• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 2008.04a
• /
• pp.154-156
• /
• 2008

• Journal of Navigation and Port Research
• /
• v.31 no.3 s.119
• /
• pp.223-228
• /
• 2007

In recent trends of the enlargement and specialization, container ship, LNCG, PCC and passenger ship which have relatively large hull and superstructure above the water line, are already being operated in the world It is very important information for the safety operation of these vessels to estimate the ship's performance under the specific wind condition while berthing, unberthing or low-speed sailing. In this paper, the effect of wind force and moment acting on the training ship HANNARA is investigated by using the numerical calculations. The results of drift angle and counter rudder angle with the relative wind direction and force, the critical wind velocity with the ratio of wind velocity and ship's speed and maximum heeling angle with the wind velocity are shown The presented results can be applied directly to T/S HANNARA in berthing maneuver and avoiding typhoons, and utilized as an educational materials.

• 한국지구과학회:학술대회논문집
• /
• 2010.04a
• /
• pp.51-51
• /
• 2010

본 연구에서는 태풍 초기화된 수치모델과 AWS (Automatic Weather System) data를 이용하여 제주도를 통과하는 태풍들의 바람 강도 특성을 분석하였다. 태풍이 내습했을 때 제주도 전 지역에서 동시 관측을 하기에는 불가능하다. 따라서 중규모 수치 모델인 Advanced Research WRF v3.0.1을 사용하여 분석하였으며 더욱 정확한 태풍 모의를 위해 Kwon and Cheong (2009)에 의해 개발된 정교한 태풍 초기화 기법을 적용하였다. 태풍 초기화된 자료에 의해 모의된 결과는 The Regional Specialized Meteorological Center (RSMC) Tokyo의 예보 오차와 비교했을 때 더 향상된 결과를 보였으므로 태풍 초기화 기법의 사용은 본 연구에서 하고자하는 태풍들의 바람 강도 분석에 타당하다고 판단하였다. 그리고 모의된 결과는 그에 상응하는 AWS data와의 joint distribution (Moskaitis, 2008) 분석을 통해 비교되었다. 태풍 경로에 따른 제주도 지역의강 풍을 고려하기 위해 각각 제주도의 오른쪽과 왼쪽을 지나가는 2003년 6호 태풍 'SOUDELOR'와 2004년 7호 태풍 'MINDULLE'를 선정하였다. 또한, 모의 결과로부터 제주도 지역에 태풍이 내습했을 때 강풍의 상대적인 크기의 비교를 위해 모의된 태풍의 최대 풍속을 수치 모의로 얻은 10m 바람장의 모든 격자점에 나누어 정규화 하였다. 이를 시간에 대해 평균하여 태풍이 제주도 지역을 통과하는 전체시간에 대한 상대적인 강도 특성을 분석하였다. 수치 모의 결과와 관측 자료와의 joint distribution 분석 결과, 바람의 크기와 경향이 비교적 잘 일치하였다. 강한 풍속과 약한 풍속이 나타나는 지역은 제주도 지역의 주풍향과 지형의 영향에 크게 좌우되었다. 정규화된 바람은 산악의 정상에서 강풍이 관측되고 주 풍향에 대해 풍상측과 풍하측에서 비교적 낮은 풍속이 관측되는 결과를 보였다. 이는 Hoinka (1985)의 산악 위에서의 바람의 특성에 관한 연구에서 얻어진 결과와 유사하다. 서로 다른 경로로 통과하는 두 태풍의 모의 결과에서 제주도의 북서쪽 지역과 남동쪽 지역에서 상대적으로 약한 풍속이 관측되었다. 따라서 해당지역에서는 태풍에 동반되는 강풍의 피해를 적게 입을 것이라는 것을 알 수 있었다.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.12
• /
• pp.88-92
• /
• 2017

