• 한국해양공학회지
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• 제38권3호
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• pp.103-114
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• 2024

Remote sensing wave observation data are crucial when analyzing ocean waves, the main external force of coastal disasters. Nevertheless, it has limitations in accuracy when used in low-wind environments. Therefore, this study collected the raw data from MIROS Wave and Current Radar (MWR) and wave radar at the Ieodo Ocean Research Station (IORS) and applied the optimal filter by combining filters provided by MIROS software. The data were validated by a comparison with South Jeju ocean buoy data. The results showed it maintained accuracy for significant wave height, but errors were observed in significant wave periods and extreme waves. Hence, this study used an artificial neural network (ANN) to improve these errors. The ANN was generalized by separating the data into training and test datasets through stratified sampling, and the optimal model structure was derived by adjusting the hyperparameters. The application of ANN effectively improved the accuracy in significant wave periods and high wave conditions. Consequently, this study reproduced past wave data by enhancing the reliability of the MWR, contributing to understanding wave generation and propagation in storm conditions, and improving the accuracy of wave prediction. On the other hand, errors persisted under high wave conditions because of wave shadow effects, necessitating more data collection and future research.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2003년도 춘계공동학술대회논문집
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• pp.147-156
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• 2003

해상수송의 안전성을 개선하는 하나의 수단으로서, 해상풍 정보로부터 예정 항로상에서 조우하게될 파랑정보를 높은 정밀도로 예측하여 단시간에 본선에 제공할 수 있는 시스템을 개발할 필요가 있다. 본 연구에서는 이의 제1단계로서 대양에서의 다방향 불규칙 예측을 위한 파랑추산모델을 제시하였다. 검토방법으로는 과거 실제 해역에서 발생한 황천에 기인한 선박 침몰사고를 대상으로 선박의 항행 일정에 따른 해상풍의 분석 및 파랑추산시뮬레이션을 수행하였으며, 이로부터 사고 선박이 조우한 해상을 평가하고 모델의 재현성 및 정도를 검토하였다.연구의 결과, 사고 선박은 침몰사고의 원인이 Okhotsk해에서 발랄한 저기압에 의해 급속히 성장한 고파랑 해역을 회피하지 못하여 발생한 것에 있음을 명백히 하였으며, 본 계산에 이용한 제3세대 파랑추산모델(WAM)로부터의 결과는 실제 관측 파랑의 유의파고, 주기, 방향 스펙트럼 등 항행관련의 파랑제원과 잘 부합되었으며, 실용 선박에서의 예측시스템 구축에 적용성이 양호한 것으로 나타났다.

• 대기
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• 제20권4호
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• pp.505-518
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• 2010

We investigated the impacts of the diabatic heating location, vertical profile and basic state on the Rossby wave propagation. To examine the dynamical process of individual responses on the regional heat source, a dry version of the linear baroclinic model was used with climatological summertime (JJA) mean basic state and vertical structure of the diabatic heating for 1979-2008. Two sets of diabatic heating were constructed of those positioned in the mid-latitudes (Tibetan Plateau, eastern Mediterranean Sea, and the west-central Asia) and the tropics (the southern India, Bay of Bengal, and western Pacific). It was found that using the principal component analysis, atmospheric response to diabatic heating reaches to the steady state in 19th days in time. The prescribed mid-latitude forcing forms equivalent barotropic Rossby wave propagation along the westerly Asia jets, whereas the tropical forcing generates the Rossby wave train extending from the tropics to mid-latitudes. In relation to the maximum vertical profile, the mid-level forcing reveals a stronger response than the lower-level forcing, which may be caused by more effective Rossby wave response by the upper-level divergent flow. Under the different sub-seasonal mean state, both of the tropical and mid-latitude forcing induce the different sub-seasonal response intensity, due to the different basic-state wind.

• 한국항해항만학회지
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• 제31권6호
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• pp.479-484
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• 2007

항만 및 해안구조물의 설계시 사용되는 천해역에서의 파랑장 계산은 내륙 관측소의 바람자료를 이용하거나 심해파 추산모형에 의하여 추출된 심해파제원을 사용하는 것이 일반적이다. 그러나 전자의 경우는 관측소가 대부분 내륙에 위치하여 파랑발달을 모의하기 위한 정확한 바람자료를 얻기란 매우 어렵다. 또한, 후자의 경우는 아주 넓은 영역에서 큰 격자크기로 계산이 이루어지기 때문에 연안 및 천해역 지형을 상세히 재현하지 못하므로 임의의 정점에 대한 정확한 정보를 파악하기도 어렵다. 따라서, 본 연구에서는 우리나라 동남부 해역의 태풍 ‘매미’ 내습시의 파랑 관측자료를 사용하여 천해역에서의 파랑장 계산을 수행하였다. 또한, 계산된 파랑장의 정확도를 확인하기 위하여 울산해역 인근의 파고 및 파향 관측결과를 비교 검토하였다. 울산해역에 대한 파고분포 산출결과, 관측정점에서 파고는 ${\pm}1.3%$의 차이를 보여 기존의 방법 보다 높은 정확도를 보이는 것으로 나타났다.

