와류입자 재배열과 운동량 보존

박외철 釜慶大學校 1998 釜慶大學校 論文集 Vol.3 No.2

As part of study on the vortex particle method, the numerical parameters in the method were examined for stability analysis, and the particle redistribution was investigated to understand its purposes. Investigation focused on stability analysis and conservation of momentums with and without the particle redistribution scheme. The Gaussian vortices were considered to make the problem simple by eliminating the complexity due to presence of walls. It showed that there exists a limit in selection of the time step size, the fluid viscosity and size of the particle redistribution grid. In all the stable cases computed the circulation and the linear momentums were conserved, but the angular momentum was severely attenuated without the particle redistribution.

대구 지하철역 제연의 문제점과 대책 : Ⅰ.제연방식 Ⅰ.Smoke Control System

박외철 한국화재소방학회 2003 한국화재소방학회논문지 Vol.17 No.4

대구 지하철역 제연의 문제점과 그 대책을 조사하기위해 지하철역 승강장 계단 주위 10m×3×5.4m의 공간에서의 제연을 FDS로 모사하였다. 200 kW의 폴리우레탄 화재와 각 급기구와 배기구의 공기유량0.9 m³/s에 대한 급기방식의 제연성능을 온도와 연기입자의 분포로 조사한 결과, 급기방식은 제연효과가 거의 없어 연기를 신속하게 배출하지 못함을 알 수 있었다. 또 세가지 기계제연방식 중에서 배기방식의 제연성능이 가장 우수하므로, 급기방식을 단순히 배기방식으로 전환함으로써 제연성능을 대폭 개선할 수 있음을 확인하였다. Smoke control in a space 10 m x 3 m floor and 5.4 m high around the stairway of a subway station platform was simulated by using FDS to investigate problems of smoke control in Daegue subway stations. Distributions of temperature and smoke particles, and variation of the number of particles with time for a 200 kW polyurethane fire were compared. It was shown that the purge system fails to remove smoke efficiently and that the extraction system has the highest performance among the three smoke control systems for the given situations. Simply switching the purge system into extraction mode might improve much the smoke removal performance.

경주시 인왕동 교통사고 가해차량의 운전자 규명

박외철,이광진 釜慶大學校 1999 釜慶大學校 論文集 Vol.4 No.1

A Sonata II collided with two vehicles in consequence in Kyongju. There were two occupants in the car, but each of them insisted that he was not driving the car. We investigated the accident ot determine the driver through careful review of the collision report, the statements of accident and witness, photographs taken at the scene, and the expert report of the National Scientific Investigation Institute. The accident was reconstructed based on the physical principles, injuries of occupants, damages of the involved vehicles and their final stops.

제연방식과 풍량에 따른 제연성능의 수치적 연구

박외철 한국화재소방학회 2003 한국화재소방학회논문지 Vol.17 No.2

제연방식과 풍량에 따른 실내에 유입된 연기의 제연성능을 조사하기 위해 Fire Dynamics Simulator의 대와류모사를 사용하였다. 급기구와 배기구, 개구부가 있는 크기 2 m×2 m×2.4 m의 실내에 급기방식과 배기방식, 급배기방식의 제연설비를 각각 가동했을 때 실내에 무작위로 분포한 입자의 감소율을 조사하였고, 급배기방식에서 풍량에 따른 입자의 감소율을 비교하였다. 세가지 제연발식 중 배기방식과 급배기방식은 제연성능에 차이가 없었으나, 개구부가 있는 경우에는 급기방식이 다른 두 제연방식에 비해 제연성능이 떨어졌다. 또 급배기방식에서 풍량이 감소하면 제연성능이 급격히 떨어지는 것으로 나타났다. 이 결과로부터 대형 개구부가 많은 지하철 역 등에는 급기방식 대신에 급배기방식 또는 배기방식의 제연설비를 사용해야 하며, 신속하게 연기를 배출하기 위해 풍량을 높게 할 필요가 있음을 알 수 있었다. The smoke removal rate from a room with an opening was investigated for different smoke control systems by using the large eddy simulation turbulence model of the Fire Dynamics Simulator. The decreasing rate of the particles randomly distributed in the 2 m×2 m×2.4 m room was com-pared for the ventilation system, pressurization system and extraction system, and for the air flowrate of the ventilation system. Difference in the smoke removal rate among the three smoke control systems was small when the opening was closed. The pressurization system showed less smoke removal rate than the other two systems when the opening existed, and hence is not recommended for subway stations with large openings. It was also shown that a less flowrate in the ventilation system leads to a much longer smoke removal time.

