• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.468-473
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• 2004

본 연구에서는 기존의 ㅡ자형, ㄴ자형, ㄷ자형 조파시스템이 경사진 방향으로 가동될 때 발생되는 에너지의 불연속성으로 인한 회절철상이나 구조물에서 반사된 파가 조파판에서 발생하는 재 반사 철상의 단점을 보완할 수 있도록 곡선형태의 조파판을 배치하여 수치실험을 행하였다. 조파판을 곡선형으로 배치시켜 실험 대상물에서부터 반사된 파가 가능한 조파판에 직각으로 부딪치도록 유도하였다. 편미분 격자생성기법을 도입하여 구성된 곡선형 격자망에서 Copeland(1985)의 완경사 방정식을 이용하여 수치해석 하였다. 우선, 1차원 실험영역에서 파를 생성하여 대상구조물에서 반사되어 돌아온 반사파 성분을 조파판에서 흡수하면서 입사파를 생성하는 현상을 재현하였다. 그 후, 실험영역을 2차원으로 확장시켜 조파판을 곡선형으로 배치하여 수치 실험하여 진행파와 회절파의 중첩으로 고안된 해석해와 수치 해를 비교하려다. 그 결과, 기존의 조파시스템에 비하여 에너지 불연속선에서의 회절 현상도 발생하지 않고 반사파 성분을 효율적으로 흡수하는데 효과적임을 알아냈다.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1993.07a
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• pp.51-54
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• 1993

수조안 주 실험구간에서의 유황이 주로 파랑에 의해서 영향을 받는 경우에는 실험결과의 정확도는 바로 사용된 조파기의 성능에 의해서 좌우된다. 컴퓨터를 이용한 조파기 제어시스템을 구축하기 위해서는 특정 조파판 운동에 대한 조파판에서의 수면변화 양상을 정확히 예측할 필요가 있다. 본 연구에서는 복소수 해석을 통하여 조파판 전달함수를 재구성하였으며 시간영역에서 전달함수를 개별적으로 구현할 수 있는 수치 필터를 제시한다. (중략)

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.2
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• pp.133-142
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• 1993

In a computer-controlling wave generating system. it is sometimes necessary to incorporate the discrete transfer operation of wave board into control circuit in order to control the system in a more delicate way. A numerical filter simulating the transfer operation of wave board in time domain is designed in the form of a discrete recursive filter. The filter was applied to some example board inputs f3r either regular or irregular wave conditions in order to evaluate the filter performance. The filter outputs were compared with the results of theoretical analysis or the discrete convolution method. showing their excellent agreements. The discrete realization of the filter presented hen is in fact of the bilinear transformation. It was shown that the transformation always avoids the aliasing errors, being surely applicable with a sufficient accuracy even for the band-unlimited transfer function of wave board.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.4
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• pp.58-65
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• 1992

In this paper, wave resistance for a submerged body is calculated by a higher order panel method. The Neumann-Kelvin problem is solved by the source or normal dipole distribution method. The body surface is represented by a bicubic B-spline and the singularity strengths are approximated by a bilinear form. The results calculated by the higher order panel method are compared with those by the lowest order panel method developed by Hess & Smith. The convergence rate of the higher order panel method is much better than the lowest order panel method. But the wave resistance calculated by the higher order panel method still shows discrepancy with an analytic solution at low Froude number like that by the lowest order panel method.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.6
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• pp.461-469
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• 2017

A segment of the wave board has been expressed as a submerged line segment in the two dimensional wave flume. The lower end of the line segment could be extended to the bottom of the wave flume and the other opposite upper end of the board could be extended to the free surface. It is assumed that the motion of the wave board could be defined by the sinusoidal motion in horizontal direction on either end of the wave board. When the amplitude of sinusoidal motion of the wave board on lower and upper end are equal, the wave board motion could express the horizontally oscillating submerged segment of piston type wave generator. The submerged segment of flap type wave generator also could be expressed by taking the motion amplitude differently for the either end of the board. The pivot point of the segment motion could play a role of hinge point of the flap type wave generator. Simplified analytic solution of oscillating submerged wave board segment in water of finite depth has been derived through the first order perturbation method at two dimensional domain. The case study of the analytic solution has been carried out and it is found out that the solution could be utilized for the design of wave generator with arbitrary shape by linear superposition.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1995.10a
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• pp.85-90
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• 1995

