• Journal of Ocean Engineering and Technology
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• v.2 no.1
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• pp.106-115
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• 1988

반잠수식 시추선의 설계에 있어서 구조의 피로수명을 정확하게 추정하는 것은 매우 중요하며, 또한 어려운 일이다. 본 논문에서는 이미 실용화된 Aker H-3모델에 대하여 Palmgren-Miner 가정에 의하여 시추선의 hot-point인 수평 및 수직 K-brace 멤버에 대하여 피로수명을 로이드 선급의 커브에 따라 계산한 결과 북해의 해성환경 조건에서는 16년 동안 계속 작업을 할 수 있다는 결론을 얻었으나 응력 집중계수 (SCF)를 선정하는데 불확실성으로 인하여 사용하는데 주위를 요한다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.1 no.1
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• pp.71-80
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• 1989

In this paper, the concept of the infinite element is applied to the linear wave diffraction and radiation problems. The hydrodynamic pressure forces are assumed to be inertially dominated, and viscous effects are neglected. The near field region surrounding the solid body is modelled using the conventional finite elements, and the far field region is represented using the infinite elements .In order to represent the scattered wave potentials in the far field region more accurately, the infinite elements are developed using special shape functions derived from the asymptotic expressions for the analytical eigenseries solution of the scattered waves. The system matrices of the infinite elements are constructed by performing the integration in the infinite direction analytically to achieve computational efficiency. Numerical analyses are carried out for vertical axisymmetric bodies to validate the infinite elements developed here. Comparisons with the results by other available numerical solution methods show that the present method using the infinite elements gives fairly good results. Numerical experiments are per-formed to determine the suitable location of the infinite elements and the appropriate size of the finite elements which directly affect accuracy and efficiency of the solution.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.6
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• pp.270-285
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• 2018

The behavior of wave-induced pore water pressure inside the rubble mound and seabed, and the resultant structure failure are investigated, which are used in design of the composite breakwater representing the coastal and harbor structures. Numerical simulation techniques have been widely used to assess these behaviors through linear and nonlinear methods in many researches. While the combination of strongly nonlinear analytical method and turbulence model have not been applied yet, which can simulate these characteristics more accurately. In this study, olaFlow model considering the wave-breaking and turbulent phenomena is applied through VOF and LES methods, which gives more exact solution by using the multiphase flow analytical method. The verification of olaFlow model is demonstrated by comparing the experimental and numerical results for the interactions of regular waves-seabed and regular waves-composite breakwater-seabed. The characteristics of the spatial distributions of horizontal wave pressure, excess-pore-water pressure, mean flow velocity and mean vorticity on the upright caisson, and inside the rubble mound and seabed are discussed, as well as the relation between the mean distribution of vorticity size and mean turbulent kinetic energy. And the stability of composite breakwater are also discussed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.2
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• pp.92-100
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• 2016

Reliability analysis of tripod support structure for offshore wind turbine was performed. Extreme distribution function of peak response due to wind and wave loads was estimated by applying peak over threshold(POT) method. Then, stress based limit state function was defined by using maximum stress of support structure which was obtained by multiplying beam stress and concentration factor. The reliability analysis result was compared when maximum stress was calculated from shell element. Reliability index was evaluated using first order reliability method(FORM).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.5
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• pp.327-334
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• 2013

The interaction of oblique incident waves with a surface-mounted horizontal porous plate is investigated using matched eigenfunction expansion method under the assumption of linear potential theory. The new boundary condition on the porous plate suggested by Zhao et al.(2010) when it is situated at the still water surface is used. The imaginary part of the first propagating-mode eigenvalue in the fluid region under a horizontal porous plate, is closely related to the energy dissipation across the porous plate. By changing the porosity, plate width, wave frequencies, and incidence angles, the reflection and transmission coefficients as well as the wave loads on the porous plate are obtained. It is found that the transmission coefficients can be significantly reduced by selecting optimal porous parameter b = 5.0, also increasing the plate width and incidence angle.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.3
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• pp.99-109
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• 2000

