해양에서 내부파 (internal wave)는 수직적으로 밀도가 크게 다른 두 층의 경계면에서 생성되는데, 일반적으로 경계면은 수온약층 (thermocline)에 해당된다. 본 연구에서는 간단한 단주기(하나의 주기만을 갖는)내부파를 가정하고 이 내부파에 의해서 야기될 수 있는 저주파 (100-400 HZ) 전파손실의 변동 정도를 모델링을 통해 추정하였다. 내부파의 파장은 1Km이고 진폭은 25m이며 수심 50-100m 사이에 존재하는 것으로 가정하였다. 전파손실 계산은 PE (parabolic equation) 기법을 도입한 모델을 이용하였다.수층의 두께는 2000m로 균일하고 퇴적층 및 기반암층의 두께는 각각 500m로 가정하였다. 모델링 결과 단주기 내부파의 1 파장이 진행하는 동안 고정된 수신 깊이별로 20km 거리에서 10 dB 이상의 큰 변동이 야기 될 수 있음을 확인하였다. 이는 내부파 내에서 큰 굴절을 변화로 인한 음파의 산란 때문으로 볼 수 있다. 실제 해양에서는 내부파가 단주기 파동 형태로 나타나기 보다는 여러 주기의 파동이 중첩되어 나타나므로 정확한 내부파 영향을 추정하기 위해서는 보다 실제에 가까운 내부파를 모델링할 필요가 있다.

• 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 Coastal and Ocean Engineers Conference
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• 1993.07a
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• pp.42-44
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• 1993

최근, 불규칙파를 조파시킴으로서 발생하는 실험실 스케일의 해빈변형에 대해서 그 정선변화 뿐만아니라 수심변화까지 포함한 수치 simulation모델이 개발되었다. 그러나 현지파랑은 파고, 주기가 불규칙하고, 또한 입사파향도 일정하지 않기때문에, 앞서 논한 예측법에 의해 현지연안에서 발생하는 지형변동을 예측하기 위해서는, 현지파랑중 어떠한 방법으로 대표파고를 선정할 것인가가 큰 문제가 된다. (중략)

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.1
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• pp.30-42
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• 2010

The effects of internal waves on dynamics of hypoxic waters were investigated by numerical simulation by means of a hydrostatic-ecosystem coupled numerical model for Lake Biwa. The numerical model consists of hydrostatic and ecosystem submodels. Numerical simulation was carried out for a period during April 2007 and March 2008, after preliminary numerical simulation for three years. As a result, the numerical model could capture the vertical profiles of the observed water quality. During September 30 and October 21 in 2007, the major internal waves were Kelvin and Poincare waves, the periods of which were 1.63 or 1.77 days and 0.48 days, respectively. Hypoxic waters appeared in bottom boundary layer around October and were still when thermocline locates in upper layer. During late autumn and winter seasons, differences in density between upper and lower layers were reduced and the amplitude of internal waves increased. Hypoxic waters began to move under the effects of internal waves. Movement of hypoxic waters will diminish the habitat for aquatic organisms in deeper waters.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.4
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• pp.199-208
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• 2019

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.