Modelling the dynamic behaviour of junction fires with a coupled atmosphere–fire model

2017 ◽  
Vol 26 (4) ◽  
pp. 331 ◽  
Author(s):  
C. M. Thomas ◽  
J. J. Sharples ◽  
J. P. Evans
Keyword(s):  
Fire Spread ◽  
Community Safety ◽  
Fire Behaviour ◽  
Ambient Conditions ◽  
Fire Model ◽  
Fire Propagation ◽  
Dynamic Propagation ◽  
Rate Of Spread ◽  
Steady Rate ◽  
In Fire

Dynamic fire behaviour involves rapid changes in fire behaviour without significant changes in ambient conditions, and can compromise firefighter and community safety. Dynamic fire behaviour cannot be captured using spatial implementations of empirical fire-spread models predicated on the assumption of an equilibrium, or quasi-steady, rate of spread. In this study, a coupled atmosphere–fire model is used to model the dynamic propagation of junction fires, i.e. when two firelines merge at an oblique angle. This involves very rapid initial rates of spread, even with no ambient wind. The simulations are in good qualitative agreement with a previous experimental study, and indicate that pyro-convective interaction between the fire and the atmosphere is the key mechanism driving the dynamic fire propagation. An examination of the vertical vorticity in the simulations, and its relationship to the fireline geometry, gives insight into this mechanism. Junction fires have been modelled previously using curvature-dependent rates of spread. In this study, however, although fireline geometry clearly influences rate of spread, no relationship is found between local fireline curvature and the simulated instantaneous local rate of spread. It is possible that such a relationship may be found at larger scales.

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.

scholarly journals Shrubland fire behaviour modelling with microplot data

2000 ◽  
Vol 30 (6) ◽  
pp. 889-899 ◽  
Author(s):  
Paulo M Fernandes ◽  
Wendy R Catchpole ◽  
Francisco C Rego
Keyword(s):  
Wind Speed ◽  
Field Studies ◽  
Fire Spread ◽  
Flame Length ◽  
Fire Behaviour ◽  
Fire Propagation ◽  
Average Value ◽  
Behaviour Modelling ◽  
Rate Of Spread ◽  
Behaviour Models

Fire behaviour modelling has been based primarily on experiments involving the measurement of a certain number of fires, where each variable is represented by an average value per fire. The main objective of this study was to examine if data collected from a microplot sampling design could be used to derive meaningful fire behaviour models. Three burns were conducted in low shrubland of Erica umbellata Loefl., and Chamaespartium tridentatum (L.) P. Gibbs in northeastern Portugal. Wind speed and aerial dead fuel moisture content varied from 5 to 27 km/h and from 14 to 21%, respectively. Rate of spread and flame length ranged from 0.3 to 14.1 m/min and from 0.2 to 3.1 m, respectively. Rate of fire spread could be described effectively in terms of an empirical model with wind speed and fuel height as independent variables. The coefficients that describe the effects of wind speed and fuel height on fire propagation were consistent with published values for similar fuel types. Flame length was strongly related to Byram's fireline intensity. Microplot sampling is not free from methodological problems, which are discussed, but can be effectively used in field studies of fire behaviour.

Modelling the effects of landscape fuel treatments on fire growth and behaviour in a Mediterranean landscape (eastern Spain)

2007 ◽  
Vol 16 (5) ◽  
pp. 619 ◽  
Author(s):  
Beatriz Duguy ◽  
José Antonio Alloza ◽  
Achim Röder ◽  
Ramón Vallejo ◽  
Francisco Pastor
Keyword(s):  
Spatial Distribution ◽  
Fire Spread ◽  
Fire Growth ◽  
Fire Size ◽  
Fire Propagation ◽  
Area Burned ◽  
Rate Of Spread ◽  
Mediterranean Countries ◽  
Fuel Accumulation ◽  
Fire Characteristics

The number of large fires increased in the 1970s in the Valencia region (eastern Spain), as in most northern Mediterranean countries, owing to the fuel accumulation that affected large areas as a consequence of an intensive land abandonment. The Ayora site (Valencia province) was affected by a large fire in July 1979. We parameterised the fire growth model FARSITE for the 1979 fire conditions using remote sensing-derived fuel cartography. We simulated different fuel scenarios to study the interactions between fuel spatial distribution and fire characteristics (area burned, rate of spread and fireline intensity). We then tested the effectiveness of several firebreak networks on fire spread control. Simulations showed that fire propagation and behaviour were greatly influenced by fuel spatial distribution. The fragmentation of large dense shrubland areas through the introduction of wooded patches strongly reduced fire size, generally slowing fire and limiting fireline intensity. Both the introduction of forest corridors connecting woodlands and the promotion of complex shapes for wooded patches decreased the area burned. Firebreak networks were always very effective in reducing fire size and their effect was enhanced in appropriate fuel-altered scenarios. Most firebreak alternatives, however, did not reduce either rate of fire spread or fireline intensity.

