Modelling wildfire spread and spotfire merger using conformal mapping and AAA-least squares methods

A two-dimensional model of wildfire spread and merger is presented. Three features affect the wildfire propagation: (i) a constant basic rate of spread term accounting for radiative and convective heat transfer, (ii) the unidirectional, constant ambient wind, and (iii) a fire-induced pyrogenic wind. Two numerical methods are proposed to solve for the pyrogenic potential. The first utilises the conformal invariance of Laplace’s equation, reducing the wildfire system to a single Polubarinova–Galin type equation. The second method uses a AAA-least squares method to find a rational approximation of the pyrogenic potential. Various wildfire scenarios are presented and the effects of the pyrogenic wind and the radiative/convective basic rate of spread terms investigated. Firebreaks such as roads and lakes are also included and solutions are found to match well with existing numerical and experimental results. The methods proposed in this work are suitably fast and new to the field of wildfire modelling. • The rate of spread is split into radiative, convective and two distinct wind effects. • Single wildfire spread is modelled using a conformal mapping method. • The AAA-least squares algorithm is used in the multiple spotfires numerical method. • The results show good agreement with existing model results and experimental data. • Firebreaks and the merging of wildfires are also incorporated into the model.