Complex permittivity study of a Pinus Pinaster needle bed on fire

Abstract

In this paper, a range of complex permittivity values, estimated from a Pinus Pinaster fuel bed on fire is presented. The Fire Dynamics Simulator (FDS) was used to model the fire environment and the Cold Plasma Model (CPM) was applied to evaluate the complex permittivities of such turbulent media. The retrieved values served as input parameters describing the propagation medium, enabling a full-wave analysis based on the Finite-Difference TimeDomain (FDTD) method to evaluate and ascertain the impact of a weakly ionised plasma generated during vegetation combustion on radiowave propagation. Comparisons were obtained against two other methods, namely the Transmission-Line Method (TLM) and the Full-Stack (FS) technique, as a way to reduce the computational time. These analyses yielded attenuation values up to 6 dB for the simulated scenario, in which good agreement among techniques was obtained. Preliminary results clearly indicated that fire may degrade communications in real fire situations.