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Analytical Model to Predict the Self-induced Acceleration and Deceleration of a Head Fire
Domingos Viegas, Carlos Ribeiro 
, Luis Ribeiro , Miguel Almeida, Tiago Rodrigues, Thiago Barbosa
Abstract
Background Current fire behaviour modelling assumes that the head fire rate of spread depends on the three factors of the classical fire environment triangle (fuel, meteorology and topography) without considering the convective processes resulting from the interaction between fire and the environment. Aims Observing that large amplitude oscillations of the fire ROS often lead to rapid acceleration and deceleration of the fire, an analytical model to predict these processes and the temporal variation of the ROS is proposed. Methods A mathematical model proposed earlier is applied to a head fire's acceleration and deceleration phases. Results from a series of laboratory and field-scale experiments, as well as from real fires, were used to develop the parameters of the model. Key results Two sets of model parameters were proposed to predict the temporal variation of the ROS in the acceleration and deceleration phases of laboratory or field-scale fires. Using data from real fires, it was found that the present model predicts the time lapses of given periods of acceleration or deceleration with sufficient accuracy for practical operations. Conclusions An analytical model is proposed to predict the large amplitude temporal variation of the head fire ROS during large fires. Most current fire behaviour models do not explain and model these acceleration and deceleration processes. Implications The present analytical model to predict the acceleration and deceleration of the head fire proposes a novel interpretation of the fire behaviour, considering its dynamic effects and their inclusion in fire spread modelling.
WF24166 Accepted 22 May 2025
© CSIRO 2025
