Fire Propagation in Vertical Stick Arrays - the Effects of Wind

1995 ◽  
Vol 5 (1) ◽  
pp. 43 ◽  
Author(s):  
T Beer
Keyword(s):  
Fuel Element ◽  
Fire Spread ◽  
Geometrical Model ◽  
Flame Height ◽  
Significant Finding ◽  
Wind Speeds ◽  
Rate Of Spread ◽  
Temperature Isotherm ◽  
Simple Geometrical Model ◽  
Fuel Elements

A simple geometrical model of fire spread through arrays of vertically mounted fuel elements performs well in the absence of wind. The theory assumes that an adjacent fuel element ignites when the flame from the previous fuel element moves downward sufficiently that its temperature isotherm corresponding to the temperature of ignition intersects the top of the adjacent fuel element. This simple geometrical model is extended to incorporate the effects of wind, and its predictions are compared to wind tunnel observations of burning arrays. The model performs well at low wind speeds, but underestimates the wind speed at which the flame makes contact with adjacent fuel elements. The reason for this underestimate is likely to arise because of a weakness in one or more of the assumptions concerning, (1) the laminar nature of the flame, (2) the constancy of the flame height as the wind increases, or (3) the existence of a constant ignition temperature. The most significant finding is that this simple conceptual theory indicates that the rate of spread of a fire front as a result of wind is unlikely to be a simple function such as a power-law or an exponential, but is likely to be the solution to a set of differential equations that can be approximated by such simple functions over a portion of their range.

Got to burn to learn: the effect of fuel load on grassland fire behaviour and its management implications

2018 ◽  
Vol 27 (11) ◽  
pp. 727 ◽  
Author(s):  
Miguel G. Cruz ◽  
Andrew L. Sullivan ◽  
James S. Gould ◽  
Richard J. Hurley ◽  
Matt P. Plucinski
Keyword(s):  
Fire Spread ◽  
Flame Height ◽  
Fuel Load ◽  
Limiting Factor ◽  
Fire Behaviour ◽  
Load Effect ◽  
Fire Propagation ◽  
Rate Of Spread ◽  
Eastern Australia ◽  
Modelling Assumptions

The effect of grass fuel load on fire behaviour and fire danger has been a contentious issue for some time in Australia. Existing operational models have placed different emphases on the effect of fuel load on model outputs, which has created uncertainty in the operational assessment of fire potential and has led to end-user and public distrust of model outcomes. A field-based experimental burning program was conducted to quantify the effect of fuel load on headfire rate of spread and other fire behaviour characteristics in grasslands. A total of 58 experimental fires conducted at six sites across eastern Australia were analysed. We found an inverse relationship between fuel load and the rate of spread in grasslands, which is contrary to current, untested, modelling assumptions. This result is valid for grasslands where fuel load is not a limiting factor for fire propagation. We discuss the reasons for this effect and model it to produce a fuel load effect function that can be applied to operational grassfire spread models used in Australia. We also analyse the effect of fuel load on flame characteristics and develop a model for flame height as a function of rate of fire spread and fuel load.

Exploring fire response to high wind speeds: fire rate of spread, energy release and flame residence time from fires burned in pine needle beds under winds up to 27 ms−1

2020 ◽  
Vol 29 (1) ◽  
pp. 81
Author(s):  
Bret Butler ◽  
Steve Quarles ◽  
Christine Standohar-Alfano ◽  
Murray Morrison ◽  
Daniel Jimenez ◽  
...  
Keyword(s):  
Wind Speed ◽  
Energy Release ◽  
Residence Time ◽  
Wildland Fire ◽  
Ground Level ◽  
Fire Spread ◽  
Convective Heating ◽  
Atmospheric Conditions ◽  
Wind Speeds ◽  
Rate Of Spread

