In addition, the rise of informal settlement communities in Southeast Asia and Africa continues to result in large outdoor fires capable of great destruction.A common feature in the rapid spread of large outdoor fires are the generation of smaller combustible fragments from the original fire source, referred to as firebrands. In the case of WUI fires, the production of firebrands occurs from the combustion dynamics of vegetative, such as trees and shrubs, and human-made fuel elements, such as homes and other structures. For urban fires and informal settlement fires, firebrands are produced primarily from human-made fuel elements.Firebrand combustion has a series of important aspects: initial generation or formation from the combustion of both vegetative and structural fuel types, transport, deposition, and ignition of fuel sources generally far removed the original fire source. Post-fire investigations, for WUI fires, have reported that firebrand processes are responsible for a majority of structure losses in these fires [https://link.springer.com/referenceworkentry/10.1007/978-3-319-51727-8_46-1].
Editorial23 February 2022
Editorial: Improved Understanding of Firebrand Processes During Large Scale Fire Disasters
ORIGINAL RESEARCH
24 May 2021
Miguel Almeida, 1 more and Domingos Viegas
3 Authors
- MA
Miguel Almeida
ADAI, Department of Mechanical Engineering, University of Coimbra, Portugal
- LP
Leonardo Porto
Department of Mechanical Engineering, University of Coimbra, Portugal
- DV
Domingos Viegas
ADAI, Department of Mechanical Engineering, University of Coimbra, Portugal
The number, dimensions and initial velocity of the firebrands released from burning Quercus suber, Eucalyptus globulus, Quercus robur and Pinus pinaster trees were analyzed in laboratory experiments using a particle image velocimetry system. Additionally, the flame height, tree mass decay, vertical flow velocity and temperature at the top of the trees were measured during the experiments. The relationship between the various parameters was analyzed and a good rapport connection between the flame height and the number and total estimated volume of the firebrands was found.
The specimens burnt were mostly young trees, so. Therefore, large particles like (e.g., pine cones, or thick pieces of trunk barks, and branches) were not included in this study because they were not present. considered in the analysis. Actually, the firebrands produced in the laboratory tests, mainly burning leaves, had less than 1600mm2 of cross-sectional area, having potential to cause short distance spotting (up to tens of meters).
Quercus suber and Quercus robur trees were the species that produced more firebrands, both in terms of number and of total volume. On the other hand, Eucalyptus globulus was the species that showed the lowest production of firebrands. Experiments with Eucalyptus globulus and Quercus suber trees were those resulting in larger values of temperature and vertical airflow velocity during the burning process.
Quercus trees are often considered to have a lower fire risk than eucalyptus or pine trees. However, in this study Quercus suber and Quercus robur were the species that produced more firebrands, both in terms of number and of total volume. The tests with Quercus suber were the only ones using specimens from an adult tree, confirming the great importance of the age of trees in the propensity to release firebrands. The results obtained with Quercus robur confirmed the high tendency of this species to originate spot fires at short distance. Thus, these results are of great relevance to afforestation plans and to evaluate the risk of the presence of these species in wildland-urban interface areas.
ORIGINAL RESEARCH
28 January 2021
Sayaka Suzukiand Samuel L. Manzello
5,769 views
23 citations