수조에서 조파기로 규칙파와 불규픽파를 발생하는 실험은 오래전부터 수행되었고, 최근에는 이를 수치계산으로 검증하려는 노력이 이루어지고 있다. 본 논문에서는 2차원 수조에서 조파판의 작동을 적절히 조절하여 임의의 지점에 plunger 형 쇄파를 발생시키고, 수치계산으로 이를 확인한 내용을 담았다. 쇄파를 만드는 연구는 Chan(1988)이 조화함수를 합성시키는 기법으로 실험을 수행한 바가 있고, Dommermuth 등(1988)이 이를 수치적으로 검증하였다. (중략)

• Bulletin of the Society of Naval Architects of Korea
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• v.16 no.1
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• pp.1-6
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• 1979

A method to determine the optimum drafts of waveboards of single and double-flap wavemaker is presented by using a linearized first-order wave theory and a linear regression method. A linear regression is verified to be quite simpler than the local disturbance consideration or regular-wave forming distance. It is pointed out that lower hinge should be deep enough to keep the upper flap vertical for a long wave length.

• Journal of the Society of Naval Architects of Korea
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• v.56 no.5
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• pp.418-426
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• 2019

To derive a simplified analytic solution which can be utilized as a fundamental solution for the wave maker design, a segment of the wave board has been idealized as a submerged line segment in a two dimensional domain of a wave flume. The lower end of the line segment could be located at arbitrary depth of the wave flume and the upper end of the board could be also submerged to any depth from the free surface. The freely oscillating motion of the wave board is assumed to be defined by determining the condition of horizontal oscillation on both ends differently. The submerged wave board oscillating in horizontal direction could be specified by selecting the amplitude, frequency and the phase lag differently on lower and upper ends of the board. The simplified two dimensional wave generated by the wave board segment has been obtained by the first order perturbation method. It is found that the general solution of the freely oscillating wave board in two dimensional domain could be decomposed into the solution of flap motion with lower end hinge and swing motion with upper end hinge. The case study of the analytic solutions has been carried out to evaluate the effect on the wave height due to the difference of oscillation frequency, phase difference and variation of stroke between for the motion of both ends. It is found that the solution of the freely oscillating wave board could be utilized for the development of high performance wavemaker especially for irregular waves.

• Journal of Ocean Engineering and Technology
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• v.33 no.6
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• pp.504-509
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• 2019

The wave-generation performance of a piston-type wave maker was analyzed using the numerical wave tank technique, and the numerical results were compared with theoretical solutions. A two-dimensional frequency domain analysis was conducted based on the Rankine panel method. Various parameters were used to examine the wave-generation performance, such as the width and gap of the wave board. The effects of the thickness of the wave board and of the gap from the bottom of the tank were evaluated. The difference in the amplitude of the generated wave between the analytical solution and the numerical result was examined, and its causes were addressed due to the gap flow between the bottom of the tank and the wave board. This parametric analysis can be utilized to design an optimum wave make parametric analysis to design an optimum wave maker that can generate waves with amplitudes that can be predicted accurately.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4_1
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• pp.137-150
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• 1992

A complete solution, exact to second-order, for wave motion forced by a hinged-wavemaker of variable-draft is presented. A solution for a piston type wavemaker is also obtained as a special case of a hinged-wavemaker. The laboratory waves generated by a plane wave board are shown to be composed of two components; viz., a Stokes second-order wave and a second-harnomic free wave which travels at a different speed. The amplitude of the second-harmonic free wave is relatively large in shallow water and decreases to less than 10% of the amplitude of the primary wave in deep water. Wavemakers with relatively deeper draft (i.e., hinged near the bottom) generate the free waves of smaller amplitude in shallow and intermediate water depths than the wavemakers with shallow draft. However, the opposite is predicted by theory in deep water.