Enhancing resilience to ember attack on the urban fringe

Black Summer Bushfire Recovery Project

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Project outline and motivation

This project developed a computational framework for simulating ember storms at the rural urban interface using advanced Computational Fluid Dynamics (CFD) simulation techniques. CFD simulations of wind over forests, buildings, and the transportation of windborne particles are all established in the broader scientific literature, however, no study has attempted to combine all these elements to simulate the transport of embers.

Embers, burning debris common in bushfires, are the leading cause of house destruction and damage during bushfires, particularly in suburban developments that abut rural or wildland areas.

The robust simulation framework developed as part of this project has given unprecedented insights into the physical mechanisms that transport embers from forests, across asset protection zones and into suburban areas. These insights subsequently provide guidance on how suburban areas may be better designed, constructed, and maintained to be more resilient to ember hazards.

A complimentary part of this project generated a novel process to map areas where developed areas abut wildland across Australia.

For an ember storm to occur, there must be a fire in a fuel type prone to embers (such as a eucalypt or pine forest). The simulation results revealed that ember storms occur in asset protection zones near sparse forests. Dense forests create turbulence that impedes the transport of embers. A model was constructed from this information to identify regions where ember storms are likely to occur.

Simulations of ember accumulation around idealised urban structures reveal that embers accumulate on the side of the structure furthest from the forest. The spacing between structures does influence how far the embers travel into the suburban development, but no significant enhancements due to local wind speed increases were observed.

Dr Paul Barnes (Research Fellow): Involved in conceptualising grant application and characterisation of risk framework, but left ��¼� soon after the project commenced. Dr Victor Huang (research assistant) Contracted for 3 months to develop postprocessing code to read plot3d files.

Prof. Shawn Laffan: Secondary supervisor of N. Mehnaz, contributing to the definition and characterisation of the WUI.

Nusrat Mehnaz (PhD Student): Characterisation of the Australian WUI. Developed all maps of the WUI used to investigate risk around the ACT.

Dr Methma Rajamuni (Research Associate): conducted and analysed simulations of ember transport across the asset protection zone, and conducted simulations of flow through canopies of varying density.

Prof. David Sanderson (Judith Neilson Fellow): contributed to the original proposal with a view to resilience building.

Tanvir Saurav (PhD Student): Development of a computational framework for ember storm simulation. Developed the framework used for all simulations. Investigated ember impact on idealised structures.

Prof. Jason Sharples (��¼� Bushfire Director): mentored the entire project.

Dr Duncan Sutherland: Conceived, managed and intellectually guided the project.

Dr Johnny Valbuena (Research Assistant): attempted to apply dynamical systems identification techniques to particle trajectories.
Saurav TM, Sutherland D, Sharples JJ, (2023) 'A computational framework for phenomenological modelling of ember storms at the wildland-urban interface', in Proceedings of the International Congress on Modelling and Simulation, MODSIM, pp. 816 – 822

Saurav TM, Best student oral presentation, (2023) International Congress on Modelling and Simulation MODSIM.

Saurav TM, (2023) recipient HPC-AI Talent Program, National Computational Infrastructure.

Mehnaz, N, Saurav TM, Sutherland D, Laffan S, Sharples JJ, (2024) ‘Defining the extent of the wildland-urban interface across Australia’ (submitted, under revision).

Rajamuni, MM, Saurav TM, Sutherland D, Sharples JJ (2024) ‘Ember storms in an asset protection zone: effects of wind speed and canopy density’ (submitted, under revision).

Saurav TM, Sutherland D, Sharples JJ, (2024) Effect of threshold gradient on ember Accumulation at the Wildland Urban Interface (Oral presentation) Supercomputing Asia Sydney 2024

Valbuena Soler J, Sutherland D, Sharples JJ, (2024) Modelling Ember Trajectories Using Data-driven Methods (oral presentation) 7^th International Fire Behaviour and Fuels Conference Canberra.

Rajamuni MM, Saurav TM, Sutherland D, Sharples JJ, (2024) Investigating the effect of tree canopy heterogeneity on canopy flow and ember transport (Poster presentation) 7^th International Fire Behaviour and Fuels Conference Canberra.

Rajamuni MM, Saurav TM Sutherland D, Sharples JJ, (2024) Canopy Edge Effects on Ember Storm Dynamics, 24^th Australasian Fluid Mechanics Conference, Canberra.

Workshops

Exploring the state of the science of ember transport and impacts, (2024) 7^th International Fire Behaviour and Fuels Conference Canberra.

This workshop brought together researchers and interested end-users to communicate recent advances in modelling embers at the wildland-urban interface, and to discuss emerging state-of-the-art ember research including new avenues of inquiry.

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