Numerical simulation of surface forest fire in Brazilian Amazon

• Brazilian Amazon surface fires are simulated using WFDS, a physics-based model.
• It is examined the relative importance of five parameters.
• The important parameters to numerical ROS determination are highlighted.
• It is used fire observations from two different sites in the Brazilian Amazon

This paper investigates fire spread through surface fuels of the Brazilian Amazon by using a three-dimensional, fully transient, physics-based computer simulation approach. Computer simulations are obtained through the solution to governing equations of fluid dynamics, combustion, heat transfer and thermal degradation of the vegetative fuel. Surface fuel fires composed mostly of dead leaves and twigs were numerically simulated and the calculated rate of spread was compared to findings from field observations. The importance of air humidity, vegetation temperature, moisture content, surface to volume ratio and bulk density was evaluated through the variation of each one individually in numerical simulation runs. Conclusions show that in the range of parameter variation considered, the most important parameters are the vegetation moisture, surface area to volume ratio, and bulk density. The vegetation initial temperature and air humidity, in the range of variation studied, did not influence the fire rate of spread. The numerical simulations also showed that the radiation process is very important and directly affects the fire rate of spread. Convection is less important because of the absence of external wind. The model is able to capture the main effects of a surface forest fire typical of the Amazon, and can be used as a numerical tool for studying such fires.