The relationship between wildland fire spread rate and wind has been a topic of study for over a century, but few laboratory studies report measurements in controlled winds exceeding 5ms−1. In this study, measurements of fire rate of spread, flame residence time and energy release are reported for fires burning under controlled atmospheric conditions in shallow beds of pine needles subject to winds ranging from 0 to 27ms−1 (measured 5m above ground level). The data suggested that under constant flow conditions when winds are less than 10ms−1, fire rate of spread increases linearly at a rate of ~3% of the wind speed, which generally agrees with other laboratory-based models. When wind speed exceeds 10ms−1, the fire rate of spread response to wind remains linear but with a much stronger dependence, spreading at a rate of ~13% of the wind speed. Radiative and convective heating correlated directly to wind speed, with radiant heating increasing approximately three-fold as much as convective heating over the range of winds explored. The data suggested that residence time is inversely related to wind speed and appeared to approach a lower limit of ~20s as wind exceeded 15ms−1. Average flame residence time over the range of wind speeds was nominally 26s.

Coupled slope and wind effects on fire spread with influences of fire size: a numerical study using FIRETEC

2012 ◽  
Vol 21 (7) ◽  
pp. 828 ◽  
Author(s):  
F. Pimont ◽  
J.-L. Dupuy ◽  
R. R. Linn
Keyword(s):  
Blow Up ◽  
Numerical Study ◽  
Fire Spread ◽  
Combined Effects ◽  
Fire Behaviour ◽  
Factors Affecting ◽  
Wind Speeds ◽  
Topographic Slope ◽  
Rate Of Spread ◽  
Operational Models

Wind and slope are commonly accepted to be major environmental factors affecting the manner in which wildfires propagate. Fire-line width has been observed as having a significant effect on fire behaviour in some experimental fires. Most wildfire behaviour models and fire behaviour prediction systems take wind and slope effects into account when determining the rate of spread, but do not take into account the influence of fire width on the coupled effects of slope and wind. In the present study, the effect of topographic slope on rate of spread under weak (1 m s–1), moderate (5 m s–1) and strong (12 m s–1) wind speeds is investigated for two different initial fire widths (20 and 50 m) in a typical Mediterranean garrigue, using the coupled atmosphere–fire HIGRAD-FIRETEC model. The results show non-trivial combined effects and suggest a strong effect of fire width under low-wind conditions, especially for steep slopes. Simulated spread rates were compared with predictions of existing models of operational systems and a reasonable agreement was found. Additional exploratory simulations of fire behaviour in small canyons are provided. These simulations show how combined effects of wind, slope and fire-front size can induce different fire behaviours that operational models could fail to predict and provide insight that could be valuable for analysis of blow-up fires. These preliminary results also suggest that 3D physically based models could be used in the future to investigate how operational models can include non-local effects of fire propagation.

Development and validation of a model for predicting fire behaviour in spinifex grasslands of arid Australia

2018 ◽  
Vol 27 (4) ◽  
pp. 271 ◽  
Author(s):  
Neil Burrows ◽  
Malcolm Gill ◽  
Jason Sharples
Keyword(s):  
Prescribed Burning ◽  
Weather Conditions ◽  
Fire Spread ◽  
Flame Height ◽  
Mitigation Measures ◽  
Fire Behaviour ◽  
Rate Of Spread ◽  
Wide Range ◽  
Wildfire Suppression ◽  
Fuel Moisture Content

Large wildfires are common in spinifex grasslands of arid Australia. Threat mitigation measures including fire preparedness, prescribed burning and wildfire suppression are greatly enhanced by the ability to predict fire behaviour. The new spinifex fire behaviour model presented here was developed and validated from 186 experimental fires across a wide range of fuel and weather conditions. Because spinifex fuels are discontinuous, modelling is a two-step process; once ignition is achieved, the first step is to determine the likelihood of fire spread, which is dependent on conditions of wind speed, fuel cover and fuel moisture content. If spread thresholds are met, the second step is to predict rate of spread and flame height using the same three independent variables. Thirty-six of the 186 experimental fires not used in modelling were used to validate the model, which proved to be reasonably accurate and an improvement on the previous model.

