• Journal of the Korean earth science society
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• v.35 no.4
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• pp.237-248
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• 2014

To analyze the characteristics of deposition and dispersion of volcanic ash emitted from Mt. Kirishima on January 26, 2011, several numerical simulations were carried out by using the numerical models including Weather and Research Forecast (WRF) and FLEXPART. The dispersion of ash located under 1 km high tends to be concentrated along the prevailing wind direction on January 26 2011. On the other hand, volcanic ash released on the following day spreads to Kirishima bay due to the intensified high pressure air mass in southern Kyushu. When Siberian air mass was intensified January 26, 2011, the deposition of volcanic ash is concentrated restrictedly in the narrow area along the wind direction of the downwind side of Mt. Kirishima. The development of high pressure air mass over the eruption area tends to induce the intensified horizontal diffusion of volcanic ash. Since the estimated deposition of volcanic ash is agreed well with observed values, the proposed numerical simulation is reasonable to use the assessment on the behavior of volcanic ash.

• Korean Journal of Remote Sensing
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• v.33 no.5_1
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• pp.587-598
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• 2017

Volcanic ash is a fine particle smaller than 2 mm in diameters. It falls after the volcanic eruption and causes various damages to transportation, manufacturing industry and respiration of living things. Therefore diffusion information of volcanic ash is highly significant for preventing the damages from it. It is advantageous to utilize satellites for observing the widely diffusing volcanic ash. In this study volcanic ash diffusion information about two eruptions of Mt. Sakurajima were calculated using the geostationary satellite, Communication, Ocean and Meteorological Satellite (COMS) Meteorological Imager (MI) and polar-orbiting satellite, Landsat-8 Operational Land Imager (OLI) and the Thermal InfraRed Sensor (TIRS). The direction and velocity of volcanic ash diffusion were analyzed by extracting the volcanic ash pixels from COMS-MI images and the height was retrieved by adjusting the shadow method to Landsat-8 images. In comparison between the results of this study and those of Volcanic Ash Advisories center (VAAC), the volcanic ash tend to diffuse the same direction in both case. However, the diffusion velocity was about four times slower than VAAC information. Moreover, VAAC only provide an ash height while our study produced a variety of height information with respect to ash diffusion. The reason for different results is measured location. In case of VAAC, they produced approximate ash information around volcano crater to rapid response, while we conducted an analysis of the ash diffusion whole area using ash observed images. It is important to measure ash diffusion when large-scale eruption occurs around the Korean peninsula. In this study, it can be used to produce various ash information about the ash diffusion area using different characteristics satellite images.

• Journal of the Korean earth science society
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• v.33 no.3
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• pp.280-293
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• 2012

In order to clarify the characteristics of dispersion of volcanic tephra emitted from the Mt. Baegdu with various eruption environment, numerical analysis were performed using numerical models, Weather Research and Forecast (WRF) and FLEXPART. Synoptic conditions at 12 October 2010 was adopted because the volcanic ash of Mt. Baegdu can reach the Korean peninsula and its dispersion pattern was compared with different Volcanic Explosivity Index (VEI) and particle size. Predominant size of falling out ash flowing in the peninsular is smaller than 0.5 mm and the ash large than the size is difficult to get in the peninsular due to the its weak ability of truculent diffusion. the difference of ash distribution with various VEI scenarios is not so much but number density of ash in the air is dramatically changed. Volcanic ash tends to be deposited easily in eastern coastal area such as Gangneung and Busan, because of the inflow of ash from East Sea and barrier effect of the Taeback mountains along the east coast of the Korean Peninsula. Accumulated amount of ash deposition can be increased in short period in several urban areas.

• Journal of the Korean earth science society
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• v.34 no.6
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• pp.536-549
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• 2013

This study investigates the damages of and analyzes the social and economic impacts of volcanic ash eruptions in the world in order to estimate the potential volcanic ash impacts in South Korea when Mt. Baekdusan volcano erupts in the future. First, we build a comparison chart called "the impact of volcanic ash" on each economic and social sector by using major volcanic eruptions and we compare the damage with respect to volcanic ash thickness/weights. Secondly, we analyze the social and economic impact from volcanic ash. The economic damage is not likely to occur in South Korea, unless Mt. Baekdusan erupts in winter. However, the potential damage should not be overlooked because the volcanic ash may have a global impact around the world. If Mt. Baekdusan volcano erupts when the wind blows from north or northeast, the volcanic ash may then significantly affect South Korea of which economy is highly dependent on exports. Particularly when the volcanic ash moves to the densely populated metropolitan areas or agricultural areas, the damage can be significant. In preparation for the potential volcanic disasters, the volcanic ash forecast table suitable for South Korea should be prepared. In addition, building a Korean volcanic ash hazard map in advance will have a strategic significance.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.188-188
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• 2011

