Measurements of radiant emissive power and temperatures in crown fires

Butler, Bret W.; Cohen, Jonathan; Latham, Don; Schuette, Robert D.; Sopko, Paul; Shannon, Kyle; Jiménez, Daniel M.; Bradshaw, Larry

doi:10.1139/x04-060

Cited by 132 publications

(86 citation statements)

References 11 publications

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“…Our data are a first contribution, referred to the Mediterranean conifers, and show temperature peak values and transient responses fairly similar to those observed in boreal forests (Taylor et al, 2004;Butler et al, 2004b;Butler, 2010). Although the limitations of the thermocouples to reflect the true values of temperature in the flaming area are well known (e.g.…”

Section: Discussionsupporting

confidence: 79%

“…Although the limitations of the thermocouples to reflect the true values of temperature in the flaming area are well known (e.g. Pitts et al, 2002;Shannon & Butler, 2003;Bova & Dickinson, 2008), the errors when fine thermocouples are used can be considered as to relatively be minor for peaks temperatures (Butler et al, 2004b). Still, in our study, temperature records were primary used to determine fire spread in the full-scale experiment and the distance between fire front and crown to initiate a passive crown fire in the small-scale experiment.…”

Section: Discussionmentioning

confidence: 99%

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Assessment of crown fire initiation and spread models in Mediterranean conifer forests by using data from field and laboratory experiments

et al. 2017

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Aim of study: To conduct the first full-scale crown fire experiment carried out in a Mediterranean conifer stand in Spain; to use different data sources to assess crown fire initiation and spread models, and to evaluate the role of convection in crown fire initiation.Area of study: The Sierra Morena mountains (Coordinates ETRS89 30N: X: 284793-285038; Y: 4218650-4218766), southern Spain, and the outdoor facilities of the Lourizán Forest Research Centre, northwestern Spain. Material and methods:The full-scale crown fire experiment was conducted in a young Pinus pinea stand. Field data were compared with data predicted using the most used crown fire spread models. A small-scale experiment was developed with Pinus pinaster trees to evaluate the role of convection in crown fire initiation. Mass loss calorimeter tests were conducted with P. pinea needles to estimate residence time of the flame, which was used to validate the crown fire spread model.Main results: The commonly used crown fire models underestimated the crown fire spread rate observed in the full-scale experiment, but the proposed new integrated approach yielded better fits. Without wind-forced convection, tree crowns did not ignite until flames from an intense surface fire contacted tree foliage. Bench-scale tests based on radiation heat flux therefore offer a limited insight to full-scale phenomena.Research highlights: Existing crown fire behaviour models may underestimate the rate of spread of crown fires in many Mediterranean ecosystems. New bench-scale methods based on flame buoyancy and more crown field experiments allowing detailed measurements of fire behaviour are needed.

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Section: Discussionsupporting

confidence: 79%

Section: Discussionmentioning

confidence: 99%

Assessment of crown fire initiation and spread models in Mediterranean conifer forests by using data from field and laboratory experiments

et al. 2017

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“…Visible flaming edges are at lower temperature of about 600 K [11] than at the combustion zone, which can be up to 1300 • C [5]. This produces temperature gradients between the edges and fire center.…”

Section: Wildfire Flame Modelmentioning

confidence: 99%

“…Mack lake crown fire had a wide range of behavior, and ICFME's Plot 9-crown fire [5] is taken as a case study. Plot 9's fire-intensity was about 90 MWm −1 , RoS and observed flame heights were 1.16 m/s and 20-30 m respectively.…”

Section: Refractive Index-height Variation In the Crown Firementioning

confidence: 99%

Effect of Wildfire-Induced Thermal Bubble on Radio Communication

Mphale¹,

Heron²,

Verma³

2007

PIER

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Abstract-Horizontal roll vortex pairs are dynamical structures that transfer energy and emissions from wildfires into the atmosphere. The vortices form at the edges of an intense line wildfire and emulate two cylinders, which form two curvatures of a biconcave thermal lens. Wildfire plume provides a dielectric material for the dielectric lens, whose permittivity is influenced by the nature, quantity of constituents (e.g., potassium and graphitic carbon) and variation of temperature with height in the plume. The environment created by the plume is radio sub-refractive with an effect of spreading radio wave beams. A numerical experiment was carried out to quantify loss of Ultra High Frequency (UHF) radio signal intensity when high intensity wildfireinduced horizontal roll vortices intercept UHF propagation path. In the numerical experiment, a collimated radio wave beam was caused to propagate along fuel-fire interface of a very high intensity wildfire in which up to two roll vortex pairs are formed. Maximum temperature of the simulated wildfire was 1200 K. Flame potassium content was varied from 0.5-3.0%. At 3.0% potassium content, a vortex pair imposed a maximum radio ray divergence of 2.1 arcmins while two vortex respectively.

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“…Flame temperatures in the combustion zone of a wildfire could be as high as 1330 • C [13]. The fierce temperature could thermally excite the flame species (FPS(g)) and consequently ionise them to produce electrons on selective basis determined by temperature and ionization potential.…”

Section: Flame Ionisationmentioning

confidence: 99%

Microwave attenuation in forest fuel flames

Mphale

Luhanga

Heron

2008

Combustion and Flame

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The flames of forest fuels form a weakly ionized gas. Assuming a Maxwellian velocity distribution of flame particle and collision frequencies much higher than plasma frequencies, the propagation of microwaves through forest fuel flames is predicted to have attenuation and phase shift. A controlled fire burner was constructed where various natural vegetation materials could be used as fuel. The burner was equipped with thermocouples and used as a cavity for microwaves with a laboratory quality network analyzer to measure phase and attenuation. The controlled fires had temperatures in the range of 500-1000 K and microwave attenuation of 1.0-4.5 dB m −1 was observed across the 0.5 m diameter cavity. Attenuations of this magnitude could affect active remote sensing systems signals at microwave frequencies in forest fire environments where flame depths of up to 50 m are possible. In the experiment, temperature was not the only controlling parameter for the ionisation; type of fuel burnt also influenced it. Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) analysis of the composition of the fuel confirmed that a higher content of alkali (with low ionization potential) lead to higher electron densities. Electron densities in the range of 0.32-3.21 × 10 16 m −3 and collision frequencies of 1.1-4.0 × 10 10 s −1 were observed for flames with temperature in the range of 730-1000 K.

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Measurements of radiant emissive power and temperatures in crown fires

Cited by 132 publications

References 11 publications

Assessment of crown fire initiation and spread models in Mediterranean conifer forests by using data from field and laboratory experiments

Assessment of crown fire initiation and spread models in Mediterranean conifer forests by using data from field and laboratory experiments

Effect of Wildfire-Induced Thermal Bubble on Radio Communication

Microwave attenuation in forest fuel flames

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