• 한국해양공학회지
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• 제38권5호
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• pp.218-231
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• 2024

In harsh environments, an floating production storage and offloading (FPSO) is occasionally damaged by impact loads, such as bow flare slamming and green water. This study conducted an impact load measurement experiment on a model of an FPSO bow in a 2D wave tank. Three types of frequency-focused waves (steep, spilling, and plunging) were generated, and the speed and slope of the waves were measured. Seven wave probes were placed in a row, and the wave elevation was measured to determine the speed and slope of the waves. In addition, the side of the 2D wave tank was photographed with a high-speed camera. The speed and slope of the waves obtained from the wave probe array agreed well with those obtained from the photographs taken using a high-speed camera. In the case of a steep wave, wave runup occurred at the bow before the wave reached the bow of the FPSO, so no impact load was generated, and only hydrostatic pressure was measured. Impact loads were generated in the spilling and plunging waves, and the magnitude of impact loads using the Von Karman's estimation formula and the impact loads measured in model tests showed similar values.

• 한국해양공학회지
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• 제35권2호
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• pp.113-120
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• 2021

In order to perform a precise wave tank experiment, it is necessary to maintain the incident wave generated by the wavemaker in a steady state and to effectively remove the reflected waves. In this paper, a combined sloping-wall-type punching plate wave absorber was proposed to attenuate reflected waves effectively in a two-dimensional mini wave tank. Using the four-point reflection separation method, the reflected waves were measured to determine the reflection coefficients. Experiments were conducted under various punching plate porosities, sloping plate angles, and incident wave conditions to evaluate the performance of the combined punching plate wave absorber. The most effective wave absorbing performance was achieved when the porosity was 10% and the inclination angle of the punching plate was 18.6° under the present condition. It was also found that the installation of the sloping plate could improve the wave attenuation performance by generating the shoaling effect of the incident wave.

• 한국해양공학회지
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• 제21권5호
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• pp.1-8
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• 2007

A long wave induced by a Gaussian-shape submarine landslide is simulated by a 2D fully nonlinear numerical wave tank (NWT). The NWT is based on the boundary element method and the mixed Eulerian/Lagrangian approach. Using the NWT, physical characteristics of land-slide tsunami, including wave generation, propagation, particle kinematics, hydrodynamic pressure, run-up and depression, are simulated for the early stage of long wave generation and propagation. Various sliding mass heights are applied to the developed model for a systematic sensitivity analysis. In particular, the fully nonlinear NWT results are compared with linear results (exact body-boundary conditions with linear free-surface conditions) to identify the nonlinear effects in the respective cases.

• International Journal of Naval Architecture and Ocean Engineering
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• 제4권3호
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• pp.281-290
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• 2012

Hydrodynamic analysis of a surface-piercing body with an open chamber was performed with incident regular waves and forced-heaving body motions. The floating body was simulated in the time domain using a 2D fully nonlinear numerical wave tank (NWT) technique based on potential theory. This paper focuses on the hydrodynamic behavior of the free surfaces inside the chamber for various input conditions, including a two-input system: both incident wave profiles and forced body velocities were implemented in order to calculate the maximum surface elevations for the respective inputs and evaluate their interactions. An appropriate equivalent linear or quadratic viscous damping coefficient, which was selected from experimental data, was employed on the free surface boundary inside the chamber to account for the viscous energy loss on the system. Then a comprehensive parametric study was performed to investigate the nonlinear behavior of the wave-body interaction.

• 해양환경안전학회지
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• 제18권5호
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• pp.388-397
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• 2012

본 연구에서는 3차원수치파동수조에 규칙파뿐만 아니라 안정적인 불규칙파가 조파될 수 있는 새로운 조파시스템 3D-NIT(3-Dimensional Numerical Irregular wave Tank)모델을 제안한다. 그의 타당성을 검증하기 위하여 1) 조파지점에서 계산파형과 목표파형을 비교 검토하고, 2) 경사수심역에 설치된 호안구조물을 대상으로 산정된 기존 월파량에 대한 실험치와 비교 검토하며, 3) 연직원주 구조물에 작용하는 파력 및 구조물에 의한 파랑변형의 해석에 적용하여 기존의 수치 및 수리실험결과와 비교한다. 이상의 결과를 기초로 3D-NIT모델을 경사수심역에 설치된 원주구조물에 작용하는 쇄파력의 해석에 적용하여 입사파고, 구조물의 이격거리 등에 따른 작용쇄파력의 특성을 규명하고, 더불어 국내현장의 특수방파제에 적용하여 반사율, 월파량 등을 검토하였다. 그 결과 본 연구에서 제안하는 3D-NIT모델을 이용한 수치실험결과는 기존의 수리모형실험을 잘 재현하고 있음을 확인하였고 복잡한 형상을 갖는 해안구조물의 해석에 적용할 수 있음이 확인되었다.

