• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.1
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• pp.58-65
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• 2012

In this study, to reduce the motion of the vessels resulting from resonance and secondary undulation by long-period waves, numerical review on the control performance of resonator was carried out by attaching the resonator to the established harbor of real waters. In the numerical analysis, CGWAVE MODULE of commercial software SMS(Surface water Modeling System), a finite element model based on 2-dimensional elliptical mild slope equation was applied, and through comparative analysis of the existing experiments and analysis results on the rectangular model ports, the validity of the friction coefficients in which validity and effectiveness of SMS on the secondary undulation analysis is applied was verified. Based on this, the control performance of resonator was confirmed through comparative review of the secondary undulation according to whether or not to attach the resonator to rectangular harbor. In addition, to reduce long-period motion of the moored vessels and the secondary undulation which may occur in Pohang new port, the method to move the resonant period which causes abnormal motion of the vessels to long-term one was discussed through application of the resonators with various sizes, thereby identifying the availability.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.4
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• pp.318-328
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• 1993

A series of long wave measurements was made in the region of Shikotan Island (the South Kuril Islands) during 1990-1992: 7 bottom pressure stations were installed in 5 bays and inlets of Shikotan and 3 precise microbarographs were situated at the shore. The observations were taken in order to monitor tsunami waves, estimate resonance features of coastal topography, and investigate seiche generation mechanism. It was found that forced long waves dominate in the motions with periods exceeding 2 hours, freely propagating long waves prevail at periods of 30-120 min and eigen-oscillations of bays (seiches) are the predominant type of long waves at periods less than 30 min. The Helmholtz mode with period 30 min in Krabovaya Bay and 18.5 min in Malokurilskaya Bay is the most important type of wave motion in the inner Shikotan basins. There is a good correlation between passages of atmospheric disturbances and generation of seiches near the coast of Shikotan Island. In particular, jumps in atmospheric pressure excite seiches in different bays simultaneously, in each one with the corresponding dominant period. The atmospheric spectra were remarkably smooth and stable, and could be described by a $\omega$$^{-2}$26/ power law.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.9
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• pp.743-748
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• 2016

Ship's diesel engines have intrinsic problem to make vibrations caused by cylinder explosion and unbalanced rotating mass. These vibrations might induce noises, are transferred to hull and neighboring structures and cause secondary vibrations. This paper suggests the use of an additional dynamic absorber with a sub-vibration system to reduce the aforementioned vibrations. This dynamic absorber is designed based on an analysis of the free vibration of the engine shafting system and the forced vibrations.

• Journal of Ocean Engineering and Technology
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• v.24 no.6
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• pp.51-60
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• 2010

In this study, the performance evaluation of a conventional wave resonator at the entrance of a port or a pier against secondary undulation has been performed using 2D hydrodynamic modeling within port. A wave resonator has been designed for the attenuation of the secondary undulation induced by the long-periodic waves. The controlled performance of the wave resonator has been numerically investigated for CGWAVE MODULE of finite-element model of SMS (Surface water Modeling System) based on the elliptic mild-slope wave equation. SMS was verified though the comparisons with analytical solution performed by Ippen and Goda (1963). Also, It was confirmed that a wave resonator of a rectangular model harbor is effective enough to control the secondary undulation when it compares variation of water level with the case of no resonance system. From the above results, amplification phenomenon induced by long-period waves transferred from 1900 sec to 2100 sec when it applied a wave resonator in Busan Gamcheon Port which is a deep-sea. And it was confirmed that a wave resonator of Pohang New Port attenuates largely long-period waves which are within the range of 300 sec induced by long-period motion of the moored ship.