Empirical modelling of surface fire behaviour in maritime pine stands

2009 ◽  
Vol 18 (6) ◽  
pp. 698 ◽  
Author(s):  
Paulo M. Fernandes ◽  
Hermínio S. Botelho ◽  
Francisco C. Rego ◽  
Carlos Loureiro
Keyword(s):  
Wind Speed ◽  
Moisture Content ◽  
Fire Spread ◽  
Fire Intensity ◽  
Fuel Moisture ◽  
Fire Behaviour ◽  
Spread Rate ◽  
Surface Fire ◽  
Rate Of Spread ◽  
Fuel Moisture Content

An experimental burning program took place in maritime pine (Pinus pinaster Ait.) stands in Portugal to increase the understanding of surface fire behaviour under mild weather. The spread rate and flame geometry of the forward and backward sections of a line-ignited fire front were measured in 94 plots 10–15 m wide. Measured head fire rate of spread, flame length and Byram’s fire intensity varied respectively in the intervals of 0.3–13.9 m min–1, 0.1–4.2 m and 30–3527 kW m–1. Fire behaviour was modelled through an empirical approach. Rate of forward fire spread was described as a function of surface wind speed, terrain slope, moisture content of fine dead surface fuel, and fuel height, while back fire spread rate was correlated with fuel moisture content and cover of understorey vegetation. Flame dimensions were related to Byram’s fire intensity but relationships with rate of spread and fine dead surface fuel load and moisture are preferred, particularly for the head fire. The equations are expected to be more reliable when wind speed and slope are less than 8 km h–1 and 15°, and when fuel moisture content is higher than 12%. The results offer a quantitative basis for prescribed fire management.

Numerical simulation of pyro-convection caused by intense wildfire in Portugal

2020 ◽  
Author(s):  
Martín Senande Rivera ◽  
Gonzalo Miguez-Macho
Keyword(s):  
Numerical Simulation ◽  
Fuel Consumption ◽  
Decisive Role ◽  
Fire Spread ◽  
Major Influence ◽  
Atmospheric Conditions ◽  
Severe Storms ◽  
Fire Model ◽  
In Fire

<p><span>Weather has a major influence on wildfire behaviour, but heat and vapor fluxes produced by fuel consumption can also alter atmospheric conditions. Severe storms can develop from the intense convection that occurs in large wildfires. During Pedrógao Grande (Portugal) 17 June 2017 wildfire, atmospheric storm conditions played a decisive role in fire spread, with the fire becoming uncontrollable and ultimately causing 66 fatalities.</span></p><p><span>We present here preliminary simulations of the Pedrógrao Grande wildfire with the WRF-FIRE model, identifying the role that the fire could have played in the development of the storm and how the storm could have influenced the spread of the fire.</span>​</p>

Effects of fuel load and moisture content on fire behaviour and heating in masticated litter-dominated fuels

2013 ◽  
Vol 22 (4) ◽  
pp. 440 ◽  
Author(s):  
Jesse K. Kreye ◽  
Leda N. Kobziar ◽  
Wayne C. Zipperer
Keyword(s):  
Moisture Content ◽  
Fuel Load ◽  
Maximum Temperature ◽  
Fire Behaviour ◽  
Fuel Loading ◽  
Pine Flatwoods ◽  
Rate Of Spread ◽  
Soil Temperatures ◽  
Fuel Moisture Content ◽  
In Fire

Mechanical fuels treatments are being used in fire-prone ecosystems where fuel loading poses a hazard, yet little research elucidating subsequent fire behaviour exists, especially in litter-dominated fuelbeds. To address this deficiency, we burned constructed fuelbeds from masticated sites in pine flatwoods forests in northern Florida with palmetto-dominated understoreys and examined the effects of fuel load and fuel moisture content (FMC) on fire behaviour. Flame lengths (49–140 cm) and fireline intensity (183–773 kJ m–1 s–1) increased with loading (10–30 Mg ha–1) and were reduced by 40 and 47% with increasing FMC from 9 to 13%. Rate of spread was not influenced by fuel load, but doubled under drier FMC. Fuel consumption was >90% for all burns. Soil temperatures were influenced by both fuel load and FMC, but never reached lethal temperatures (60°C). However, temperatures of thermocouple probes placed at the fuelbed surface reached 274–503°C. Probe maximum temperature and duration at temperatures ≥60°C (9.5–20.0°C min) both increased with fuel load, but were unaffected by FMC. The fire behaviour observed in these unique litter-dominated fuelbeds provides additional insight into the burning characteristics of masticated fuels in general.

Grassfires

2008 ◽  
Author(s):  
Phil Cheney ◽  
Andrew Sullivan
Keyword(s):  
Diffusion Flames ◽  
Fire Suppression ