• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.3
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• pp.248-257
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• 2011

In the present study, we proposed a new numerical wave tank model to analyze the vertical tension-leg circular floating bodies, using a 2-D Navier-Stokes solver. An IBM(Immersed Boundary Method) capable of handling interactions between waves and moving structures with complex geometry on a standard regular Cartesian grid system is coupled to the VOF(Volume of Fluid) method for tracking the free surface. Present numerical results for the motions of the floating body were compared with existing experimental data as well as numerical results based on FAVOR(Fractional Area Volume Obstacle Representation) algorithm. For detailed examinations of the present model, the additional hydraulic experiments for floating motions and free surface transformations were conducted. Further, the versatility of the proposed numerical model was verified via the numerical and physical experiments for the general rectangular floating bodies. Numerical results were compared with experiments and good agreement was archived.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.1
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• pp.38-45
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• 2019

In this paper, the stability of the tunnel boring machine (TBM), used in tunnel excavation, according to the thrust force of the thrust jack was investigated. The existing hydraulic cylinder analysis method is fluid-structure interaction (FSI) analysis, where all of the flow setting and dynamic characteristics should be considered. Therefore, there is a need for a method to solve this problem simply and quickly. To facilitate this, the theoretical pressure in the hydraulic cylinder was calculated and compared with the analytical and experimental results. In the case of the analysis, the pressure generated inside the cylinder was analyzed statically, considering the operating characteristics of the shield TBM, and the stress and pressure were calculated. This method simplifies the analysis environment and shortens the analysis time compared to the existing analysis method. The obtained theoretical and analytical data were compared with the measured data during actual tunneling, and the analysis and experimental data showed a relative error of approximately 23.89%.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.4
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• pp.414-420
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• 2011

Thermal stress analysis of a planar anode-supported SOFC considering electrochemical reactions has been performed under operating conditions where average current density varies from 0 to 2000 $A/m^2$. For the case of the 2000 $A/m^2$ operating condition, Structural stress analysis based on the temperature distributions obtained from the CFD analysis of the unit cell has also been done. From this one way Fluid-Structure Interaction(FSI) analysis, Maximum Von-Mises stress under negligible temperature gradient fields occurs when cell components are perfectly bonded. The maximum stress of the electrolyte, cathode and anode in a unit cell SOFC is 262.58MPa, 28.55MPa and 15.1MPa respectively. The maximum thermal stress is critically dependent on static friction coefficient.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.4
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• pp.341-349
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• 2018

Recently, it has been reported that the whipping response, which is the elastic phenomenon of the ship, may be one of the causes of the ship accident. Unfortunately, the commonly used methodology for evaluating the whipping effect effectively has not been developed yet. In this study, we developed a procedure to estimate the whipping effect of hull in actual design stage. Fluid-structure interaction analysis was performed for a dominant short term sea state to obtain the time series data of vertical wave bending moment including the whipping response by slamming. In order to estimate the whipping effect by using the time series, some signal processing and statistical techniques such as low pass filtering, Weibull fitting and so on, were applied. the hydro-elasticity analysis was performed on container ships of various sizes to evaluate the whipping effect. The parameters that can affect the response of the hull vibration was selected and the effect of these parameters on whipping was analyzed.

• Special Issue of the Society of Naval Architects of Korea
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• 2017.10a
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• pp.80-87
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• 2017

This paper is related to structural assessment considering the hydroelastic response of ultra large container ships, especially from whipping (bow or stern impacts) and from springing (resonance). In general, whipping contributes both to increased fatigue and extreme loading, while springing does mainly contribute to increased fatigue loading. To evaluate the hydroelastic response quantitatively with high accuracy, numerical code considering hydro-structure coupling was applied and fatigue strength of a 13,100 TEU class containership was verified. The segmented model test and full scale measurement were also needed to assess the effect of whipping and springing on the fatigue and extreme capacity in more realistic way and for verification of the numerical tools. With reference to class rule, fatigue assessment considering springing effect and extreme assessment considering whipping effect were introduced.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.420-425
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• 2006

Measurements results of flow-structure-interactions (FSI) of an air-lifted body are introduced. An adaptive stereoscopic-PIV system has been constructed for the measurements of the air-lifted body. The measurement system consists of two cameras and optical sensors. The flow characteristics around a lifted cylinder body(length=60mmm, diameter =10mm, polystyrene) in the swirling flow field in a vertical pipe (length=600mm, inner diameter=) are investigated by the use of the constructed adaptive stereoscopic-PIV system. The images of the two cameras were used for the analysis of the flow fields around the floated cylinder body. The images of the cylinder body captured by the two cameras were used for the analyses of its motions. Four optical sensors (LED) were used for the detection of the postures of the freely-lifted cylinder body. The FSI analyses have been carried out to find the physical conditions at which the floating body is stabilized with its upright postures.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.65-70
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• 2005

A liquid storage rectangular tank structures are used in many fields of civil, mechanical and marine engineering. Especially, Ship structures have many tanks in contact with inner or outer fluid, like ballast, fuel and cargo tanks. Fatigue damages are sometimes observed in these tanks which seem to be caused by resonance with exciting force of engine and propeller. Vibration characteristics of these thin walled tanks in contact with fluid near engine propeller are strongly affected by added mass of containing fluid. Therefore it is essentially important to estimate the added mass effect to predict vibration of the tank structures. Many authors have studied vibration of cylindrical and rectangular tanks structures containing fluid. Few research on dynamic interaction among tank walls through fluid are reported in the vibration of rectangular tanks recently. In case of rectangular tanks, structural coupling between adjacent panels and effect of vibration modes of multiple panels on added mass have to be considered. In the present paper, coupling effect between panels of tank structure on added mass of containing fluid, the effect of structural constraint between panels on each vibration mode for fluid region have investigated numerically and experimentally.

