@article {bnh-8379, title = {Fire coalescence and mass spot fire dynamics - final project report}, number = {736}, year = {2023}, month = {04/2023}, institution = {Natural Hazards Research Australia}, abstract = {

The Fire coalescence and mass spot fire dynamics project (the Spotfire Project) was one of the core research projects within the Bushfire and Natural Hazards CRC{\textquoteright}s Bushfire Predictive Services research cluster. Specifically, the Spotfire Project was focused on enhancing our understanding of the physical processes involved in spot fire development and coalescence and developing computationally efficient mathematical models that can accurately account for these the patterns of bushfire propagation associated with mass spotting and other modes of dynamic fire behaviour. Current operational models and associated simulation platforms are predicated on the assumptions that fires spread in a quasi-steady manner and that different parts of a fire line evolve independently of other parts {\textendash} both of these assumptions are manifestly untrue during mass spotting events.

The research took a multifaceted approach, which drew upon experimentation, computer simulation and mathematical modelling to develop a new dynamic modelling framework that permits faster-than-real-time simulation of fire propagation incorporating dynamic drivers. Experimentation took place at both laboratory and field scales. Laboratory experimentation was conducted in the CSIRO Pyrotron and in collaboration with Portuguese colleagues at the Centre for the Study of Forest Fires. Field scale experiments were also conducted in Portugal. The experiments provided insights into the dynamic nature of fire behaviour and provided data for calibration and validation of the models under development.

Coupled fire-atmosphere models were used to perform idealized simulations of various scenarios involving dynamic fire propagation. The model output provided detailed quantitative insights into the physical processes driving dynamic fire propagation and were used to inform development of new mathematical models. The mathematical model developed during the project is essentially a two-dimensional version of a coupled fire-atmosphere model {\textendash} it incorporates the feedback between the fire and the atmosphere but within the two-dimensional Spark fire simulation platform.

The research has yielded many important and significant insights into the behaviour of coalescing spot fires, and these insights have enhanced our understanding of the processes driving fire propagation and the way we model dynamic fire behaviours. These have in turn provided new understanding of violent pyroconvective events and extreme bushfire development.

The most significant research outcome was the development of the pyrogenic potential model, which permits world{\textquoteright}s first capability to model dynamic modes of fire propagation (e.g., vorticity-driven lateral spread) using a two-dimensional simulation framework. This means that explicitly modelling such effects in operational timeframes is now a feasible option. The research has also examined various other issues related to the spotting process and dynamic fire propagation more generally. These include: the effects of wind-terrain interaction on ember trajectories and the likely distribution of spot fires downwind of complex terrain, the influence of spot fires on the overall rate of spread of a fire, the influence of terminal velocity assumptions on ember trajectory modelling, the influence of fuel characteristics (e.g., bulk density) on spot fire development and pyroconvective feedback, the role of fine scale vorticity effects on dynamic fire behaviour, and development of simple measures of pyroconvective potential.

There is considerable utilisation potential for the research findings. The advances in fire behaviour modelling are easily incorporated within the Spark simulator platform. Given that Spark has been formally chosen by AFAC to be the new national bushfire prediction platform, the project{\textquoteright}s research findings will eventually be available to all involved in operational prediction of bushfire propagation. Moreover, the insights into dynamic fire behaviours provided by the project will form the basis for new firefighter training and education materials that will equip operational personnel with better knowledge of the full spectrum of possible fire behaviours in given scenarios. This will improve situational awareness, with benefits for firefighter safety.

The project has also developed a new mapping product that identifies regions prone to mass spotting in association with vorticity-driven lateral spread. This will be available to fire management agencies and other relevant organisations, to assist with fire behaviour prediction, with special relevance to anticipating blow-up fire events and extreme bushfire development.

Overall, the Spotfire Project has presented a new paradigm for understanding fire behaviour and has made the first significant advances towards the next generation of operational models. The insights gained from the research complements and extends existing fire behaviour knowledge in a way that enhances our ability to deal with the increasing bushfire threat into the future.

