Spotting ignition by lofted firebrands is a significant mechanism of fire spread, as observed in many large-scale fires. The role of firebrands in fire propagation and the important parameters involved in spot fire development are studied. Historical large-scale fires, including wind-driven urban and wildland conflagrations and post-earthquake fires are given as examples. In addition, research on firebrand behaviour is reviewed. The phenomenon of spotting fires comprises three sequential mechanisms: generation, transport and ignition of recipient fuel. In order to understand these mechanisms, many experiments have been performed, such as measuring drag on firebrands, analysing the flow fields of flame and plume structures, collecting firebrands from burning materials, houses and wildfires, and observing firebrand burning characteristics in wind tunnels under the terminal velocity condition and ignition characteristics of fuel beds. The knowledge obtained from the experiments was used to develop firebrand models. Since Tarifa developed a firebrand model based on the terminal velocity approximation, many firebrand transport models have been developed to predict maximum spot fire distance. Combustion models of a firebrand were developed empirically and the maximum spot fire distance was found at the burnout limit. Recommendations for future research and development are provided.

https://www.fs.fed.us/psw/publications/weise/psw_2010_weise(koo)001.pdf

Firebrands and spotting ignition in large-scale fires

Experimental study on flame height and temperature profile of buoyant window spill plume from an under-ventilated compartment fire

While the wildland–urban interface (WUI) is not a new concept, fires in WUI communities have rapidly expanded in frequency and severity over the past few decades. The number of structures lost per year has increased significantly, due in part to increased development in rural areas, fuel management policies, and climate change, all of which are projected to increase in the future. This two-part review presents an overview of research on the pathways for fire spread in the WUI. Recent involvement of the fire science community in WUI fire research has led to some great advances in knowledge; however, much work is left to be done. While the general pathways for fire spread in the WUI (radiative, flame, and ember exposure) are known, the exposure conditions generated by surrounding wildland fuels, nearby structures or other system-wide factors, and the subsequent response of WUI structures and communities are not well known or well understood. This first part of the review covers the current state of the WUI and existing knowledge on exposure conditions. Recommendations for future research and development are also presented for each part of the review.

Review of Pathways for Building Fire Spread in the Wildland Urban Interface Part I: Exposure Conditions

Wildland fire spot ignition by sparks and firebrands

An experimental investigation and statistical characterization of intermittent flame ejecting behavior of enclosure fires with an opening

https://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/93452/1/j.firesaf.2007.12.008.pdf

Development and validation of a physics-based urban fire spread model

http://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/93450/3/j.firesaf.2008.06.005.pdf

Modeling thermal behaviors of window flame ejected from a fire compartment

A transport model for a disk-shaped firebrand in 3D space has been formulated for the purpose of spotting simulation. In the model, firebrand transport is described by solving the conservation equations of momentum and angular-momentum, simultaneously. The airborne firebrand receives the aerodynamic forces and moment from the surrounding fluid, which varies in time and space due to the change in its location and orientation. An approximate form of the Navier-Stokes equations appropriate for low-Mach number flow was applied for the fluid motion. LES (Large Eddy Simulation) on buoyant flow downstream of a square heat source was carried out, and transport behaviors of various firebrands were investigated. Then, a scaling dimensionless parameter * B for the transport was derived. Numerically obtained mean travel distance to the windward direction, as well as its s.d. (standard deviation), were correlated with * B with reasonable accuracy.

https://www.iafss.org/publications/fss/8/433/view

Transport Of Disk-shaped Firebrands In A Turbulent Boundary Layer

http://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/93451/1/j.firesaf.2008.06.007.pdf

Modeling the trajectory of window flames with regard to flow attachment to the adjacent wall

In this article, we develop statistical models to predict the number and geographic distribution of fires caused by earthquake ground motion and tsunami inundation in Japan. Using new, uniquely large, and consistent data sets from the 2011 Tōhoku earthquake and tsunami, we fitted three types of models-generalized linear models (GLMs), generalized additive models (GAMs), and boosted regression trees (BRTs). This is the first time the latter two have been used in this application. A simple conceptual framework guided identification of candidate covariates. Models were then compared based on their out-of-sample predictive power, goodness of fit to the data, ease of implementation, and relative importance of the framework concepts. For the ground motion data set, we recommend a Poisson GAM; for the tsunami data set, a negative binomial (NB) GLM or NB GAM. The best models generate out-of-sample predictions of the total number of ignitions in the region within one or two. Prefecture-level prediction errors average approximately three. All models demonstrate predictive power far superior to four from the literature that were also tested. A nonlinear relationship is apparent between ignitions and ground motion, so for GLMs, which assume a linear response-covariate relationship, instrumental intensity was the preferred ground motion covariate because it captures part of that nonlinearity. Measures of commercial exposure were preferred over measures of residential exposure for both ground motion and tsunami ignition models. This may vary in other regions, but nevertheless highlights the value of testing alternative measures for each concept. Models with the best predictive power included two or three covariates.

Keisuke Himoto

Papers

Development and validation of a physics-based urban fire spread model

Modeling thermal behaviors of window flame ejected from a fire compartment

Transport Of Disk-shaped Firebrands In A Turbulent Boundary Layer

Modeling the trajectory of window flames with regard to flow attachment to the adjacent wall

Statistical Modeling of Fire Occurrence Using Data from the Tōhoku, Japan Earthquake and Tsunami