• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2001년도 추계학술대회 논문집
• /
• pp.144-149
• /
• 2001

The failure at the head section of rubble-mound detached breakwaters is more important than other failure modes. because this initial failures will occur the failure of the trunk section and lead to the instability of the structure. The three-dimensional failure modes are discussed using the experimental data with multi-directional waves considering the failure modes occurring around the head of the rubble-mound detached breakwater. The spacial characteristics of failure mode around the rubble-mound structures can be summarized as follows: 1) It was clarified that the failure modes at the round head of a detached breakwater are classified as failure by plunging breaker on the slope, failure by direct incident wave force and failure by scouring at the toe of the detached breakwater. 2) The failure mode was found in the lower wave height than the design wave by the breaker depth effects. It is clarified that the structure monitored was safely designed for the design wave but the failure was occurred by the reason of breaker waves and scouring processes at the toe 3) It was observed that scouring at the toe developed in the region where steady stream due to vorticity was generated and the spatial variation of scour at the toe of the round head was predominated by incident wave direction.

• 한국해안해양공학회지
• /
• 제3권3호
• /
• pp.163-169
• /
• 1991

불규칙 사면에서의 파랑변형을 분석하기 위해 파랑-흐름 복합수조에서 67 종류의 규칙파에 대한 실험을 실시하였다. 사면은 합판과 Angle을 이용하여 제작하였으며 경사는 1/10, 1/20이다. 균일한 경사면에서는 쇄파수심 지수, 파의 쳐오름 등은 기존의 실험 결과와 큰 차이가 없었으나, 심해 파랑경사가 작은 경우 이들의 값은 더 작았다. 또, 파의 쳐오름은 Hunt식과 잘 일치하였으며, 쇄파가 발생하는 횟수와도 관계가 있다. 사주가 있는 경우, 쇄파수심 지수는 기존의 식과 큰 차이가 있다. 쇄파후의 파고는 Dally 등(1984)의 이론식에 비해 작게 관측되었다.

• 대한조선학회논문집
• /
• 제37권3호
• /
• pp.37-44
• /
• 2000

수면 하에서 정속으로 움직이는 MACA0012 수중익에 의하여 생성되는 정상파 및 쇄파에 대한 실험적 연구를 회류수조에서 수행하였다. 실린더의 몰수깊이에 따른 자유표면 파형을 관측하였고, PIV를 이용하여 수중익과 자유표면 사이 유동장의 순간속도와 평균속도를 계측한 후 와도분포를 구하였다. 쇄파의 발생, 전개 그리고 소멸과정을 조사하였고, 특히 자유표면 부근의 와류 구조와 같은 복잡 순간유동장의 가시화를 통하여 수중익과 쇄파 간의 상호작용을 해석하고자 하였다. 본 실험으로 PIV 계측기법은 조선해양공학의 다양한 연구분야에 훌륭히 적용될 수 있음을 보았고 더욱이 정량적인 해석이 필요한 실험에도 사용이 가능함을 확인하였다.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2004년도 학술대회지
• /
• pp.303-308
• /
• 2004

The failure at the head section of rubble mound breakwaters is more important than other failure modes. because this initial failures will occur the failure of the trunk section and lead to the instability of the structure. The three-dimensional failure modes are discussed using the experimental data with multi-directional waves considering the failure modes. It was occurred by the topographical characteristics around the head of rubble mound breakwater. The spacial characteristics of failure mode around the rubble-mound structures can be summarized as follows: 1) It was clarified that the failure modes at the round head of a detached breakwater are classified as failure by plunging breaker on the slope, failure by direct incident wave force and failure at the rubble mound breakwaters. 2) The failure mode was found in the lower wave height than the design wave by the breaker depth effects and topography around structures. It is clarified that the structure was monitored safely designed for the design wave but the failure was occurred by the reason of breaker waves.

• 대한조선학회논문집
• /
• 제47권4호
• /
• pp.525-532
• /
• 2010

In this paper, wave breakers which occur in two dimensional coasts are simulated using a SPH(Smoothed Particle Hydrodynamics) method which represents the movement of fluidic physical volume with particles. As continuative fluid is approximated to the particles, the simulations are performed using fully Lagrangian method without any grid system. Two-dimensional Navier-Stokes equations and continuity equation are used for the numerical simulations. To generate incident waves, a piston type wavemaker is employed. The accuracy of the wave which is numerically generated by the wavemaker is verified by comparing with analytical results. The computations are carried out with various wave heights and slopes. The wave patterns generated through the numerical simulations are compared with several existing experimental and computational results. Agreement between the experimental data and the computation results is comparatively good. Also, the breaker depth index and the breaker height index from the present calculations are compared with the existing experimental results, and the tendency is very similar.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제9권6호
• /
• pp.624-640
• /
• 2017