}, issn = {736}, author = {Jason J. Sharples and James Hilton and Sullivan, Andrew and Badlan, R} } @article {bnh-8338, title = {A guide to reconstructing cropland wildfires {\textendash} data collection, collation and analysis for case study construction}, number = {729}, year = {2022}, month = {04/2022}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

This guide is intended to provide the fire behaviour analyst tasked with preparing a case study of a cropland wildfire with the basic set of methods, tools and information necessary to create a meaningful summary of the behaviour and spread of that fire. While the information and examples provided are specific to the case of wildfires burning in cropland fuels, the methods and tools are such that they can be applied to wildfires burning in any vegetation type given due consideration of the differences in the applicable factors and conditions.

This guide provides background information on the importance of undertaking case studies of wildfires, particularly across the broad range of wildfire types and intensities, for developing a case study library from which a large range of lessons may be learned{\textemdash}those immediately related to the incident itself but also those that may be gained from a perspective of time and space later.

A detailed discussion of fire behaviour in cropland fuels and the factors that affect fire perimeter shape and growth are discussed. The effects of suppression efforts, their effectiveness and likely impact on fire shape and spread are also discussed. Understanding the fuels and landscape features across which a cropland wildfire burns, in particular those non-crop fuels such as roadside verges and grazing paddocks, and their condition and state, are critical to interpreting observed fire behaviour and fire propagation across the landscape. Similarly, detailed information on the weather driving the wildfire is critical to understanding how and why a fire spread the way it did.\  These data can be divided into two groups{\textemdash}those that should be collected during the fire, such as observations of fire behaviour and spotting, and those that can be collected after the fire, such as fire progression and burnt area and crop status and distribution. Assessment of the reliability of the data collected for the purpose of compiling a case study is essential to providing context and informing assessment of dependability of data used for later analysis.

Finally, the guide provides suggestions for documenting the fire event, building the chronology and development of the incident, and writing a case study that is pithy and to the point. Checklists of essential information to be collected during and immediately after the fire (including sample fire spread observation forms), suggested observations to be collected from first attack personnel and prompter questions for when doing firefighter debriefs and interviews of eyewitnesses are also provided.

}, issn = {729}, author = {Sullivan, Andrew and Cruz, Miguel G. and Matt P Plucinski} } @article {bnh-8303, title = {Initial growth of fires in eucalypt litter, from ignition to steady-state rate of spread: laboratory studies}, journal = {International Journal of Wildland Fire}, year = {2021}, month = {12/2021}, abstract = {

As part of an investigation of wildfire growth and acceleration, the initial growth of incipient fires burning in uniform dry eucalypt forest (Eucalyptus rossii,\ E. macrorhyncha) litter fuel of 1.2 kg m-2\ was studied in a combustion wind tunnel with a fuel bed width of 1.5 m. Fifty-eight fires of three ignition patterns (point, 400-mm line and 800-mm line) were carried out at two air speeds (1.25 and 2.0 m s-1) and two dead fuel moisture content (FMC) groups for each air speed (<=7.5\% and \>7.5\% oven-dry weight for the low air speed and <=5\% and \>5\% for the high air speed). The fraction of steady-state rate of spread reached as a function of time was determined and fitted to two theoretical fire growth models from the literature. The best model suggests the times for a point ignition fire to reach steady-state spread rate were ~38 and 50 min under the higher FMC for 2.0 m s-1\ and 1.25 m s-1\ air speeds, respectively, and ~25 min under the lower FMC for 2.0 m s-1. Future work will extend these results to field-scale fire behaviour, which will help improve operational response to wildfire outbreaks and planning of ignition patterns for prescribed burning.

}, keywords = {acceleration, combustion wind tunnel, experiments, Fire behaviour, fire development, fire growth, Pyrotron, Rate of spread}, doi = {https://doi.org/10.1071/WF21094}, url = {https://www.publish.csiro.au/WF/WF21094}, author = {J.S. Gould and Sullivan, Andrew} } @article {bnh-7495, title = {Fire coalescence and mass spot fire dynamics: experimentation, modelling and simulation {\textendash} annual project report 2019-2020}, number = {625}, year = {2020}, month = {11/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {MELBOURNE}, abstract = {

This report outlines the progress of the Fire Coalescence and Mass Spot Fire Dynamics project, which is one of the projects within the Next Generation Fire Modelling cluster. Specifically, the report summarises progress of the first two years of the second phase of the project, which has been extended over 2018-2021.

