• Proceedings of KOSOMES biannual meeting
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• 2017.04a
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• pp.250-250
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• 2017

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.5
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• pp.220-230
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• 2017

In this study we apply and compare a variety of numerical methods for calculating residence time distribution in decay tanks, a major design component in the for reducing N-16 radioactivity. Our research group has used a streamlined method using user-defined particle numbers. However, this streamlined method has several problems, including low exiting particle ratios, particle diminishing, and unphysical time distribution, among others. We utilize three numerical methods to establish residence time and time distribution (streamlined, discrete phase method [DPM], and user defined scalar [UDS]) and subsequently compare the averaged results of each. The three tests demonstrate the flow features within the decay tanks, which are then numerically simulated to enable comparison. We conclude that although each simulation predicts similar time averages, the UDS methodology provides a smoother time distribution and tracer contour plots at specific times.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2017.11a
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• pp.130-131
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• 2017

부유체의 횡동요는 부유체의 안정성을 헤칠 뿐 아니라 승조원의 피로를 누적시키고, 기자재의 안정적인 운용과 수명에도 영향을 미친다. 본 연구에서는 점성감쇠 안티롤링진자를 이용하여 부유체의 횡동요를 줄이는 방법을 제안하고, 안티롤링진자의 효용성을 보인다. 약 1m, 7.7kg의 모형선에 32g, 40g, 50g의 안티롤링진자를 탑재하여 16%~23.5%의 롤링 저감 효과를 얻을 수 있었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.52-58
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• 2016

Recently, interest in structural stability has increased due to earthquakes. Isolation systems can improve seismic ability without harming the functions and appearance of existing and new constructions, and they have established efficiency in foreign country that have experienced earthquakes. In this study, an isolation system is suggested using a natural rubber bearing (NRB) on a stainless water tank for stability assurance in an earthquake. A shaking table test was carried out to evaluate the seismic capacity of a non-isolated water tank and an isolated tank. Displacement meters in the water tank measured the behavior characteristics of the tanks, which were compared using artificial seismic waves of 0.154 g, 0.231 g, 0.341 g, and 0.348 g with water levels of 0.0 m, 1.5 m, and 2.5 m. At 2.5 m, a decrement effect was generally shown in the isolated water tank, and a bigger displacement occurred in the non-isolated water tank than in the isolated one at water levels of 0.0 m and 1.5 m. It is interpreted that the weight of different water levels affects the decrement effect. If seismic reinforcement is done, the isolated bearing should be designed while considering the fluid storage level.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.3
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• pp.107-116
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• 1990

The liquid sloshing in an elastic tank is a fluid-structure interaction problem. It requires nonlinear analysis to solve the complicated physics involved in the large interaction of fluid-structure, the variation of dynamic characteristics of structure due to hydrodynamic loading, and the distorsion of fluid flow due to structural vibration. In this paper a Lagrangian FEM is introduced to analyze the liquid sloshing in an elastic tank assuming that the elastic wall is one degree of freedom rigid wall. Numerical integration is performed using an implicit-explicit algorithm, which is formed by mixing the predictor-corrector method and the Runge-Kutta 4th order method. The influence of dynamic characteristics of the sloshing tank on the fluid flow is discussed. The numerical method is also applied for the simulation of the wall generated wave in the tank.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.765-772
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• 2002

Many researchers have studied several vibration control devices such as TMD, TLD, and VED to reduce the acceleration level for tall buildings. Advantages of TLD (tuned liquid damper) include easy installation, low cost, and less maintenance. However, the dynamic characteristics of TLD must be verified by experiment and analysis due to the difficulties in evaluating the characteristics of water sloshing. In this study, free vibration and dynamic excitation experiments of structure with TLD were conducted to verify vibration control force of the proposed TLD for high-rise building. The parameters were mass ratio of water to structure, number of damping nets, and aspect ratio. From the test results, the responses of structure with water tank were observed to be smaller than those of structure alone. Furthermore, better damping effect could be achieved with larger mass ratio, more damping nets, and larger aspect ratio. However, in the case of water tank with no damping net, little damping effect was obtained.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.4
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• pp.27-37
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• 1998

