• Journal of Navigation and Port Research
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• v.37 no.6
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• pp.663-671
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• 2013

The width of Haeundae beach has been decreasing annually due to the loss of sand from land, high waves, reflected waves, etc.. The accurate prediction of wave-induced currents is indispensible to analyze the beach deformation due to the sediment transport. In the this study, Numerical experiments were performed with seasonal representative wave on the basis of a long term and comprehensive survey data. In summer, we found the deposition of Mipo by longshore current eastly by ordinary and S waves, and in winter, the deposition of Dongback-island by longshore current westly by ordinary and E waves. In addition, rip current occurs in the middle of Haeundae beach by 50 year return period wave and current westly along the coast by ESE directional wave.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.4
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• pp.151-158
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• 1990

Various factors may contribute on the mixing processes in the surf zone formed by irregular waves. The turbulence motion driven by wave breaking may be one of the major causes, the effect due to spatial variation on current velocity be a secondary one, and the additional process may result from the irregular superposition of radiation stresses or wave breaking dissipation incurred by random breaking waves in a broadened surf zone. In the present study a numerical model of spectral waves and induced currents was developed using a superposition technique with ${\kappa}-{\varepsilon}$ closure for mixing process and applied to a field situation of longshore current generated by spectral waves on a uniform beach. It was found from the application that the surf-zone mixing processes formed by irregular waves can be well described by using ${\kappa}-{\varepsilon}$ equations if the source of ${\kappa}$ is properly represented. The nonlinear energy transfer was also found to have some influence on the velocity profile of longshore current particularly in very shallow water region near coast.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.1
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• pp.12-23
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• 1995

Currents driven by irregular waves are modelled using numerical model with various empirical relations improved. Kitaigorodskii's equilibrium equation is refined to account for shoaling effect and used for checking the breaking condition. In order to compute the bottom friction realistically. equivalent roughness blights are estimated considering the ripple shape and bed load transport which may be significant the surf zone. Two sets of equations are employed to evaluate the ripple shape: one is suggested by Nielsen and the other by Madsen and Rogengaus. Both equations give similar shape of ripples. but Madsen et al. give lower value of ripple factor than Swart suggesting that the equivalent roughness becomes relatively small. Optimization technique is used to determine the proper values for the empirical parameters of $\kappa$-ι equations, and the longshore current velocity is computed using the values of empirical parameters determined by the optimization technique.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.1
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• pp.59-65
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• 2003

The changes of beach profile with a natural longshore bar and beach profile with a fixed artificial bar are studied, respectively, using a numerical model. The quasi three dimensional wave-current-sediment transport model is applied with an addition of boundary condition for sediment transport on the artificial structure under water. The study shows that the natural bar adapts itself to the change of coastal physical environment by adjusting its location but the fixed artificial bar causes the formation of a second natural bar seaward of the fixed bar and scouring at the rear of the fixed bar. This study can be applied to work on the change of beach profile with submerged breakwaters.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.3
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• pp.234-244
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• 1994

Longshore currents driven by monochromatic waves have been described using 2-equation $textsc{k}$-ι turbulence transport model. When using $textsc{k}$-ι closure both profiles of eddy viscosity and current velocity are found to be satisfactory. Several terms of ι equation are related to various variables concerned with turbulence mechanism. New form of turbulence frequency used in ι equation is suggested in the present approach, and non-dimensional parameters are evaluated by comparing the computational results with the laboratory measurements. Various values of a large range are applied to the non-dimensional parameters for the sensitivity test and in order to improve the predictability common values of constants are deduced, which produce similarly good computational results for the well-controlled laboratory measurements.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1993.07a
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• pp.142-145
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• 1993

쇄파대 내에서는 여러가지 흐름이 상호 간섭하면서 작용하기 때문에 극히 복잡한 흐름장이 형성 된다. 해빈의 제반 동역학에 있어서 최우선되는 작용력은 파동 이지만, 흐름 또한 표사와 확산현상을 지배하는 중요한 요인이다. 특히 쇄파대 내외의 천수역에서는 해류나 조류 등 지구 물리학적 크기의 흐름보다는 소위 해빈류가 문제가 되는 경우가 많다. 해빈류계는 그 평면적인 흐름의 형태에 따라 연안류계(longshore current system), 순환류계(symmetrical celluar system), 사행류계(meandering system) 등 3가지로 분류된다(Basco, 1982). (중략)

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.3 s.14
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• pp.1-8
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• 2004

