• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.5
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• pp.294-304
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• 2019

This study evaluates the variation characteristics of wave fields (transmission ratio, wave height, time-averaged velocity and time-averaged turbulent kinetic energy) for two-dimensional low-crested structure by olaFlow model based on the two-phases flow numerically. In addition, the present numerical results are verified by comparing with the existing experimental results. The time-averaged velocity, one of various numerical results is formed counterclockwise circulating cell on the front of structure and is occurred strong uni-directional flow on onshore side. It is shown that these are closely related to the factors such as overtopping, etc.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.195-195
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• 2016

Kon - Ha Thanh River basin is the largest and the most important river basin in Binh Dinh, a province in the South Central Coast of Vietnam. In the lower rivers, frequent flooding and inundation caused by heavy rains, upstream flood and or uncontrolled flood released from upstream reservoirs, are very serious, causing damage to agriculture, socio-economic activity, human livelihood, property and lives. The damage is expected to increase in the future as a result of climate change. An advanced flood warning system could provide achievable non-structural measures for reducing such damages. In this study, we applied a modelling system which intergrates a 1-D river flow model and a 2-D surface flow model for simulating hydrodynamic flows in the river system and floodplain inundation. In the model, exchange of flows between the river and surface floodplain is calculated through established links, which determine the overflow from river nodes to surface grids or vice versa. These occur due to overtopping or failure of the levee when water height surpasses levee height. A GIS based comprehensive raster database of different spatial data layers was prepared and used in the model that incorporated detailed information about urban terrain features like embankments, roads, bridges, culverts, etc. in the simulation. The model calibration and validation were made using observed data in some gauging stations and flood extents in the floodplain. This research serves as an example how advanced modelling combined with GIS data can be used to support the development of efficient strategies for flood emergency and evacuation but also for designing flood mitigation measures.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.5
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• pp.102-108
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• 2023

In this study, hydraulic model tests were performed to investigate the stability of armor units at harbor side slope for rubble mound structures. The armor units on the rear slope were rocks. The Korean design standard for harbor and fishery port suggested the design figures that showed the ratio of the armor weight for each location of rubble mound structures and it could be known that the same weight ratio was needed to the sea side and rear side slope of rubble mound structures. The crest elements were commonly applied to the design process of rubble mound structures in Korea and the investigation of the effects of super structures would be needed. The damage rate (S =2) was applied and the stable wave height was measured for each test condition. The results were suggested as the armor weight ratio of the rear side slope(armor rock) to the sea side slope (tetrapod) in relation to the relative crest height.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.286-304
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• 2017

In this study, we proposed a new-type of circular perforated caisson breakwater consisting of a bundle of latticed blocks that can be applied to a small port such as a fishing port, and numerically investigated the hydraulic characteristics of the breakwater. The numerical method used in this study is OLAFOAM which newly added wave generation module, porous media analysis module and reflected wave control module based on OpenFOAM that is open source CFD software published under the GPL license. To investigate the applicability of OLAFOAM, the variations of wave pressure acting on the three-dimensional slit caisson were compared to the previous experimental results under the regular wave conditions, and then the performance for irregular waves was examined from the reproducibility of the target irregular waves and frequency spectrum analysis. As a result, a series of numerical simulations for the new-type of circular perforated caisson breakwaters, which is similar to slit caisson breakwater, was carried out under the irregular wave actions. The hydraulic characteristics of the breakwater such as wave overtopping, reflection, and wave pressure distribution were carefully investigated respect to the significant wave height and period, the wave chamber width, and the interconnectivity between them. The numerical results revealed that the wave pressure acting on the new-type of circular perforated caisson breakwaters was considerably smaller than the result of the impermeable vertical wall computed by the Goda equation. Also, the reflection of the new-type caisson breakwater was similar to the variation range of the reflection coefficient of the existing slit caisson breakwater.

