@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-8377, title = {Implementation of spatially-varying wind adjustment factor for wildfire simulations}, journal = {Environmental Modelling \& Software}, volume = {163}, year = {2023}, month = {05/2023}, pages = {105660}, abstract = {

The behaviour and rate of spread of a wildfire is strongly affected by local wind conditions depending on topography and surrounding vegetation. The wind speed within dense vegetation can be substantially lower than the open wind speed above the vegetation. This is commonly accounted for by applying a local correction factor to the local wind speed which can be called the wind adjustment factor (WAF). WAFs are often difficult to calculate and are usually based estimates for a particular vegetation type. Variation in the vegetation may result in spatially varying WAFs. We implement a model for spatially-varying WAFs based on leaf area index (LAI) and vegetation height data, which can be derived from remote sensing data sources. The model is implemented within Spark an operational wildfire prediction framework. Simulations of historical fires using the spatially-varying WAF model generally provided improved predictions compared to recorded fire extents than simulations without a spatially-varying WAF.

}, keywords = {Bushfire, modeling, spread, WAF, Wildfire, wind adjustment factor}, doi = {https://doi.org/10.1016/j.envsoft.2023.105660}, url = {https://www.sciencedirect.com/science/article/abs/pii/S1364815223000464?dgcid=coauthor}, author = {Duncan Sutherland and Mahmood Rashid and James Hilton and Khalid Moinuddin} } @article {bnh-8368, title = {Up-scaling fuel hazard metrics derived from terrestrial laser scanning using a machine learning model}, journal = {Remote Sensing}, volume = {15}, year = {2023}, month = {02/2023}, pages = {1273}, abstract = {

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}, keywords = {ALS, canopy, cover, elevated, field data, fuel hazard, fuel layers, fuel metrics, height, near-surface, random forest, up-scaling, visual assessments}, doi = {https://doi.org/10.3390/rs15051273}, url = {https://www.mdpi.com/2072-4292/15/5/1273}, author = {Ritu Taneja and Luke Wallace and Samuel Hillman and Karin Reinke and James Hilton and Simon Jones and Bryan Hally} } @article {bnh-6993, title = {Case study: use of remote sensing data to derive spatial and temporal explicit fuel accumulation curves across defence lands}, number = {579}, year = {2020}, month = {06/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

Fuel loads are a main driver of fire rate of spread. Therefore, a spatially explicit estimation of fuel loads, coupled with their variation through time may improve wildland fuel management and contribute to the design of more efficient active fire response strategies. However, the high frequency of planned and unplanned fires in large wild areas linked to varying fire severity levels that affect the rate at which fuels re-accumulate, make the continuous monitoring of wildland fuels challenging with field-based survey methods. Here we propose the use of satellite remote sensing to map fuel loads with a revisit time of 16 days. Fuel load maps are produced for five Defence Lands using Landsat and Sentinel-2 optical remote sensing data available at Digital Earth Australia and the National Computation Infrastructure. The fuel load maps are obtained by calculating the time series of the Vegetation Structure Perpendicular Index, an index that measures post-fire disturbance, and fitting these to fuel accumulation curves derived from literature.

}, keywords = {data analysis, defence lands, fuel accumulation, remote sensing}, issn = {579}, author = {Andrea Massetti and Marta Yebra and James Hilton and Christoph R{\"u}diger} } @article {bnh-7343, title = {Effect of weather forecast errors on fire growth model projections}, journal = {International Journal of Wildland Fire}, year = {2020}, month = {08/2020}, abstract = {

Fire management agencies use fire behaviour simulation tools to predict the potential spread of a fire in both risk planning and operationally during wildfires. These models are generally based on underlying empirical or quasi-empirical relations and rarely are uncertainties considered. Little attention has been given to the quality of the input data used during operational fire predictions. We examined the extent to which error in weather forecasts can affect fire simulation results. The study was conducted using data representing the State of Victoria in south-eastern Australia, including grassland and forest conditions. Two fire simulator software packages were used to compare fire growth under observed and forecast weather. We found that error in the weather forecast data significantly altered the predicted size and location of fires. Large errors in wind speed and temperature resulted in an overprediction of fire size, whereas large errors in wind direction resulted in an increased spatial error in the fire{\textquoteright}s location. As the fire weather intensified, fire predictions using forecast weather under predicted fire size, potentially resulting in greater risks to the community. These results highlight the importance of on-ground intelligence during wildfires and the use of ensembles to improve operational fire predictions.