• Journal of Power System Engineering
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• v.14 no.6
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• pp.67-74
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• 2010

Many tanks are installed in ship and marine structures. They are often in contact with inner or outer fluid, like ballast, fuel and cargo tanks. Fatigue damages are sometimes observed in these tanks which seem to be caused by resonance with exciting force of engine and propeller. Vibration characteristics of these thin walled tanks in contact with fluid near engine and propeller are strongly affected by added mass of containing fluid. Therefore it is essentially important to estimate the added mass effect to predict vibration of the tanks. Many authors have studied vibration of cylindrical and rectangular tanks containing fluid. Few research on dynamic interaction among tank walls through fluid are reported in the vibration of rectangular tanks recently. In case of rectangular tanks, structural coupling between adjacent panels and effect of vibration modes of multiple panels on added mass have to be considered. In the previous report, A numerical tool of vibration analysis of a 3-dimensional tank is developed by using finite element method for plates and boundary element method for fluid region. In this paper, the coupling effect between panels of a tank on added mass of containing fluid, the effect of structural constraint between panels on each vibration mode for fluid region and mode characteristics in accordance with changing breadth of the plates are investigated numerically and discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.11-21
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• 1996

선박은 화물 및 여객을 수송하는 해상교통 수단으로써 여객 및 승무원의 안락성, 탑재장비, 기기의 성능 보전 상, 화물 및 구조부재의 안전성 차원에서 진동제어가 주요 해결 기술의 하나이다. 또한 최근 선박의 대형화, 고속화로 인해 엔진과 프로펠러의 기진력은 커지는데 반해 구조 강도계산 기술의 발달로 인해 선체구조 경량화가 촉진되어 선체의 유연성이 커질 뿐 아니라 전통적인 선체 구조와 기관, 축계 강성사이의 균형이 깨어짐으로 선박의 진동제어는 더욱 중요시 되고 있다. 선박의 경우 건조 후에 진동제어를 위한 조치를 취하는 일은 매우 제한적이고 많은 비용이 들기 때문에 설계단게에서 선박진동제어를 위한 사전 노력이 충분히 이루어지는 것이 중요하다. 따라서 선박의 주 기진원인 프로펠러, 주기관 등의 기진력 자체를 적정화하는 노력과 함께 그로 인한 응답을 극소화하기 위해 설계 단계부터 인도까지 단게별로 많은 노력을 기울이고 있다. 단계별 진동제어의 한 예를 Fig.1에서 보여주고 있다[1]. 선체와 같이 복잡한 대형구조물의 진동특성 및 응답을 계산함에 있어서 컴퓨터의 발달과 유한요소법과 같은 해석기술의 발달로 실제 구조와 매우 유사한 3차원 모델링이 가능하게 되어 해석의 정도를 높일 수 있게 되었다. 그러나 프로펠러 기진력, 유체와의 연성효과, 감쇠특성 등을 정도 높게 산정하는 데는 아직도 많은 어려움이 있다. 이와같은 문제는 진동응답의 계산정도를 저하시키는 주요 요인이 되어 설게단계에서 충분히 진동 제어가 이루어졌다 하더라도 건조 후 실제운항 시 진동문제가 발생되는 경우가 있다. 건조 후 진동문제 발생시 구조변경을 통한 해결은 한계가 있기 때문에 각종 진동제어 장치의 연구개발이 최근에 활발히 이루어지고 있다[2]. 본 고에서는 설계단계에서부터 건조 후까지의 선박진동제어 과정[1,2,5,6]을 단계별로 고찰하여, 점점 까다로워져 가는 선박 진동규제[3,4]에 대처하고 승무원의 안락성에 대한 욕구, 구조물의 안전성, 장비의 성능보존이 만족되는 저진동 선박의 건조를 위해 향후 해결해야할 과제들을 도출하여 선박진동분야이 연구개발 방향을 제시하고자 한다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.1
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• pp.82-89
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• 2016

In this study, we proposed a pier of pontoon-type, "Very Large Floating Structure" (VLFS), with the length of 500m, breadth of 200 m and height of 2 m in Yeosu domestic port. Since this structure ought to endure wave loads for long periods at sea, it is essential to analyze the wave response characteristics. Direct-method is used to analyze the fluid-structure problem and the coupled motion of equation is used to obtain response results. The structural part is calculated by using finite element method (FEM) and the fluid part is analyzed by using boundary element method (BEM). Dynamic responses caused by the elastic deformation and rigid motion of structure are analyzed by numerical calculation. To investigate response characteristics of the pier in regular waves, several factors such as the wavelength, water depth, wave direction and flexural rigidity of structure are considered. As a result, wave response of pier changed at the point of $L/{\lambda}$ 1.5 and represented the torsional phenomenon according to the various incident waves. And the responses showed increasing tendency as the water depths increase at the incident point in case of $L/{\lambda}=8.0$ and peak point of vertical displacement amplitude moved from side to side as the flexural rigidity of structure changes.