Oscillation of the elements of combustible forest materials and its effect on ignition and combustion

Oscillations of the elements of combustible forest materials in a laminar air flow were studied experimentally using optoelectronic equipment. The values of the Young's modulus and rigidity are found to agree well with the available data. It is shown that interaction of the elements of combustible forest materials with air flows leads to asymmetric separation of the flow, which makes needles and twigs oscillate at frequencies comparable to the frequencies of their natural oscillations. An analysis of the experimental data gives limiting values for the equilibrium wind speed in a forest canopy for which forest fires can arise or extinguish.