Understanding and Mitigating Hazards

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Ngarkat, Sth Australia, fire and smoke
Ngarkat, South Australia, fire and smoke
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This project is applying physics-based approaches to fire scenarios. It attempts to simulate fire with unprecedented detail and in the process obtain useful application tools for end-users.

Bushfires occur on a scale that may be measured in kilometres. However, a challenge faced in developing next generation bushfire models is to capture the significant contributions that small scale phenomena make to the spread of bushfires.

This project is applying physics-based approaches to fire scenarios. It attempts to simulate fire with unprecedented detail and in the process obtain useful application tools for end-users. To address existing gaps in the mathematical and computational modelling of bushfire dynamics, an ideal fire scenario is subdivided into four parts.

Modelling wind speed through tree canopies

The rate of spread of a bushfire depends both on fuel types and the wind velocity profiles at ground and tree canopy levels. Ground cover, tree trunks, branches and leaves all affect the velocity profile. This particular aspect of the project aims to understand the velocity profile within the tree canopy in order to predict the wind reduction factor, which is present in some empirical models of fire spread. This work will improve the modelling of wind-driven fire behaviour as it enters, traverses and leaves a wooded area. The project will develop a set of user-friendly tools to calculate wind reduction factor (WRF) and improved wind field generating software. WRF will be computed as a function of existing forest parameters and prevailing weather conditions and will assist fire behaviour analysts to utilise WRF to predict the rate-of-spread and intensity of a fire.

Spread and distribution of firebrands

Embers and firebrands carried ahead of the main fire front often dominate the rate of spread of bushfires. The team is harnessing its expertise in aerodynamics to design, construct and operate a firebrand generator to accurately quantify how embers disperse. Along with wind speed, bushfire spread rates strongly depend on the physical and chemical properties of vegetative materials, such as grasses, wood and leaves. To prepare for experiments using the generator, the team invested in equipment and training for measuring properties such as thermal conductivity, specific heat, density, heat of pyrolysis, heat of combustion and reaction rate constants. These studies will assist in understanding the propensity of grasses and litter fuels to ignite from firebrands.

Improving computational methods

Physics-based models of bushfires must consider phenomena that occur on length scales that range from a fraction of a millimetre (e.g. flame thickness) up to several hundred metres (e.g. in terrain). The researchers have addressed this challenge by considering how the average of the small-scale phenomena would affect large-scale phenomena, such as the length and intensity of flames.

Bushfire-driven airflow over surface features

This aspect of the study applies the principles of engineering science to calculate bushfire-generated airflows above buildings, structures and forests. The aim is to quantify the behaviour of airflow and heat transfer in order to calculate how the wind profiles above the surface features of variable heights changes. The approach is to calculate details of the flow and heat transfer to produce highly accurate solutions, from which simple-to-use equations are extracted for operational use.

8 February, 2017
New journal articles and reports on CRC research are available online.
14 September, 2016
New journal articles and reports on CRC research are available online.
Burning tree
10 December, 2014
This is the December 2014 newsletter from the Fire spread prediction across fuel types project, with updates for project end users.
25 August, 2014
Whilst in France during July 2014 I took the opportunity of meeting up with researchers in three laboratories.
Year Type Citation
2017 Conference Paper Sutherland, D., Moinuddin, K. & Ooi, A. Large-eddy simulation of neutral atmospheric surface layer flow over heterogeneous tree canopies. AFAC17 (Bushfire and Natural Hazards CRC, 2017).
2017 Conference Paper Rumsewicz, M. Research proceedings from the 2017 Bushfire and Natural Hazards CRC and AFAC Conference. Bushfire and Natural Hazards CRC & AFAC annual conference 2017 (Bushfire and Natural Hazards CRC, 2017).
2017 Journal Article Wadhwani, R., Sutherland, D., Ooi, A., Moinuddin, K. & Thorpe, G. Verification of a Lagrangian particle model for short-range firebrand transport. Fire Safety Journal 91, 776-783 (2017).
2017 Journal Article Wadhwani, R., Sutherland, D., Moinuddin, K. & Joseph, P. Kinetics of pyrolysis of litter materials from pine and eucalyptus forests. Journal of Thermal Analysis and Calorimetry (2017). doi:10.1007/s10973-017-6512-0
2017 Report Moinuddin, K. & Sutherland, D. Numerical modelling of fires on forest floor and canopy fires. (Bushfire and Natural Hazards CRC, 2017).
2016 Journal Article MacDonald, M., Chan, L., Chung, D., Hutchins, N. & Ooi, A. Turbulent flow over transitionally rough surfaces with varying roughness densities. Journal of Fluid Dynamics October 2016, (2016).
2016 Report Moinuddin, K., Sutherland, D. & Thorpe, G. Fire spread prediction across fuel types: Annual project report 2015-2016. (Bushfire and Natural Hazards CRC, 2016).
2015 Presentation Chung, D. et al. The spread of fires in landscapes. (2015).
2015 Report Thorpe, G. Fire spread prediction across fuel types: Annual project report 2014-2015. (Bushfire and Natural Hazards CRC, 2015).
2015 Report Thorpe, G. Fire Spread Across Fuel Types Annual Report 2014. (2015).
Next generation models for predicting the behaviour of bushfires: Challenges and prospects
25 Aug 2014

Bushfires occur on a scale that may be measured in kilometers.  However, a challenge faced in developing next generation bushfire models is to capture the significant contributions that small scale phenomena make to the propagation of bushfires.   

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Flow Prediction Through Canopies
18 Aug 2015

A simple model of flow through a tree canopy and comparison with large-eddy simulations.

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Refinement and Validation of Firebrand Transport Sub Model for a Physics Based Bushfire Prediction Model: Design of  a Firebrand Generator
18 Aug 2015

Firebrands are burning pieces of, for example, bark, leaf litter, and twigs. Firebrands can be transported by wind from metres to kilometres from the head fire. Firebrands are responsible for causing spot fires during the spread of bushfire. Firebrands are the primary factor in house loss during bushfire.

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Duncan Sutherland Conference Poster 2016
14 Aug 2016

Operational fire models rely on wind reduction factors to relate the standard meteorological measured or forecast wind speed to the flame-height wind speeds within a tree canopy.

Simulated rate-of-spread of a grassfire propagating under a tree canopy
29 Jun 2017
  • Simulations of a fire entering, propagating under and leaving a tree canopy are conducted using FDS [1], a physics-based model.
  • The presence of a tree canopy effects the wind speed, which in turn effects the rate-of-spread of a fire.
  • From the simulated data we extract the average sub-canopy wind speeds in the absence of a fire and measure the rate-of-spread of a fire.
  • This is the first step to testing the wind-reduction factor approach used in current operational models.
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