• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.168-177
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• 2020

Many coastal engineering designs utilize empirical formulas containing the Equivalent Deep-water Wave Height (EDWH), which is normally given a priori. However, no studies have explicitly discussed a method for determining the EDWH and the resulting design wave heights (DEWH) under irregular wave conditions. Unfortunately, it has been the case in many design practices that the EDWH is incorrectly estimated by dividing the Shallow-water Wave Height (SWH) at the structural position with its corresponding shoaling coefficient of regular wave. The present study reexamines the relationship between the Shallow-water Wave Height (SWH) at the structural position and its corresponding EDWH. Then, a new procedure is proposed to facilitate the correct estimation of EDWH. In this procedure, the EDWH and DEWH are determined differently according to the wave propagation model used to estimate the SWH. For this, Goda's original method for nonlinear irregular wave deformation is extended to produce values for linear shoaling. Finally, exemplary calculations are performed to assess the possible errors caused by a misuse of the wave height calculation procedure. The relative errors with respect to the correct values could exceed 20%, potentially leading to a significant under-design of coastal or harbor structures in some cases.

• 산업기술연구
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• 제17권
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• pp.261-275
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• 1997

The objective of this paper is to develop two numerical model for predicting the wave height with set-up/down near the surfzone on a arbitrary beach profile. Two wave models, regular wave model and random wave model, are based on the energy flux equation with the energy dissipation effects. The developed numerical models are verified by comparison of numerical results with analytical solutions that are derived under the simple conditions. The characteristics of parameters included in each model are then investigated and decided to the range of behaviour by the sensitivity analysis. For sensitivity analysis, we carried out total 46 laboratory tests. Finally, the developed numerical models are applied to the field where the wave height near the surfzone has been measured. From the applications of numerical models, it is concluded that the developed numerical models may accurately predict the wave height with the set-up/down near the surfzone on a arbitrary beach profile.

• 한국해양공학회지
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• 제1권1호
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• pp.33-38
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• 1987

The first order mation responses of a floating structure and the hydrodynamic forces in regular waves are obtained by means of the linear potential theory. The first order potential is obtained directly from the numerical solution of the improved Green integral equation which is characterized by the combined surface distribution of sources and normal doublets. The mean second order wave drift force is also calculated by means of the near field method. It seems that the present method gives more accurate numerical results than other methods and the agreement between numerical and experimental results appears to be satisfactory.

• 한국해안해양공학회지
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• 제5권4호
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• pp.395-405
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• 1993

불규칙 파낭이 갖는 중요한 특성 중의 하나인 파군특성을 파낭 연이음개염과 에너지 이역 개념을 이용하여 해석하였다. 일정한 주기와 파고를 가지고 임의로 발생시킨 규칙파군에 적용하여 파군에 대한 기초적 특성을 파악한 후, 동해안에서 관측된 불규칙 파랑의 파군특성을 해석하였다. 불규칙 파낭의 파군특성을 정확히 해석하기 위해서는 기존의 스펙트럼 해석뿐만 아니라 파낭 연이음개념 및 에너지 이역개염을 함께 검토하여야 한다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.733-742
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• 2020

Taking the cylindrical float of the floating fence of a floating litter collection device as the research object, based on the shallow immersion characteristics of the cylindrical float, the Morison equation is modified, and the interaction between regular waves and the partially immersed horizontal cylindrical float is discussed in combination with scale model test. The results show that the modified Morison equation can accurately predict the wave force of the horizontal cylindrical float and reveal the influence of amplitude, immersion depth and period on the wave force of the cylindrical float. For partially immersed cylindrical floats, the wave force increases with the increase in wave height and decays with the increase in period. The positive value distribution of the wave force is larger than that of the negative direction, and the difference between the positive and negative directions is mainly affected by the immersion depth.

• 한국해양공학회지
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• 제19권6호통권67호
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• pp.8-15
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• 2005

Wave energy has been considered to be one of the most promising energy resources for the future, as it is pollution-free and an abundant natural resource. However, since it has drawbacks of non-stationary energy density, it is necessary to change the wave energy into a simple concentrated energy. Progressive waves in a coastal area can be amplified, swashed, and overtopped by a wave overtopping control structure. By conserving the quantity of overflow in a reservoir, the kinetic energy of the waves can be converted to the potential energy with a hydraulic head above the mean sea level. The potential energy in the form of a hydraulic head can be utilized to produce electric power, similar to hydro-electric power generation. This study aims to find the most optimal shape of wave overtopping structure for maximum overtopping volume of sea water; for this purpose, we carried out the wave overtopping experiment in a wave tank, under both regular and irregular wave conditions.

