Fireline Rotation Analysis

Abstract

The concepts of fire line rotation and fire line extension are introduced as a complement to the usual rate of spread to describe the movement of surface fires. It is shown that both rotation and translation of the fire line elements contribute to increasing their length and reducing the curvature of the fire line. It is shown that in the case when the wind velocity is not parallel to the rate of spread vector, the transverse convective flux along the fire front induces a change of the rate of spread and consequently a rotation movement of the fire line. Using empirical formulations for the dependence of the rate of spread on wind velocity, a model for the rotational velocity of a wind and slope driven fire front is developed. The model is compared with experimental laboratory results for wind- and slope-induced extension and rotation of linear fire fronts.

Keywords:

• Fire behavior
• Fire dynamics
• Forest fires

ACKNOWLEDGMENTS

The collaboration given to the experimental program that supports this paper by several collaborators—namely, by Mr. A. Cardoso, Mr. N. Luís, and Miss Telma Domingues—is gratefully acknowledged. The authors are thankful to the critical comments made to this text by their colleagues Dr. Shankar Mahalingham and Dr. A. Rui Figueiredo. The authors also wish to thank the reviewers for the careful revision of this paper and for the comments and criticism that was made, which helped us to improve it.

The second author performed this study with the support given by the Fundação para a Ciência e a Tecnologia, under the fellowship ref. SFRH/BD/17669/2004. The support given by the Junta Nacional de Investigação Científica, under project CODINF- Modelo Dinâmico de Propagação de um Incêndio Florestal (Contract PPCDT/EME/60821/2004), and by the DG XII of the European Commission, under project SPREAD – Forest Fire Spread Prevention and Mitigation (Contract EVG1-CT-2001-00043) of the Environment program, is also gratefully acknowledged.