• 대한조선학회논문집
• /
• 제29권3호
• /
• pp.53-58
• /
• 1992

파랑중(波浪中)에서 조종운동(操縱運動)을 하는 선박(船舶)에 있어, 실용적으로 선형(線形) 계산(計算)의 경우 파랑력(波浪力)을 단순한 정상(定常) 변동(變動) 외력(外力)으로 취급하는 수가 많다. 본 논문은 이와같은 경우에 있어서 파랑력에 의한 조종(操縱) 운동(運動)에 있어서의 Memory Effect를 조사하여, 이러한 실용 계산법(計算法)의 타당성(妥當性)을 논하였다. 그 결과를 요약하면 (1) $\omega_e$의 주파수(周波數)로 선체에 작용하는 정상(定常) 파랑력에 의한 Memory Effect도 거의 무시(無視)할 수 있다. (2) 따라서, 파랑중(波浪中)에서 조종 운동을 취급하는 경우, 간이 계산법으로서, 정수(靜水)중에서의 조타(操舵) 응답과 규칙파(規則波)중에서의 선체응답(船體應答)을 계산하여 이 둘을 합(合)하여도 무방하다. 그러나, 이상의 결론(結論)은 선형 운동에 국한(局限)된 것으로서, 실제의 조종 운동은 비선형성(非線形性)이 중요시(重要視)되므로 정상(定常) 파랑(波浪) 외력(外力)에 의한 Memory Effect를 좀더 엄밀(嚴密)하게 고찰(考察)하기 위해서는 비선형(非線形) Impulse Response Function을 구(求)하고 이를 이용하여 파랑력(波浪力)에 의한 Memory Effect를 평가(評價)하여야 할 것이다.

• 대한조선학회논문집
• /
• 제46권6호
• /
• pp.688-698
• /
• 2009

In this paper, the steady lift force acting on a slender body moving beneath regular wave systems of arbitrary wavelengths and directions of propagation is considered. The momentum conservation theorem and the strip method are used to obtain the hydrodynamic forces acting on the body and affecting its motions on the assumption that the body is slender. In order to obtain the vertical steady force acting on it, or the free surface suction force, the second-order hydrodynamic forces caused by mutual interactions between the components of the first-order hydrodynamic forces are averaged over time. The validity of the method is tested by comparison of the calculated results with experimental data and found to be satisfactory. Through some parametric calculations performed for a typical model, some useful results are obtained as to the depth of submergence of the body, wavelengths, directions, etc.

• Ocean Systems Engineering
• /
• 제10권4호
• /
• pp.399-414
• /
• 2020

A floating bridge is an innovative solution for deep-water and long-distance crossing. This paper presents a curved floating bridge's dynamic behaviors under the wind, wave, and current loads. Since the present curved bridge need not have mooring lines, its deep-water application can be more straightforward than conventional straight floating bridges with mooring lines. We solve the coupled interaction among the bridge girders, pontoons, and columns in the time-domain and to consider various load combinations to evaluate each force's contribution to overall dynamic responses. Discrete pontoons are uniformly spaced, and the pontoon's hydrodynamic coefficients and excitation forces are computed in the frequency domain by using the potential-theory-based 3D diffraction/radiation program. In the successive time-domain simulation, the Cummins equation is used for solving the pontoon's dynamics, and the bridge girders and columns are modeled by the beam theory and finite element formulation. Then, all the components are fully coupled to solve the fully-coupled equation of motion. Subsequently, the wet natural frequencies for various bending modes are identified. Then, the time histories and spectra of the girder's dynamic responses are presented and systematically analyzed. The second-order difference-frequency wave force and slowly-varying wind force may significantly affect the girder's lateral responses through resonance if the bridge's lateral bending stiffness is not sufficient. On the other hand, the first-order wave-frequency forces play a crucial role in the vertical responses.

• 한국해안·해양공학회논문집
• /
• 제29권2호
• /
• pp.92-108
• /
• 2017

본 연구에서는 Navier-Stokes solver에 기초한 3차원혼상류해석법인 TWOPM-3D를 적용하여 고립파와 연안교량과의 상호작용을 수치해석적으로 수행하였다. 이 때, 고립파는 수치파동수로에서 수치조파되었고, 작용파력의 타당성은 본 수치해석결과와 기존의 실험결과와의 비교 분석으로부터 검증되었다. 이로부터 고립파의 파고, 교량의 종류와 위치 및 거더 수 등의 변화에 따른 수위변화와 유속변화를 포함하여 수평파력과 연직파력(연직상방파력과 연직하방파력)의 변동특성을 면밀히 검토하였다. 거더교의 경우 입사파고의 증가에 따라 수평파력과 연직파력의 각 최대치는 증가하는 경향을 나타낸 반면, 거더 수의 변화에 따라서는 서로 상이한 변동특성을 나타내었으며, 연직파력에 수중에 연행되는 공기가 큰 영향을 미치는 것 등을 결과로부터 알 수 있었다.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2010년도 추계학술대회 초록집
• /
• pp.171-171
• /
• 2010

