• Journal of Navigation and Port Research
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• v.28 no.1
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• pp.97-104
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• 2004

Introduction of wave model, take into account the effect of tide, wind and wave induced currents at the coastal waters of complex bathymetry, is a very important factor for most coastal engineering design and disaster protection problems. As the steady state spectral wave model could simulate depth induced wave shoaling and refraction, current induced refraction effect, steepness induced wave breaking, diffraction, wind wave growth, wave-wave interaction, and wave-current interaction that redistribute energy, this would support and compensate the gap in the real field of design where other wave models could not deal and cause wrong estimation. In this study, for better understanding and analysis of wave transformation process, we applied the spectral wave model to the large coastal waters near Gaduck Island where the Busan new port construction project is going on. We also compared the simulation results with the calculatea from the existing model. From such a trial of this study, we hope that broader and safer use of the spectral model in the area of port design and disaster prevention system come through in near future.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3B
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• pp.323-334
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• 2008

Present study examined the functionality of the solitary wave (tsunami) control of the two-rowed porous submerged breakwater by numerical experiments, using a numerical wave tank which is based on the Navier-Stokes equation to explain fluid fields and uses a Volume of Fluid (VOF) method to capture the free water surface. Solitary wave was generated by the internal wave source installed within the computational zone in the numerical wave tank and its wave transformations by structure were compared with those in the previous study. Comparisons with the precious numerical results showed a good agreement. Based on these results, several tow-dimensional numerical modeling investigations of the water fields, including wave transformations, reflection, transmission and energy flux, by the one- and two-rowed permeable submerged breakwater under solitary waves were performed. Even if, it is a research of the limited scope, in case of two-rowed permeable submerged breakwater with $h_0/h=0.925$ ($h_0$ is height of submerged breakwater and h is water depth), the wave height damping in range of $l/L_{eff}>0.4$($L_{eff}$ is effective distance of solitary wave) can reach nearly 60% of the incident wave height. In addition, it is found that reflection coefficient increases nearly 47% and transmission coefficient decreases nearly 18% than one-rowed one. The numerical results revealed that the tow-rowed submerged breakwater can control the incident solitary wave economically and more efficiently than the one-rowed one.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.227-234
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• 2004

Recently huge typhoons had attacked to the coastal waters in Korea and caused disastrous casualties in those area. There are some discussions on correction to the design parameters for the coastal structures. Wave transformation computations with the extreme waves are of value in planning and constructing engineering works, especially in coastal regions. Prediction of typhoon surge elevations is based primarily on the use of a numerical model in this study, since it is difficult to study these events in real time or with use of physical models. Wave prediction with a two dimensional numerical model for a site with complicated coastal lines and structures at the period of typhoon 'Maemi' is discussed. In order to input parameters for the extreme wave conditions, we analyzed the observed and predicted typhoon data. Finally we applied the model discussed above to the storm surge and extreme wave problem at Busan Harbor, the southeast coast of Korea. Effects of water level variation and transformation of the extreme waves in relation with the flooding in coastal waters interested are analyzed. We then mack an attempt to presen a basic hazard map for the corresponding site.

• Geophysics and Geophysical Exploration
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• v.2 no.1
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• pp.17-25
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• 1999

A traveltime tomography has been carried out by transforming electromagnetic data in frequency domain to wave-like domain. The transform uniquely relates a field satisfying a diffusion equation to an integral of the corresponding wavefield. But direct transform of frequency domain magnetic fields to wave-field domain is ill-posed problem because the kernel of the integral transform is highly damped. In this study, instead of solving such an unstable problem, it is assumed that wave-fields in transformed domain can be approximated by sum of ray series. And for further simplicity, reflection and refraction energy compared to that of direct wave is weak enough to be neglected. Then first arrival can be approximated by calculating the traveltime of direct wave only. But these assumptions are valid when the conductivity contrast between background medium and the target anomalous body is low enough. So this approach can only be applied to the models with low conductivity contrast. To verify the algorithm, traveltime calculated by this approach was compared to that of direct transform method and exact traveltime, calculated analytically, for homogeneous whole space. The error in first arrival picked by this study was less than that of direct transformation method, especially when the number of frequency samples is less than 10, or when the data are noisy. Layered earth model with varying conductivity contrasts and inclined dyke model have been successfully imaged by applying nonlinear traveltime tomography in 30 iterations within three CPU minutes on a IBM Pentium Pro 200 MHz.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.1
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• pp.27-38
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• 2004