All milestones from the 2015-2018 phase of the project have now been delivered, and the project is continuing to build upon this work in delivering important insights into the dynamics of fire behaviour and fire line interaction. Phase 2 of the experimental program is in progress, and will extend recently published work from Phase 1. The project continues to yield important and significant insights into the behaviour of coalescing fires, and these insights are enhancing our understanding of the processes driving fire propagation and the way we model dynamic fire behaviours. \ 

In particular, the research has continued to develop the pyrogenic potential model by incorporating firebrand dynamics. This has resulted in the world{\textquoteright}s first capability to model dynamic modes of fire propagation such as vorticity-driven lateral spread using a two-dimensional simulation framework with a spotting module. This means that explicitly modelling such effects in operational timeframes is now a feasible option. The research has also examined how wind-terrain interaction influences ember trajectories and the likely distribution of spot fires down wind of complex terrain.

In the past year, the project team have delivered a number of research outputs, including conference presentations and posters and journal publications. Still more publications are in preparation. The project team has also delivered on a number of key utilisation activities. These have mainly involved discussions with key end users about the prospects of the research being incorporated into education materials and training resources for firefighters and fire behaviour analysts. The project has also begun working on a dedicated utilisation project aimed at development of spot fire spatial mapping tools.

After providing some background information on the project{\textquoteright}s aims and methodology, this report provides details on the progress of the project to date. In particular, this includes:

At the time of writing, the project is on-schedule.

}, keywords = {experimentation, fire coalescence, mass spot fire dynamics, modelling, simulation}, issn = {625}, author = {Jason J. Sharples and James Hilton and Sullivan, Andrew and Badlan, R} } @article {bnh-6811, title = {Fire coalescence and mass spot fire dynamics: experimentation, modelling and simulation - Annual project report 2018-2019}, number = {559}, year = {2020}, month = {03/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

This report outlines the progress of the Fire Coalescence and Mass Spot Fire Dynamics project, which is one of the projects within the Next Generation Fire Modelling cluster. Specifically, the report summarises progress of the first year of the second phase of the project, which has been extended over 2018-2021.

All milestones from the 2015-2018 phase of the project have now been delivered, and the project is continuing to build upon this work in delivering important insights into the dynamics of fire behaviour and fire line interaction. Phase 2 of the experimental program is in progress, and will extend recently published work from Phase 1. The project continues to yield important and significant insights into the behaviour of coalescing fires, and these insights are enhancing our understanding of the processes driving fire propagation and the way we model dynamic fire behaviours. \ 

In particular, the research has continued to develop the pyrogenic potential model by incorporating the effects of pyrogenic vorticity. This has resulted in the world{\textquoteright}s first capability to model dynamic modes of fire propagation such as vorticity-driven lateral spread using a two-dimensional simulation framework. This means that explicitly modelling such effects in operational timeframes is now a feasible option. Coupled fire-atmosphere simulations continue to provide fundamental insights that will be drawn upon to inform further the development of the pyrogenic potential model.

In the past year, the project team have delivered a number of research outputs, including conference presentations and posters and a journal publication (currently under review). A number of other publications are in preparation. The project team has also delivered on a number of key utilisation activities. These have mainly involved discussions with key end-users about the prospects of the research being incorporated into education materials and training resources for firefighters and fire behaviour analysts.

After providing some background information on the project{\textquoteright}s aims and methodology, this report provides details on the progress of the project to date. In particular, this includes:

At the time of writing, the project is on schedule.