}, keywords = {Bayesian Network, fire prediction, meteorological forecast, sensitivity, simulation}, doi = {https://doi.org/10.1071/WF19199}, url = {https://www.publish.csiro.au/wf/wf19199}, author = {Trent Penman and Dan Ababei and Jane Cawson and Brett Cirulis and Thomas Duff and Swedosh, W and James Hilton} } @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-6736, title = {Modeling Vorticity-Driven Wildfire Behavior Using Near-Field Techniques}, journal = {Frontiers in Mechanical Engineering}, year = {2020}, month = {01/2020}, abstract = {

Dynamic modes of fire propagation present a significant challenge for operational fire spread simulation. Current two-dimensional operational fire simulation platforms are not generally able to account for the complex interactions that drive such behaviors, and while fully coupled fire-atmosphere models are able to account for dynamic effects to an extent, their computational demands are prohibitive in an operational context. In this paper we consider techniques for extending two-dimensional fire spread simulators so that they are able to simulate certain dynamic fire behaviors. In particular, we consider modeling vorticity-driven lateral spread (VLS), which is characterized by rapid lateral fire propagation across steep, leeward slopes. Specifically, we consider modeling the influence of the fire on the local surface airflow via a {\textquotedblleft}pyrogenic potential{\textquotedblright} model, which allows for vertical vorticity effects (in a near-field sense) using the Helmholtz decomposition. The ability of the resulting model to emulate fire propagation associated with VLS is demonstrated using a number of examples.

}, keywords = {Fire, fire-atmosphere, modelling, vorticity-driven lateral spread}, doi = {https://doi.org/10.3389/fmech.2019.00069}, url = {https://www.frontiersin.org/articles/10.3389/fmech.2019.00069/full}, author = {Jason J. Sharples and James Hilton} } @article {bnh-6642, title = {A report on WRF software development (preliminary)}, number = {539}, year = {2020}, month = {01/2020}, institution = {Bushfire \& Natural Hazards CRC}, address = {Melbourne}, abstract = {

Bushfire is one of the major natural hazards Australia encounters every year because of its dry weather and widespread bushlands. During the dry season, occurrence of simultaneous bushfires at different locations is quite common. The fire management authorities face challenges on deployment of resources (human and other logistics) properly to mitigate multiple bushfires. To prioritize, they depend on the modelling of real-time behaviours of the fire under consideration. Fire rate of spread (RoS) is one of the most important parameters that the authority wants to determine before proceeding to resource allocation. RoS during forest fire can be slowed by reduced sub-canopy wind. In operational models, it is accounted by a parameter, wind reduction factor (WRF). Current values used as WRF are not based on science. In this work, we are presenting a software (preliminary version) that can calculate WRF scientifically. We apply a dynamic WRF obtained from a mathematical model in an operation model, Spark. This will lead to better prediction of RoS, once fully implemented.

}, keywords = {Bushfire, fire management, model, Rate of spread, software development}, issn = {539}, author = {Mahmood Rashid and James Hilton and Nazmul Khan and Duncan Sutherland and Khalid Moinuddin} } @conference {bnh-6292, title = {Incorporating firebrands and spot fires into vorticity-driven wildfire behaviour models}, booktitle = {23rd International Congress on Modelling and Simulation}, year = {2019}, month = {12/2019}, abstract = {

Complex modes of fire behaviour resulting from local coupling between the fire and the atmosphere are a significant challenge for rapid operational wildfire spread simulations. While threedimensional fully coupled fire-atmosphere models are able to account for many types of fire behaviour, their computational demands are prohibitive in an operational context. Two-dimensional fire spread models have much lower computational overhead, but are generally not able to account for complex local coupling effects and cannot provide a three-dimensional flow structure suitable for modelling the transport of firebrands. In this paper we investigate extending two-dimensional fire spread simulations to model local coupling effects resulting from wind flow over a ridge that can result in a number of non-intuitive modes of fire behaviour. These include fire propagation opposite to the direction of the prevailing wind on the lee slope of ridges caused by re-circulation on the lee slope, called vorticity-driven lateral spread (VLS). Furthermore we develop extensions of these two-dimensional models to incorporate three-dimensional firebrand transport and show that enhanced downwind spot fire formation can result under certain VLS conditions.

