Experimental and numerical investigation of a single-tree fire.

This article focuses on the numerical and experimental study of static fire dynamics in single Douglas fir trees, using the physics-based computational fluid dynamics (CFD) code FireStar3D. Two fuel descriptions were tested—one with a single fuel-type (needles) and another with four fuel-types (needles and twigs of varying diameters)—at fuel moisture contents (FMC) of 14% and 50%. The simulations, compared to laboratory experiments conducted at Worcester Polytechnic Institute, showed that considering multiple fuel-types improved model accuracy, particularly in capturing mass loss rate (MLR) and radiative heat flux (RHF) dynamics, although simulations exhibited faster burning than experiments due to the inability to model slow-burning branches and trunks. The study also highlighted the significant influence of ignition parameters (burner power, duration, and symmetry) on burning behavior and emphasized the need for precise ignition control to reduce experimental variability. Overall, FireStar3D demonstrated promising results at this intermediate scale, advancing the understanding of fire spread physics while acknowledging limitations related to fuel heterogeneity and radiative heat transfer modeling.