Physics-based modelling of junction fires: parametric study
Ahmad Hassan A * , Gilbert Accary B , Duncan Sutherland C and Khalid Moinuddin A
+ Author Affiliations
- Author Affiliations
A Institute for Sustainable Industries and Liveable Cities, Victoria University, Melbourne, Vic. 8001, Australia.
B Scientific Research Centre in Engineering, Lebanese University, Museum Square, 1106 Beirut Lebanon.
C School of Science, University of New South Wales, Canberra, ACT 2610, Australia.
* Correspondence to: ahmad.hassan6@live.vu.edu.au
International Journal of Wildland Fire 32(3) 336-350 https://doi.org/10.1071/WF22121
Submitted: 30 June 2022 Accepted: 10 February 2023 Published: 2 March 2023
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of IAWF. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)
Abstract
Background: Junction fires occur when two fire fronts merge. The rate of spread (ROS) and heat release rate (HRR) of the junction increase more quickly than that of each fire front, this effect exacerbated by slopes.
Aims: Numerical modelling of junction fires and an interpretation of their behaviour are given examining the key influencing factors.
Methods: Twenty physics-based simulations of laboratory-scale junction fires were performed for a shrub fuel bed using FIRESTAR3D, varying slope (0°–40°) and junction angles (15°–90°).
Key results: Accelerative and decelerative behaviours were observed for junction angles lower than 45°, but above this, deceleration was absent. The behaviour was firmly related to junction angle evolution, which controlled the flame and interactions between fire fronts. HRR followed similar trends; maximum HRR increased with increasing junction angle. Convection was the primary heat transfer mode in the initial propagation phase. In no-slope cases, radiation was the dominant method of heat transfer, but convection dominated fires on slopes.
Conclusions: The physics-based model provided great insight into junction fire behaviour. The junction angle was critical for determining ROS and fire behaviour.
Implications: The research helped to assess the effects of some topographical parameters in extreme fires. Situational awareness, operational predictions and firefighter safety will consequently improve.
Keywords: bushfire, eruption, fully physical model, high-performance computing, merging fire, multiphysics and multiscale CFD-based model, sloping terrain, unsteady forest fire, zippering effect.
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