On the non-monotonic behaviour of fire spread

A conceptual model based on the dynamic interaction between fire, fuel bed and surrounding flow to explain non-monotonic or intermittent behaviour of fires is proposed. According model, even in nominally permanent uniform boundary conditions, fire-induced modifies geometry flame its rate spread. After an initial acceleration, there a reduction spread followed by one more cycles growth. Carefully controlled experiments slopes canyons show that evolution fire properties, namely angle spread, have high-frequency oscillations superimposed low-frequency growth cycle described above.