• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.5
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• pp.314-326
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• 2014

On 31 March 2007, the abnormal wave occurred along the western coast of Korea. In order to investigate the generation mechanism of abnormal waves and to understand the amplification process of the abnormal waves, the observed data were analyzed and one-dimensional numerical model experiments were performed by using both the linear shallow water equation and the linear Boussinesq equation models. Various types of pressure jump for the abnormal waves previously proposed by other researchers were reviewed. As a result, it was not possible to reproduce the abnormal waves from the previously proposed pressure jumps. In this study, we proposed a new form of pressure jump, and numerical simulations were performed in order to check the validity of the proposed pressure jump. The numerical results showed that the calculated period of abnormal waves and the maximum water elevations agreed reasonably well with those of the observations.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.2
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• pp.75-82
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• 1990

A Wave transformation including wave breaking in shallow water region is a non-linear and discontinuous Phenomenon. Therefore, a so-called individual wave analysis (or a wave by wave analysis) rather than spectral approach seems to be adequate to investigate the wave transformation in such regions. In this study, a theoretical joint distribution of wave height, period and wave direction of zero-down crossing waves, which is required in the individual wave analysis in the shallow water region, is derived based on the hypothesis that sea surface is a Gaussian stochastic process and that a band-width of energy spectra is sufficiently narrow. The derived i oint distribution is found to be an effective measure to investigate characteristics of three-dimensional random wave field in shallow water through field measurements.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.139-148
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• 2000

A numerical model is represented to calculate the wave fields such as the reflected waves, the transmitted waves, and depth averaged velocities over submerged breakwaters for the normally incident wave trains of nonlinear monochromatic wave. The numerical model is correctly formulated by using both the finite amplitude shallow water equations with the effects of bottom friction and the explicit dissipative Lax-Wendroff finite difference scheme, also satisfactorily verified by comparison with the other results. The behaviors of reflected and transmitted waves with respect to geometric parameters of submerged breakwater such as the slope, crest depth, and crest width are numerically analyzed in this study. In particular, the reflection and transmission coefficients are quantitatively calculated as the function of geometric parameter of submerged breakwater. It is found that the crest depth among parameters related to practical design may be the most important parameter in designing the submerged breakwater. Therefore, the effective and economic performances of submerged breakwater should be depended on the determination of optimal crest depth.

• Bulletin of the Society of Naval Architects of Korea
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• v.23 no.2
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• pp.21-26
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• 1986

An analysis is made of hydrodynamic forces acting horizontally on a two-dimensional cylinder, when it is exposed to incident waves and consequently undergoes a swaying motion in shallow water. Applying the method of matched asymptotic expansions the added mass, wave damping and the wave exciting force are obtained in terms of the difference in potential across the cylinder in a simple manner. The potential jump is related to the so-called blockage coefficient which is determined purely from geometry. It is found that the wave damping coefficient can not exceed the blockage coefficient.

• Journal of applied mathematics & informatics
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• v.28 no.1_2
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• pp.383-395
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• 2010

In the present paper, we construct the traveling wave solutions involving parameters of nonlinear evolution equations in the mathematical physics via the (3+1)- dimensional potential- YTSF equation, the (3+1)- dimensional generalized shallow water equation, the (3+1)- dimensional Kadomtsev- Petviashvili equation, the (3+1)- dimensional modified KdV-Zakharov- Kuznetsev equation and the (3+1)- dimensional Jimbo-Miwa equation by using a simple method which is called the ($\frac{G'}{G}$)- expansion method, where $G\;=\;G(\xi)$ satisfies a second order linear ordinary differential equation. When the parameters are taken special values, the solitary waves are derived from the travelling waves. The travelling wave solutions are expressed by hyperbolic, trigonometric and rational functions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.2
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• pp.77-89
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• 1991

Based on Boussinesq equation, the parabolic approximation equation is used to analyse the propagation of shallow water waves with currents over slowly varying depth. Rip currents (jet-like) occur mainly in shallow waters where the Ursell parameter significatly exceeds the range of application of Stokes wave theory. We employ the nonlinear parabolic approximation equation which is valid for waves of large Ursell parameters and small scale currents. Two types of currents are considered; relatively strong and relatively weak currents. The wave propagating over rip currents on a sloping bottom experiences a shoaling due to the variations of depth and current velocity as well as refraction and diffraction due to the vorticity of currents. Numerical analyses for a nonlinear theory are valid before the breaking point.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.3
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• pp.212-220
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• 1993

A numerical model for the transformation of irregular waves in a coastal area is developed, which takes account of shoaling, refraction, diffraction, bottom friction and wave breaking. The governing equations are the usual energy conservation equation and kinematic conservation equations, but to consider the diffraction effects additional terms are included in the usual kinematic conservation or wave number equations. A linear superposition technique is used to represent the spectral formation. and an explicit formula is developed for the estimation of friction factor of irregular waves. A breaking criterion of component waves, which is the modified form of the Kitaigorodskii saturation relation, is employed to restrict the growth of shoaling waves in very shallow waters. The model was applied to a laboratory test and satisfactory agreement was obtained between the computation and measurement.

• Bulletin of the Society of Naval Architects of Korea
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• v.17 no.3
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• pp.1-4
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• 1980

It is well known that discrepancies between measured and predicted ship motions are significant in the range of low frequencies. In this paper, the vertical ship motions in regular longitudinal waves in a shallow water are briefly discussed. The investigation is focussed on the role of wave exciting forces and moments to the motion responses in these low frequencies. It is confirmed that diffraction forces are in general small in a shallow water as one may expect. Furthermore the wave exciting forces and moments on a displacement-type ship will be larger practicularly in low frequencies, when the contribution of the diffraction effect is neglected. As a result of this fact theoretically predicted responses for the pitch motion becomes closer to the experimental one. The discrepancies for the heave motion, however, are still apparent.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.4
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• pp.355-360
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• 2007

The process of the nonlinear shallow water wave transformation in a basin of a constant depth is studied. Characteristics of the first breaking of the wave are analyzed in details. The Fourier spectrum and steepness of the nonlinear wave are calculated. It is shown that the spectral amplitudes can be expressed using the wave front steepness, which allows the practical estimations.

• Journal of Korea Water Resources Association
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• v.50 no.9
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• pp.647-652
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• 2017

Many islands are scattered around the southern area of the Korean Peninsula and they may be very vulnerable to unexpected tsunami attacks. During the East Japan Tsunami Event occurred on March 11, 2011, many islands located at the southern area were affected by tsunamis. In this study, maximum run-up heights of solitary waves on a circular island with asymmetrical crest lengths investigated by using a numerical model based on the shallow-water theory. The obtained results could be used by local authorities to establish a defense plan against unexpected tsunami invasion.