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Analysis of the physical processes associated with junction fires at laboratory and field scales

Author(s): J. R. Raposo, Domingos Xavier Viegas, X. Xie, Miguel Almeida, A. R. Figueiredo, L. Porto, J. Sharples
Year Published: 2018

Junction fires, which involve the merging of two linear fire fronts intersecting at a small angle, are associated with very intense fire behaviour. The dynamic displacement of the intersection point of the two lines and the flow along the symmetry plane of the fire are analysed for symmetric boundary conditions. It is observed that the velocity of displacement of this point increases very rapidly owing to strong convective effects created by the fire that are similar to those of an eruptive fire. The change of fire geometry and of its associated flow gradually blocks the rate of spread increase and creates a strong deceleration of the fire, which ends up behaving like a linear fire front. Results from laboratory and field-scale experiments, using various fuel beds and slope angles and from a large-scale fire show that the processes are similar at a wide range of scales with little dependence on the initial boundary conditions. Numerical simulation of the heat flux from two flame surfaces to an element of the fuel bed show that radiation can be considered as the main mechanism of fire spread only during the deceleration phase of the fire.

Citation: Raposo JR, Viegas DX, Xie X, Almeida M, Figueiredo AR, Porto L, Sharples J. 2018. Analysis of the physical processes associated with junction fires at laboratory and field scales. International Journal of Wildland Fire 27, p. 52–68. https://doi.org/10.1071/WF16173
Topic(s): Fire Behavior, Extreme Fire Behavior
Ecosystem(s): None
Document Type: Book or Chapter or Journal Article
NRFSN number: 16747
FRAMES RCS number: 25678
Record updated: May 18, 2018