Extension of the Balbi fire spread model to include the field scale conditions of shrubland fires

Abstract

The ‘Balbi model’ is a simplified rate of fire spread model aimed at providing computationally fast and accurate simulations of fire propagation that can be used by fire managers under operational conditions. This model describes the steady-state spread rate of surface fires by accounting for both radiation and convection heat transfer processes. In the present work the original Balbi model developed for laboratory conditions is improved by addressing specificities of outdoor fires, such as fuel complexes with a mix of live and dead materials, a larger scale and an open environment. The model is calibrated against a small training dataset (n = 25) of shrubland fires conducted in Turkey. A sensitivity analysis of model output is presented and its predictive capacity against a larger independent dataset of experimental fires in shrubland fuels from different regions of the world (Europe, Australia, New Zealand and South Africa) is tested. A comparison with older versions of the model and a generic empirical model is also conducted with encouraging results. The improved model remains physics-based, faster than real time and fully predictive.

Physical modelling of fires spreading upslope, involved in fire eruption triggering

“…The Balbi model presented by Chatelon et al (2022) calculates the ROS as the sum of three components (see fig. 1): (1) the radiation from the free flame F1 on the unburnt fuel (Rr), (2) the radiation from the flame base (the fuel burning particles area, Rb) and (3) the convection inside the vegetal stratum (Rc).…”

“…The flame F2 is due to the flame base radiative and convective heat fluxes. All details and nomenclature can be found in (Chatelon et al 2022).…”

“…This fire fell into the very high fire severity (Cheney, 1981) with a fireline intensity close to 10 MW m -1 and a very fast ROS (0.45 m s -1 ). As the Balbi model (Chatelon et al 2022) does not include any fire induced wind sub-model, it provides poor results with a predicted ROS equal to 0.1 m s -1 . The ROS calculated with the proposed induced wind model (eq.…”

“…In this work, the explanation provided by Viegas is selected and a first attempt of a physical modelling of this induced wind is proposed. It is based on a brand-new Balbi model formulation derived from (Chatelon et al 2022) tested against more than 300 shrubland and grassland fires at the field scale with a very good agreement. This induced wind modelling is supposed to provide a good representation of a fire spreading upslope without wind (or with weak wind conditions).…”

A simplified physical propagation model for surface fires designed for an implementation into fire decision making tools

“…Simplified physical models (Pagni and Peterson, 1973;Albini, 1985;Balbi et al 2010) combines the advantages of the three previous categories. The Balbi model (Balbi et al 2020;Chatelon et al 2022) is a simplified physical propagation model for surface fires at the field scale. It consists in a set of non-linear algebraic equations depending on the triangle of fire (fuel, wind and slope) and built over three heat transfer mechanisms:…”