Citation

Kuwana K. J. Combust. Soc. Jpn. 2019; 61(196): 101-111.

Copyright

(Copyright © 2019, Combustion Society of Japan)

DOI

10.20619/jcombsj.61.196_101

PMID

unavailable

Abstract

The formation of a fire whirl in a large-scale urban or wildland fire leads to a significant increase in the fire spread rate, and its strong whirlwind (whose maximum speed may reach 60-80 m/s) also causes a serious damage. It is therefore important from a fire safety point of view to understand when and how fire whirls are generated. This article reviews previous fire whirl studies with particular focus on the mechanism of flame-height increase and the condition of fire whirl generation. Studies that used rotating or fixed-frame fire-whirl generators are first reviewed to discuss mechanisms of flameheight increase. Enhanced heat transfer to the combustible material within the Ekman layer and flow laminarization in the rotating fluid are identified as factors that increase the height of a fire whirl. The critical crosswind velocity that leads to the formation of strong fire whirls and its scaling law are then discussed by reviewing studies on fire whirls in crossflows.

Language: ja

Keywords

Burning rate; Critical crosswind velocity; Ekman layer; Fire whirl; Flame height; Scaling law