In this study, the reliability design method developed by Shimosako and Takahashi in 1999 for calculation of the expected sliding distance of the caisson of a vertical breakwater is extended to take into account the variability in wave direction such as directional spreading of waves, obliquity of the deep-water design principal wave direction from the shore-normal direction, and its variation about the design value. To calculate the transformation of random directional waves, the model developed by Kweon et al. in 1997 is used instead of Goda's model, which was developed in 1975 for unidirectional random waves normally incident to a straight coast with parallel depth contours and has been used by Shimosako and Takahashi. The effects of directional spreading and the variation of deep-water principal wave directions were minor compared with those of the obliquity of the deep-water design principal wave direction from the shore-normal direction, which tends to reduce the expected sliding distance as it increases. Especially when we used the field data in a part of east coast of Korea, considering the variability in wave directions reduced the expected sliding distance to about one third of that not considering the directional variability. Reducing the significant wave height calculated at the design site by 6％ to correct the effect of wave refraction neglected in using Goda's model was found to be proper when the deep-water design principal wave direction is about 20 degrees. When it is smaller than 20 degrees, a value smaller than 6％ should be used, or vice versa. When we designed the caisson with the expected sliding distance to be 30㎝, in the area of water depth of 25 m or smaller, we could reduce the caisson width by about 30％ at the maximum compared with the deterministic design, even if we did not consider the variability in wave directions. When we used the field data in a part of east coast of Korea, considering the variability in wave directions reduced the necessary caisson width by about 10% at the maximum compared with that not considering the directional variability, and is needed a caisson width smaller than that of the deterministic design in the whole range of water depth considered (10∼30 m).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.2
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• pp.101-115
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• 2007

The pound net fishery is very important one in Korean coastal fishery and it need to grasp the characteristics of the net affected by many factors. It is considered that the structure and the shape of the pound net can be changed by the direction and speed of current, wave height, depth and conditions of sea bed. However, most of all, the speed of current and wave height influence more upon the pound net than any other factors to deform and flutter. In this study, author carried out the experiments with a model of double one-side pound net made by the similarity law as 1:100 scales at a real experimental area, and additionally the model net experiments were conducted in the circulating water channel in Pukyong National University. The author analyzed the data of transformation of shape and tension of the model pound net to recognize the characteristics of the current and wave acting on it. Regardless of the direction of flow affecting on the fish court net or bag net, the deformed angle and depth to the side panel and bottom of box nets becomes bigger as the wave gets higher and the period of wave is faster. The tension in both upward or downward tends to be changed by the speed of wave. Those value of changes occurred similarly in either fish court net or bag net. Generally, when bag net is located at upward of flow, the value of tension was bigger 10% than any other location or nets. Regardless of the setting direction, the tension of the pound net is increased in proportion to flow speed, wave height and period of wave, and it becomes bigger about 15-30% at upward to flow than downward. Where the flow is upward in the court net, the tension in the wave increased to 37% compared to the one in the flow only in the condition of flow of 0.1-0.3m/s. Where the flow is upward in the bag net, the tension in the wave increased to 52% in the flow of 0.1m/s, and the tension increased to 48% in the flow of 0.2-0.3m/s.

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

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.1
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• pp.21-32
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• 2003

In this study, the reliability design method developed by Hanzawa et al. in 1996 for calculation of the expected damage to armor blocks of a horizontally composite breakwater is extended to take into account the variability in wave direction such as directional spreading of waves, obliquity of the design principal wave direction from the shore-normal direction, and its variation about the design value. To calculate the transformation of random directional waves. the model developed by Kweon et al. in 1997 is used instead of Goda's model, which was developed in 1975 for unidirectional random waves normally incident to a straight coast with parallel depth contours and has been used by Hanzawa et al. It was found that the variability in wave direction had great influence on the computed expected damage to armor blocks. The previous design, which disregarded wave directionality, could either overestimate or underestimate the expected damage by a factor of two depending on water depth and seabed slope, if the assumption of the present study that the stability formula for breakwater armor blocks proposed for normal incidence can be used for obliquely incident waves is valid.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.329-329
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• 2017

In this study attempted to evaluate the stability of the protection methods by examining hydraulic characteristics of the area around the point in which marine cable protector is installed such as surf zone occurrence point of shore-end submarine cables suitable for coastal marine environmental conditions, flow rate t the tope of the protector and maximum wave height, and to provide basic data for the selection of the optimal protection method. In performing hydraulic model experiments, the topography of submarine cable installation location was reproduced in 2-D sectional channel, and models appropriate for experimental scale and similitude law were produced and installed for each condition of submarine cables and protectors. Since the topography and submarine cable protectors were reproduced and installed in 2-D sectional channel, the exact reproduction of surf and transformation in shallow water zone was possible, and thus the physical properties could be clearly analyzed. For stability review, an experiment to examine the stability was conducted using a wave maker with 50-year frequency design waves as target, and wave height and cycles were applied based on the approximate lowest low water level(Approx. L.L.W), which is the most dangerous in submarine cable protection methods. As for experimental time, typhoon passing time in summer (about 3 hours) was applied, and wave patterns and deviation ratio of the submarine cable protector were investigated after making irregular waves corresponding to design waves. In addition, current meter and wave height meter were installed at the installation location of the submarine cable protector, and the flow rates and wave height at the top of the protector were measured and analyzed to review hydraulic properties.

• 한국해양학회지
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• v.16 no.2
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• pp.99-107
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• 1981

A partial differential equation for the adjusted sea level, obtained from the long wave equations in shallow water, is reduced to a simpler one by the use of physically reasonable approximations based on the observations. The similar equation for the stream function indicates that shelf waves are generated by the longshore wind stress. This indication is in good agreement with the high correlation between the adjusted sea levels and the longshore wind stress. From the dispersion relationship and the boundary conditions, there exist a countable infinite number of modes which satisfy a first-order wave equations. The adjusted sea level for a given wind stress can easily be calculated by utilizing the convolution and the Fourier transformation. Some detailed solutions are presented here for sinusoidal and exponential wind stress.