• Journal of Ocean Engineering and Technology
• /
• v.8 no.2
• /
• pp.31-37
• /
• 1994

3-Dimensional panel method is now developed to the level that one can calculate the lift of a three dimensional body with the same accuracy of wind tunnel test and some current codes can consider the boundary layer effects due to the viscosity and unsteady motion in the calculation of lift. This paper is also aimed to develop these kinds of computing programs, and as a beginning, the authors restricted the problems to the steady potential flow cases. The calculation of 3-Dimensional body, wing and tandem wing carried out, using source panel and vortex ring panel. Finally, the interactions between 3-Dimension symmetric body and a wing are also calculated.

• Journal of Navigation and Port Research
• /
• v.27 no.1
• /
• pp.49-54
• /
• 2003

Recently, mega-float offshore structure is studied as of the effective utilization of the ocean space. And mega-float structure are now being considered for various applications such as floating airports. container yard, offshore cities and so on. This mega-float structure is relatively flexible compared with floating structures like large ship. When we estimate dynamic responses of these structures in waves, the elastic deformation is important, because vertical dimension is small compare with horizontal. the analysis of the dynamic reponses as it receive regular wave is studied. The finite element method is used in the analysis of structural section of this model. And the analysis is carried out using the boundary element method in the fluid division. In oder to know the characteristics of the dynamic response of the mega-float structures, effects of wavelength, water depth, and wave direction on the dynamic response of the floating structure are studied by use of numerical calculation.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.34 no.6
• /
• pp.335-345
• /
• 2022

Climate change is accelerating worldwide due to the recent rise in global temperature, and the intensity of typhoons is increasing due to the rise in seawater temperature around the Korean Peninsula. An increase in typhoon intensity is expected to increase not only wind damage, but also coastal damage caused by storm surge. Accordingly, in this study, a study of the method of reducing storm surges was conducted for the purpose of disaster prevention in order to respond to the increasing damage from storm surges. Storm surges caused by typhoons can be expected to be affected by structures located on the track of typhoon, and the effects of storm surges were studied by the eastern coast and the barrier island along the coast of the Gulf of Mexico in the United States. This study focused on this aspect and conducted related research, considering that storm surges in the southern coastal area of the Korean Peninsula could be directly or indirectly affected by Jeju Island, which is located on the track of typhoon. In order to analyze the impact of Jeju Island on storm surges, simulations were performed in various situations using a numerical analysis model. The results of using Jeju Island are thought to be able to be used to study new disaster prevention structures that respond to super typhoons.

• Journal of Ocean Engineering and Technology
• /
• v.22 no.5
• /
• pp.25-30
• /
• 2008

A B-spline based high order panel method was developed for the motion of bodies in an ideal fluid, either of infinite extent or with a free boundarysurface. In this method, both the geometry and the potential are represented by the B-spline, which guarantees more accurate results than most potential based low order methods. In the present work, we applied this B-spline based high order method to the radiation problem of floating bodies. The boundary condition on the free surface was satisfied by adopting a Kelvin-type Green function and irregular frequencies were removed by placing additional control points on the free surface surrounding the body. The numerical results were validated by comparison with existing numerical and experimental results.

• Journal of the Society of Naval Architects of Korea
• /
• v.52 no.6
• /
• pp.509-519
• /
• 2015

Mooring stability of floating dock for construction of Ichthys CPF (central processing facilities), an ultra large offshore structure, was studied. Normal and typhoon conditions were considered for mooring analysis. There have been changes in construction stages of the CPF as project progresses. These changes were reflected on the mooring stability analysis for both conditions. In order to secure the mooring stability of the floating dock for Ichthys CPF under typhoon, maximum loads of mooring chains and maximum offset of the floating dock with Ichthys CPF were examined. Also the shapes of the catenary mooring were investigated to check interferences among mooring chains. As it was confirmed that the mooring loads were within SWL (safe working load) of mooring chains and underwater sinkers, the mooring stability of the floating dock for construction of Ichthys CPF was secured. By achieving security of mooring stability of the floating dock, it is assured that Ichthys project is on its way to success.

• Journal of the Society of Naval Architects of Korea
• /
• v.32 no.4
• /
• pp.123-135
• /
• 1995

A numerical procedure is described for predicting steady drift forces an multiple three-dimensional bodies of arbitrary shape freely floating in waves. The developed numerical approach is based on combination of a three-dimensional source distribution method, wave interaction theory art the far-field method using momentum theory. Numerical results are compared with the experimental or numerical ones, which are obtained in the literature, of steady drift forces on 33(3 by 11) floating composite vertical cylinders in waves. The results of comparison confirmed the validity of the proposed approach. Finally, the interaction effects are examined in the case of an array of 40(4 by 10) freely floating rectangular bodies in shallow water.

• Journal of Ocean Engineering and Technology
• /
• v.20 no.6 s.73
• /
• pp.101-107
• /
• 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
• /
• v.32 no.1
• /
• pp.1-8
• /
• 2018

In order to analyze the response of the offshore structure numerically, the linear potential theory is generally applied for simplicity, and only the radiation damping is considered among various damping forces. Therefore, the results of a numerical simulation can be different from the motion of the structure in a real environment. To reduce the differences between the simulation results and experimental results, the viscous damping, which affects the motion of the structure, is also taken into account. The appropriate damping model is essential for the numerical simulation in order to obtain precise responses of the offshore structure. In this study, various damping models such as linear or quadratic damping and the nonlinear drag force from numerous slender bodies were used to simulate the free decay motion of the platform, and its characteristics were confirmed. The optimized damping model was found by comparing the simulation results to the experimental results. The hydrodynamic forces and wave exciting forces of the structure were obtained using WAMIT, and the free decay test was simulated using OrcaFlex. A free decay test of the scale model was performed by KRISO.

• Journal of the Society of Naval Architects of Korea
• /
• v.43 no.3 s.147
• /
• pp.351-361
• /
• 2006

The fatigue strength analysis of VLFS is carried out by using a 3-dimensional plate finite element model with a zooming technology which performs the modeling of wide portions of the structure by a coarse mesh but the concerned parts by a very fine mesh of t by t level. And a stepwise substructure modeling technique for global loading conditions is applied which uses the motion response of the global structure from 2-D plate hydroelastic analysis as the enforcing nodal displacements of the concern 3-D structural zooming model. Seven incident wave angles and whole ranges of frequency domains of wave spectrum are considered. In order to consider the effect of breakwater, the modified JONSWAP wave spectrum is used. Applying the wave data of installation region, the longterm spectrum analysis is done based on stochastic process and the fatigue life of the structure is estimated. Finally some design considerations from the view point of fatigue strength analysis of VLFS are discussed.

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