Owing to the depletion of fossil energy, wind power is attracting attention as a promising environmentally friendly alternative energy source, because it is abundant, renewable, and non-polluting. Wind turbines are divided into horizontal axis wind turbines (HAWTs) and vertical axis wind turbines (VAWTs) according to the direction of the rotating shaft. VAWTs have a low power generation efficiency, but are not affected by the wind direction and, thus, no yaw system is required and their structure is simple. Small VAWTs are attracting much attention because they can generate power even at low wind speeds. In this study, the output voltages and output currents of small VAWTs with gyromill type, hinge type and double door type blades capable of generating power even at low wind speeds were analyzed at variable wind speeds in the range of 1~11 m/s. At the maximum wind speed of 11m/s, the application of the double door type blades achieved 67% and 9% higher wind turbine output voltages than that of the gyromill type and hinge type blades, respectively. As regards the wind turbine output currents, the application of the double door type blades gave rise to 93% and 5% higher results than that of the gyromill type and hinge type blades, respectively. Through this study, the excellent output characteristics and commercialization potential of the double door type blades, which can generate power both at low and high wind speeds, were confirmed.

• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.4
• /
• pp.344-350
• /
• 2013

The purpose of this study is to examine the structural stability of a low speed 200 W class gyromill type vertical axis wind turbine system. For the analysis, a commercial code is adopted. The pressure distribution on the rotor blade surface is examined in detail. In order to perform unidirectional FSI(Fluid-Structure Interaction) analysis, the pressure resulted from CFD analysis has been mapped on the surface of wind turbine as load condition. The rotational speed and gravitational force of wind turbine are also considered. The results of FSI analysis show that the wind turbine reveals an enough structural margin. The maximum structural displacement occurs at trailing edge of blade and the maximum stress occurs at the strut.

• Journal of Navigation and Port Research
• /
• v.34 no.6
• /
• pp.453-458
• /
• 2010

This paper studies relationship between global warming and trends of typhoon variation by using the meteorological long-term data. The results show that yearly mean typhoon's occurrence numbers decrease and maximum wind speeds strengthen gradually. These results are in accord with most of simulated results. While the normal course of typhoon is increased, the westward course of that is decreased. Typhoon trajectories show that the ratios of normal course 6 : westward course 3 : abnormal course 1 in the last 10 years. Among typhoons which affect to the Korea ones pass through the southern coast of Korea are the most. The numbers of typhoon pass through the western coast of Korea are decreased and those pass through the eastern coast of Korea show increasing trend lately. The notable point in relation to the global warming is that typhoon intensity is strengthened gradually. Watch and counterplan in the viewpoint of prevention to the meteorological disasters are required.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2011.06a
• /
• pp.232-233
• /
• 2011

이 연구에서는 최근 25년간(1986-2010년)의 우리나라 기상청 및 일본 기상청 자료를 사용하여 엘니뇨 라니냐 현상과 태풍과의 관계를 분석하였다. 여기서는 엘니뇨감시해역의 해면수온의 기준치와의 차의 5개월 이동평균치가 6개월 이상 계속하여 $+0.5^{\circ}C$ 이상 이 된 경우를 엘니뇨현상, $-0.5^{\circ}C$ 이하가 된 경우를 라니냐현상이라고 정의한다. 그리고 엘니뇨 발생년은 엘니뇨현상이 시작된 해부터 종료된 해까지를, 라니냐 발생년은 라니냐현상이 시작된 해부터 종료된 해까지로 정의한다. 주요 분석 결과는 다음과 같다. 전 기간에 대한 태풍의 연평균 발생 수는 25.4개이다. 이는 60년간(1951-2010년)의 연평균 태풍 발생 수 26.3개보다 약 1개 적은 결과로 최근 지구온난화와 관련하여 태풍의 발생 수가 감소 추세를 보이고 있다는 연구 결과를 뒷받침한다. 엘니뇨 발생년의 연평균 태풍 발생 수는 23.9개이고, 라니냐 발생년의 그것은 24.9개이다. 적도 부근 서부 태평양의 따뜻한 물이 동쪽으로 이동하여 동부 태평양의 해면수온이 평년 이상으로 높아지는 엘니뇨 발생년에 태풍의 발생 수가 감소한다는 사실을 알 수 있다. 태풍의 세기를 나타내는 평균 중심최저기압과 평균 최대풍속은 엘니뇨 발생년에 959.3hPa과 35.8m/s, 라니냐 발생년에 965.5hPa과 33.7m/s 그리고 25년 전 기간에 대하여는 962.3hPa과 35.0m/s이었다. 엘니뇨 발생년의 태풍의 세기가 라니냐 발생년의 태풍의 세기보다 강함을 알 수 있다.