작년 아이슬란드에서의 화산폭발로 발생된 화산재가 대기 중으로 이동하면서 유럽 공항 곳곳의 항공기 수천 편이 운항 중지되기도 하였다. 한반도내의 백두산은 약 1000전(서기 946년~947년 경) 대규모로 분화하였고, 서기 1903년, 소규모 분화한 후, 앞으로 수년~수십 년 사이에 폭발적인 분화를 재개할 가능성이 제기되고 있으며, 백두산 분화 시, 아이슬란드 화산폭발 때보다 훨씬 심각한 피해가 예상되고 있다. 따라서 백두산 화산에 대한 현지 자료의 수집과 꾸준한 모니터링(감시, 관측) 자료의 분석과 재해 예상 범위 및 대응 방안의 모색이 필요한 시점이다. 본 연구에서는 지리적으로 가까이 있으며 108개 활화산의 화산재해 방재에 관하여 꾸준히 활동하고 있는 일본에서의 화산감시 및 분화대응 시스템을 파악하고, 우리나라의 화산재해대책을 수립하기위한 시사점들을 고찰하였다. 화산의 평균적인 분화 간격은 풍수해나 지진 등 다른 재해에 비해 길기 때문에 일본 기상청에서는 과거１만년 이내에 분화한 증거가 있는 화산이 활화산으로서 인정되고 있다. 백두산은 약 1000년 전에 분화한 뒤 최근 분화의 전조현상을 보이고 있으며, 중국과 북한에 인접하여 있으므로 우리나라에 직접적인 피해는 예상되지 않으나, 우리나라에 일본과 같은 활화산이 존재하지 않기 때문에 생소하였던 화산재해란 어떠한 것이며, 향후 잠재적인 분화 가능성을 가지고 있는 백두산폭발로 인한 재해의 종류를 미리 예상하고 준비할 필요가 있다. 일본의 경우 계속적인 감시와 관측을 통한 분화예보, 경보를 발령하고 분화 시 즉각적인 방재정보를 전달, 지역주민들이 빠르게 인지, 주의하도록 화산재해 대책 시스템이 갖추어져 있다. 우리나라는 아직 중국과 북한에 인접한 백두산에 대한 관측 자료가 거의 없고, 연구를 위한 접근 또한 쉽지 않은 상황이다. 분화로 인한 직접적인 영향권에서는 벗어난다할지라도 계절적인 기상장의 영향 및 아직 예측 불가능한 백두산의 잠재적인 폭발규모에 따라 간접적인 영향을 받을 경우에 대비하여야 할 필요성이 있다고 사료된다. 또한 우리나라의 화산재해 방재력을 향상시키기 위하여 백두산 폭발로 인한 재해위험범위를 가시화하고, 분화 시에 대한 구체적인 가상시나리오를 작성하여, 화산재 및 대기오염물질의 확산시뮬레이션, 기후변화에 끼치는 영향 등을 포함하는 화산재해대책을 미리 세워 피해를 저감시킬 수 있는 방재대책을 수립해야 할 것이다.

• KIISE Transactions on Computing Practices
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• v.23 no.12
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• pp.691-697
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• 2017

Volcanic ash has been predicted to be the main source of damage caused by a potential volcanic disaster around Mount Baekdu and the regions of the Korean peninsula. Computer simulations to predict the diffusion of volcanic ash should be performed according to prevalent meteorological situations within a predetermined time. Therefore, a workflow using pipelining is proposed to parallelize the software used for this computation. Due to the nature of volcanic calamities, the simulations need to be carried out for various plausible conditions given that the parameters cannot be precisely determined during the simulations, even at the time of a volcanic eruption. Among the given conditions, computations need to be first performed for the condition with the highest probability so that a response to the volcanic disaster can be provided using these results. Further action can then be performed later based on subsequent results. The computations need to be performed using a volcanic disaster damage prediction system on a computing server with limited computing performance. Hence, an optimal distribution of the computing resources is required. We propose a method through which specific data can be provided first to the proposed pipeline-based workflow.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.10-10
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• 1998

