Published works

Firebrand is known as one of the most dangerous airborne components of wildfires having the potential to ignite structures in Wildland-Urban Interface (WUI). Quantifying the firebrand and heat flux on structures is essential to determine the wildfire risks and prepare strategic plans to mitigate the hazard. We endeavor to use a physics-based model, Fire Dynamic Simulator (FDS) to map firebrand and heat flux to determine the vulnerability of structures in WUI. In this study, we have validated FDS’ tree burning and firebrand transporting sub-models against the experiment conducted in no wind condition at the National Institute of Standards and Technology (NIST). The experimental data of firebands were processed to use as inputs in the numerical simulation and the grid convergence was appraised in terms of mass loss rate (MLR). The intial velocity and direction of firebrands, the number of generations were determined as model inputs by a reverse analysis through comparing firebrand distribution with the experiment. As the FDS’ sub-models were validated, we attempted to quantify the heat flux and firebrand risk on a structure at three different driving wind velocities. Increasing wind speed showed more firebrands transported towards the structure but none of them landed on the house because of the low height of the tree and insufficiency of fire-induced buoyancy to lift them enough to carry a longer distance by the wind field. Similarly, heat flux computed on the structure is well below Australian building standard AS3959’s bushfire attack level (BAL). it is due to the low heat release by single tree burning instead of a 100m wide fire line assumed in the standard. In future study, simulations will be conducted with a cluster of taller trees (100m wide) to quantify the heat flux and firebrand hazard on structures to apprise AS3959.