• Journal of the Korean earth science society
• /
• v.29 no.7
• /
• pp.567-578
• /
• 2008

The extratropically transitioning cyclones have been shown to have a large effect on weather system in the midlatitues and cause sometimes the severe weather phenomena. However, both operational forecasting and research aspect of ET remain a significant challenge. Because it is difficult to distinguish ET stage due to obscure configuration of the cyclone itself. Furthermore, any definition of ET should not only be precise enough to satisfy the needs of the operational and research communities. Therefore, the "operational deterministic process for ET" was proposed and has been used to diagnose both structure and subsequent process of ET in 2007. In this study, it has been examined the maximum wind and SST in the 1st step, satellite image in the 2nd step, sounding in the 3rd step, surface weather chart analysis in the final step. This operational manual has allowed better monitoring and understanding of the changes in the structure as ET occurs.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.24 no.4
• /
• pp.305-316
• /
• 2022

Hydrogen energy is emerging as an alternative to the depletion of fossil fuels and environmental problems, and the use of hydrogen vehicles is increasing in the automobile industry as well. However, since hydrogen has a wide flammability limit of 4 to 75%, there is a high concern about safety in case of a hydrogen car accident. In particular, in semi-enclosed spaces such as tunnels and underground parking lots, a fire or explosion accompanied by hydrogen leakage is highly likely to cause a major accident. Therefore, it is necessary to review hydrogen safety through analysis of flammability areas caused by hydrogen leakage. Therefore, in this study, the effect of the air velocity in the tunnel on the flammability area was investigated by analyzing the hydrogen concentration according to the hydrogen leakage conditions of hydrogen vehicles and the air velocity in the tunnel in a road tunnel with standard section. Hydrogen leakage conditions were set as one tank leaking and three tanks leaking through the TPRD at the same time and a condition in which a large crack occurred and leaked. And the air velocity in the tunnel were considered 0, 1, 2.5, and 4.0 m/s. As a result of the analysis of the flammability area, it is shown that when the air velocity of 1 m/s or more exists, it is reduced by up to 25% compared to the case of air velocity of 0 m/s. But there is little effect of reducing the flammability area according to the increase of the wind speed. In particular, when a large crack occurs and completely leaks in about 2.5 seconds, the flammability area slightly increases as the air velocity increases. It was found that in the case of downward ejection, hydrogen gas remains under the vehicle for a considerably long time.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.12 no.4
• /
• pp.251-261
• /
• 2007

The wind-wave interaction around the Kyung-gi Bay, Korea, was studied using the observed data from ocean buoy at DeuckJeuck-Do from Jan. to Dec., 2005, and from waverider data at KeuckYeulBee-Do on Mar. 19-26 and May 23-28, 2005. Wind-driven surface waves and wave-driven wind speed decrease were estimated from the ocean buoy data, and the characteristics of wave spectrum response were also investigated from the waverider data for the wave developing and calm stages of sea surface, including the time series of spectrum pattern change, frequency trend of the maximum energy level and spectrum slope for the equilibrium state range. The wind speed difference between before and after considering the wave effect was about $2ms^{-1}$ (wind stress ${\sim}0.1Nm^{-2}$) for the wind speed range $5-10ms^{-1}$ and about $3ms^{-1}$ (wind stress ${\sim}0.4Nm^{-2}$) for the wind speed range $10-15ms^{-1}$. Correlation coefficient between wind and wave height was increased from 0.71 to 0.75 after the wave effect considered on the observed wind speed. When surface waves were generated by wind, the initial waves were short waves about 4-5 sec in period and become in gradual longer period waves about 9-10 sec. For the developed wave, the frequency of maximum energy was showed a constant value taking 6-7 hours to reach at the state. The spectrum slope for the equilibrium state range varied with an amplitude in the initial stage of wave developing, however it finally became a constant value 4.11. Linear correlation between the frictional velocity and wave spectrum for each frequency showed a trend of higher correlation coefficient at the frequency of the maximum energy level. In average, the correlation coefficients were 0.80 and 0.82 for the frequencies 0.30 Hz and 0.35 Hz, respectively.