}, keywords = {experimentation, fire coalescence, modelling, simulation, spot fire dynamics}, issn = {559}, author = {Jason J. Sharples and James Hilton and Sullivan, Andrew} } @article {bnh-5192, title = {Incorporating convective feedback in wildfire simulations using pyrogenic potential}, journal = {Environmental Modelling \& Software}, volume = {107}, year = {2018}, month = {09/2018}, pages = {12-24}, chapter = {12}, abstract = {

Modelling the dynamics of wildfires is very computationally challenging. Although three-dimensional\ computational fluid dynamics\ (CFD) models have been successfully applied to wildfires, the\ computational time\ required makes them currently impractical for operational usage. In this study, we develop a two-dimensional\ propagation model\ coupled to a {\textquoteleft}pyrogenic{\textquoteright}\ potential flowformulation representing the inflow of air generated by the fire. This model can accurately replicate features of fires previously unable to be simulated using current\ two-dimensional models, including development of a fire line into a parabolic shape, attraction between nearby fires and the observed closing behaviour of {\textquoteleft}V{\textquoteright} shaped fires. The model is compared to\ experimental resultswith good agreement. The pyrogenic potential model is orders of magnitude faster than a full\ CFD\ model, and could be used for improved operational wildfire prediction.

}, doi = {https://doi.org/10.1016/j.envsoft.2018.05.009}, url = {https://www.sciencedirect.com/science/article/pii/S1364815217309593}, author = {James Hilton and Sullivan, Andrew and Swedosh, W and Jason J. Sharples and Christopher Thomas} } @conference {bnh-5024, title = {Pyroconvective interactions and dynamic fire propagation}, booktitle = {AFAC18}, year = {2018}, month = {09/2018}, address = {Perth}, abstract = {

Modelling the dynamic propagation of wildfires remains a significant challenge. Pyroconvective interactions between the fire and the atmosphere, or between different parts of the fire itself, can produce distinctly non-steady modes of fire propagation that cannot be accounted for using current operational models.


While sophisticated three-dimensional models (e.g. computational fluid dynamics (CFD) models or coupled fire-atmosphere models) have been successfully applied to wildfires, their computational requirements render them impractical for operational usage.


Here we discuss a computationally efficient two-dimensional propagation model, which can accurately replicate dynamic features of fire spread that cannot be simulated using existing two-dimensional models. These features include the development of a wind-driven fire line into a parabolic shape, attraction between nearby fires and the observed closing behaviour of junction fires. The model is compared to experimental results with good agreement.
The model incorporates a simple sub-model to account for the inflow of air generated by a fire, which allows the model to run orders of magnitude faster than full physical models, while still capturing many of the essential features of dynamic fire propagation. We argue that such a model could lead to significant improvements in operational wildfire prediction.
In addition, we will highlight some recent insights in to how the geometry of a fire line and the flaming zone influences development of the pyroconvective plume above a fire. In particular, we present evidence that the geometry of the burning region can affect plume development in a way that is comparable to the effect of total energy release.

}, author = {James Hilton and Badlan, R and Sullivan, Andrew and Swedosh, W and Thomas, C. M. and Jason J. Sharples} } @article {bnh-4205, title = {Fire coalescence and mass spotfire dynamics - experimentation, modelling and simulation: annual project report 2016-17}, number = {312}, year = {2017}, month = {09/2017}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

This report outlines the progress of the Fire Coalescence and Mass Spot Fire Dynamics project, which is one of the projects within the Next Generation Fire Modelling cluster.

The project has now been running for approximately 2.4 years. Phase 1 of the experimental program has now been completed and initial results are in the process of being published. Phase 2 of the experimental program is being considered. The project has continued to yield important and significant insights into the behaviour of coalescing fires, and these insights have broader implications for our understanding of the processes driving fire propagation and the way we model dynamic fire behaviours. \ 

In particular, the research has continued to address the role that fire line geometry plays in the dynamic propagation of wildfires. The project team has identified a number of circumstances where the curvature-based models that they previously developed do not provide accurate simulation. This included a number of the particular experimental scenarios considered in Phase 1 of the experimental program. However, coupled fire-atmosphere simulations provided a number of fundamental insights that motivated the development of more broadly applicable two-dimensional models.\  These new models are able to explain why the curvature-based models worked when they did, and are able to provide accurate predictions in a broader number of circumstances, including those for which the curvature-based models had failed. \ 

At this stage the project has published three journal papers and three conference papers. Three more journal papers and four more peer-reviewed conference papers are in the final stages of preparation. Several conference posters have also been produced. In addition, the project team has delivered a significant number of presentations to stakeholders and researchers

After providing some background information on the project{\textquoteright}s aims and methodology, this report provides details on the progress of the project to date. In particular this includes:

At the time of writing, the project is several months behind schedule. However, the project team is confident that all milestones will be successfully delivered along with a number of unscheduled, yet significant research outputs.

