• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.3
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• pp.228-234
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• 2012

Two-dimensional hydraulic experiments for wave overtopping under non-breaking wave condition are conducted. The wave overtopping formula for vertical structure is suggested and the results are compared with EurOtop (2007). The relative water depth coefficient (${\gamma}_{kh}$) shows that almost the same coefficient is obtained for certain range (kh > 1.55) regardless of relative water depth, that is, although the relative water depth becomes larger, the relative water depth coefficient is almost same. When the wave steepness becomes larger the wave steepness coefficient decreases. The overtopping formula are expressed by relative freeboard(R) and non-dimensional wave overtopping rate(Q) and this formula has the form of exponential function. In this formula, the effects of wave period on wave overtopping are quantitatively investigated and suggested through the relative water depth coefficient(${\gamma}_{kh}$) and wave steepness coefficient(${\gamma}_s$).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.3
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• pp.300-309
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• 2008

The partial safety factors of armor stones have been calculated on the assumption that all random variables are independent one another. However, wave height and wave steepness are not independent in the van der Meer's formula of armor stones but they are correlated. In the present study, we calculated the partial safety factors considering the correlation and compared them with those of other researchers who did not consider the correlation. The correlation between wave height and steepness is closely related to the variability of wave period. As the variability of wave period decreases, the correlation between wave height and steepness becomes strong, and hence the calculation results with and without consideration of the correlation show more difference. Therefore, the correlation should be taken into account in the calculation of partial safety factors in the area where the variability of wave period is small.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.4
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• pp.198-205
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• 2017

Two-dimensional hydraulic model experiments on rubble mound structure armoring with the tetrapods and the superstructure were conducted to investigate wave transmission characteristics under irregular wave conditions. The previous studies about the wave transmission coefficients dealt with the low crested structures, therefore the rock was the main armor units and the superstructure was not constructed. In this study, the new empirical design formula for the wave transmission coefficient about rubble mound structure with the tetrapods and the superstructure was suggested and the effects of wave steepness and the row of the tetrapods in front of the superstructure could be considered.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.2
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• pp.108-115
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• 1991

This paper aims at the elucidation of the characteristics of longshore current profile after wave breaking. Wave breakers are always accompanied by complex turbulent process, wave energy losess occur and the mean water level also varies due to the gradient of radiation stress. These with other factors result in the development of longshore currents. Longshore currents have relations to the alongshore sand transport and to the diffusion of contaminants in nearshore region, thus the understanding and elucidation of them are very important from the engineering point of view. Using the calculated results, the factors such as lateral mixing cofficients, bed shear stress. wave angle. wave steepness and bottom slope. which are influencing the longshore current profile. are examined. Also, by comparing the results of longshore currents with the experimental data obtained by other investigators, the procedure proposed in the present study is shown to be valid.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.1
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• pp.93-99
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• 2011

In this study, a series of laboratory experiments are carried out to analyze fluid behaviors around multi-arranged (2 pieces) floating breakwaters with various parameters such as distance between structures, wave periods and steepness. The rate of wave transmission is shown to be affected directly by wave periods of incident waves and the breakwaters with multi-arranged structures show the highest rate of wave protection compared with other cases. The velocity fields around the breakwaters are measured by using the Laser Doppler Velocimetry system. The transmission coefficients are also measured in laboratory experiments. Finally, laboratory observed data are compared with numerical experimental results and analyzed in detail.

• Proceedings of the Korea Water Resources Association Conference
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• 1980.08a
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• pp.44-46
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• 1980

파의 에너지 감쇠기구의 관점에서 볼 때 분류손실방식인 유공벽식 방파제 중에서 원형공이 벽 전체에 균일하게 분포되어 있고 구멍 직경에 비해 벽 두께가 얇은 삼중 유공벽형 Caisson의 각 벽에 작용하는 파력에 고나해 이론적 접근과 실험을 통한 실증을 시도해 보았다. 이론적인 방법으로는 토굴구효남의 이론을 응용하였으며 주어진 파랑조건에 대해 각 유공벽 전 후면에 연속방정식과 Bernoulli 방정식을 이용하여, 각 영역별 연속 Potential의 진폭과 위상각에 대한 비선형 12원 연립방정식을 만들었고 Computer를 이용하여 반복법으로 각 속도 Potential을 확정하였다. 이렇게 구한 속도 Potential을 압력방정식에 대입하여 각 벽별 파력을 계산하였으며 동일한 파랑조건하의 실험에서 각 벽별 파력을 측정하여 양자를 서로 비교검토하였다. Bernoulli의 방정식중 에너지 손실항은 의사비선형으로 처리하였다. 유공율조합 0.25-0.3-0.2이고, 판두께가 1cm인 모형의 실험결과, 각 벽별 최대파력치의 특성으로서는 첫때, S-2, S-3등 간벽에 작용하는 파력이 전벽 및 후벽에 비해 두드러지게 작다는 사실과, 둘째 작용파력의 크기 순이 파형경사가 작을 때는 대략 S-4, S-1, S-2, S-3순이고 파형경사가 클 때에는 대략 S-1, S-4, S-2, S-3순이라는 점 등을 들 수 있겠다. 굴구효남이 가정한 f의 치 1.5를 사용하여 계산한 각 벽별 최대파력을 실험치와 비교해 본 결과, 파가 각 유공벽을 통과할 때의 손실수두를 실험에서의 양만큼 fr=1.5를 가정한 수학적 model이 설명해 주지 못한다고 볼 수 있으므로 두가지 방법에 의하여 본 실험에서 사용한 유공판의 손실계수를 근사적으로 추정하여 보았다. 추정한 f를 사용하여 다시금 각 벽별 최대파력을 계산하고 실험치와 비교해 보면 훨씬 서로 근접함을 알 수 있었다. 결국 본 논문의 이론을 사용하면 유공Caisson문제의 전체적인 윤곽 및 각 변수들의 파력에 대한 영향을 파악할 수 있겠다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.3
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• pp.221-230
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• 1996

The Suh and Park's analytical model. originally developed to calculate wave reflection from a conventional fully perforated caisson breakwater, is applied to a partially perforated caisson breakwater by approximating the vertical wall of the lower part of the front face of the caisson as a very steep sloping wall. Also, in the model, the inertial resistance term at the perforated wall is modified by using the blockage coefficient proposed by Kakuno and Liu. The model is compared against the hydraulic experimental data reported by Park et al. in 1993. Both the experimental data and the analytical model results show that the influence of inertial resistance is important so that wave reflection becomes minimum when B/L. is approximately 0.2 (in which R : wave chamber width, and 1, : wave length inside the wave chamber), which is somewhat smaller than the theoretical value B/L, : 0.25 obtained by assuming that the influence of inertial resistance is negligible. It is also shown that the analytical model based on a linear wave theory tends to overpredict the reflection coefficient as the wave nonlinearity increases, thus the model is preferably to be used for ordinary waves of small steepness.