Stochastic modeling of firebrand shower scenarios

Tohidi, Ali; Kaye, Nigel B.

doi:10.1016/j.firesaf.2017.04.039

Cited by 41 publications

(19 citation statements)

References 39 publications

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“…One of the key aspects of fire propagation is the so-called fire-spotting [5]. It occurs 20 when burning embers tear off from the main fuel source and cause new independent ignitions. Hence the hazard increases because the fire spread accelerates bringing harmful consequences.…”

Section: Introductionmentioning

confidence: 99%

“…In this regard, there are recent works that analyse the generation and downwind distribution of firebrands (see [16,17,18]). Other stochastic models of fire-spotting are also proposed in [19,20,21]. 55 Recent trend in operational codes is model based on coupling the wildfire propagation with the atmospheric models, as it is implemented in WRF-Sfire [10].…”

Section: Introductionmentioning

confidence: 99%

“…where = (x) is a generic evolution operator, equation (20) can be rewritten 220 in the following form…”

mentioning

confidence: 99%

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Fire-spotting generated fires. Part I: The role of atmospheric stability

Egorova

Trucchia

Pagnini

2020

Applied Mathematical Modelling

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This is the first part of two papers concerning fire-spotting generated fires. In this part we deal with the impact of macroscale factors, such as the atmospheric stability, and in the second part we deal with mesoscale factors, such as the flame geometry. For this study we adopt an approach where the motion of the front is split into a drifting part and a fluctuating part. The drifting part, that can be provided by choosing an existing operational model, is here based on the levelset method in analogy with WRF-SFIRE model. The fluctuating part, that is the result of a comprehensive statistical description of the physics of the system and includes the random effects, is here physically parametrized to include turbulent hot-air transport and firebrand landing distance. In order to highlight the net effects of the random contributions due to turbulence and firebrand flying, a simplified model without fire-atmosphere coupling is considered. Numerical simulations show that the atmospheric stability is an important factor for wildfire propagation. In particular, unstable conditions boost the number of fire-spotting generated fires at small elapsed times as well as the strength of turbulence leading to rapid merging and the formation of unburned islands surrounded by the fire. Stability conditions have then an effect on the risk and the management associated to fire-spotting generated fires. In fact, with stable conditions (corresponding for example to the night-time) the turbulence is not strong enough to merge the fires and, at large elapsed times, this results into a higher number of independent fires but lower burned area with respect to un- stable conditions (corresponding for example to the day-time) when the push of turbulence leads to faster merging resulting into a lower number of independent fires but higher burned area. Finally, with stable conditions less fire fronts need to be managed at short time, but more fire fronts need to be managed than with unstable conditions that however show a higher risk because of the merging of independent fires.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fire-spotting generated fires. Part I: The role of atmospheric stability

Egorova

Trucchia

Pagnini

2020

Applied Mathematical Modelling

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“…In a recent study, Martin and Hillen (2016) also discuss the underlying physical processes for firebrands in detail and they derive a landing distribution based on these physical processes. Besides these statistical approaches, few numerical models based on Large Eddy Simulation (LES) (Himoto and 25 Tanaka, 2005;Thurston et al, 2017;Tohidi and Kaye, 2017) or Computational Fluid Dynamics (CFD) (Wadhwani et al, 2017), small world networks , cellular automata models (Perryman et al, 2013) also exist in the literature. Bhutia et al (2010) present one such study based on coupled fire/atmosphere LES for predicting the short range fire-spotting.…”

Section: Introductionmentioning

confidence: 99%

Physical parametrisation of fire-spotting for operational fire spread models: response analysis with a model based on the Level Set Method

Kaur

Butenko

Pagnini

2018

Preprint

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Abstract. Fire-spotting is often responsible for a dangerous flare up in the wildfire and causes secondary ignitions isolated from the primary fire zone leading to perilous situations. In this paper a complete physical parametrisation of fire-spotting is presented within a formulation aimed to include random processes into operational fire spread models. This formulation can be implemented into existing operational models as a post-processing scheme at each time step, without calling for any major changes in the original framework. In particular, the efficacy of this formulation has already been shown for wildfire

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“…Schematic of a firebrand shower scenario in the wildland-urban interface (WUI); excerpted fromTohidi and Kaye (2017c) with permission.…”

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confidence: 99%

Firebrand Generation From Thermally-Degraded Cylindrical Wooden Dowels

2019

Self Cite

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During wildland fires, firebrands form once they break off of burning vegetation or structures. Many are then lofted into the fire plume where they are transported long distances ahead of the fire front, igniting new "spot" fires as they land. To date, very few studies have been conducted on the breakage mechanism of thermally-degraded vegetative elements. Knowledge of these mechanisms is needed to feed mathematical models of firebrand transport from traditional wildfires as well as those that spread into communities. First, a framework to understand the behavior of thermally-degraded wooden elements under simultaneous external loading is presented. A set of experiments were designed such that cylindrical wooden dowels of different species are exposed to different heating conditions similar to wildland fires, in order to model the breakage mechanisms of these elements in the absence of wind. The thermally-degraded elements are subjected to the three-point bending test to obtain the mechanical response of the materials after combustion. Assuming Hookean Orthotropic behavior for combusted dowels, dimensional analysis of the results reveals that the ultimate strength of the dowels is affected by the recoverable elastic strain during loading, which is found to occur under two distinct regimes. These results are not only important for better understanding of the breakage mechanisms but also are advantageous for developing a failure theory of thermally degrading wooden elements under simultaneous wind loading conditions.

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Stochastic modeling of firebrand shower scenarios

Cited by 41 publications

References 39 publications

Fire-spotting generated fires. Part I: The role of atmospheric stability

Fire-spotting generated fires. Part I: The role of atmospheric stability

Physical parametrisation of fire-spotting for operational fire spread models: response analysis with a model based on the Level Set Method

Firebrand Generation From Thermally-Degraded Cylindrical Wooden Dowels

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