Dimensional analysis of flame angles versus wind speed

Abstract

Dimensional analysis has potential to help explain and predict physical phenomena, but has been used very little in studies of wildland fire behavior. By combining variables into dimensionless groups, the number of variables to be handled and the experiments to be run is greatly reduced. A low velocity wind tunnel was constructed, and methyl, ethyl, and isopropyl alcohol were used as buoyancy sources. Three diameters of pans, 4, 10, and 15 cm, were used and the order of six wind speeds was randomized in three replications. Flame angle was plotted against Byram's dimensionless group gl_B/ρC_pTv³ (1959) in this preliminary study. Flames remained almost vertical at low wind speeds, inclined rapidly after critical wind speeds were attained, then inclined only slightly more as wind speeds continued to increase. A critical point in the value of the Byram number appears to be at a value of about 100.

Citation

Martin, Robert E.; Finney, Mark A.; Molina, Domingo M.; Sapsis, David B.; Stephens, Scott L.; Scott, Joe H.; Weise, David R. 1991. Dimensional analysis of flame angles versus wind speed. In Proc. 11th Conference on Fire and Forest Meteorology (Andrews, Patricia L. and Donald F. Potts, eds.), April 16-19, 1991, Missoula, MT. Society of American Foresters, Bethesda, MD. pp. 212-217.