• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.2
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• pp.89-99
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• 2001

In the present paper, Helmholtz resonator, which is widely used as a sound-amplification device, is applied to the development of seawater-exchanging breakwater. The incident waves can induce a large response in the resonator when incident wave frequency is close to one of natural modes of the resonator. Largely amplified potential energy due to the resonance supplies clean seawater into the harbor side throughout the channel. Flow supplied by the resonator circulates the seawater of harbor and helps to improve water quality. Within the framework of linear potential theory, matched asymptotic expansion method is employed to analyze the wave responses in a resonator. The semi-circular shape of the resonator has been chosen as an analytic model for mathematical simplicity. The wave responses of both single and arrays of Helmholtz resonator are investi¬gated. To validate an analytic solution, model test is conducted at 2-dimensional wave tanle Wave hcights in the resonator and velocity at the channel are measured for the state of valve-on and valve-off.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.87-93
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• 1993

The motion response of a ship moored in a rectangular harbor excited by long waves has been studied theoretically and experimentally. Experiments are performed in a shallow basin. A ship model is set moored by soft springs at various positions in a model harbor subjected to regular waves with period ranging from 2 to 3 seconds. Wave and ship responses are measured and compared with theory. It is found that theoretical results agree qualitatively with experimental results. The main source of quantitative discrepancies is presumably due to real fluid effects such as separation at the harbor entrance and friction on harbor boundaries.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.1 no.1
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• pp.81-86
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• 1989

Herein the surge-heave-pitch motion of a ship has been analyzed within the framework of linear potential theory. The ship is assumed slender weakly moored along the centerline of a rectangular harbor with constant depth and straight coastline. The method of matched asymptotic expansion is us-ed to obtain the leading-order solution. The ship and harbor responses to incident long waves can be re-presented in terms of Green's function, which is the solution of the Helmholtz equation satisfying necessary boundary conditions. Numerical results clearly indicate the importance of the surge motion.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.1
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• pp.72-80
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• 1996

Two analytical solutions for oscillations in a rectangular harbour are presented. In this paper, the correct solution is obtained by use of matched asymptotic expansion method, which was first derived by Mei(1989). The other solution derived from eigenfunction expansion method is also presented, in which more accurate numerical integration is employed. In order to check the solutions, amplification factors inside the harbor are calculated and plotted by both analytical methods and numerical boundary integral equation method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.1
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• pp.56-63
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• 1985

Methods for evaluating the added masses of square and hexagonal structures with fluid gap are presented. For a sufficiently small fluid gap, an analytical expression for the added mass is found using the method of matched asymptotic expansion. Experimental data and numerical results using finite element method are also obtained for various sizes of fluid gap. It is shown that added masses increase in inverse proportion to the fluid gap as it becomes smaller. Experimental data, theoretical and numerical results are in good agreement.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.3
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• pp.170-179
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• 2019

In this study, the wave responses in a 'Y'shape water channel resonator for amplifying wave energy of a low density has been investigated. A water channel resonator is composed of the long channel and wave guider installed at the entrance. If the period of the incident waves coincides with the natural period of the fluid in a water channel resonator, resonance occurs and the internal fluid amplifies highly to a standing wave form. In order to analyze the wave response in a water channel resonator, we used the matched asymptotic expansion method and boundary element method. The both results were in good agreement with the results of the model test carried out in the two-dimensional wave tank of Jeju National University. Wave guider has an optimum length and installation angle according to the period of the incident wave, and especially effective in enhancing the amplification factor in a period range deviated from the resonance period. It is expected that the wave energy can be effectively extracted by placing the point absorber wave energy converter at the position of anti-node where the maximum wave height is formed by the internal fluid resonance.