Fire and explosion - a study of flame spread in engineered cardboard fuel beds part I: Correlations and observations of flame spread

Wind-aided laboratory fires spreading through laser-cut cardboard fuel beds were instrumented and analyzed for physical processes associated with spread. Flames in the spanwise direction appeared as a regular series of peaks and troughs that scaled directly with flame length. Flame structure in the stream-wise direction fluctuated with the forward advection of coherent parcels that originated near the rear edge of the flame zone. Thermocouples arranged longitudinally in the fuel beds revealed the frequency of temperature fluctuations decreased with flame length but increased with wind speed. The downstream extent of these fluctuations from the leading flame edge scaled with Froude number and flame zone depth. The behaviors are remarkably similar to those of boundary layers, suggesting a dominant role for buoyancy in determining wildland fire spread.