본 연구에서는 제트 추진 기관의 터빈 익렬에서의 유동과 대기 중에 부유되어 있는 입자 또는 연소 생성물들이 제트엔진 내부로 유입될 경우 이에 따른 압축기 및 터빈 날개의 마모 및 충돌 부위를 예측하기 위하여 수치해석을 수행하였다. 일반적으로 각종 항공기의 추진 기관용 가스 터빈 엔진은 대기중에 부유되어 있는 각종 입자들의 영향을 받게 된다. 특히, 확산 지역을 통과하는 항공기나 먼지 입자 부유물이 많은 공업지대 또는 사막지역을 비행하는 항공기의 경우는 모래 알갱이, 먼지 및 연소 입자의 직접적인 영향을 받아 각 요소들에 심각한 부식 및 마모가 발생됨으로써 성능 저하 및 냉각 통로의 막힘, 압축기와 터빈 날개의 손상 등이 예측되어진다. 특히 항공기용 추진 기관은 엔진 입구에 유입 공기를 정화하기 위한 여과장치의 설치가 불가능하며, 자동차용 가스터빈 엔진의 경우는 여과 장치를 부착하여도 미세한 입자들이 여과 장치에 여과되지 않고 엔진 내부로 침투하게 되므로 치명적인 손상이 예상된다. 이러한 손상들은 초기에는 미세하게 발생하지만, 손상 정도가 점점 누적됨에 따라서 항공기의 안전 운전에 심각한 위험 요소로서 작용할 수 있으며, 경제적으로도 기관의 유지 보수비용의 증가를 가져올 수 있다. 따라서 압축기에 화산재 또는 대기중에 부유되어 있는 금속 입자나 먼지입자 등이 유입되었을 경우, 압축기 날개의 손상 부위와 정도를 예측하는 것이 필요하다. 따라서 본 연구에서는 Lagangian방법을 적용하여 압축기 날개위의 부유 입자 충돌 부위를 예측하고, 설계 시 이를 보완할 수 있는 기준을 제시하였다. 아울러 설계 입구각과 크게 벗어난 유동의 유입시에 발생되는 박리 현상과 이에 따른 입자의 유동 및 날개의 입자 접착 부위를 예측하였다. 본 연구에서는 여러 크기의 입자(다양한 Stokes 수)들을 주어진 속도에서 유선을 따라 압축기 입구에서 압축기 유로로 여러 위치에서 부유 시켜서 그 입자들의 궤적 및 충돌, 점착 위지를 고찰하고, 정량적인 충돌량을 해석하기 위하여 입자 충돌 계수를 정의하여 압축기 날개 표면의 충돌특성을 알아보았다. 이러한 예측을 통하여 압축기 날개 표면의 충돌 부위를 예측하고, 날개의 표면을 코팅하는 등 보호 개선책을 제시할 수 있고, 연소의 반응물 입자가 터빈 날개에 충돌하여 발생되는 날개 표면의 파손, 냉각 홀의 막임, 연소 입자의 점착 부위 등을 예측하여 보완책을 준비할 수 있도록 하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.4
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• pp.78-86
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• 2000

The objective of this research is to understand the characteristics of a nonpremixed, turbulent, hydrogen jet flame which is stabilized in Mach 1.8 coflowing air flows. In order to investigate the flame structure, flame lengths and fuel trajectories were measured by using direct photography, acetone PLIF, Mie scattering techniques, and numerical simulation. Effect of increasing air velocity was investigated when fuel velocity is fixed. The subsonic flame length was decreased drastically, however the supersonic flame length was increased slowly Then the change of flame blow out characteristics was observed as varying fuel nozzle lip thickness. The flame stability can be increased when fuel nozzle lip thickness was increased, which indicates that the minimum fuel lip thickness ratio is required for the stable supersonic flames. Also, it is found that fuel jet is blocked by high pressure zone and low scattering zone is made. Then the fuel that was moving along the recirculation zone had longer residence time within the supersonic flames, which made partially premixed zone.

• Journal of Energy Engineering
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• v.10 no.3
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• pp.223-232
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• 2001

To study the stabilization characteristics of diffusion flame formed in the wake of a cylindrical bluff body with fuel injection, the flame stability limits, length and temperature of recirculation zone of flame, turbulence intensity distribution near the recirculation zone of flame were measured and analyzed. The length of recirculation zone is independent on main fuel injection quantity, but it is dependent on fuel injection angles, air stream velocity, and auxiliary fuel injection into recirculation zone. For diffusion flame, in general, the flame stabilization is deteriorated with increase of he length of recirculation zone, but if the turbulence generator is installed, the flame stabilization is improved with increase of the length of recirculation zone. The temperature of recirculation zone is dependent on fuel injection angles, auxiliary fuel injection into recirculation zone, turbulence generators, and it dependent on fuel injection angles, auxiliary fuel injection into recirculation zone, turbulence generators, and it has a maximum value at the condition of each theoretical mixture. In general, the more temperature of recirculation zone is low, the more flame is stable. But when the turbulence generator is installed, the more temperature of recirculation zone is low, the more flame is unstable. The turbulence intensity in the wake of bluff body is increased with increase of diameter or blockage ratio of grid. The more turbulence intensity is increased by installation of turbulence generator, the more flame is unstable. Finally, It is clear that the stabilization characteristics of diffuser flame can be controlled by some parameters such as fuel injection angles, auxiliary fuel injection into recirculation zone, turbulence generators.