• Smart Structures and Systems
• /
• v.18 no.5
• /
• pp.911-930
• /
• 2016

The main purpose of this paper is to study the effects of initial stress, gravity, anisotropy and porosity on the propagation of shear wave (SH-waves) in a fiber-reinforced layer placed over a porous media. The frequency equations in a closed form have been derived for SH-waves by applying suitable boundary conditions. The frequency equations have been expanded and approximated up to $2^{nd}$ order of Whittaker's function. It has been observed that the SH-wave velocity decreases as width of fiber-reinforced layer increases. However, with the increase of initial stress, gravity parameter and porosity, the phase velocity increases. The results obtained are in perfect agreement with the standard results investigated by other relevant researchers.

• Journal of Ocean Engineering and Technology
• /
• v.10 no.3
• /
• pp.50-61
• /
• 1996

The breaking phenomenon of regular periodic waves generated by a numerical wave maker is simulated by finite-difference method which can cope with strong interface motions. The air and water flows are simultaneously solved in the time-marching solution procedure for the Navier-Stokes equation. A density-function technique is devised for the implemenation of the interface conditions. The accuracy is examined and applied to the simulation of two-dimensional breaking phenomena of periodic gravity waves.

• Journal of Ocean Engineering and Technology
• /
• v.20 no.1 s.68
• /
• pp.43-47
• /
• 2006

Superposition of three wave trains on finite depth is investigated. This paper is focused on how to improve the linear superposition of three waves. This was realized by introducing the scheme. The idea of the scheme is based on a fixed point approach. Application of the scheme to the superposition makes it possible to obtain a wave profile of wave-wave interaction. With the help of FFT, it was possible to analyze high-order nonlinear frequencies for three interacting Stokes' waves on finite depth.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.30 no.2
• /
• pp.51-60
• /
• 2018

This study was conducted to observe the effects of gravity and infra-gravity wave of detached submerged breakwater in the coast of Yeongnang-dong, Sokcho, as analyzing continuous wave data by performing field observations on the front area (W0) and rear area (W1, W2). Wave transmission coefficient ($K_t$) of submerged breakwater was analyzed in two parts, short-period wave (gravity wave) and infra-gravity wave. The wave energy reduction effect was analyzed and compared with the value of the design. In case of above wave height 2.0 m at the front area (W0) of the submerged breakwater, the short-period wave height at point W1 is reduced by about 65% and the short-period wave height at point W2 is reduced by about 59%. The depth of crest of submerged breakwater conducted in a sea area differs from the design, and the wave energy reduction effect is analyzed to be smaller than the design plan. The infra-gravity waves were amplified to 2.11 and 1.71 at the W1 and W2 points, respectively, and the wave height at W2 point was smaller than that at W1 point.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.14 no.1
• /
• pp.51-64
• /
• 2002

To investigate long-period wave responses in Sokcho Harbor and Cheongcho lagoon, field measurements were made for long-and short-period waves and current velocities using a Directional Waverider, a ultrasonic-type wave gauge, four pressure-type wave gauges, and a current meter. From the data analysis, it was found that the Helmholtz resonant periods of Sokcho Harbor and Cheongcho lagoon are about 13.6 and 54.5 minutes, respectively, and the dominant period of wave induced current in the passage between Sokcho Harbor and Cheongcho lagoon is about 55.2 minutes which depends on Helmholtz resonant condition of the Cheongcho lagoon. It was also found that the energy level of the far-infra-gravity waves during storm conditions is very high compared with that during calm sea conditions. To investigate relationships between far-infra-gravity waves and short-period waves at offshore station, regression analyses were carried out especially for 1) heights, 2) periods, 3) direction and height, 4) height and period between short-and far-infra-gravity waves, respectively. The results showed that the long-period wave height is highly correlated with the short-period wave height. However, no special trend was found for the other relations. In the future far-infra-gravity wave heights on return period around Sokcho Harbor region can be suggested by using extreme value analyses of long term measured data.

• Journal of Astronomy and Space Sciences
• /
• v.24 no.4
• /
• pp.327-338
• /
• 2007

