Modeling of the Velocity of the Ceiling Jet Front

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Journal of Korean Institute of Fire Science and Engineering 2001;15(2):91-95.
Published online June 30, 2001.

연기선단의 전파속도 모델에 관한 연구

김명배한용식

¹한국기계연구원 환경설비연구부²한국기계연구원 환경설비연구부

Modeling of the Velocity of the Ceiling Jet Front

요약

복도나 터널과 같이 특정한 방향성을 가지는 공간에서는 천장아래에 형성되는 연기선단의 성상해석이 학술적인 면에서나 실용적인 면에서도 매우 중요하다. 본 연구는 2차원 축대칭 천장제트 선단의 전파속도를 모델화하기 위하여 상사해석 및 차원해석을 수행하였다. 실험에서는 질소와 헬륨의 혼합가스를 원형 천장에 노즐로 분출시켜 화재로 인한 연기를 구현하였으며 속도측정을 위하여 레이저와 고속카메라를 이용한 가시화 기법이 사용되었다.

Abstract

Decays of the ceiling jet front velocity under a circular ceiling are investigated. To simulate the ceiling jet in fires He and $N_2$gas were injected from a nozzle to the center of the ceiling. The jet fronts in the form of turbulent eddies were traced by a high-speed camera system. The instantaneous locations of the front were obtained from visual readings of visualized front, and the radial velocity was calculated from the information of the time and the location with respect to the front. The similarity and dimensional analysis were also carried out to reveal the relationship between the velocity decay and the radial distance. It was shown that the radial velocity of the front was inversely proportional to the radial distance in the fully developed region from the experimental results and the theoretical analysis.

Key Words: Ceiling jet, Front, Velocity decay, Similarity, Dimensional analysis