An innovative design of a floating-buoy wave energy converter (WEC) using hydrostatic transmission (HST), named HSTWEC, is presented in this paper. The system is designed to convert ocean wave fluctuation into electricity by using the HST circuit and an electric generator. Based on the floating-buoy concept, the wave forces the sub-buoy to move up and down. Consequently, the electric power can be obtained from the generator in both the moving directions of the sub-buoy through the HST circuit as shown in Fig. 1. In order to investigate the HSTWEC operations, a mathematical model of the system is indispensible. In addition, the method to control the HSTWEC, including: pump displacement control, tension adjustment control and ballast weight control, is also discussed in this paper. Finally, the design concept as well as simulation results indicated that this HSTWEC design is an effective solution and possible to fabricate for wave energy generation.

• Ocean Systems Engineering
• /
• 제5권4호
• /
• pp.245-259
• /
• 2015

The numerical simulation of wave slamming on a 3D platform deck was investigated using a coupled Level-Set and Volume-of-Fluid (CLSVOF) method for overset grid system incorporated into the Finite-Analytic Navier-Stokes (FANS) method. The predicted slamming impact forces were compared with the corresponding experimental data. The comparisons showed that the CLSVOF method is capable of accurately predicting the slamming impact and capturing the violent free surface flow including wave slamming, wave inundation and wave recession. Moreover, the capability of the present CLSVOF method for overset grid system is a prominent feature to handle the prediction of wave slamming on offshore structure.

• 대한토목학회논문집
• /
• 제5권4호
• /
• pp.87-94
• /
• 1985

본 논문에서는 최근에 개발된 심해용 구조물인 guyed tower 의 동력학적 해석방법과 이의 주요 설계인자인 guying system 의 강성 및 구조물기초부에서의 회전강성이 구조물의 거동에 미치는 영향에 대하여 연구하였다. 해석기법으로는 guying system 의 초기강성을 사용하여 구한 자유진동 모우드의 중첩법을 주로 고찰하였으며, 그 결과를 몇가지의 다른방법에 의한 결과와 비교검토하였다. 예제해석은 세계최초의 guyed tower 인 Lena tower 를 표준구조물로 택하여 수행되었다.

• 한국소음진동공학회논문집
• /
• 제20권8호
• /
• pp.753-760
• /
• 2010

In this paper, the lifting analysis of a floating crane with a shipbuilding block is performed. Since floating cranes are operated in ocean waves, six degree-of-freedom motions are considered in the dynamic equations of motions of the floating crane and the block. The boom of the floating crane is considered as an elastic body in the analysis, and is modeled as three dimensional beam based on the finite element formulation. The hydrostatic and hydrodynamic forces by a regular wave are considered as external forces. By solving the equations of motions numerically, the dynamic responses of the floating crane and the block are simulated. The simulation results with different wave directions are compared and the conditions which cause maximum responses are discussed.

• 한국해양공학회지
• /
• 제11권2호
• /
• pp.91-99
• /
• 1997

This paper presents theoretical formulations and numerical computations for predicting first-and second-order hydrodynamic force on a ship advvancing in waves. The theoretical formulation leads to linearized radiation and diffration problems solving the three-dimensional Green function integral equations over the mean wetted body surface. Green function representing a translating and pulsating source potantial for infinite water depth is used. In order to solve integral equations for three dimentional flows using Green function efficiently, the Hoff's method is adopted for numerical calculation of the Green function. Based on the first-order solution, the mean seconder-order forces and moments are obtained by directly integrating second-order pressure over the mean wetted body surface. The calculated items are carried out for analyzing the seakeeping characteristics of Series 60. The calculated items are hydrodynamic coefficients, wave exciting forces, frequency response functions and addd resistance in waves.

• 한국해양공학회지
• /
• 제6권2호
• /
• pp.94-102
• /
• 1992

This paper presents the method of numerical analysis concerned with the hydropdynamic forces and moments of the floating bodies exerted by waves. The analytic methods of hydrodynamic wave forces and moments for large volume structures are generally classified into four categories ; the strip method, the boundary element method, the finite element method, and the potential matching method. In the case of the comparatively large structures, diffraction theory can be applied. However, there are no application limits of diffraction theory which have been known concerning with the analytic method of the rectangular structures. In this paper, the two-dimensional B.E.M. is treated for a moored small rectangular structure in order to evaluate applicability of diffraction theory. Numerical calculation is carried out for the structure. The results are compared with some other ones for verification. The result shows that diffraction theory is applicable to structures smaller than 0.15 in the ratio of the representative structure length d to wave length L for rectangular ones.