닥트두께가 대향류 화염구조에 미치는 영향의 조사

박외철,고경찬 한국산업안전학회 2002 한국안전학회지 Vol.17 No.4

Nonpremixed counterflow flames at low strain rates, ag= 12 s^-1, were numerically simulated to investigate the effects of the duct thickness on the flame structure in normal gravity. For small values of the duct thickness, the positions of the flame and stagnation point were highly sensitive to the duct thickness. When the duct thickness was greater than 6 ㎜, however, the effects of the duct thickness on the flame structure were negligible. The computed temperature along the duct centerline agreed well with measurements.

수정와류입자법에 의한 사각형실린더 주위 유동의 전산

박외철 釜慶大學校 1999 釜慶大學校 論文集 Vol.4 No.1

Two modifications were made in the vortex particle method: reduction of the number of numerical parameters and improvement of accuracy of the integration scheme. The method was applied to a 0.2 rectangle where the original method yielded poor results. Structure of vortex formation and its shedding in the wake was clearly shown, and vortex shedding was more regular than that of the original method. The averaged drag coefficient was 2.55 that was not improved by the modifications. The modified method was shown that it could be used in the viscous vortex particle method.

대와류모사를 이용한 연기이동의 연구 : Ⅱ. 제연방식과 개구부의 크기 Ⅱ. Smoke Control Systems and Opening Size

박외철 한국안전학회 2003 한국안전학회지 Vol.18 No.3

The large eddy simulation based Fire Dynamics Simulator was utilized to investigate the effects of the size of an opening on smoke removal performance for the three smoke control systems-ventilation, purge, and extraction. Three different opening sizes, r_(A)= 1, 2, and 3 were investigated while the flow rate remained 0.75 m³/s at the inlet or outlet depending on the systems. Increase of the opening size did not give a significant difference in the smoke removal rate for the three smoke control systems, though the increasing opening size slightly improved smoke removal. The extraction system was shown the best smoke control system, and the purge system yielded low performance compared to the other two systems for all the different opening sizes.

휴대용 유출기름회수기의 개발(Ⅰ) : 기름회수기의 특성과 공기흡입회수기의 개념설계 Characteristics of Oil Skimmers and Conceptual Design of an Air Suction Skimmer

박외철 釜山工業大學校 1993 論文集 Vol.35 No.-

Marine polution by spilt oil is a growing problem. A potable oil skimmer applicable to various situations of oil viscosity, spill location, curent, tides, waves and wind is in need to remove spilt oils before they widely spread. Development of such an oil skimmer is the objective of the study. The air suction skimmer is selected as the best one to be developed among the reviewed skimmers. Characteristics of the oil skimmers and conceptual design of the suction skimmer are described.

대와류모사를 이용한 연기이동의 연구 : Ⅰ. 제연방식과 배기풍량 Ⅰ. Smoke Control Systems and Extraction Flowrate

박외철 한국안전학회 2003 한국안전학회지 Vol.18 No.2

To evaluate the smoke control systems, the large eddy simulation turbulence model based Fire Dynamics Simulator was applied to a 2 m × 2 m × 2.4 in room with an opening. The smoke removal rate was investigated for three different smoke control systems: ventilation, extraction and pressurization. When the opening was closed, the smoke removal rates of the smoke control systems were almost the same as expected. The pressurization system showed a lower smoke removal rate compared with the other two smoke control systems for the room with the opening, and hence the pressurization system might not be efficient for a place with large openings. It was shown that the lower extraction flowrate is, the longer time the ventilation system requires to remove smoke. From these results, the ventilation system is recommended for subway stations where several large openings exist.

FDS를 이용한 실내화재 모사의 문제점 : Ⅰ. 중심형 화재 Ⅰ. Center Fire

고경찬,박외철 한국안전학회 2004 한국안전학회지 Vol.19 No.1

The Fire Dynamics Simulator (FDS) was applied to a center fire in a room, of which dimensions were 1.8m x 1.8m x 1.38m with an opening of 0.45m x 1.2m doorway, to evaluate the numerical method The time-variation of temperature at a top point of the doorway centerline and distributions of average temperature along the doorway centerline and comer stack were compared with measurements for three different fire sizes, 7.65, 21.25 and 51.71M. The results showed FDS predicted a very rapid fire growth compared with the experiment for all the three fire sizes, that is an importand shortcoming of FDS in compartment fire simulations. The average temperature distributions, and heights of hot gas layers and neutral planes in steady state were in reasonable agreement with the measurements.