• 한국해양공학회지
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• 제17권6호
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• pp.7-15
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• 2003

A Digital Wave Tank simulation technique, based on a finite-difference method and a modified marker-and-cell (MAC) algorithm, is applied in order to investigate the characteristics of nonlinear Tsunami propagations and their interactions with a 2D sloping beach, Ohkushiri Island, and to predict maximum wove run-up around the island. The Navier-Stokes (NS) and continuity equation are governed in the computational domain, and the boundary values are updated at each time step, by a finite-difference time-marching scheme in the frame of the rectangular coordinate system. The fully nonlinear, kinematic, free-surface condition is satisfied by the modified marker-density function technique. The near shore Tsunami is assumed to be a solitary wave, and is generated from the numerical wave-maker in the developed Digital Wave Tank. The simulation results are compared with the experiments and other numerical methods, based on the shallow-water wave theory.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.231-239
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• 2003

A Digital Wave Tank simulation technique based on a finite-difference method and a modified marker-and-cell (MAC) algorithm is applied to investigate the characteristics of nonlinear Tsunami propagations and their interactions with a 2D sloping beach and Ohkushiri island, and to predict maximum wave run-up around the island. The Navier-Stokes (NS) and continuity equation are governed in the computational domain and the boundary values updated at each time step by a finite-difference time-marching scheme in the frame of rectangular coordinate system. The fully nonlinear kinematic free-surface condition is satisfied by the modified marker-density function technique. The Nearshore Tsunami is assumed to be a solitary wave and generated from the numerical wavemaker in the developed Digital Wave Tank. The simulation results are compared with the experiments and other numerical methods based on the shallow-water wave theory.

• 한국전산구조공학회논문집
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• 제33권5호
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• pp.287-296
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• 2020

본 연구에서는 2D 조파수조를 통해 수행된 모형시험결과를 기반으로 원형실린더에 분포하는 파랑충격압력을 시간에 따라 계측하고 이를 CFD해석 결과와 비교하였다. 전산유체역학 해석을 통해 파랑충격력에 직접평가법에 관한 효용성을 확인할 수 있었고, 실험으로부터 구한 파랑충격 시계열 데이터를 그대로 원형단면을 갖는 실제 해양구조물의 부재에 적용하였다. 실린더에 분포하는 변위 및 응력의 특성과 특이점이 바뀌는 것을 확인하였고 실제 시계열을 적용하는 것이 해양구조물의 강도평가를 보다 정확하게 평가할 수 있음을 확인할 수 있었다. 또한, 선수부에 요구되는 외판의 최소선급규정에 따른 두께 경험식들을 분석하여 적용하고자 하였다. 동일한 재료 물성치를 갖는 강재에 관해 선수외판에 요구되는 구조물의 최소두께와 원형단면 부재에 요구되는 최소두께를 비교·분석하였고 이를 통해 NORSOK standard에 제시되어 있는 구조물의 손상기준을 활용하여 허용 두께치를 추정하고자 하였다. 특히 해양구조물의 갑판충격력(wave in deck)의 경우 이와 관련된 경험식이나 최소두께 요구사항들이 정립되어 있지 않기 때문에 본 연구를 통해 파랑충격력에 따라 요구되는 판재의 최소두께를 제안하고자 하였다.

• 대한토목학회논문집
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• 제36권5호
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• pp.831-838
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• 2016

최근 해안공학분야에서 식생을 활용하는 연안방재시스템에 관한 관심이 증가하고 있다. 이에 본 연구에서는 쓰나미-식생 비선형 상호작용에 의한 파동장과 유동장을 해석하기 위하여 식생항력에 따른 에너지소산을 직접 해석할 수 있는 3차원 수치파동수조를 기존의 3-D N-S solver (LES-WASS-3D ver. 2.0, HYMO-WASS-3D)를 토대로 개발하였다. 그리고 기존의 실험결과와 비교 및 검토를 통한 수치파동수조의 적용성을 평가하였다. 그 결과 레이놀즈수에 따라 능동적으로 추정되는 항력계수를 고려한 경우가 평균 항력계수를 적용한 경우보다 실험에서 얻어진 각 지점의 시간파형을 잘 재현하였다. 또한 식생밀도 및 입사파고에 따라 계산된 고립파의 전달률이 실험의 측정값과 높은 일치도를 나타내었다. 이로써 본 연구에서 식생에 의한 항력으로서 동적항력계수를 적용한 3차원 수치파동수조의 타당성 및 유효성을 확인하였다.

• 한국해양공학회지
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• 제23권6호
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• pp.1-6
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• 2009

An Overtopping Wave Energy Convertor (OWEC) is an offshore wave energy convertor used for collecting overtopping waves and converting the water pressure head into electric power through hydro turbines installed in a vertical duct affixed to the sea bed. A numerical wave tank based on the commercial computational fluid dynamics code Fluent is established for the corresponding analysis. The Reynolds Averaged Navier-Stokes equation and two-phase VOF model are utilized to generate the 2D numerical linear propagating waves, which are validated by the overtopping experiment results. Calculations are made for several incident wave conditions and shape parameters for the overtopping device. Both the incident wave periods and heights have evident effects on the overtopping performance of the OWEC device. The computational analysis demonstrates that the present overtopping device is more compatible with longer incident wave periods.