The sloshing is very important in a safe transport of the liquid cargo by a ship. With the increasing number of supertanker and LNG carriers, this problem has become increasingly more important. In order to study the magnitude and characteristics of impact pressures due to sloshing, experiments ware performed with a rectangular tank and compared with numerical results. Structural responses of tank wall under impulsive pressures were measured. Structural vibrations induced by the sloshing load were analysed by including hydroelastic erects in terms of added mass and damping. To check the validity of the numerical model, the natural frequencies of plate in air and water were compared with measurements, and a good agreement was found. In the case that a plate vibrates under impulsive loads, the pressure on the flexible plate is larger than that on the rigid plate without hydroelastic effects, which was confirmed experimentally. The frequency of oscillatory pressure as well as accel%pion coincides with the natural frequency of plate in water.

• Journal of Navigation and Port Research
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• v.41 no.6
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• pp.365-372
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• 2017

The rolling motion of a floating body makes crews and passengers exhausted and/or applies forces to the structure to cause damage; it might even upset the body. Therefore, almost all ships are equipped with bilge keels for anti-rolling; in special cases, an anti-rolling tank(ART) or fin stabilizer or gyroscope could be installed. But an ART requires a large capacity to install it, and a fin stabilizer and gyroscope need great costs to install and also many expenses to operate. The authors suggest the use of an anti-rolling pendulum(ARP), and they showed that the ARP is effective to reduce rolling by experiments and via a Runge-Kutta analysis. This paper introduces the linearized 2 degrees of freedom with a viscous damping system for a ship equipped with ARP; it also shows the validation of the linearized analysis for the ship's roll motion. The paper proposes an optimum ARP on the basis of the justified model. The case of the 7.7kg model with ship 20g ARP of a mass ratio of 0.26%, is the most effective for reducing roll motion. The paper shows the ARPs with various mass ratios are effective for reducing the roll motion of a ship by free decaying roll experiments.

• Journal of the Korea Convergence Society
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• v.9 no.4
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• pp.161-167
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• 2018

The amount of CNG was measured using a pressure sensor in the case of CNG vehicles. However, the current measurement method causes anxiety to the driver because it is difficult to measure the detailed amount of CNG according to various environmental conditions. This study was performed to measure the amount of CNG in CNG fuel system, and presented the method of measurement by simulating the detection system of CNG. In this experiment, a detection simulator with an ultrasonic sensor in CNG tank of Type-3 was designed, and the reception signal of the ultrasonic sensor was verified by reducing the pressure from 100 bars to 0 bars (increment=5 bars) using compressed air. As a result, the output signal voltage of the ultrasonic sensor decreased as the pressure in the tank decreased, and the it was verified that the shape of the graph was linearity.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.367-374
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• 2019

We investigate the effect of soil-structure interaction (SSI) on the response of LNG storage tanks to vertical seismic excitation depending on the type of foundation. An LNG storage tank with a diameter of 71 m on a clay layer with a thickness of 30 m upon bedrock, was selected as an example. The nonlinear behavior of the soil was considered in an equivalent linear method. Four types of foundation were considered, including shallow, piled raft, and pile foundations (surface and floating types). In addition, the effect of soil compaction within the group pile on the seismic response of the tank was investigated. KIESSI-3D, an analysis package in the frequency domain, was used to study the SSI and the stress in the outer tank was calculated. Based on an analysis of the numerical results, we arrived at three main conclusions: (1) for a shallow foundation, the vertical stress in the outer tank is less than the fixed base response due to the SSI effect; (2) for foundations supported by piles, the vertical stress can be greater than the fixed base stress due to the increase in the vertical impedance due to the piles and the decrease in radiation damping; and (3) soil compaction had a miniscule impact on the seismic response of the outer tank.