Published works

The prediction of the rate of spread and intensity of bushfires is crucial for emergency and disaster management organisations for operational planning and the deployment of resources.  Currently, simplified operational models are used since the prediction can be obtained on time scales commensurate with those required by emergency managers. Our aim is to refine these non-physics-based operational tools so that they can predict fire behaviour under a wide range of localised topographic and weather conditions, and also that they are able to account for a range of inhomogeneity, slope, and thermal instability within vegetation and over the terrain. Furthermore, a more physically-motivated firebrand model needs to be included in operational models to predict firebrand landing and the increased rate of fire spread (RoS).

In the last few years, we have numerically tested and established a reliable physics-based model that is based on basic fire dynamics theory and corresponding differential equations to simulate bushfire scenarios. We now embark upon utilization of our research as well as extending parametric study using the physics-based model. The following aspects have been the highlights of our endeavour:

• The effect of a tree canopy on the near surface wind speed with a view to modelling the wind reduction factor (WRF). The wind reduction factor is used in operational fire prediction models, such as the McArthur model, to account for the reduction in wind velocity due to a tree canopy. We developed an understanding of subcanopy wind flow through homogenous, longitudinally heterogeneous and vertically heterogeneous forest canopies. We are now attempting to simulate flow through canopies with varying atmospheric stability and homogenous canopy over a hill. We have also begun implementation of WRF based on our research into an operational platform (SPARK of CSIRO’s Data61).
• Simulations’ rate of grassfire as functions of wind, grassheight, slope, initial windfield etc. with view to improve the Australian Standard AS3959. Foundations of rigorous simulation have been laid through a number of journal paper publications, and we are now exploring various parametric studies. In one such study, we evaluated the heat load from an incoming grassfire on structures in relation to AS3959.
• Transport of non-burning firebrand (three particle shapes, cubical, cylindrical, and disc-shaped particles, representing idealised firebrands) and their landing distribution with a view to develop operational models of ember attacks for quantification in AS3959.  We have extended the simulation work to study the transport of ember particles across realistic forest edges. The results show that lower sphericity of the firebrand can increase lateral dispersion.
• Reducing the spin-up time for the physics-based model and initialise the wind fields for faster and more efficient fire predictions. This is attempted by using Windninja, which is a program used to compute spatially varying wind fields over a complex terrain. We have successfully mapped the terrain modified wind fields generated by Windninja onto the physics-based model using the penalization method. We are also able to implement gusting behaviour in the physics-based model.

Overall we have achieved our goal to obtain greater insight into bushfire physics and we are now utilising these insights to parameterise various phenomenon for operational models.