• 한국항해학회지
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• 제8권2호
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• pp.51-70
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• 1984

In the North Pacific Ocean a lot of large waves set up in winter, affected by continued winds and swells owing to severe extratropical cyclones. Under this sea condition, if the ship is about 100,000L/T (in deadweight capacity tonnage), we can't find the danger involved in the ship at sea apparently. But when we compare the seaworthiness of ship's building strength with the stress given to the hull by waves, we can't insist that the former be more stronger than the latter. As a result, VLCC is in danger of destroying and cutting for lack of longitudinal strength in heavy weather. Up to this time, Naval Architects have actively studied the relation between ship's longitudinal strength and waves as a ship's projector; however, actually, they have never made more profound study on the problem of longitudinal strength in relation to navigation. The main puprpose of this thesis is to clarify these vivid actual states of ship's trouble unknown to ship's masters. In this thesis we picked up VLCC Pan Yard, a vessel of Pan Ocean Bulk Carrier company's, as a model ship. And in the North Pacific Ocean, we have chosen for this research the basins where the wind speed and the wave height are greater than average. The data used this thesis are quotes from the "winds and waves of the North Pacific Ocean('64-'73)", and wind speed more than 30 knots was made use of as an ocject of this study. By usinh the ITTC wave spectrum, we found out the significant waves for every 5 knots within the range of 20 knots to 45 knots of wind speed. According to this H1/1000 was calculated. The stress of ship's hull is determined by ship's speed and wave height. We compared the ship's longitudinal strength with a planned wave height by rules of several famous classification societies in the world. In the last analysis, we found out that ship's present planned strength in heavy weather is not enough. Finally we made a graph for avoiding heavy weather, with which we studied safe ship's handling in the North pacafic Ocean in winter.

• 한국해안해양공학회:학술대회논문집
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• 한국해안해양공학회 2006년도 추계학술대회 발표논문집 Proceedings of Coastal and Ocean Engineering in Korea
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• pp.41-44
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• 2006

• 한국추진공학회지
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• 제22권2호
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• pp.52-58
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• 2018

유체 유동 시스템에서 히스테리시스 현상은 다양한 산업 및 공학 응용 분야에서 발생하며, 최근 이에 대한 많은 연구가 수행되어 왔다. 이러한 현상은 주로 압력비가 일시적으로 변화하는 과정에서 발생하며 초음속 풍동에 영향을 미칠 것으로 예상되나, 이에 대한 연구는 찾아보기 힘들다. 본 연구에서는 초음속 풍동 내부에서 발생하는 히스테리시스 현상을 수치해석으로 조사하였다. 비정상, 축대칭, 압축성 N-S 방정식을 유한 체적법으로 이산화 하였으며, 난류모델은 Spalart-Allmaras을 적용하였다. 본 연구의 결과로 전압의 증감에 따라, 동일한 압력비에서 발생하는 충격파의 위치가 다르게 나타났으며, 이를 통해 초음속 풍동을 효율적으로 작동시킬 수 있는 최적의 압력비를 찾을 수 있음을 알았다.

• 한국해양공학회지
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• 제33권5호
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• pp.435-446
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• 2019

Because offshore structures are affected by various environmental loads, the risk of damage is high. As a result of ever-changing ocean environmental loads, damage to offshore structures is expected to differ from year to year. However, in previous studies, it was assumed that a relatively short period of load acts repeatedly during the design life of a structure. In this study, the residual life of an offshore wind turbine support structure was evaluated in consideration of the timing uncertainty of the ocean environmental load. Sampling points for the wind velocity, wave height, and wave period were generated using a central composites design, and a transfer function was constructed from the numerical analysis results. A simulation was performed using the joint probability model of ocean environmental loads. The stress time history was calculated by entering the load samples generated by the simulation into the transfer function. The damage to the structure was calculated using the rain-flow counting method, Goodman equation, Miner's rule, and S-N curve. The results confirmed that the wind speed generated at a specific time could not represent the wind speed that could occur during the design life of the structure.

• 한국환경과학회지
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• 제11권10호
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• pp.1133-1140
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• 2002

The growth and extent of the local pressure field at any point is of primary importance as it supplies the driving force for the local wind circulation which causes a medium-range transport of air pollutants. The local pressure field is produced by the variation of temperature in the lower layers of the atmosphere, and is called the thermal wave. The thermal wave is influenced by the difference in the diurnal variations between two regions with different surface condition, for example land and sea. This difference produces the land- and sea-breeze phenomenon, and brings corresponding variations in the form of the thermal wave. Daytime temperature over the inland area (Daegu) was higher than that of the coastal area (Busan). The temperature difference reached about 5~6$^{\circ}C$ in the late afternoon(30-31 May 1999). The low pressure system of Daegu was most fully developed at the time. In this study, we investigated the possibility of thermal low onset around Daegu in summer with an analytical model. The topography effect was neglected in the model. We could predict a thermal low-pressure of about 3.4hPa at Daegu with wide flat land surface, when the inland area is about 6K warmer than the coastal area temperature. The pressure decrease is somewhat less than the observed value(4~5 hPa).

• 한국해안해양공학회지
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• 제2권1호
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• pp.51-57
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• 1990

수심변화가 완만하고 흐름이 없는 곳을 파가 전파할 때 겪게되는 침수, 굴절 및 회절현상의 해석에는 3차 Stokes파 이론에 의한 선형, 비선형, 포물형 방정식이 이용되며, 여기서는 바닥마찰과 바람의 영향은 고려하지 않는다. 이 포물형 방정식으로 암초가 있는 경우에 대해 수치해석을 수행하여 기존의 실험치와 비교 검토하였고, 회절과 굴절효과의 중요성을 고찰했다. 천해파의 특성변화 해석에는 Boussinesq방정식에 기초한 포물형 방정식이 이용된다. 흐름이 없는 경우에 방파제를 따라 전파하는 Cnoidal파의 회절현상을 수심이 변하고 입사각이 변하는 경우에 대해 수치해석을 하여 Stem wave의 특성에 대해 논의하였다.