• Nuclear Engineering and Technology
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• 제48권1호
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• pp.246-258
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• 2016

The shield building of AP1000 was designed to protect the steel containment vessel of the nuclear reactor. Therefore, the safety and integrity must be ensured during the plant life in any conditions such as an earthquake. The aim of this paper is to study the effect of water in the water tank on the response of the AP1000 shield building when subjected to three-dimensional seismic ground acceleration. The smoothed particle hydrodynamics method (SPH) and finite element method (FEM) coupling method is used to numerically simulate the fluid and structure interaction (FSI) between water in the water tank and the AP1000 shield building. Then the grid convergence of FEM and SPH for the AP1000 shield building is analyzed. Next the modal analysis of the AP1000 shield building with various water levels (WLs) in the water tank is taken. Meanwhile, the pressure due to sloshing and oscillation of the water in the gravity drain water tank is studied. The influences of the height of water in the water tank on the time history of acceleration of the AP1000 shield building are discussed, as well as the distributions of amplification, acceleration, displacement, and stresses of the AP1000 shield building. Research on the relationship between the WLs in the water tank and the response spectrums of the structure are also taken. The results show that the high WL in the water tank can limit the vibration of the AP1000 shield building and can more efficiently dissipate the kinetic energy of the AP1000 shield building by fluid-structure interaction.

• 대한조선학회논문집
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• 제56권6호
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• pp.515-522
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• 2019

Since Liquefied Natural Gas (LNG) is normally carried at 1.1 bar pressure and at -163℃, special Cargo Containment System (CCS) are used. As LNG carrier is becoming larger, typical LNG insulation systems adopt a method to increase the thickness of insulation panel to reduce sloshing load and Boil-off Rate (BOR). However, this will decrease LNG cargo volume and increase insulation material costs. In this paper, silica aerogel, glass bubble were synthesized in polyurethane foam to increase volumetric efficiency by improving mechanical and thermal performance of insulation. In order to increase dispersibility of particles, ultrasonic dispersion was used. Dynamic impact test, quasi-static compression test at room temperature (20℃) and cryogenic temperature (-163℃) was evaluated. To evaluate the thermal performance, the thermal conductivity at room temperature (20℃) was measured. As a result, specimens without ultrasonic dispersion have a little effect on strength under the compressive load, although they show high mechanical performance under the impact load. In contrast, specimens with ultrasonic dispersion have significantly increased impact strength and compressive strength. Recently, as the density of Polyurethane foam (PUF) has been increasing, these results can be a method for improving the mechanical and thermal performance of insulation panel.

• 한국해양공학회지
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• 제33권5호
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• pp.394-399
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• 2019

Plywood is a laminated wood material where alternating layers are perpendicular to each other. It is used in a liquefied natural gas (LNG) carrier for an insulation system because it has excellent durability, a light weight, and high stiffness. An LNG cargo containment system (LNG CCS) is subjected to loads from gravity, sloshing impact, hydrostatic pressure, and thermal expansion. Shear forces are applied to an LNG CCS locally by these loads. For these reasons, the materials in an LNG CCS must have good mechanical performance. This study evaluated the shear behavior of plywood. This evaluation was conducted from room temperature ($25^{\circ}C$) to cryogenic temperature ($-163^{\circ}C$), which is the actual operating environment of an LNG storage tank. Based on the plywood used in an LNG storage tank, a shear test was conducted on specimens with thicknesses of 9 mm and 12 mm. Analyses were performed on how the temperature and thickness of the plywood affected the shear strength. Regardless of the thickness, the strength increased as the temperature decreased. The 9 mm thick plywood had greater strength than the 12 mm thick specimen, and this tendency became clearer as the temperature decreased.

• 한국수자원학회논문집
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• 제43권10호
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• pp.911-920
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• 2010

저수지와 같은 갇혀진 수체는 상류에서 유입되는 오염물질 뿐만 아니라 성층현상에 의해서도 오염될 수 있다. 갇혀진 수체에서의 연직순환은 이러한 오염을 줄이는데 중요한 역할을 하는데, 연직순환을 일으키는 인자로는 빛의 입사, 바람, 물의 온도 및 열의 확산 등이 있으며, 그중에서도 가장 중요한 것은 바람의 영향이다. 그러므로 성층화된 흐름에서 바람에 의해 발생하는 연직순환에 대한 수치모형을 개발하고 적용하는 것이 필요하다. 본 연구는 수온성층흐름을 해석할 수 있는 3차원 수치모형을 제시하였다. 유속성분은x-축과 y-축 방향에서의 운동량방정식으로부터 3단계에 걸쳐 계산되고, 자유수면 변위와 온도변화 등의 스칼라양은 각각 자유수면방정식과 이송-확산 방정식으로부터 계산된다. 본 연구에서 제시한 모형의 정확도를 검증하기 위하여 정사각형수조에서 진동하는 자유수면의 해석해와 비교하였고, 성층화된 흐름에서 발생하는 연직순환에 대하여 수치모의를 실시하였다. 그 결과, 본 연구에서 개발된 수치모형이 흐름 내부의 현상을 잘 묘사함을 알 수 있었다.