Field Guide: Fire in Dry Eucalypt Forest

2008 ◽  
Author(s):  
JS Gould ◽  
WL McCaw ◽  
NP Cheney ◽  
PF Ellis ◽  
S Matthews
Keyword(s):  
Fire Spread ◽  
Flame Height ◽  
Fire Behaviour ◽  
Effective Response ◽  
Understorey Vegetation ◽  
Near Surface ◽  
Field Guide ◽  
Eucalypt Forest ◽  
Rate Of Spread ◽  
Eucalypt Forests

An effective response to bushfires relies on accurate predictions of fire behaviour, particularly the rate of spread, intensity and ‘spotting’. This field guide has been developed to provide a systematic method for assessing fuel hazard and predicting potential fire behaviour in dry eucalypt forest. It will assist in making vital decisions that ensure the protection of fire crews and the community. This guide integrates Project Vesta research findings with the Victorian Overall Fuel Hazard Guide and is applicable to dry eucalypt forests throughout southern Australia. Fuel assessment is based on the hazard scoring system employed during Project Vesta which investigated the effects of fuel age and understorey vegetation structure on fire behaviour in these forests. Information provided in this guide can be used to: Define and identify different fuel layers and components of fuel structure and hazard; Determine the hazard score of surface and near-surface fuel layers and the height of the near-surface fuel for fire spread prediction; Determine elevated fuel height for flame height prediction; and determine surface fuel hazard score and bark hazard score for spotting distance prediction. The Field Guide provides tables to predict the potential rate of spread of a bushfire burning in dry eucalypt forest under summer conditions, and can also be used to predict flame height and maximum spotting distance. The guide also allows users to determine the moisture content of fine dead fuels throughout the day, and to account for the effect of slope on the rate of spread of a fire.

scholarly journals COMPORTAMENTO DO FOGO, EM CONDIÇÕES DE LABORATÓRIO, EM COMBUSTÍVEIS PROVENIENTES DE UM POVOAMENTO DE Pinus elliottii L.

FLORESTA ◽  
2004 ◽  
Vol 34 (2) ◽  
Author(s):  
Luciana Valle De Loro ◽  
Nelson Akira Hiramatsu
Keyword(s):  
Laboratory Test ◽  
Fire Behavior ◽  
Pinus Elliottii ◽  
Fire Spread ◽  
Flame Length ◽  
Flame Height ◽  
Fire Intensity ◽  
Forest Fuels ◽  
Rate Of Spread ◽  
Fire Laboratory

De um povoamento de Pinus elliottii localizado na Fazenda Canguiri-UFPR, foram coletadas seis amostras de material combustível superficial. Este material foi separado em classes, pesado e levado para o laboratório. Efetuou-se a queima da classe acículas num leito de areia no laboratorio, em seis queimas, sendo cada queima com acículas proveniente de cada uma das amostras coletadas. Foram medidas a altura, o comprimento e a velocidade de propagação do fogo. Aplicou-se para cada queima cerca de 746 g de acículas, equivalente a 0,678 Kg/m2, com uma espessura média de 3 cm. Foram obtidos como dados médios: velocidade de propagação de 0,00423 m/s, comprimento da chama de 35,22 cm e altura de 38,79 cm, resultando numa intensidade do fogo igual a 57,07 kW/m. O resíduo médio ficou na ordem de 40,3 %. FIRE BEHAVIOR, IN LABORATORY CONDITIONS, OF FOREST FUELS FROM A Pinus elliottii L. STAND Abstract Pinus elliottii needles from a stand located at Fazenda Canguiri-UFPR were collected to run a laboratory test on fire behavior. The fuel from six samples was separated in classes, weight, and taken to the Federal University of Paraná Forest Fire Laboratory. The pine needles were burned in a sand bed. About 746.0g of each one of the six samples, equivalent to 0.678kg.m-2 and 3cm depth, were used in each fire run. Flame height and length, and rate of spread were measured. The average values obtained were: fire spread, 0,00423 m.s-1, flame length, 35,22cm, and flame height, 38,79cm. Fire intensity was of 57,07 kW.m-1 and residual fuel content about 40,3%.

