SCALING LAWS OF TURBULENT CEILING FIRES

A fundamental dimensionless number appropriate for studying buoyancy d riven flames, Pi(beta) similar to Ra/(1 + B)/1 + (1 + B)/sigma, is dev eloped by considering the balance of momentum, thermal energy, and spe cies flux. In the particular case of laminar ceiling fires, it is show n that a modified Pi(beta) scales with the ratio of the integral lengt h scale and the boundary layer thickness as l/delta(beta) similar to P i(f)(1/5). Here, Pi(f) is based on a flame Rayleigh number, Ra-f, whic h is defined as [GRAPHICS] For turbulent ceiling fires, it is shown th at the ratio of integral length scale and the flame Kolmogorov scale i s given by l/eta(beta) similar to Pi(f)(1/4). These fundamental relati ons for laminar and turbulent ceiling fires are correlated to experime ntally measured flame stand-off distances for ceiling fires [1-3]. Bas ed on the limited data available, the agreement with experiments is ve ry good. Additional experiments are needed to further verify the valid ity of the scaling laws in the two flow regimes. (C) 1998 by The Combu stion Institute