The spread of fires under VLS conditions is driven by vortices in the ground plane. A model for the production and effects of these vortices was incorporated into computational simulations using a vector potential formu-lation in similar manner to a scalar {\textquoteleft}pyrogenic potential{\textquoteright} model, detailed in earlier studies. Firebrands were incorporated using a Lagrangian scheme to model transport through the atmosphere and a sub-scale model for spot fire creation and growth. The firebrand transport took factors such as drag, gravity and buoyancy into account. As effect of plume buoyancy on firebrands under real-world conditions for this scenario is currently unknown, the plume buoyancy was parameterised using a exponential decay model. The sensitivity of the decay parameter in this model was then examined in relation to the resulting spot fire distribution and area burnt. All simulations were carried out using Spark, a wildfire prediction framework.

The coupled VLS and firebrand transport simulations indicated that a higher value of decay parameter, rep-resenting a higher cooling rate of the plume, acted to enhance the lateral spread as firebrands were lofted for shorter times and were caught in the vortices at the edge of the lateral spread region. In contrast, a lower value of decay parameter, representing a lower cooling of the plume, resulted in widespread downwind spot fires and larger burnt areas. This appeared to be due to longer lofting times resulting in firebrands being transported further downwind and away from the vortices within the lateral spread region. The model appears, at least qualitatively, to match observed lateral spread and {\textquoteright}deep flaming{\textquoteright} fire behaviour although many of the parame-ters in the model require further research and experimental calibration. Further development of the model may allow these complex modes

}, keywords = {dynamic fire propagation, embers, Firebrands, spotting, wildfire simulation}, doi = {https://doi.org/10.36334/modsim.2019.H7.hilton2}, url = {https://mssanz.org.au/modsim2019/H7/hilton2.pdf}, author = {James Hilton and Garg, N and Jason J. Sharples} } @article {bnh-5646, title = {River reconstruction using a conformal mapping method}, journal = {Environmental Modelling \& Software}, volume = {119}, year = {2019}, month = {06/2019}, pages = {197-213}, abstract = {

Accurate river bathymetry is required for applications including hydrodynamic flow modelling and understanding morphological processes. Bathymetric measurements are typically a set of depths at discrete points that must be reconstructed into a continuous surface. A number of algorithms exist for this reconstruction, including spline-based techniques and kriging methods. A novel and efficient method is introduced to produce a co-ordinate system fitted to the river path suitable for bathymetric reconstructions. The method is based on numerical conformal mapping and can handle topological features such as islands and branches in the river. Bathymetric surfaces generated using interpolation over a conformal map are compared to spline-based and kriging methods on a section of the Balonne River, Australia. The results show that the conformal mapping algorithm produces reconstructions comparable in quality to existing methods, preserves flow-wise features and is relatively insensitive to the number of sample points, enabling faster data collection in the field.

}, keywords = {Conformal mapping, Depth reconstruction, flood management, River bathymetry, Spatial interpolation}, issn = {1364-8152}, doi = {https://doi.org/10.1016/j.envsoft.2019.06.006}, url = {https://www.sciencedirect.com/science/article/pii/S1364815219301082}, author = {James Hilton and Stefania Grimaldi and Cohen, R and Garg, N and Yuan Li and Marvanek, S and Valentijn Pauwels and Jeffrey Walker} } @article {bnh-5388, title = {The Vegetation Structure Perpendicular Index (VSPI): A forest condition index for wildlife predictions}, journal = {Remote Sensing of Environment}, volume = {224}, year = {2019}, month = {04/2019}, chapter = {167}, abstract = {

