Possible effects of free convection on fire behavior - laminar and turbulent line and point sources of heat
| Authors: | S. Scesa, F. M. Sauer |
| Year: | 1954 |
| Type: | Technical Paper |
| Station: | Pacific Southwest Research Station |
| Source: | Tech. Pap. 8. Berkeley, CA: U.S. Department of Agriculture, Forest Service, California Forest and Range Experiment Station. 47 p. |
Abstract
The transfer theory is applied to the problem of atmospheric diffusion of momentum and heat induced by line and point sources of heat on the surface of the earth. In order that the validity of the approximations of the boundary layer theory be realized, the thickness of the layer in which the temperatures and velocities differ appreciably from the values at infinity must be small compared to the height of the region of influence. Variations of four dependent variables--inflow rate, inflow velocities, maximum velocities, and maximum temperature--as a function of elevation for representative heat source strengths are compared for the four cases investigated. In addition, the shape of the region of influence and the factors affecting the shape are investigated.
Results indicate that laminar sources tend to become uniform in cross-section with large vertical velocities and temperatures, thereby indicating a low lateral tendency to diffuse bouyancy and momentum. The turbulent sources diverge with a rapid diffusion of bouyancy and momentum depending upon the mixing length proportionality constant.
Application of the turbulent point source results to a finite area source has been presented by postulating that the dependent variables of indraft velocity, maximum temperature and maximum vertical velocity of the finite area source can be produced by a point source of equivalent heat strength functioning at a specified distance below the finite source. Data concerning the behavior of the aforementioned variables induced by a finite area heat source do not exist. Therefore, experimental investigations are necessary to provide guidance for further analysis.