Fire Growth in Grassland Fuels

1995 ◽  
Vol 5 (4) ◽  
pp. 237 ◽  
Author(s):  
NP Cheney ◽  
JS Gould
Keyword(s):  
Wind Speed ◽  
Fire Spread ◽  
Small Scale ◽  
Fire Growth ◽  
Spread Rate ◽  
Wind Speeds ◽  
Rate Of Spread ◽  
Steady Rate ◽  
Scale Field ◽  
Wildfire Spread

The development of grass fires originating from both point and line ignitions and burning in both open grasslands and woodlands with a grassy understorey was studied using 487 periods of fire spread and associated fuel, weather and fire-shape observations. The largest fires travelled more than 1000 m from the origin and the fastest 2-minute spread rate was over 2 m s-1. Given continuous fuel of uniform moisture content, the rate of forward spread was related to both the wind speed and the width of the head fire measured normal to the direction of fire travel. The head fire width required to achieve the potential quasi-steady rate of forward spread for the prevailing conditions increased with increasing wind speeds. These findings have important implications for relating small-scale field or laboratory measurements of fire spread to predictions of wildfire spread. The time taken to reach the potential quasi-steady rate of spread at any wind speed was highly variable. This time was strongly influenced by the frequency of changes in wind direction and the rate of development of a wide head fire.

Fine-Scale Fire Spread in Pine Straw

Fire ◽  
2021 ◽  
Vol 4 (4) ◽  
pp. 69
Author(s):  
Daryn Sagel ◽  
Kevin Speer ◽  
Scott Pokswinski ◽  
Bryan Quaife
Keyword(s):  
Fire Spread ◽  
Small Scale ◽  
Natural Setting ◽  
Fine Scale ◽  
Prescribed Burn ◽  
Fire Dynamics ◽  
Rate Of Spread ◽  
Scale Models ◽  
Fire Front ◽  
Visible Images

Most wildland and prescribed fire spread occurs through ground fuels, and the rate of spread (RoS) in such environments is often summarized with empirical models that assume uniform environmental conditions and produce a unique RoS. On the other hand, representing the effects of local, small-scale variations of fuel and wind experienced in the field is challenging and, for landscape-scale models, impractical. Moreover, the level of uncertainty associated with characterizing RoS and flame dynamics in the presence of turbulent flow demonstrates the need for further understanding of fire dynamics at small scales in realistic settings. This work describes adapted computer vision techniques used to form fine-scale measurements of the spatially and temporally varying RoS in a natural setting. These algorithms are applied to infrared and visible images of a small-scale prescribed burn of a quasi-homogeneous pine needle bed under stationary wind conditions. A large number of distinct fire front displacements are then used statistically to analyze the fire spread. We find that the fine-scale forward RoS is characterized by an exponential distribution, suggesting a model for fire spread as a random process at this scale.

Studying the Effect of Fuel Elements Structural Materials Corrosion on their Operating Life

2021 ◽  
Vol 1038 ◽  
pp. 108-115
Author(s):  
Yuliana Hapon ◽  
Maksym Kustov ◽  
Volodumur Kalugin ◽  
Alexander Savchenko
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Fuel Element ◽  
State Level ◽  
External Factors ◽  
Economic Losses ◽  
Operating Life ◽  
Hydrodynamic Mode ◽  
Internal And External Factors ◽  
Fuel Elements

The paper deals with experimental data regarding the effect of internal and external factors on the corrosion decay of Zr1Nb alloy fuel elements. Based on the analysis results, losses of zirconium that transfers to oxide or coolant as per the fuel element wall weight and thickness as well as economic losses from their corrosion decay have been theoretically calculated. To avoid a state-level emergency occurrence, an increase in the fuel element wall thickness up to 660 μm is proposed, which can increase the operating life under the conditions of trouble-free coolant mass transfer hydrodynamic mode.

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