• Journal of Korea Water Resources Association
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• v.41 no.10
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• pp.983-993
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• 2008

In recent times, sea level increasing caused by abnormal weather and global warming, sea-sand dredging and complex development causes various kind of erosion damages onto the coastal area in the world. The various types of erosion control and protection methods are applied but there are no signs of fruitful effectiveness. The PC concrete protection block for shore protection structure is practically installed in globally but most of structures in the present day became villainous because of bad accessability. In this study, hydrophilic revetments for control and protection of coastline erosion will be developed in order to make up for a faculty of the shore erosion protection block with better accessibility and excellent protection ability. Experimental measurements were researched to insure for the capacity and facility on reflection coefficient, overtopping volume, and overtopping height characteristics of newly developed shore erosion protection block in model tests. As the result, hydraulic model tests show much excellent than the general step block. Field tests were carried out also to verify through vegetative test on an affinity and construction work test of control-protection on coastline erosion with actual utilization. In the latter case, deposition of sand accumulation occurred in fairly short time at the established reaches and then we can be confirmed to utilize for newly developed block as the revetments for control and protection of coastline erosion.

• Journal of Korea Water Resources Association
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• v.33 no.3
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• pp.331-340
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• 2000

This study aims to develop a methodology of real time forecasting of mundation risk based on DAMBRK model and Kalman filter. The model is based on implicit, nonlinear finite difference approximatIons of the one-dimensional dynamic wave equations. The stochastic estimator uses on extended Kalman filter to provide optimal updating estimates. These are accomplished by combining the predictions of the determurustic model with real time observauons modified by the Kalman filter gain ractor. Inundation risks are also estimated by applying Monte Carlo simulation to consider the variability in cross section geometry and Manning's roughness coefficient. The model calibrated by applying to the floods ot South Han River on September, 1990 and August, 1995. The Kalman tilter model indicates that significant improvement compared to deteriministic analysis in flood routing predictions in the river. Overtopping risk of levee is also presented by comparing levee height with simulated flood level. level.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.211-211
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• 2021

최근에 기후변화로 인한 한반도에 내습하는 태풍에 빈도는 점차 증가하고 있다. 2020년도 8월 26일 태풍 '바비', 9월 2일 태풍 '마이삭', 9월 7일 태풍 '하이선'은 일주일 내의 간격으로 한반도를 내습하였다. 한반도에 내습한 태풍 중에서 마이삭과 하이선은 동쪽 해역을 지나가면서 강풍과 많은 강우를 초래하였다. 그 결과 특정 원전은 자동 가동중지가 발생되는 사태를 야기 시켰다. 본 연구에서는 원자력 발전소 인근 해역에서 폭풍해일에 의한 가능최대파고 높이를 추정함으로써 발전소 안전성에 대한 검토에 목적을 두고 있다. 이를 위해 첫 번째로 '2019 전국 심해 설계파 산출 보고서'를 바탕으로 원전 인근 해역 심해 설계파 지점에 대해 파고, 주기, 해상풍과 같은 변수들을 분석하였다. 그 결과를 바탕으로 100년부터 1000만년까지의 변수들을 예측하였다. 두 번째로 해도자료를 바탕으로 GIS를 통한 지형자료를 구축하였다. 구축된 지형자료를 바탕으로 SWAN 모델의 기초자료를 구성하였다. 세 번째로 추정된 변수들과 구축된 지형자료를 바탕으로 100년부터 1000만년까지의 시나리오별 SWAN 시뮬레이션을 통해서 원전 인근 해역에 대한 가능 최대 파고 높이를 분석하였다. 그 결과를 바탕으로 특정 원전인근 해역에서의 평균적인 파고 높이에 대한 재해도 곡선을 추정하고 제시하였다. 본 연구를 바탕으로 향후 확률론적인 분석 방법을 적용하여 불확실성을 고려한 재해도 곡선 추정 과정의 기초자료로 활용될 수 있다. 또한 EurOtop을 적용하여 파고 높이에 따른 원전부지의 Overtopping을 추정하고, 최종적으로 폭풍해일에 의한 원전부지의 2차원 침수해석의 기초자료로 활용할 수 있을 것으로 판단된다. 이를 통해 홍수 방지 및 예방과 관련한 홍수저감 활동과 관련된 통제실 외부 시설물에 대한 수동 조작에 대한 안전성 평가가 이루어질 수 있겠다.