In this study, the change of the current in the coastal zone before and after the construction of Jeju new harbor was predicted by using the numerical model, which uses Hardy-Cross method. The numerical model was carried out for the present state, before the construction, and the state after the construction, and for the wave direction the NNW direction for winter and NE direction for summer were tested so that the seasonal change may be considered. The computation result shows that a large amount of the wave induced current was occurred when there were high waves coming in from NNW direction before and after the construction. Also, before the construction a longshore current occurred moving from the west to the east at the new harbor construction site so that it formed a rip current in the Hwabuk-dong front sea. And also, after the construction, the tip current produced changed into nearshore circulating current and a small circulating current appeared at the harbor entrance. On the other hand, at Samyang 4each, which is 3.0km away from the new harbor in the NE direction, shows that there was a longshore current occurred from the west to the east, which is in the opposite direction the new harbor, and the effect on the new harbor by sediment transport at Samyang beach is thought to be very small.

• Journal of Navigation and Port Research
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• v.41 no.2
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• pp.55-62
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• 2017

A nearshore current or a wave-induced current is an important phenomenon in a nearshore zone, which is composed of longshore, cross-shore, and rip currents. The nearshore current is closely related to the occurrence of coastal accidents by beachgoers. A considerable number of coastal accidents by beachgoers involving the rip current have been reported at Jungmun Beach. However, in studies and observations of the nearshore current of Jungmun Beach, understanding of the rip current pattern remains unclear. In this study, a scientific approach is taken to understand the nearshore current and the rip current patterns at Jungmun Beach by numerical computation for year of 2015. From results of numerical computation, the occurrence and spatial characteristics of the rip current, and the similarities between the rip current and incident wave conditions are analyzed. The primary results of this study reveal that the rip currents are frequently generated at Jungmun Beach, especially in the western parts of the beach, and that the rip currents often occur with a wave breaking height of around 0.5 ~ 0.7 m, a wave period of around 6 ~ 8 seconds, and a breaking angle of around 0 ~ 15 degrees.

• Ocean and Polar Research
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• v.36 no.2
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• pp.87-101
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• 2014

Recently, more attention has been paid to the geomorphological changes in the Nakdong River Estuary, because those changes are caused by artificial activities including weirs, reclamation and construction. In order to analyze quantitatively the recent geomorphological variability in the Nakdong River Estuary, we surveyed the depth and elevation of submarine topography near Jinwoodo and Sinjado from March 2007 to February 2012. A statistical method (based on Digital Shoreline Analysis System) and an Empirical Orthogonal Functions method were used to evaluate the morphological changes. According to the statistical variables (DCE, NDC, EPR, LRR), the highest amount and rate of accumulation were recorded around the Gadeokdo whereas the greatest amount of erosion appeared around the coast off the eastern part of Sinjado. In particular, a dynamic variation of morphology was clearly observed in the vicinity of the sub-tidal channel located between Jinwoodo and Sinjado, which seems to be attributable to channel migration. As a result of the EOF method, the first mode (48.7%) is most closely related to the pattern of morphological variability that might be associated with the westerly movement of sediment by longshore current. The spatial variability of the second mode (16.6%) was high in the shoreface of Sinjado, showing a 4-year periodicity of temporal variability. The strong correlation (coefficient 0.73) between the time coefficient and suspended sediment discharge from Nakdong River emphasizes the role of sediment discharge to deposition in this area. The spatial variability of the third mode (11.3%) was distributed mainly around the coast off the eastern part of Sinjado, which is related to the movement of the coastline of Sinjado. Based on the last 5 year's data, our results suggest that the study area is characterized on the whole by a depositional pattern, but the extent of sedimentation is different locally.

• Journal of The Geomorphological Association of Korea
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• v.20 no.3
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• pp.27-39
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• 2013

This study grasped long-term changing tendency of shoreline during lately about 30 years in five region of South East coast, and analyzed long-term changing tendency of East coast shoreline and the factors that synthesized studies of Central and South East coast. As a result of calculating of shoreline variations using DSAS, each shoreline of Mangyangjeong and Josa region regressed mean 28.9m and 6.4m, but each shoreline of Goraebul, Daejin and Bonggil region progressed mean 25.0m, 10.6m and 18.8m. Synthesizing changing tendency of East coast shoreline, 1) progressive and regressive zones of shoreline in all regions seem to repeat. 2) looking at shoreline of south zone adjacent to lately constructed or extended breakwater progressed, because it is thought due to effect of a longshore current flowing north. 3) zones using beach relatively tends to regress shorelines. 4) progress and regress of shoreline in zones including estuary of stream are various features as change of deposit supply from a upstream region.