@article {bnh-7795, title = {Experiments on the influence of spot fire and topography interaction on fire rate of spread}, journal = {PLOS ONE}, volume = {16}, year = {2021}, month = {01/2021}, abstract = {

Spotting is thought to increase wildfire rate of spread (ROS) and in some cases become the main mechanism for spread. The role of spotting in wildfire spread is controlled by many factors including fire intensity, number of and distance between spot fires, weather, fuel characteristics and topography. Through a set of 30 laboratory fire experiments on a 3 m x 4 m fuel bed, subject to air flow, we explored the influence of manually ignited spot fires (0, 1 or 2), the presence or absence of a model hill and their interaction on combined fire ROS (i.e. ROS incorporating main fire and merged spot fires). During experiments conducted on a flat fuel bed, spot fires (whether 1 or 2) had only a small influence on combined ROS. Slowest combined ROS was recorded when a hill was present and no spot fires were ignited, because the fires crept very slowly downslope and downwind of the hill. This was up to, depending on measurement interval, 5 times slower than ROS in the flat fuel bed experiments. However, ignition of 1 or 2 spot fires (with hill present) greatly increased combined ROS to similar levels as those recorded in the flat fuel bed experiments (depending on spread interval). The effect was strongest on the head fire, where spot fires merged directly with the main fire, but significant increases in off-centre ROS were also detected. Our findings suggest that under certain topographic conditions, spot fires can allow a fire to overcome the low spread potential of downslopes. Current models may underestimate wildfire ROS and fire arrival time in hilly terrain if the influence of spot fires on ROS is not incorporated into predictions.

}, keywords = {air flow, analysis of variance, Bushfire, combustion, fire research, fire suppression technology, fuels, rotors}, doi = {https://doi.org/10.1371/journal.pone.0245132}, url = {https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0245132}, author = {Michael Storey and Owen Price and M. Almeida and Carlos Ribeiro and Ross Bradstock and Jason J. Sharples} } @article {bnh-4427, title = {Analysis of the physical processes associated with junction fires at laboratory and field scales}, journal = {International Journal of Wildland Fire }, volume = {27}, year = {2018}, month = {01/2018}, abstract = {

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.

}, keywords = {accelerating fires, convective effects, dynamic fire behaviour, extreme fire behaviour, Fire behaviour, merging fires.}, doi = {10.1071/WF16173}, url = {http://www.publish.csiro.au/WF/WF16173}, author = {J. R. Raposo and D. X. Viegas and X. Xie and M. Almeida and A. R. Figueiredo and L. Porto and Jason J. Sharples} }