Citation

Ju X, Conkling M, Hajilou M, Lin S, Mostafa F, Ayyar A, McDowell A, Lisano M, Gollner MJ. Fire Safety J. 2023; 141: e103921.

Copyright

(Copyright © 2023, Elsevier Publishing)

DOI

10.1016/j.firesaf.2023.103921

PMID

unavailable

Abstract

Firebrands play a critical role in the propagation of wildland fires, particularly in the wildland-urban interface (WUI). The mechanism behind fire spread by firebrands is not well understood despite being responsible for a majority of structure losses during WUI fires. This study quantifies the generation of firebrands from three typical WUI fuels (Douglas fir, eucalyptus globulus, and coast live oak) inside a laboratory-scale wind tunnel, to provide necessary data to model the spread of wildland fires into and within communities by burning embers. A comprehensive set of test conditions were considered, including the initial fuel mass, fuel moisture content, mean twig diameter, and crosswind speed.

RESULTS showed that the firebrand yields for all three fuel species were independent of the total dry mass lost, but positively correlated with the crosswind speed and negatively correlated to fuel moisture content and mean twig diameter. Meanwhile, the firebrand yields by mass of the fuels under the same test conditions have the following order: coast live oak >Douglas fir >eucalyptus globulus. Scaling analysis was performed to organize the data under different test conditions, and unique firebrand yield correlations were then obtained for each fuel species. In addition, the masses and projected areas of the firebrands for each fuel species had a linear fitting correlation, and the slope of the fitting line was positively correlated to fuel moisture content but insensitive to crosswind speed and mean twig diameter. The data and correlations disclosed in this study could be vital for future simulations of fire spread in both the wildland and WUI.

Language: en

Keywords

Ember; Firebrand generation; Model development; Scaling analysis; Vegetative fuels; Wildfire; Wildland-urban interface (WUI)