• Journal of the Korea Concrete Institute
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• v.27 no.5
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• pp.531-539
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• 2015

Properties of normal-strength mortar containing coarsely-crushed coal bottom ash considering standard particle size distribution of fine aggregate were investigated. Mortar containing raw bottom ash was applied as a reference. By crushing the bottom ash with a particle size larger than fine binder but smaller than fine aggregates, i.e., coarse-crushing, water absorption and specific gravity of the particles could be controlled as similar levels to those of natural fine aggregates. Workability and strength of the mortar were not changed and even increased when the coarsely-crushed bottom ash was added considering standard particle size distribution in Standard Specification for Concrete, while those were decreased when raw bottom ash was added without any treatment. When a replacement ratio of coarsely-crushed bottom ash was less than 30 vol.%, there were no significant decrease in dynamic modulus of elasticity and dry shrinkage of the mortar.

• Journal of Korea Ship Safrty Technology Authority
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• v.6
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• pp.76-84
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• 2001

수중익선과 같은 고속선의 경우 수중익이 수면근처에 접근하면 여러형태의 파를 유기하게 되며 그에 의한 압력의 변화를 유발시킨다. 이에따라 양력이 감소하고 조파저항이 증가하다가 한계 Froude 수에 이르게 되면 파가 더이상 자신의 형태를 유지하지 못하고 부서지는 쇄파가 발생하면서 조파저항은 감소하고 그대신 쇄파저항이 급격히 증가하게 된다. 이에대한 연구의 한 방법으로 수면하에서 정속으로 움직이는 수중익에 의하여 생성되는 정상파 및 쇄파현상에 대한 연구를 회류수조에서 수행하였다.

• 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.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1998.09a
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• pp.143-148
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• 1998

경사면 쇄파특성의 도출을 위한 기존의 연구는 주로 실험에 의존하여 왔다. 이들 실험적 연구들은 주로 임의 경사면에서 쇄파가 발생하는 수심과 쇄파고를 산출하는데 목적을 두었으며, CERC(1984)는 이들의 연구결과를 위합하여 쇄파제원을 산출할 수 있는 도표를 제시하였다. 본 연구에서는 수치조파경계와 천해 경사면으로 구성되는 파동장에서 경사면 쇄파거동에 대한 경계요소기법을 직접 수립하여 기법의 적용성을 세부적으로 고찰하기로 한다. (중략)

• Journal of Korea Water Resources Association
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• v.54 no.1
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• pp.39-48
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• 2021

The experiment of rip current at successive ends of breaking wave crests was conducted in a laboratory wave basin, and its time-varying evolution according to incident wave durations was observed by using ortho-rectified images. The experiment utilized the generation of a quasi nodal line of the honeycomb-pattern waves (i.e., intersecting wave trains) formed by out-of-phase motion of two piston-type wave makers arranged in the transverse direction, instead of the original honeycomb pattern waves which are generated when two wave trains propagate with slightly different wave directions. The particle moving distance and velocity caused by the rip current were measured by using the particle tracking technique. As a result, the rip current was survived for a while even without incident waves after its generation due to several successive ends of wave crests, and it moved the particles further out to sea.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.4
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• pp.1-10
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• 2002

For the time-domain simulation of incipient breaking waves, usually the boundary integral method has been used so far, and it seems to be successful except a problem of too much computation time. The present paper shows a new computation technique for the simulation of breaking wave experiment. This technique uses the high-order spectral/boundary element method and the boundary integral method in sequence, and reduces the computation time remarkably. The wave generation and energy focusing process is efficiently simulated by the high-order spectral/boundary element method. Only the wave over-turning process is simulated by the boundary integral method. In the example calculation result, salient features of breaking waves such as high particle velocities and accelerations are shown.

• Journal of the Korean Society for Marine Environment & Energy
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• v.5 no.1
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• pp.11-18
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• 2002

Directional breaking waves are generated by the component wave focusing both in direction and frequency based on constant wave steepness and constant wave amplitude spectrum models. The generated breaking waves are classified in the incipient, single and multi breaking waves. The characteristics of directional breaking waves are investigated in terms of surface profile parameters of wave crest steepness and asymmetry. The evolution of breaking wave characteristics is analyzed in a view of focusing efficiency. It shows that the front steepness and vertical asymmetry play an important role in breaking process, while the crest rear steepness and horizontal asymmetry are nearly constant during the process. The superposition of directional components greatly enhances the focusing efficiency and it suggests that characteristics of directional breaking waves may significantly different from uni-directional ones.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.89-89
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• 2015

항만 및 어항 구조물을 구성하는 다양한 해안구조물은 파랑의 천수효과, 굴절, 회절, 부분반사, 해저마찰, 쇄파의 영향 등을 고려해야하며 파고 및 파향 등의 해양특성의 검토가 반드시 이루어져야 한다. 실제의 해양파가 방향스펙트럼을 갖는 다방향 불규칙파라는 것은 잘 알려져 있으며, 기존의 해안구조물의 내파설계 또는 천해역의 파랑변형 검토에 있어서도 실제 해양파에 보다 가까운 다방향 불규칙파를 이용한 수리모형실험에 의해 파랑현상을 정도 높게 재현하는 것은 매우 중요하다. 본 연구에서는 실제 해양파를 정도 높게 재현할 수 있는 다방향 불규칙파 조파장치를 사용하여 구조물 전면해역에서의 파랑스펙트럼을 재현하고, 심해에서 발달된 파랑이 천해로 진행될 때 지형에 의해 발생되는 천수변형과 구조물 주위에서 나타나는 파랑변형의 현상을 고려하여 항내로 유입되는 파랑의 분포 특성을 검토하였다. 특히, 다방향 불규칙파로 인한 항내 파고분포 특성을 검토하기 위하여 동일 파랑에 대한 규칙파 및 불규칙파랑을 조파하여 그 결과를 상호 비교하였다. 아울러, 정온수역유지를 위한 월파현상을 수리적으로 재현할 수 있는 3차원 수리모형실험 수행하여 월파현상이 항내정온도에 미치는 영향을 고찰, 해석하여 항만 시설물 계획시 안정한 정박 및 이용에 대한 가능한 정온유지여부를 검토하였다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.5
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• pp.388-397
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• 2012

In this study, 3D-NIT(3-Dimensional Numerical Irregular wave Tank) model in which regular wave as well as stable irregular wave can be generated in 3-dimensional numerical irregular wave tank was proposed. To verify validity, the following steps need to be conducted: 1) comparative analysis between calculated waveforms and targeted waveforms at the wave generating point, 2) comparative analysis with the existing experimental values of overtopping volume estimated, targeting shore protection structures installed on a slope bed, 3) comparison with the existing numerical and hydraulic experimental results through application in the analysis on the wave deformation by structures and wave force acting on the vertical cylindrical structures. Based on the results, characteristics of the breaking wave forces according to incident waves and interval distance of structures were identified through application of 3D-NIT model in the analysis on the breaking wave forces acting on the cylindrical structures installed on a slope bed, and reflection and overtopping was reviewed through application in the special breakwaters on the domestic fields. The numerical results obtained the 3D-NIT model are in good agreement with experimental results, and its applicaion to the complex-shpaed coastal structures is verified.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.264-269
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• 2002

The wave profiles of directional breaking waves are investigated experimentally in a directional wave basin. The directional breaking waves are generated by component wave focusing both in direction and frequency based on constant wave steepness and constant wave amplitude spectrum models. the profile parameters of wave crest steepness and asymmetry are adapted to analyze the evolution of breaking ware characteristics in a view of focusing efficiency. The generated breaking waves are classified into the incipient, single and multi breaking waves.