• Journal of Korea Water Resources Association
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• v.54 no.1
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• pp.39-48
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• 2021

The experiment of rip current at successive ends of breaking wave crests was conducted in a laboratory wave basin, and its time-varying evolution according to incident wave durations was observed by using ortho-rectified images. The experiment utilized the generation of a quasi nodal line of the honeycomb-pattern waves (i.e., intersecting wave trains) formed by out-of-phase motion of two piston-type wave makers arranged in the transverse direction, instead of the original honeycomb pattern waves which are generated when two wave trains propagate with slightly different wave directions. The particle moving distance and velocity caused by the rip current were measured by using the particle tracking technique. As a result, the rip current was survived for a while even without incident waves after its generation due to several successive ends of wave crests, and it moved the particles further out to sea.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.446-457
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• 2020

Crescentic sand bar in the coastal zone of eastern Korea is a common morphological feature and the rhythmic patterns exist constantly except for high wave energy events. However, four consecutive typhoons that directly and indirectly affected the East Sea of Korea from September to October in 2019 impacted the formation of longshore uniform sand bar and overall shoreline retreats (approx. 2 m) although repetitive erosion and accretion patterns exist near the shoreline. Widely used XBeach to predict storm erosions in the beach is utilized to investigate the morphological response to a series of storms and each storm impact (NE-E wave incidence). Several calibration processes for improved XBeach modeling are conducted by recently reported calibration methods and the optimal calibration set obtained is applied to the numerical simulation. Using observed wave, tide, and pre & post-storm bathymetries data with optimal calibration set for XBeach input, XBeach successfully reproduces erosion and accretion patterns near MSL (BSS = 0.77 (Erosion profile), 0.87 (Accretion profile)) and observed the formation of the longshore uniform sandbar. As a result of analysis of simulated total sediment transport vectors and bed level changes at each storm peak Hs, the incident wave direction contributes considerable impact to the behavior of crescentic sandbar. Moreover, not only the wave height but also storm duration affects the magnitude of the sediment transport. However, model results suggest that additional calibration processes are needed to predict the exact crest position of bar and bed level changes across the inner surfzone.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.11a
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• pp.69-70
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• 2011

최근 해저지진의 활동에 따른 극한 쯔나미 파랑이 해안도시와 항만에 어마어마한 손상을 가져오고 있다. 전세계에 걸쳐 특정해역에서는 강한 정진형태의 부진동과 처오름이 관측되고 있다. 한반도에서는 그렇게 빈번한 발생을 나타내고 있지는 않으나, 과거기록을 보면 동해에서 몇 개의 중요한 발생사례도 존재한다. 본 연구에서는 특히 만이나 내수해역에서 최근 해저지진의 발생 추이를 분석하고 이에 따른 쯔나미 발생 메카니즘을 해석하여 새롭게 내수역에서의 수치모델에의 적용을 통해 공진을 통한 쯔나미 파랑의 변환을 다루어 통항선박에 대한 안정성 확보에 기초자료를 제공하고자 하였다. 내수역에서의 쯔나미 파랑에 대한 반응을 정합성 및 웨이블릿 해석으로 탁월 주기와 지속시간에 대한 분석으로 파악하였으며, 쯔나미파의 입사와 독립적인 공진모드의 도출은 쯔나미 재해의 경감을 위한 시설물 및 재난지역을 식별하는데 도움을 주고, 나아가서는 장래 재난에 대한 적절한 대비에 기여할 수 있을 것으로 본다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.315-323
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• 2015

Damage level of coastal structures has been scaled up according to increase of wave height and duration of the storm due to the abnormal global climate change. So, the design criteria for new breakwaters is being intensified and structural strengthening is also conducted for the existing breakwaters. Recently, interlocking concept has been much attention to enhance the structural stability of the conventional caisson structure designed individually to resist waves. The interlocking caisson breakwater may be survival even if unusual high wave occurs because the maximum wave force may be reduced by phase lags among the wave forces acting on each caisson. In this study, the dispersion characteristics of wave forces using interlocking system that connect the upper part of caisson with cable in the normal direction of breakwater was investigated. A simplified linear model was developed for computational efficiency, in which the foundation and connection cables were modelled as linear springs, and caisson structures were assumed to be rigid. From numerical experiments, it can be found that the higher wave forces are transmitted through the cable as the angle of incident wave is larger, and the larger the stiffness of the interlocking cable makes larger wave dispersion effect.