• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.1
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• pp.28-33
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• 1990

A parabolic model is presented for the effective calculation of refraction-diffraction of regular water while they are propagating on the water of slowly varying sea bed with currents. Parabolic wave equation has been used in the model, which is derived from a mild-slope equation using Pade' approximation. With the corrections of Kirby's (1986) model some numerical experiments were carried out to analyze the model accuracy.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.3
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• pp.254-261
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• 2001

It is well known that when long waves propagate from deep ocean onto a continental shelf with a very steep continental slope, the waves reflected from the shore can not propagate offshore and are re-reflected from the continental slope so that large water level fluctuations are induced near the shore. Liu(1986) has analyzed this phenomenon by assuming a topography which has a depth discontinuity along a semicircular offshore boundary, but his solution is erroneous. In the present paper, we correct his analytical solutions for a straight shoreline and a rectangular harbor. The corrected solution is then compared with the numerical results of the Galerkin finite element model of Jeong et al.(1998), which is based on the extended mild-slope equation.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.137-147
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• 2008

The relative magnitudes of the individual terms of the momentum equation are analyzed and compared by analytical methods. The temporal variations of each term are analyzed for the influence factors to runoff expressed by the parameters of the momentum equation, stream slopes and roughness coefficients. The magnitudes of local acceleration and convective acceleration offset each other. The peak time of each term except the gravity term coincides with inflection point of the hydrograph rising limb each other. The magnitudes of each term vary with the channel characteristics, especially when the roughness coefficients are dominant or for the mild stream slopes the pressure term can not be negligible.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.2
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• pp.83-90
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• 1989

A runoff model was estabilished for the direct runoff hydrograph at each subareas by obtaining the storage coefficient based on stream magnitudes of geomorphic parameters. For this, the relationship between flowsection and channel distance from the outlet of each subareas was assumed as nonlinear equation, and compared with linear one. The applicability of the runoff model to the real watershed was tested for the Bochung river basin. The results of the analysis show that the model was approved to be used for the prediction of small watershed having no runoff records and a linear equation between flowsection and channel distance from the outlet of each subareas was more similar to the observed data for the upper subarea with a steep slope and small area, on the other hand, nonlinear equation for the lower subarea with mild slope and relatively large area.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.4
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• pp.223-234
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• 1991

In this paper, the harbor tranquility problem is analysed by an improved boundary integral equation method. The effect of the diffracted wave transformation induced by the breakwater and structures located at a harbor mouth is considered. Partial reflection concept is also used to consider energy dissipation effects. The present model is verified by comparing the results of the model for rectangular and semi-circular harbors with the analytic solutions. they show a reasonable agreement. Also the wave height distribution of the HUPO harbor computed using the present model agree well to those from the previous hydraulic model tests. It also shows a good agreement with the results from the time-dependent mild slope equation model.

• Journal of Navigation and Port Research
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• v.34 no.1
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• pp.51-57
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• 2010

When estimating the calmness in a harbor, it is important that diffraction and reflection of irregular waves should be exactly calculated. The basic equation of the numerical model in this study was used Mild-slope equation, which has the advantage of which non-linearity with great influence for the wave behavior can be considered, and a triangular mesh was generated by using finite element method. So as to verify the nonlinear effects, the results of the numerical model developed in this study are compared with the experimental and numerical results by other researchers. As a result, it is shown that the results in case of considering nonlinear wave are more exact for wave analysis than in case of not considering nonlinear wave. In order to apply this model, wave height distributions in Jumunjin fishery port installed a seawater-exchange breakwater are computed. From the results of this numerical analysis, when abnormal waves are intruded through the seawater-exchange breakwater, the results of the wave height distributions in the harbor are highly presented. Therefore, in order to get wave height low in the harbor, it is considered that the facility with the ability to protect the inflow of abnormal waves is needed.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.120-127
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• 1998

An Elliptic model for calculating the combined refraction/diffraction of monochromatic linear waves is developed, including a term which allows for the dissipation of wave energy. Conjugate gradient method is employed as a solution technique. Wave height variations are calculated for localized circular and rectangular dissipation areas. It is shown that the numerical results agree very well with analytical solution in the case of circular damping region. The localized dissipation area creates a shadow region of low wave energy and the recovery of wave height by diffraction occurs very slowly with distance behind the damping region.

• Journal of Ocean Engineering and Technology
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• v.9 no.2
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• pp.41-52
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• 1995

the necessity of development of the Nearshore zone greatly emphasis in recent years. In the wave deformation model, we can get the wave height and wave direction using the hyperbolic mild slope equation considered the reflection wave. Radiation Stress the driving force of flow was calculated by the Watanabe and Maruyama who proposed on the partial standing wave. In the surf zone, applying the Izumiya and Horikawa's turbulent model considered the bottom friction and energy dissipation, we compared and examined with the Numerical model and Hydraulic test result of Watanabe and Maruyama. This model results obtained for Jin-ha Beach agreed well with the Numerical results. This model is expected so helpful to solve the prediction of the wave deformation problems in the development of the Nearshore zone in the future.

• Journal of the Korean Institute of Navigation
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• v.25 no.4
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• pp.423-433
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• 2001

As a part of the development program of Ulsan Port, construction of detached breakwater is planned. In Ulsan Port, several oil-buoys exist. If the detached breakwaters have been constructed, these oil-buoys will be located within 1 km from the planned breakwaters. Construction of the breakwaters gives rise to changes of wave conditions on the sea areas, especially in front of the breakwater and it affects mooring of tankers, which supply oil to the oil-buoy In this study, in order to calculate standing wave distribution after construction of a breakwater, numerical model is proposed based on unsteady mild slope equation. Calculation is performed by testing different wave heights, directions and reflection coefficients of breakwater. In addition, the influence to working condition of tanker moored at the oil-buoy is evaluated by using measured wave conditions and calculated results.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1998.10a
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• pp.201-209
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• 1998

The propagation of water waves over irregular bottom bathymetry and around islands involves many process. In this study of numerical model is developed current in water of varying depth. The method used is splitting method and minimax approximation. This numerical method used is Crank-Nicolson scheme. This model is applied to Vincent shoal and compared with laboratory data. The results agreed well with laboratory data. The results agreed well with laboratory data. Current effect is considered in this study. So, the model is used for the estimation of rip current in the slowly varying topography.