Field and laboratory analysis of the junction fire process in the catastrophic fire of Pedrógão Grande in June 2017
Domingos X. Viegas
A * , Carlos Ribeiro A , Miguel Almeida A , Paulo Pinto B , Luís M. Ribeiro A and Álvaro Silva B
+ Author Affiliations
- Author Affiliations
A Univ Coimbra, ADAI, Department of Mechanical Engineering, Rua Luís ReisSantos, Pólo II, 3030‐788 Coimbra, Portugal.
B Portuguese Institute for Sea and Atmosphere (IPMA), Rua C do Aeroporto, 1749-077 Lisbon, Portugal.
* Correspondence to: xavier.viegas@dem.uc.pt
International Journal of Wildland Fire 32(6) 951-967 https://doi.org/10.1071/WF22161
Submitted: 14 July 2022 Accepted: 8 April 2023 Published: 15 May 2023
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of IAWF. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)
Abstract
Background: Two fire ignitions in Pedrógão Grande on 7 June 2017 had very fast due to unusual physical processes associated with the interaction between an overhead thunderstorm and the fire and the subsequent merging of the fires as a junction fire, killing 66 persons in 2 h.
Aims: Using a laboratory simulation of the merging process, we explain the fire spread conditions and verify that the junction of the two fires was responsible for the very intense fire development.
Methods: The real fire spread was reconstructed from an extensive field survey and physical modelling tests were performed in the Fire Research Laboratory combustion tunnel using various fuels and scale modelling laws.
Key results: The spread and merging of the two fires in the tests agree very well with field observations, namely the periods of rate of spread (ROS) increase and decrease, peak values of ROS and area growth process using scaling laws.
Conclusions: Analysis of the Pedrógão Grande fire evolution and its physical simulation at laboratory scale showed the importance of the mechanisms of two fires merging in producing very important convective processes.
Implications: Our study showed the validity of performing the experimental analysis of complex fire spread situations provided that the similarity conditions are fulfilled.
Keywords: convergent fire fronts, dynamic fire behaviour, extreme fire behaviour, fire acceleration, fire and atmosphere interaction, fire behaviour, fire growth, forest fires, junction fires, merging fires, physical modelling, scaling laws.
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