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Analysis of the physical processes associated to Junction Fires at Laboratory and Field Scales
JJunction fires that involve the merging of two linear fire fronts intersecting at a small angle are associated to 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 due 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 that ends 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 small dependence on the initial boundary conditions. Numerical simulation of the heat flux from two flame surfaces to an element of fuelbed show that radiation can be considered as the main mechanism of fire spread only during the deceleration phase of the fire.
WF16173 Accepted 27 September 2017
© CSIRO 2017