Interaction between two parallel fire fronts under different wind conditions
Carlos Ribeiro
A * , Luís Reis A , Jorge Raposo A , André Rodrigues A , Domingos Xavier Viegas A and Jason Sharples B C
+ Author Affiliations
- Author Affiliations
A Univ Coimbra, ADAI, Departamento de Engenharia Mecânica, Rua Luís Reis Santos, Pólo II, 3030‐788 Coimbra, Portugal.
B School of Science, University of New South Wales (UNSW), Canberra, ACT, Australia.
C Bushfire and Natural Hazards Cooperative Research Centre, East Melbourne, Vic., Australia.
* Correspondence to: carlos.ribeiro@adai.pt
International Journal of Wildland Fire 31(5) 492-506 https://doi.org/10.1071/WF21120
Submitted: 24 August 2021 Accepted: 13 March 2022 Published: 20 May 2022
© 2022 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
Wildfires often exhibit complex and dynamic behaviour arising from interactions between the fire and surrounding environment that can create a rapid fire advance and result in loss of containment and critical fire safety concerns. A series of laboratory experiments involving the interaction of two parallel fire lines on a uniform fuel bed without slope under the influence of wind is presented and discussed. The two fire lines are initially separated by a certain distance (1, 2 m) and the subsequent fire spread is described. The results show that the pyroconvective interaction between the two fire lines and ambient wind modified the rate of spread of the approaching fire lines and their associated spread characteristics, independently of the distance between them. A physical interpretation of fire evolution based on the dynamic interaction between two parallel fire lines under wind flow is proposed. We use a dimensionless physical parameter, the Froude number. The results also demonstrated the existence of a wind flow velocity between 1 and 2 m s−1, corresponding to a Froude number between 0.2 and 0.4 for which the rate of approach of the two merging fire lines is a minimum.
Keywords: accelerating fires, convergent fire fronts, dynamic fire behaviour, extreme fire behaviour, fire behaviour, forest fires, merging fires, parallel fronts.
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