- Author
-
Nielsen, H. J.
- Title
- Origin and Properties of Fire Whirls. Final Technical Report.
- Coporate
- IIT Research Inst., Chicago, IL
- Sponsor
- Office of Civil Defense, Washington, DC
- Report
-
Final Technical Report; IITRI Project J6129; OCD Work Unit 253H
August 15, 1969
55 p.
- Contract
- N0022-867-C-2760
- Keywords
-
fire whirls
|
urban fires
|
mass fires
|
vorticity
|
altitude
- Identifiers
- atmospheric vortices
- Abstract
- To determine the origin of fire whirls in fires, the origin of the vertical vorticity required to sustain them was investigated. It was found that the vertical vorticity developed by the bending upward of the horizontal vortex lines of the ambient wind boundary layer is greater than that produced by other mechanisms. The intensity and distribution pattern of the vorticity is also in agreement with the circulatory flow found to exist in experimental fire wind data. A method for estimating the intensity of fire whirls in urban fires is given which is based on the way the vorticity production scales with fire size and on existing analyses of the properties of convective vorties.