Experimental and numerical investigation of a single-tree fire

The physics and the dynamics of static fires were studied numerically and experimentally by burning single Douglas fir trees. The mass loss rate was recorded, as well as the radiative heat flux and temperature at different positions. The numerical simulations were carried out using a fully physical CFD code (FireStar3D), and two levels of description were considered: in the first one, the vegetation was represented using a single fuel-type; in the second, four fuel-types were considered. The numerical results were compared to the experimental data for fuel moisture content of 14% and 50%. The results clearly show the advantage of considering several fuel-types to represent the tree; nevertheless, compared to the experiments, faster tree burning dynamics is obtained by simulation. The role played by the ignition process was also analysed numerically, highlighting the sensitivity of the tree burning dynamics to the ignition protocol.