}, issn = {312}, author = {Jason J. Sharples and James Hilton and Sullivan, Andrew} } @article {bnh-3186, title = {Curvature effects in the dynamic propagation of wildfires}, journal = {International Journal of Wildland Fire}, volume = {25}, year = {2016}, month = {10/2016}, abstract = {

The behaviour and spread of a wildfire are driven by a range of processes including convection, radiation and the transport of burning material. The combination of these processes and their interactions with environmental conditions govern the evolution of a fire{\textquoteright}s perimeter, which can include dynamic variation in the shape and the rate of spread of the fire. It is difficult to fully parametrise the complex interactions between these processes in order to predict a fire{\textquoteright}s behaviour. We investigate whether the local curvature of a fire perimeter, defined as the interface between burnt and unburnt regions, can be used to model the dynamic evolution of a wildfire{\textquoteright}s progression. We find that incorporation of curvature dependence in an empirical fire propagation model provides closer agreement with the observed evolution of field-based experimental fires than without curvature dependence. The local curvature parameter may represent compounded radiation and convective effects near the flame zone of a fire. Our findings provide a means to incorporate these effects in a computationally efficient way and may lead to improved prediction capability for empirical models of rate of spread and other fire behaviour characteristics.

}, url = {http://www.publish.csiro.au/WF/WF16070}, author = {James Hilton and Jason J. Sharples and Sullivan, Andrew} } @article {bnh-2971, title = {Fire coalescence and mass spot fire dynamics: experimentation, modelling and simulation: Annual project report 2015-2016}, number = {171}, year = {2016}, month = {09/2016}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

This report outlines the progress of the Fire Coalescence and Mass Spot Fire Dynamics project, which is one of the projects within the Next Generation Fire Modelling cluster.
The project has now been running for approximately 15 months. The Science Plan has been finalized and the Advisory Committee has been settled. The experimental program is now up and running after a few initial delays caused by issues with sourcing adequate fuel and with development of experimental apparatus. The modelling and simulation aspects of the project have made a number of significant fire spread modelling developments and have made strong contributions to our understanding of the processes driving fire coalescence and dynamic fire spread more generally.\ In particular, the research has addressed the role that fire line geometry (especially curvature) plays in the dynamic propagation of wildfires. The project team has demonstrated that fire propagation models incorporating curvature dependence can out-perform quasi-steady (first-order) models when applied to simple wind-driven fires at both laboratory and field scales.


In addition, the research has produced a number of fundamental insights into how the shape of the fire line can affect the pyroconvective interactions between different parts of a fire. These insights have mostly been gained by targeted simulations using a coupled fire-atmosphere model.
At this stage the project has published two conference papers (one peer reviewed), and two conference posters. There are currently three journal papers submitted to international peer-reviewed journals with another one in the final stages of preparation. In addition, the project team has delivered thirteen presentations and posters to stakeholders and researchers.\ After providing some background information on the project{\textquoteright}s aims and methodology, this report provides details on the progress of the project to date. In particular this includes:

At the time of writing, the project is on schedule. The project team is confident that all milestones will be successfully delivered along with a number of unscheduled, yet significant research outputs.