Elastic dynamic responses analysis program for ship hulls considering slamming impact loads due to the voyage in large amplitude waves is developed. Ship hull structures are modeled by a thin-walled beam model in order to consider effects of shear deformation. The momentum slamming theory is used to derive nonlinear hydrodynamic forces considering intersection between wave particles and ship section. For the validation of the developed computer program, motions of a V-shaped simple section model and S-175 standard container model are calculated and analyzed. In each numerical example, time histories of relative displacement, velocity and vertical bending moment of a ship section are derived, considering the effect of slamming impacts in various wave conditions.ures near the free surface as well as the wake of the hydrofoil.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.4
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• pp.99-108
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• 1994

As a consequent result of our previous paper, "Development of Automatic Data Generation Program for Finite Element Structural Analysis of Oil Tankers"[1], the objective of this paper is to develop an automatic modeling program for the three-dimensional finite element structural analysis of hull modules of general commercial ships, especially oil tankers, bulk carriers, and container ships. Based on the proposed algorithm in [1], the followings are newly added: general applicability for three ship types, automatic mesh division interface with MSC/NASTRAN, direct wave load calculation interface, and Graphic User Interface technology in the process of input data preparation. The usefulness of this procedure is verified by calculation examples. examples.

• Journal of the Korean Geotechnical Society
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• v.27 no.12
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• pp.85-96
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• 2011

A breakwater is a important structure for both calmness of harbor and protection of the port facilities from waves generated from typhoons or wind. This study adopted the rubble mound breakwater, which is one of the most popular type of breakwaters in Korea. Rubble mound breakwater had been designed by considering only static condition previously. Recently, a dynamic wave-load due to waves has been also considered in designing breakwater. In design, the wave-load is assumed as an uniform load which only acts in the front slope of the breakwater. However, the assumption is not applicable in reality. In this study, therefore, a real-time wave-load acting on the breakwater instead of the uniform load is considered, and it is assumed to be acting on the seabed too. Based on the numerical analysis, it is found that there is a significant difference in the maximum settlement compared with the result predicted by the existing design method.

• Journal of Navigation and Port Research
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• v.37 no.2
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• pp.221-229
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• 2013

To find the influence of incident angle of wave on the moment of 3 storied steel moment resisting frame which is placed on the concrete rectangular pontoon, the fluid dynamic analysis is carried out, varying the period of wave from 5 to 15 second by 2 seconds. As increasing incident angle of wave to longitudinal axis, the influence of RAO-rolling is increased. The moment of longitudinal frame is increased apparently by the wave pressure when the incident angle is $0^{\circ}$. And the moment of the frame due to the wave pressure is decreased as the incident angle is increased. But the moment of frame due to acceleration caused from pitching and rolling is increased. It is shown that the increased moment when incident angle is $90^{\circ}$ is much greater than that of incident angle $0^{\circ}$.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.281-294
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• 2015

In order to quantitatively estimate the nonlinear destructive interaction of wave load with wind load, which is very vital for the optimal design of offshore wind energy converter, we carried out a hydraulic model test and wind tunnel test. As a substructure of offshore wind energy converter, we would deploy the monopile, which is popular due to its easiness in construction. Based on the simulation using Monte Carlo simulation using Kaimal spectrum and cross spectrum, the instantaneous maximum wind velocity is adjusted to 10 m/s. And, considering the wave conditions of the Western Sea where a pilot wind farm is planned to be constructed, $H_s=0.1m$, 0.15 m, 0.2 m is carefully chosen. It turns out that the nonlinear destructive interaction between the wind and wave loads acting on the offshore wind energy converter is more clearly visible at rough seas rather than at mild seas, which strongly support our deduction that a Large eddy, a swirling vortex developed near the bumpy water surface in the opposite direction of the wind, is the driving mechanism underlying nonlinear destructive interaction between the wind and wave loads.