• Journal of Ocean Engineering and Technology
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• v.17 no.1
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• pp.8-15
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• 2003

본 논문에서는 투과성 유연막이 수면밑 일정한 깊이에 수평으로 잠겨있을 때 투과성 유연막에 의한 파랑제어성능을 살펴보았다. 해석 방법으로는 유체문제는 고유함수전개법 (Eigenfunction expansion method)을 사용하였고, 유연막과 파랑의 상호작용문제는 Newmann 이 제시한 유탄성 이론 (hydro-elastic theory)을 채택하였다. 막의 투과성 효과를 고려하기 위하여 수평막에서의 수직속도는 수평막 상하의 압력차에 선형적으로 비례하며 그들 사이에는 위상차가 없다고 가정한 Darcy 법칙을 사용하였다. 투과성 수평막의 설계변수 (초기장력, 길이, 잠긴 깊이, 공극율)와 입사파의 주파수를 바꿔가면서 반사율과 투과율 그리고 에너지 손실율을 살펴보았다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.2
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• pp.89-96
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• 2012

Based on the hydroelastic theory and the matched eigenfunction expansion method(MEEM), the dynamic behavior of the porous flexible net sheet and wave forces have been investigated in monochromatic waves. The net sheet is installed vertically with the submergence depth. Top end of a net sheet is fixed and its lower end is attached by a clump weight. It is assumed that the initial tension is sufficiently large so that the effects of dynamictension variation can be neglected. The boundary condition on the porous flexible net sheet is derived based on Darcy's fine-pore model and body boundary condition. The developed analytic model can be extended to the impermeable/permeable vertical plate and the impermeable flexible membrane. The analytical model was used to study the influence of design parameters(wave characteristics, porosity, submergence depth, initial tension) on the response characteristics and wave load of the net sheet.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.5
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• pp.53-59
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• 2003

Ocean space utilization using VLFS(Very Large Floating Structures) can provide environmental impact free space by allowing sea water flow freely through the floating structure. Use of Pontoon type VLFS for that purpose needs employment of breakwaters for reduction of wave effects. Therefore, in order to maximize advantage of environmental impact free structure, the breakwater should be the one that can allow water flow freely through it, too. In this paper hydroelastic response of a pontoon type structure is analyzed considering breakwaters which allow water flow through its opening at bottom of the breakwaters. Mode superposition technique is used for solving equation of flexible body while interactions between the pontoon and breakwaters is considered based on generalized mode concept. Bi-quadratic nine node higher-order boundary element method is adopted for more accurate numerical treatment near sharp edged body shape. Performance of various combinations of breakwaters is investigated.

• Journal of Power System Engineering
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• v.14 no.2
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• pp.48-54
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• 2010

An improved numerical scheme, to which the hydroelastic method is adapted, is introduced for predicting the motion and structural responses of tension leg platforms(TLPs) in regular waves. The numerical approach in this work is based on a combination of the three dimensional source distribution method and the finite element method. The hydrodynamic interactions among TLP members, such as columns and pontoons, are included in the motion and structural response analysis. The drag forces on the submerged slender members, which are proportional to the square of relative velocity, are included in order to estimate the responses of members with better accuracy. Comparisons with other results verify the works in this paper.

• Journal of Power System Engineering
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• v.14 no.5
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• pp.48-55
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• 2010

When a large ship is advancing in waves, ship undergoes the hydroelastic response, which has influences on structural stability and the fatigue destruction etc. of the ship. Therefore, to predict accurate hydroelastic response, it is necessary to analyze hydroelastic response including fluid-structure interaction. In this research, a ship is divided into many hull elements to calculate the fluid forces and wave exciting forces on each elements using three-dimensional source distribution method. The calculated fluid forces and wave exciting forces are assigned to nodes of hull elements. The neighbor nodes are connected with elastic beam elements. We analyzed hydroelastic responses, and those are formulated by using finite element method. Particularly, to estimate the influence of forward speed on the hydroelastic responses, we use two different methods : Full Hull Rotation Method(FHRM) and Sectional Hull Rotation Method(SHRM).

• Computational Structural Engineering
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• v.22 no.5
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• pp.78-85
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• 2009

• Journal of Ocean Engineering and Technology
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• v.20 no.6 s.73
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• pp.101-107
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• 2006

Recently, with the increase in requirements for marine development, a marine urbanism is being visualized, with more and more huge-scale structures at the scope of the ocean space utilization. In particular, a pontoon-type structure has attracted attention, since The Floating Structures Association of Japan proposed a new concept as the most suitable one of floating airports. The Very Lage Floating Structure (VLFS) is considered a flexible structure, for a quite large length-to-breadth ratio and its geometrical flexibility. The main objective of this study is to makean exact and convenient prediction about the hydro-elastic response on very large offshore structures in waves. The numerical approach for the hydro-elastic responses is based on the combination of the three dimensional source distribution method and the dynamic response analysis method, which assumed a dividing pontoon type structure, as many rigid bodies connected elastic beam elements. The established hydo-elastic theory was applied to the radiation forces caused by motions of a whole structure, formulated using the global coordinate system, which has the origin at the center of the structure. However, in this paper, we took radiation forces, occurred by individual motions of floating bodies, into consideration. The calculated results show good agreement with the experimental and calculated results by Yago.

• Journal of Ocean Engineering and Technology
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• v.8 no.1
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• pp.16-22
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• 1994

수중 예인시스템의 동적 거동 해석을 위한 3차원 비선형 수학모델이 제시되었다. 수중 예인체는 세장보로 이상화되었으며, 보요소의 굽임강성 및 비틈강성의 영향이 수학모델에 포함되었다. 축류가 지배적인 비정상 상대유동장내의 세장예인체의 횡방향 운동에 따른 유체동역학적 반력과 기진력에 관한 비선형 3차원 수학 정식화가 수행되었다.

• Special Issue of the Society of Naval Architects of Korea
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• 2013.12a
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• pp.85-89
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• 2013

In the engine room and the aft body, there are so many fluid tanks such as fresh water tank and oil tank. The vibration analysis for the fluid tank structures has to consider the added mass effect due to the fluid. However, it is known that the result of the fluid tank has the difference according to the boundary condition of the fluid field such as infinite fluid and finite fluid. In this paper, a numerical case study is carried out for the research about the vibration characteristics of the fluid tank with various fluid field. In addition, an experimental study is carried out to verify the validity of the vibration analysis for the fluid tank structure.

• Journal of Ocean Engineering and Technology
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• v.31 no.1
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• pp.22-27
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• 2017

This paper presents the results of an experimental study on the wedge slamming impact problem, including the fluid-structure interaction. A free drop test was performed to estimate the hydroelasticity. Three wedges were fabricated of 5 mm thick steel plate. The deadrise angles were $15^{\circ}$, $20^{\circ}$, and $25^{\circ}$. Plate thicknesses of 2 mm and 3 mm were used to determine the effect of the structural rigidity. The drop heights were 25 cm, 50 cm, 75 cm, and 100 cm. The pressure on a rigid part of the wedge and strain of the elastic plate were measured at four different locations. The pressure was compared using the Wagner theory and generalized Wagner theory.