• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.5
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• pp.335-347
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• 2013

In February 2008, high storm waves due to a developed atmospheric low pressure system propagating from the west off Hokkaido, Japan, to the south and southwest throughout the East Sea (ES) caused extensive damages along the central coast of Japan and along the east coast of Korea. This study consists of two parts. In the first part, we estimate extreme storm wave characteristics in the Toyama Bay where heavy coastal damages occurred, using a non-hydrostatic meteorological model and a spectral wave model by considering the extreme conditions for two factors for wind wave growth, such as wind intensity and duration. The estimated extreme significant wave height and corresponding wave period were 6.78 m and 18.28 sec, respectively, at the Fushiki Toyama. In the second part, we perform numerical experiments on wave-structure interaction in the Fushiki Port, Toyama Bay, where the long North-Breakwater was heavily damaged by the storm waves in February 2008. The experiments are conducted using a non-linear shallow-water equation model with adaptive mesh refinement (AMR) and wet-dry scheme. The estimated extreme storm waves of 6.78 m and 18.28 sec are used for incident wave profile. The results show that the Fushiki Port would be overtopped and flooded by extreme storm waves if the North-Breakwater does not function properly after being damaged. Also the storm waves would overtop seawalls and sidewalls of the Manyou Pier behind the North-Breakwater. The results also depict that refined meshes by AMR method with wet-dry scheme applied capture the coastline and coastal structure well while keeping the computational load efficiently.

• Journal of Navigation and Port Research
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• v.42 no.6
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• pp.427-436
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• 2018

In this study, experimental and numerical analysis were performed on the survivability of a long pipe-type buoy structure in waves. The buoy structure is an articulated tower consisting of an upper structure, buoyancy module, and gravity anchor with long pipes forming the base frame. A series of experiment were performed in the ocean engineering basin of KRISO with the scaled model of 1/ 22 to evaluate the survivability of the buoy structure at West Sea in South Korea. Survival condition was considered as the wave of 50 year return period. Additional experiments were performed to investigate the effects of current and wave period. The factors considered for the evaluation of the buoy's survival were the pitch angle of the structure, anchor reaction force, and the number of submergence of the upper structure. Numerical simulations were carried out with the OrcaFlex, the commercial program for the mooring analysis, with the aim of performing mutual validation with the experimental results. Based on the evaluation, the behavior characteristics of the buoy structure were first examined according to the tidal conditions. The changes were investigated for the pitch angle and anchor reaction force at HAT and LAT conditions, and the results directly compared with those obtained from numerical simulation. Secondly, the response characteristics of the buoy structure were studied depending on the wave period and the presence of current velocity. Third, the number of submergence through video analysis was compared with the simulation results in relation to the submergence of the upper structure. Finally, the simulation results for structural responses which were not directly measured in the experiment were presented, and the structural safety discussed in the survival waves. Through a series of survivability evaluation studies, the behavior characteristics of the buoy structure were examined in survival waves. The vulnerability and utility of the buoy structure were investigated through the sensitivity studies of waves, current, and tides.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.368-368
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• 2020

최근 초대형화 되어 나타나고 있는 이상홍수와 지진 등에 의한 저수지 붕괴와 같은 대규모 비상상황 발생으로 하류지역 주민의 생명과 재산의 피해가 발생하고 있다. 국내의 경우 1996년 이후로 지속적으로 발생하고 있는 이상홍수로 인해 1998년에는 40개,1999년에는 5개의 소규모 저수지가 붕괴되었으며 최근 2013년과 2014년에도 저수지가 붕괴되는 상황이 발생했다. 댐붕괴의 원인은 구조물의 자연적 노화, 극심한 강우나 홍수, 지진, 제체전도, 파이핑, 침윤발생, 월류 및 파랑 등에 의한 자연적 상황 등이 요인이 될 수 있으며, 시공결함, 사고 또는 전쟁과 같은 인위적인 요인으로 발생할 수도 있다. 과거에 설계 및 시공기술이 부족하였거나 경제적인 이유로 부실하게 건설되어 있는 댐이 세계적으로 산재되어 있어 잠재적인 위험을 상당수 내재하고 있는 실정이다. 본연구는 댐의 점진적인 파괴에 의해 발생하는 유출수문곡선을 구하고 파괴의 성질을 예측 및 홍수파를 수리학적으로 추적하기위해 BREACH 모형과 DAMBRK 모형을 사용했으며 극한홍수(PMF)조건과와 최대지진발생(MCE)조건을 적용하여 원주시 관내 저수지 붕괴 모의 시나리오를 구축했다. 저수지 붕괴에 따른 유출수문곡선을 유도하기 위해서 본 연구에서는 기존의 EAP보고서 자료를 참고하여 붕괴지속시간, 붕괴부 평균폭, 붕괴부 측벽면 경사의 변화에 따라 다양한 모의를 수행함으로써 발생되는 붕괴부 유량 수문곡선을 도출하여 각각의 조건들이 붕괴파 형성에 미치는 영향에 대한 분석을 실시하였다. 그 결과 저수지의 붕괴시 첨두유출량에 민감한 영향을 주는 인자는 붕괴지속시간과, 붕괴부 평균폭으로서 이들 값이 붕괴유출량 변화에 많은 영향을 주는 것으로 나타났다. 최대지진발생(MCE)조건 해석결과 홍수류의 범람으로 인해 홍수파가 하류측으로 진행할수록 완만히 감소하며, 하천 중·상류부 인근 제내지로 홍수류의 범람이 발생하는 것으로 검토되었으며, 극한홍수(PMF)조건 해석결과 최대지진발생(MCE)조건과 같이 홍수파가 하류측으로 진행할수록 완만히 감소하는 특성을 보이며, 하천 전체 구간에서 인근제내지로 홍수류의 범람이 발생하는 것으로 검토되었다. 본 연구는 침수구역 피해규모 산정 및 비상대처계획도를 작성시 기초데이터가 되어 상황별 피해예상지역에 대해 응급행동요령, 주민대피계획비상대처계획을 수립하여 지역 주민생활에 안정을 기여하고자 한다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.374-382
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• 2021