We estimate the momentum fluxes of short-period gravity waves which are observed in the OI 557.7 nm nightglow emission with all-sky camera at Mt. Bohyun ($36.2^{\circ}\;N,\;128.9^{\circ}\;E$) in Korea. The intrinsic phase speed ($C_{int}$), the intrinsic period (${\tau}_{int}$), and vertical wavelength (${\lambda}_z$) are also deduced from the horizontal wavelength (${\lambda}_h$), observed period (${\tau}_{ob}$), propagation direction (${\phi}_{ob}$), observe phase speed (${\upsilon}_{ob}$) of the gravity wave on the all-sky images. The neutral winds to deduce intrinsic wave parameters are measured with Fabry-Perot interferometer on Shigaraki ($34.8^{\circ}\;N,\;13.1^{\circ}\;E$) in Japan. We selected 5-nights of observations during the period between July 2002 and December 2006 considering of the weather and instrument conditions in two observation sites. The mean values of intrinsic parameter of gravity waves are $({\tau}_{int})\;=\;12.9\;{\pm}\;6.1\;m/s,\;({\lambda}_z)\;=\;12.9\;{\pm}\;6.5,\;and\;(C_{int})\;=\;40.6\;{\pm}\;11.6\;min$. The mean value of calculated momentum fluxes for four nights besides of ${\lambda}_z\;<\;6\;km$ is $12.0\;{\pm}\;15.2\;m^2/s^2$. It is needed the long-term coherent observation to obtain typical values of momentum fluxes of the mesospheric gravity waves using all-sky camera and the neutral wind measurements.

• The KIPS Transactions:PartA
• /
• v.12A no.4 s.94
• /
• pp.327-332
• /
• 2005

In the field of computer graphics, we have several research results to display the ocean waves on the screen, while we still not have a complete solution yet. Though ocean waves are constructed from a variety of sources, the dominant one is the surface gravity wave, which is generated by the gravity and the wind. In this Paper, we Present a real-time surface gravity wave simulation method, derived from a precise ocean wave model in the oceanography. There are research results based on the Pierson-Moskowitz(PM) model[1], which assumes infinite depth of water and thus shows some mismatches in the case of shallow seas. In this paper, we started from the Texel, Marsen and Arsloe(TMA) model[2], which is a more precise wave model and thus can be used to display more realistic ocean waves. We derived its implementation model for the graphics applications and our prototype implementation shows about 30 frames per second on the Intel Pentium 4 1.6GHz-based personal computer. Our major contributions to the computer graphics area ill be (1) providing more user-controllable parameters to finally generate various wave shapes and (2) the improvement on the expression power of waves even in the shallow seas.

• Atmosphere
• /
• v.18 no.2
• /
• pp.121-136
• /
• 2008

We investigate effects of vertical resolution on a parameterization of convective gravity waves (SGWDC) developed in Song and Chun (2005) through offline and online tests of the SGWDC parameterization. For offline tests, numerical simulations of the SGWDC parameterization with different number of vertical levels (L66, L117, L168, L219 and L270) from the surface to 120 km are performed for two different saturation methods. It is found that the wave momentum forcing is overestimated or underestimated in the SGWDC parameterization with different vertical resolutions, depending on the saturation methods. The increase of the vertical resolution modifies the magnitude and distribution of the wave momentum forcing in the parameterization, and this is mainly due to modification of wave saturation levels in the wave saturation processes. However the wave momentum forcing converges in the parameterizations with vertical resolutions higher than L168. For online test, the SGWDC parameterizations with vertical resolutions of L66 and L164 are implemented into a climate model with vertical resolution of L66, separately. In the L164 experiment, the wave momentum forcing decreases in the mid-latitude winter mesosphere in July and zonal mean flows are more realistically reproduced in the tropical regions compared with those in the L66 experiment. These results demonstrate that the wave momentum forcing calculated in the parameterization is sensitive to the vertical resolution, and the implementation of the SGWDC parameterization into high resolution models is required for realistic representation of the gravity wave momentum forcing in large-scale numerical models.

• Bulletin of the Korean Space Science Society
• /
• 2001.04a
• /
• pp.23-23
• /
• 2001

• Bulletin of the Society of Naval Architects of Korea
• /
• v.19 no.2
• /
• pp.33-39
• /
• 1982

It is one of the basic problems of naval architecture and ocean engineering how to describe the wave kinematics normally under the assumption of an ideal fluid. At present, there are many wave theories available for design purposes. These can be classified into two groups: One is the analytic theory and the other is the numerical theory. This paper briefly introduces the stream function method of R.G. Dean which belongs to the latter group and shows its numerical evaluations exemplified for two cases: One is applied to observed waves and the other is for design waves. In the former case, the wave profiles are calculated by the stream function method and compared with those of the observed waves and also with the results of R.G. Dean. They show good agreement. In the latter case, the wave kinematics and wave loads on a column of diameter 1m are calculated by the stream function method and these are compared with those resulted from the 5th-order gravity wave theory. As a result of comparison the values by the stream function method are slightly larger than those by the 5th-order gravity wave theory but the difference are negligible. From this it is concluded that the stream function method is very useful. And as characteristics of the numerical theories, the stream function method of R.G. Dean can be easily extended to the higher order terms and can include easily the current velocity and the pressure distribution on the free surface. In addition, when the data of observed wave profile are given, this method can reproduced the observed wave profile as closely as possible so that this method seems to describe the ocean wave more realistically. And from standpoint of a mathematical principle the stream function method exactly satisfies the kinematic free-surface boundary condition.