• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.5 no.2
• /
• pp.76-83
• /
• 1993

In this study, an approximate method for calculating the directional spectrum of waves encountering a current in shallow water is developed. The wave trains in tile directional spectrum are assumed to be linear and Gaussian; development of the spectrum requires that the waves also be short crested. The Miche's breaking criterion is imposed to determine the upper limit of wave height and to establish an expression for the breaking wave elevation in terms of the ideal wave's elevation and the second time derivative of wave elevation. Two examples are given; one for a Wallops directional spectrum encountering a shear current and another with an upwelling current.

• Journal of Navigation and Port Research
• /
• v.33 no.2
• /
• pp.105-110
• /
• 2009

Shipwaves am have harmful effects on ships working on the sea, in a harbour or navigational channel and caused beach erosion, seawall destruction. This study aims to investigate describe the characteristics of the wave pattern generated by an individual model ship tested at different velocities and hull forms for a given water depth and to investigate the variations at a given distance from the sailing line under the same conditions. As a result, the angles a's by model ship tests are smaller than those by real ship ones. Wave heights decreases with an increasing the mid-ship cross sectional area $A_s$. The maximum wave height and period increase rapidly in the subcritical speed, and beyond the critical speed the height and period decrease with increasing depth Froude number. And the period keeps constant with the distance from the sailing line.

• Journal of the Korea Computer Graphics Society
• /
• v.25 no.5
• /
• pp.21-30
• /
• 2019

We propose a physical simulation method based on the shallow water equation(SWE) to represent water surface effectively. In this paper, the water which can be represented has a much larger width compared to the depth does not have a large vertical direction flow. In order to calculate the water flow efficiently, we start with the shallow water equation as the governing equation, which is a simplified version of the Navier-Stokes equation. In order to numerically calculate the advection term of the SWE, we introduce a new conservtive USCIP(CUSCIP) method which improves the Constrained Interpolation Profile (CIP) method to preserve the physical quantity while increasing the numerical accuracy. The proposed method is based on Kim et. al.'s Unsplit Semi-lagrangian CIP[9], and calculates advection term with additional constraints on term that consider integral values. The experimental results show that the CUSCIP method is robust to the loss of physical quantity due to numerical dissipation, which improves wave detail and persistence.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.21 no.1
• /
• pp.30-38
• /
• 2009

In recent years, there's been strong demand for coastal structures that have a permeability that serves water affinity and disaster prevention from wave attack. The aim of this study is to examine the wave transformation, including wave run-up that propagates over the coastal structures with a steep slope. A numerical model based on the nonlinear shallow water equation, together with the unsteady nonlinear Darcy law for fluid motion in permeable underlayer and laboratory measurements was carried out in terms of the free surface elevations and fluid particle velocities for the cases of regular and irregular waves over 1:5 impermeable and permeable slopes. The numerical results were used to evaluate the application and limitations of the PBREAK numerical model. The numerical model could predict the cross-shore variation of the wave profile reasonably, but showed less accurate results in the breaking zone that the mass and momentum influx is exchanged the most. Except near the wave crest, the computed depth averaged velocities could represent the measured profile below the trough level fairly well.

• The Journal of the Acoustical Society of Korea
• /
• v.25 no.6
• /
• pp.298-304
• /
• 2006

This paper proposes a ray-based forward modeling scheme which is suitable for the shallow water acoustic wave propagation simulations. The proposed model comprises of ray tracings for the layered media of which sound speed profiles are interpolated linearly. considerations of plane and spherical wave reflection coefficients. and calculations of the phases and the amplitudes of eigen rays. The main characteristic of the scheme is fast simulation time due to direct calculation of the broad-band time signals in the time-domain, i.e. without transformation of the frequency-domain solutions to the time si 밍 131s. Finally, we applied the model to 4-types of test environments and compared the resulting signals with those of ORCA and Ram in order to validate the proposed model.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.3 no.1
• /
• pp.1-13
• /
• 1991

A wave prediction model of DP type with shallow water effects is composed. An jntercomparison study of the deep water wave models has been made to clarify the capacity of this model which has source functions by Incur and propagation scheme by Gadd. It is shown that the growth rate of wave energy is rapid and. for asymmetrical wind fields. this model behaves well. In spite of various response pattern for the wind fields the energy distribution gives reasonable agreements with those of other models.

• Journal of Korea Water Resources Association
• /
• v.38 no.6 s.155
• /
• pp.429-438
• /
• 2005

In this study, a couple of ordinary differential equations which can describe random waves are derived from the Boussinesq equations. Incident random waves are generated by using the TMA(TEXEL storm, MARSEN, ARSLOE) shallow-water spectrum. The governing equations are integrated with the 4-th order Runge-Kutta method. By using newly derived wave equations, nonlinear energy interaction of propagating waves in constant depth is studied. The characteristics of random waves propagate over a sinusoidally varying topography lying on a sloping beach are also investigated numerically. Transmission and reflection of random waves are considerably affected by nonlinearity.

• Journal of the Society of Naval Architects of Korea
• /
• v.33 no.2
• /
• pp.1-12
• /
• 1996

Hydrodynamic characteristics of shipping water on deck are investigated by using a simplified two-dimensional model. Formulation of the shipping water on deck leads to a nonlinear hyperbolic system of equations based on the shallow-water wave theory. Time-domain solution of these equations are obtained numerically using a finite difference method which adopts predictor-corrector method for time-marching and 2nd upwind differencing method for convection term calculation. To confirm the validity of the present numerical method, we calculated some shallow-water wave problems accompanying a bore and compared the obtained results with the analytic solutions. We found good agreements between them. Though the calculation results of shipping water on deck, we show that the shipping water flows into the deck as a rarefying wave arid grows into a bore after colliding with a deck structure. Also we examined the effects of acceleration and slope of deck and found that they have significant influences on the flow of shipping water.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
• /
• 2002.08a
• /
• pp.35-41
• /
• 2002

천해역에서 관찰되는 장주기파는 발생 기구에 따라서 surf beat, setdown wave, locked wave, 또는 Far-infra-gravity wave 등으로 다양하게 불리 우며, 모두 0.5-수 분대의 주기를 갖는다. 이들은 정의에 따라 약간씩 다르기는 하지만 모두 계류된 선박의 동요뿐만 아니라 해안선 침식과도 밀접한 관련이 있다는 것이 일반적으로 인정되고있다(가등 등, 1989). (중략)

• Proceedings of KOSOMES biannual meeting
• /
• 2017.04a
• /
• pp.264-264
• /
• 2017