The scour risk assessment was conducted for ultimate limit state of newly developed penta pod suction bucket support structures for a 5.5 MW offshore wind turbine. The hazard was found by using an empirical formula for scour depth suitable for considering marine environmental conditions such as significant wave height, significant wave period, and current velocity. The scour fragility curve was calculated by using allowable bearing capacity criteria of suction foundation. The scour risk was assessed by combining the scour hazard and the scour fragility.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.11a
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• pp.111-112
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• 2022

자율운항 선박, 무인선 개발과 동 분야 디지털트윈 구현을 위해서는 선박 내부 데이터의 수집을 담당할 고신뢰성 선내 통신망 확보가 필수적이다. WiFi와 같은 전파 기반의 무선통신 시스템은 금속 구조물로 구성되는 선박 내 환경 자체가 원활한 통신의 장애 요소이다. 이러한 극한 환경 극복을 위해 자기장을 금속 표면에 유기하여 비 전파 기반으로 무선통신을 가능하게 하는 표면파 통신이 대안이 될 수 있다. 선박 전체의 일반 배치 관점에서 표면파 통신은 상갑판을 통해 크게 거주구역, 화물구역, 선수구역 및 기관구역 간 백본 통신망을 구성할 수 있으며 각 구역 별로는 부재의 개구부를 통해 금속 표면의 연속면을 확보하여 통신할 수 있다. 수밀 격벽의 표면파 통신 관통을 위해 비 도전체로 수밀은 유지한 채 아주 미세한 구멍을 확보하는 것으로도 금속 표면의 연속성을 확보할 수 있다. 이러한 표면파 통신을 활용하면 전파 기반의 무선통신, 비 전파 기반의 무선통신을 통합적으로 구성하여 선박 전체로는 선내 무선 백본망 구성, 그리고 각 구역 별로는 IoT 센서 네트워크 등의 선박 내부 고신뢰성 무선통신 확보가 가능하다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.211-218
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• 2004

The WAM wave model has been widely used for wave hindcasting in the ocean by many domestic and foreign researchers due to its relative simplicity and high accuracy. As this model was originally developed for the condition cf deepwater and comparatively coarse grid size covering wide area, it might produce in a fault result mused by the improper distribution of directional spreading. We extensively investigated involved problems based on WAM Cycle 4 model and suggested the improved WAM model so that it is applicable to both shallow water sea and fine mesh wave simulation. The modified WAM model is verified here by comparing the computed result with and the observed data at Ieodo Ocean Research Station for September of 2003.

• Journal of Navigation and Port Research
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• v.28 no.6
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• pp.557-564
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• 2004

The WAM wave model has been widely used for wave hindcasting in the ocean by many domestic and foreign researchers due to its relative simplicity and high accuracy. As this model was originally developed for the condition of deepwater and comparatively coarse grid size covering wide area, it might produce in a fault result caused by the improper distribution of directional spreading. We extensively investigated involved problems based on WAM Cycle 4 model and suggested the improved WAM model so that it is applicable to both shallow water sea and fine mesh wave simulation The modified W AM model is verified here by comparing the computed result with and the observed data at Ieodo Ocean Research Station for September of 2003.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.309-316
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• 2003

In this paper, The statistical properties of ocean waves in the sea area of Hong-do, Korea are examined based on 1998-2002's wave data from a directional wave buoy. Wave data aquisition rate, mean wave heights, frequency of wave direction are summarized. Wave height and period scatter diagrams and n-years return period wave heights are estimated. Wave periods of maximum wave heights are also estimated. Large amplitude wave characteristics during the typhoon Prapiroon in 2000, Rusa in 2002 are also examined.

• 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.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.5
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• pp.558-565
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• 2017

Accurate prediction of wave-structure interactions is important in the safety and design cost effectiveness of fixed and floating offshore structures exposed to extreme environmental conditions. In this study, regular waves and circular column structure interactions for four circular columns in regular waves are analyzed. To simulate 3D two-phase flow, open source computational fluid dynamics libraries, called OpenFOAM, were used. When the four circular columns are arranged in a square array, the interactions according to the incident slopes of the regular waves are analyzed. The wave run-up in the circular column surface was compared according to the slope of the incident wave. It was confirmed that high amplitude waves are generated between the circular columns due to the interaction between the circular column and the incident wave. It is expected that this analytical result will be used as the basic data of the study on the air gap due to the interaction between the structure and incident wave.