Comprehensive wind tunnel experiments of lofting and downwind transport of non-combusting rod-like model firebrands during firebrand shower scenarios

Tohidi, Ali; Kaye, Nigel B.

doi:10.1016/j.firesaf.2017.04.032

Cited by 34 publications

(8 citation statements)

References 35 publications

(48 reference statements)

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“…The total number of spot fires was correlated with plume behaviour, fuel characteristics (hazard score, age), and wildfire behaviour (rate of spread, intensity, flame height). There have been several international studies focused on determining firebrand landing distributions based on small-scale laboratory experiments and/or mathematical modelling [19][20][21][22][23][24][25][26][27]. These have generally indicated right-skewed distributions of firebrands (e.g., exponential, Rayleigh, lognormal), but normal or bi-modal distributions have also been reported.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Variation in Distance, Number, and Distribution of Spotting in Southeast Australian Wildfires

Storey

Price

Bradstock

et al. 2020

Fire

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Spotting during wildfires can significantly influence the way wildfires spread and reduce the chances of successful containment by fire crews. However, there is little published empirical evidence of the phenomenon. In this study, we have analysed spotting patterns observed from 251 wildfires from a database of over 8000 aerial line scan images capturing active wildfire across mainland southeast Australia between 2002 and 2018. The images were used to measure spot fire numbers, number of “long-distance” spot fires (> 500 m), and maximum spotting distance. We describe three types of spotting distance distributions, compare patterns among different regions of southeast Australia, and associate these with broad measures of rainfall, elevation, and fuel type. We found a relatively high correlation between spotting distance and numbers; however, there were also several cases of wildfires with low spot fire numbers producing very long-distance spot fires. Most long-distance spotting was associated with a “multi-modal” distribution type, where high numbers of spot fires ignite close to the source fire and isolated or small clumps of spot fires ignite at longer distances. The multi-modal distribution suggests that current models of spotting distance, which typically follow an exponential-shaped distribution, could underestimate long-distance spotting. We also found considerable regional variation in spotting phenomena that may be associated with significant variation in rainfall, topographic ruggedness, and fuel descriptors. East Victoria was the most spot-fire-prone of the regions, particularly in terms of long-distance spotting.

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Section: Introductionmentioning

confidence: 99%

Analysis of Variation in Distance, Number, and Distribution of Spotting in Southeast Australian Wildfires

Storey

Price

Bradstock

et al. 2020

Fire

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“…Firebrand processes are also affected by winds (Tarifa et al, 1965;Lee and Hellman 1969;Albini 1983;Ellis 2000;Albini et al, 2012;Koo et al, 2012;Suzuki et al, 2013;Tohidi et al, 2015;Suzuki and Manzello, 2017a;Tohidi and Kaye, 2017a;Tohidi and Kaye, 2017b;Fernandez-Pello, 2017;Song et al, 2017;Suzuki and Manzello, 2019;Suzuki and Manzello 2020a;Suzuki and Manzello 2021). Wind influences all aspects of firebrand behavior; firebrand generation from fuels (Suzuki et al, 2013;Tohidi et al, 2015;Suzuki and Manzello, 2019;Suzuki and Manzello 2021), transport distance (Tarifa et al, 1965;Lee and Hellman 1969;Albini 1983;Ellis 2000;Albini et al, 2012;Koo et al, 2012;Tohidi and Kaye, 2017a;Tohidi and Kaye, 2017b;Song et al, 2017), firebrand deposition patterns (Suzuki and Manzello, 2017a), and ignition behavior induced by firebrands (Ganteaume 2009;Manzello, 2014;Suzuki et al, 2015;Suzuki and Manzello, 2017b;Manzello et al, 2017;Wang et al, 2017;Suzuki and Manzello, 2020b). Out of four firebrand behaviors, the firebrand deposition is the least studied to the authors' knowledge.…”

Section: Introductionmentioning

confidence: 99%

Investigating the Effect of Structure to Structure Separation Distance on Firebrand Accumulation

Suzuki

Manzello

2021

Front. Mech. Eng.

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Wind plays an important role in the built environment. Large outdoor fires in the built environment are no exception. Under strong wind, firebrands fly far, which leads to quick fire spread. In this study, the effect of structure to structure separation distance on firebrand accumulation was investigated by using a custom designed firebrand generator installed in a real scale wind tunnel. Firebrands accumulated at 4 and 6 m s−1, but no firebrand accumulation zone was observed at 8 and 10 m s−1, regardless of separation distance (SD). Experimental results were compared with a simple CFD flow simulation (no firebrands included). The size of firebrand accumulation zone as well as distance from the structure front was compared with SD in the cases of 4 and 6 m s−1 wind speeds. It was found that firebrands behave differently from SD = 1 to 2 m, to that of SD = 2 to 3 m. The results of this study are the first to explore these important interactions between firebrands and structure separation distances. The results of this work will help develop and design sustainable communities that may better resist the destruction of increasing large outdoor fire outbreaks worldwide, as well as help develop the next generation of CFD models needed to grasp the important large outdoor fire problem and associated firebrand processes.

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“…The firebrands released in the wind-tunnel at 9 m/s experienced a mass loss of 20-40% when compared to firebrands released in no wind condition. Tohidi and Kaye (2017b), Tohidi and Kaye (2017a) experimentally and computationally studied the lofting of firebrands in a wind tunnel where in addition to wind, a convective plume was included. They observed that for higher wind speeds, the change in the initial vertical velocity of the convective column did not affect the mean or standard deviation of the heights where the firebrands lofted or the distances they traveled to land.…”

Section: Introductionmentioning

confidence: 99%

Deposition Characteristics of Firebrands on and Around Rectangular Cubic Structures

Mankame

Shotorban

2021

Front. Mech. Eng.

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The focus of the present work is on the deposition of firebrands in a flow over a rectangular cubic block representative of a structure in wildland-urban interface (WUI). The study was carried out by physics based modeling where the wind flow turbulence was dealt with by large eddy simulation (LES) and firebrands were treated by Lagrangian tracking. The Lagrangian equations coupled with the flow solver, accounted for both translational and rotational motions as well as thermochemical degradation of firebrands, assumed to be cylindrical. The dimensions of the structure were varied from 3 to 9 m in the simulations for a parametric study. The simulations were carried out by tracking many firebrands randomly released with a uniform distribution from a horizontal plane 35 m above the ground into the computational domain. The coordinates of the deposited firebrands were used to calculate their normalized number density (number of landed firebrands per unit surface area) to quantify their deposition pattern. On the leewardside of the block, an area, referred to as the safe zone, was identified right behind the structure where firebrands never deposit. The size of the safe zone in the direction perpendicular to the wind was nearly identical to the width of the structure. The length of the safe zone in the wind direction was proportional to the height of the structure. The leeward face of the blocks was never hit by a firebrand. The windward face was hit by many more firebrands than the lateral faces but much less than the top face. The distribution of the number density of the deposited firebrands on the top face was found to be correlated with the flow separation and reattachment on this face.

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Comprehensive wind tunnel experiments of lofting and downwind transport of non-combusting rod-like model firebrands during firebrand shower scenarios

Cited by 34 publications

References 35 publications

Analysis of Variation in Distance, Number, and Distribution of Spotting in Southeast Australian Wildfires

Analysis of Variation in Distance, Number, and Distribution of Spotting in Southeast Australian Wildfires

Investigating the Effect of Structure to Structure Separation Distance on Firebrand Accumulation

Deposition Characteristics of Firebrands on and Around Rectangular Cubic Structures

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