@article {bnh-7686, title = {Determination of Firebrand Characteristics Using Thermal Videos}, journal = {Fire}, volume = {3}, year = {2020}, month = {11/2020}, abstract = {

Burning firebrands generated by wildland or prescribed fires may lead to the initiation of spot fires and fire escapes. At the present time, there are no methods that provide information on the thermal characteristics and number of such firebrands with high spatial and temporal resolution. A number of algorithms have been developed to detect and track firebrands in field conditions in our previous study; however, each holds particular disadvantages. This work is devoted to the development of new algorithms and their testing and, as such, several laboratory experiments were conducted. Wood pellets, bark, and twigs of pine were used to generate firebrands. An infrared camera (JADE J530SB) was used to obtain the necessary thermal video files. The thermograms were then processed to create an annotated IR video database that was used to test both the detector and the tracker. Following these studies, the analysis showed that the Difference of Gaussians detection algorithm and the Hungarian tracking algorithm upheld the highest level of accuracy and were the easiest to implement. The study also indicated that further development of detection and tracking algorithms using the current approach will not significantly improve their accuracy. As such, convolutional neural networks hold high potential to be used as an alternative approach

}, keywords = {wildfires; firebrands; software; detection; tracking; fire management}, doi = {https://doi.org/10.3390/fire3040068}, url = {https://www.mdpi.com/2571-6255/3/4/68}, author = {Sergey Prohanov and Alex Filkov and D. P. Kasymov and Mikhail Agafontsev and Vladimir Reyno} } @article {bnh-4819, title = {Simulation of fuel bed ignition by wildland firebrands}, journal = {International Journal of Wildland Fire}, volume = {27}, year = {2018}, month = {07/2018}, abstract = {

A 3-D mathematical model of fuel bed (FB) ignition initiated by glowing firebrands originating during wildland fires is proposed. In order to test and verify the model, a series of experiments was conducted to determine the FB ignition time by a single pine bark and twig firebrand (Pinus sylvestris). Irrespective of the pine bark sample sizes and experimental conditions, the ignition of the FB was not observed. Conversely, pine twigs, under certain parameters, ignited the FB in the range of densities (60{\textendash}105 kg m-3) and with the airflow velocity of >=2 m s-1. The results of the mathematical modelling have shown that a single pine bark firebrand <=5 cm long with a temperature of T <= 1073 K does not ignite in the flaming mode the FB, and only the thermal energy of larger particles is sufficient for flaming ignition of the adjacent layers of the FB. The analysis of the results has shown that the firebrand length is a major factor in the initiation of ignition. Comparison of the calculated and observed FB ignition times by a single firebrand have shown that our modelling accords well with the experimental results.

}, keywords = {critical conditions, experiment, ignition, modelling, spotting.}, url = {https://www.publish.csiro.au/WF/WF17083}, author = {O. V. Matvienko and D. P. Kasymov and Alex Filkov and O. I. Daneyko and D. A. Gorbatov} } @article {bnh-5140, title = {Investigation of firebrand production during prescribed fires conducted in a pine forest}, journal = {Proceedings of the Combustion Institute}, volume = {36}, year = {2017}, month = {11/2016}, pages = {3270}, chapter = {3263}, abstract = {

This paper represents a study on the characterization of firebrand production which was carried out, using experimental fires conducted as prescribed fires in the New Jersey Pine Barrens, USA in March of 2013{\textendash}2015. Several preliminary techniques were tested to characterize the firebrand production. Firebrands were collected from three plots for each year and analyzed for mass and size distribution. Thermal imagery was used to measure the velocity, size and number of firebrands in 2014 and 2015. The distribution of firebrands was evaluated in a monitored volume during the experiment. It was found that not less than 70\% of collected particles were bark fragments and the rest were pine and shrub branches. The number of firebrands decreases with increasing the cross section area of firebrands. The mass of the particles varied from 5 to 50mg, and the maximum number of the particles was observed for the mass range of 10{\textendash}20mg. About 80\% of firebrands were particles with the cross section area of (5{\textendash}20) {\texttimes} 10-5\ m2. These results are consistent with the available observations of real fires\ [1],\ [2]. Processing of infrared video showed that starting from a distance of 13m from fire front, an increasing number of firebrands were observed in a controlled volume, increasing in number up to 180 per second. Relationships describing the time-variation of the number of particles that dropped on a 1.4m2\ surface and the number of particles that flew through a 1m3\ volume were obtained. Comparing the experimental and calculated data, we can conclude that these relationships allow us to describe the two numbers with an acceptable accuracy (adj. R2\ 0.74 and 0.86, respectively). In addition, the velocity of the particles, which depended on the wind velocity, was in the 0.1{\textendash}10.5m/s range, with an average value of 2.5m/s.

}, doi = {https://doi.org/10.1016/j.proci.2016.06.125}, url = {https://www.sciencedirect.com/science/article/pii/S1540748916301833$\#$!}, author = {Alex Filkov and Sergey Prohanov and Eric Mueller and D. P. Kasymov and Pavel Martynov and Mohamad El Houssami and Jan Thomas and Nicholas Skowronski and Bret Butler and Michael Gallagher and Kenneth Clark and William Mell and Robert Kremens and Rory M. Madden and Albert Simeoni} }