In this paper, the slamming coefficients on local members of a jacket structure under plunging breaker are studied based on numerical simulations. A 3D numerical model is used to investigate breaking wave forces on the local members of the jacket structure. A wide range of breaking wave conditions is considered in order to get generalized slamming coefficients on the jacket structure. In order to make quantitative comparison between CFD model and experimental data, Empirical Mode Decomposition (EMD) is employed for obtaining net breaking wave forces from the measured response, and the filtered results are compared with the computed results in order to confirm the accuracy of the numerical model. Based on the validated results, the slamming coefficients on the local members (front and back vertical members, front and back inclined members, and side inclined members) are estimated. The distribution of the slamming coefficients on local members is also discussed.

• 한국해안·해양공학회논문집
• /
• 제32권6호
• /
• pp.384-395
• /
• 2020

연안에서 천수변형에 의해 발생하는 쇄파는 표사이동, 연안류의 생성, 충격파압의 발생 등과 같은 연안역의 다양한 물리현상과 밀접한 관계를 갖고 있다. 따라서, 연안구조물의 설계 시 쇄파파고 및 쇄파수심과 같은 쇄파지표를 정확하게 예측하는 것이 중요하다. 과거부터 많은 연구자들에 의해 쇄파현상을 규명하고 예측하기 위한 많은 과학적인 노력들이 이루어져 왔다. 대표적인 쇄파에 연구들은 주로 수리모형실험을 통해 쇄파지표 예측을 위한 많은 경험식이 제안되어 왔다. 하지만, 기존의 쇄파지표에 대한 경험식은 일정한 방정식의 가정하에 자료의 통계적 분석을 통해 가정한 방정식의 계수들을 결정하고 있다. 본 논문에서는 회귀 혹은 분류문제와 관련된 다양한 연구분야에 있어서 높은 예측성능을 보여주는 대표적인 선형기반의 지도학습 머신러닝 기법을 적용하였다. 적용된 머신러닝 기법을 기반으로 기존의 쇄파에 대한 실험자료로부터 쇄파지표 예측을 위한 모델을 개발하고, 학습된 모델로부터 쇄파예측을 위한 새로운 선형식을 제시하였다. 새롭게 제안된 쇄파지표식은 단순한 선형식임에도 불구하고 기존의 경험 공식에 비해 유사한 예측성능을 보였다.

• 대한조선학회논문집
• /
• 제37권2호
• /
• pp.38-45
• /
• 2000

본 연구는 PIV 기법을 사용하여 쇄파와 몰수체의 상호작용에 의한 점성유동장의 변화를 가시화 함과 아울러 순간유동장을 해석하는데 목적을 두고 수행하였다. 몰수깊이의 변화에 따른 쇄파와 실린더의 상호작용은 S/D=1.5 정도에서 부터 감지되기 시작하여 몰수깊이가 얕아질수록 상호작용이 크게 발생하였으며 S/D=1.0 이하가 되면 쇄파로 인한 와류가 실린더로부터 유기되는 와류를 압도하여 실린더 후방의 전반적인 와도분포를 심하게 변형시킴을 알 수 있었다. 이로부터 PIV 기법은 와도분포 해석과 같은 비정상 보오텍스 유동장의 해석에 매우 유용한 방법임을 확인하였다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집E
• /
• pp.305-310
• /
• 2001

This paper presents the computational method for analyzing the compressible flow fields in a high voltage gas circuit breaker. There are many difficult problems in analyzing the gas flow in GCB due to complex geometry, moving boundary, shock wave and so on. In particular, the distortion problem of the grid due to the movement of moving parts can be worked out by the fixed grid technique. Numerical simulations are based on a fully implicit finite volume method of the compressible Reynolds-averaged Navier-Stokes equations to obtain the pressure, density, and velocity through the entire interruption process. The presented method is applied to the real circuit breaker model and the pressure in front of the piston is good agreement with the experimental one.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.30-32
• /
• 2001

There are many difficult problems in analyzing the flow characteristics in a high voltage circuit breaker such as shock wave and complex geometries, which may be either static or in relative motion. Although a variety of mesh generation techniques are now available, the generation of meshes around complicated, multi-component geometries like a gas circuit breaker is still a tedious and difficult task for the computational fluid dynamics. This paper presents the CFD program for analyzing the compressible flow fields in a high voltage gas circuit breaker using the Cartesian cut-cell method based on the CFD-CAD integration, which can achieve the accurate representation of the geometry designed by a CAD tools. This technique is frequently satisfied, and it will be almost universally so in the future, as the CFD-CAD traffic increase.