• Ocean Systems Engineering
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• 제11권1호
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• pp.1-16
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• 2021

Experimental and numerical investigations were conducted to study the performance of a surface-fixed horizontal porous wave barrier in regular waves. The characteristics of the reflection and transmission coefficients, energy dissipation, and vertical wave force were examined versus different porosities of the barrier. Numerical simulations based on 3D Reynolds Averaged Navier-Stokes equations with standard low-Re k-ε turbulent closure and volume of fluid approach were accomplished and compared with the experimental results conducted in a 2D wave tank. Experimental measurements and numerical simulations were shown to be in satisfactory agreement. The qualitative wave behavior propagating over a horizontal porous barrier such as wave run-up, wave breaking, air entrapment, jet flow, and vortex generation was reproduced by CFD computation. Through the discrete harmonic decomposition of the vertical wave force on a wave barrier, the nonlinear characteristics were revealed quantitatively. It was concluded that the surface-fixed horizontal barrier is more effective in dissipating wave energy in the short wave period region and more energy conversion was observed from the first harmonic to higher harmonics with the increase of porosity. The present numerical approach will provide a predictive tool for an accurate and efficient design of the surface-fixed horizontal porous wave barrier.

• 한국항만학회지
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• 제6권1호
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• pp.69-91
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• 1992

A new type of horizontal submerged break water or fixed structure to control waves near coastal area is introduced to focus wave energy before or behind it. Intentionally, the water depth near the structure is changed gradually to get a refraction and diffraction effect. The concentration of wave energy due to the structure was analyzed for the selected design of structure. The shape of the submerged structure in consideration is a circular combined with elliptical curve not to cause reflection of waves at the extreme edge of the structure but cause wave scattering. The direction of the structure against the incident wave is changed easily in the model Applying a regular wave train the following were examined. 1) whether a crescent plain submerged structure designed by the wave refraction theory can concentrate wave energy at a focal zone behind and before it without wave breaking phenomenon. 2) Location of maximum wave amplification factor in terms of the incident wave direction, wave period, etc. In any event the study would contribute to control waves near coastal area and to protect a beach from erosion without interruption of ocean view it is an useful study for the concentration of wave energy efficiently with the increase of wave height.

• 한국해안해양공학회지
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• 제15권3호
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• pp.167-175
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• 2003

본 연구에서는 규칙파를 적용한 수중방파제의 반사특성을 수리모형실험으로 조사하였다. 다양한 형상의 수중방파제에 의한 반사특성을 수리실험 및 수치적으로 검토하였으며, 실험에 사용된 수중방파제의 형상은 사각형, 삼각형, 사다리꼴 및 반원형이다. 수리모형실험 결과는 고유함수전개법을 이용하여 해석한 결과와 비교하였으며, 수리실험에 의한 반사계수가 해석에 의한 결과보다 약간 작게 나타났지만, 두 결과는 비교적 잘 일치하였다. 본 연구결과는 실제설계에 있어 수중방파제의 형상을 결정하는데 있어 유용한 자료가 될 수 있을 것이다.

• International Journal of Ocean System Engineering
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• 제3권4호
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• pp.188-208
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• 2013

The motion response of floating structures should be adequately low to permit the operation of rigid risers along with dry well heads. Though Spar platforms have low heave responses under lower sea state, could become unacceptable in near resonance region of wave periods. Hence the hydrodynamic response, heave in particular, must be examined to ensure that it is minimized. To reduce heave motions, external damping devices are introduced and one such effective damping device is heave plate. Addition of heave plate can provide additional viscous damping and additional added mass in the heave direction which influence the heave motion. The present study focuses on the influence of heave plate on the hydrodynamic responses of Classic Spar in regular waves. The experimental investigation has been carried out on a 1:100 scale model of Spar with single and double heave plates in regular waves. Numerical investigation has been carried out to derive the hydrodynamic responses using ANSYS AQWA. The experimental results were compared with those obtained from numerical simulation and found to be in good agreement. The influence of disk diameter ratio, wave steepness, pretension in the mooring line and relative spacing between the plates on the hydrodynamic responses of Spar are evaluated and presented.