}, issn = {171}, author = {Jason J. Sharples and James Hilton and Sullivan, Andrew} } @article {bnh-2394, title = {Dynamic modelling of fire coalescence}, year = {2015}, author = {Jason J. Sharples and James Hilton and Sullivan, Andrew} } @proceedings {BF-4341, title = {National Fire Behaviour Knowledge Base- Bringing together the best information for best decisions}, year = {2013}, url = {http://www.bushfirecrc.com/resources/research-report/national-fire-behaviour-knowledge-base-bringing-together-best-information-}, author = {J.S. Gould and Sullivan, Andrew and Cruz, Miguel G. and Rucinski, Chris and Prakash, Mahesh} } @article {BF-3466, title = {Anatomy of a catastrophic wildfire: The Black Saturday Kilmore East fire in Victoria, Australia}, journal = {Forest Ecology and Management}, year = {2012}, month = {8/2012}, abstract = {The 7 February 2009 wildfires in south-eastern Australia burned over 450,000 ha and resulted in 173 human fatalities. The Kilmore East fire was the most significant of these fires, burning 100,000 ha in less than 12 h and accounting for 70\% of the fatalities. We report on the weather conditions, fuels and propagation of this fire to gain insights into the physical processes involved in high intensity fire behaviour in eucalypt forests. Driven by a combination of exceedingly dry fuel and near-gale to gale force winds, the fire developed a dynamic of profuse short range spotting that resulted in rates of fire spread varying between 68 and 153 m min-1 and average fireline intensities up to 88,000 kW m-1. Strong winds aloft and the development of a strong convection plume led to the transport of firebrands over considerable distances causing the ignition of spotfires up to 33 km ahead of the main fire front. The passage of a wind change between 17:30 and 18:30 turned the approximately 55 km long eastern flank of the fire into a headfire. Spotting and mass fire behaviour associated with this wide front resulted in the development of a pyrocumulonimbus cloud that injected smoke and other combustion products into the lower stratosphere. The benchmark data collected in this case study will be invaluable for the evaluation of fire behaviour models. The study is also a source of real world data from which simulation studies investigating the impact of landscape fuel management on the propagation of fire under the most severe burning conditions can be undertaken.}, issn = {03781127}, doi = {10.1016/j.foreco.2012.02.035}, author = {Cruz, Miguel G. and Sullivan, Andrew and J.S. Gould and Sims, N.C. and Bannister, A.J. and Jennifer J Hollis and Hurley, R.J.} } @article {BF-3100, title = {Field evaluation of two image-based wildland fire detection systems}, journal = {Fire Safety Journal}, volume = {47}, year = {2012}, month = {1/2012}, pages = {54 - 61}, abstract = {Rapid detection of wildfire outbreaks is a critical component of fire management because suppression activities are most effective when fires are small. One method of fire detection and location is computer analysis of images from sensors mounted on towers. In this paper we report on a trial of two image-based detection systems under operational conditions in forests and pasture in south-eastern Australia. The systems were deployed for 3 months in autumn, 2010, during which time a total of 12 experimental fires, 31 planned fires lit by public land management agencies, approximately 250 planned fires lit by private individuals, and 1 unplanned fire were recorded. Both image-based systems were able to detect and locate fires. They performed well for larger planned fires but poorly for small fires (View the MathML source area) at moderate distances (10{\textendash}20 km). System performance was compared to a human observer for a subset of fires. For these fires the human observer had a higher detection rate and shorter reporting time than the image-based systems. All methods of detection had a similar level of error for locating fires in the landscape once they had been detected. Operator skill was an important factor in the performance of all systems. Image-based fire detection could be a useful complement to other detection methods already in use in Australia.}, doi = {10.1016/j.firesaf.2011.11.001}, author = {Stuart Matthews and Sullivan, Andrew and J.S. Gould and Hurley, R.J. and Ellis, Peter and Larmour, John} } @article {BF-1010, title = {Project Vesta- Fire in dry eucalypt Forest: Fuel structure, fuel dynamics and fire behaviour}, volume = {218}, year = {2007}, month = {11/01/2007}, institution = {Ensis- CSIRO \& Department of Enivironment and Conservation, WA}, url = {http://www.publish.csiro.au/nid/22/pid/5993.htm}, author = {J.S. Gould and Lachlan W. McCaw and Cheney, NP and Ellis, Peter and Knight, IK and Sullivan, Andrew} }