Visualization of Organized Structures in Buoyant Diffusion Flames

In pool fires of liquid hydrocarbons static equidensitometric structures (2 types) and dynamic radiance structures (18 types) are obtained from flame photograms evaluated with an image analysis computer system. A third kind of structures, the dynamic synchronous structures (9 types) are visualized with a holographic real‐time interferometry method. ‐ The control parameters of the observed structures are the pool diameter, the height above the fuel surface, the density of the fuel vapor and the volumetric fuel flow rate. ‐ The dynamic radiance structures have 4 monoperiodic subprocesses with a frequency of 12 Hz (n‐hexane pool fire, d = 4.6 cm) which depend strongly on the pool diameter and show 18 statistical characteristics. The dynamic synchronous structures of the same pool fire show a quasiperiodic region I with 7 sub‐processes at 11, 13 and 3 Hz. In a quasiperiodic region II, 8 sub‐processes exist at the frequencies 11, 12, 13, 39 and 41 Hz. In addition there are 17 statistical characteristics. ‐ The effects of the observed dynamic structures on turbulent exchange processes in pool fires are calculated and lead to turbulent Prandtl‐, Schmidt‐ and Lewis‐numbers between 0.3 and 1.