Wildfires are a major\ natural hazard, causing substantial damage to infrastructure as well as being a risk to lives and homes. An understanding of their progression and behaviour is necessary to reduce risks and to develop operational management strategies in the event of an active fire. Many empirical fire-spread models have been developed to predict the spread and overall behaviour of a wildfire, based on a range of parameters such as weather and fuel conditions. However, these parameters may not be available with sufficient accuracy or spatiotemporal resolution to provide reliable fire spread predictions. Fuel condition data include variables such as vegetation quantity, structure and moisture content and, in the event of previous wildfires, the burn severity and stage of ecosystem recovery. In this study, an index called the\ Vegetation Structure\ Perpendicular Index (VSPI) is introduced. The VSPI utilises the short-wave infrared reflectance in bands centred at 1.6 and 2.2 μm, essentially representing the amount and structure of the vegetation{\textquoteright}s woody biomass (as opposed to the photosynthetic activity and moisture content). The VSPI is quantified as the divergence from a linear regression between the two bands in a time series and represents vegetation disturbance and recovery more reliably than indices such as the Normalised Burn Ratio (NBR) and\ Normalised Difference Vegetation Index\ (NDVI). The VSPI index generally shows minor inter-annual variability and stronger post-wildfire detection of disturbance over a longer period than NBR and\ NDVI. The index is developed and applied to major wildfire events within eucalypt forests throughout southern Australia to estimate both burn severity and time to recovery. The VSPI can provide an improved information layer for fire risk evaluation and operational predictions of wildfire behaviour.

}, keywords = {Forest condition, Landsat, Vegetation recovery, Wildfire spread}, doi = {https://doi.org/10.1016/j.rse.2019.02.004}, url = {https://www.sciencedirect.com/science/article/pii/S0034425719300586?dgcid=coauthor}, author = {Andrea Massetti and Christoph R{\"u}diger and Marta Yebra and James Hilton} } @conference {bnh-6291, title = {Wind-terrain effects on firebrand dynamics}, booktitle = {23rd International Congress on modelling and Simulation}, year = {2019}, month = {12/2019}, abstract = {

Despite its importance in bushfire propagation, firebrand transport and the spotting process are still poorly understood, and there is no definitive model that can adequately emulate the spotting process in general. The dynamics of firebrands are difficult to predict due to the complex flow structure resulting from the interaction of a buoyant plume with a boundary layer wind field. Understanding the nature of this flow structure, especially for complex terrain, is essential for determining the likely path of firebrands and subsequent distributions of new spot fires and risk levels on structures downwind from the fire.

Although several prior computational modelling studies have carried out investigations of firebrand transport, the effect of the terrain has not previously been taken into account. It is well known that topography can significantly affect ember generation. For example, the enhanced intensity of a fire running up a steep slope can generate a large number of embers. More generally, terrain-modified flows and the strong turbulence associated with leeward slopes and flow around other prominent topographic features may have a pronounced effect on the transport of firebrands. Moreover, modes of dynamic fire propagation such as vorticity-driven lateral spread and eruptive fire spread in canyons involve a coupling between the fire, the terrain and the prevailing winds and so can affect the rate at which firebrands are produced as well as their subsequent transport.

In this study we use a coupled computational fluid dynamic (CFD) and Lagrangian particle approach to model the transport of firebrands. The model is applied to two different terrain scenarios to investigate the flow dynamics, firebrand trajectories and landing patterns resulting from the interaction with the terrain. The first scenario is a line of fire on the lee slope of a ridge burning perpendicular to an incident wind flow. The second scenario is a fire burning in a canyon aligned with the wind. The simulations indicate that the addition of terrain adds a further level of complexity to the flows generated by interaction between the wind and the fire. The terrain appears to modify the counter-rotating vortex pair in the plume structure. For the fire in the lee of the ridge line, the wind-terrain interaction resulted in a flattening and tilting of the counter-rotating vortex pair and enhanced regions of recirculation at the edges of the fire, which were conducive to lateral transport of embers. For the fire in the canyon, the channelling of the winds up the canyon resulted in the formation of a single jet-like vortex transporting firebrands upwards and over the top of the canyon. We hypothesise that this effect is caused by the shape and alignment of the canyon, which forces the vortex pair to merge into a single vortex.

}, keywords = {Climate change, Hydrograph model, parametrization, precipitation, runoff formation processes}, doi = {https://doi.org/10.36334/modsim.2019.H7.hilton}, url = {https://mssanz.org.au/modsim2019/H7/hilton.pdf}, author = {James Hilton and Jason J. Sharples and Garg, N and Murray Rudman and Swedosh, W and Commins, D} } @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} }