A new mathematical algorithm has been developed to model the propagati
on of a moving flame front in forests or grasslands in order to simula
te the spread of the perimeter of a wildfire. The fire is defined as a
closed contour propagating outwards at a velocity directly linked to
the physical process of combustion. This approach separates the propag
ation of the flame front from the combustion itself The aim of the pre
sent work is to estimate the propagation of a flame front with time an
d to assess the actual abilities of this new mathematical description
of the contour. The fire contour is modelled by a complex Fourier seri
es function. The model of the digital simulation code PROLIF is presen
ted with a description of the first tests. (C) 1998 Published by Elsev
ier Science Ltd.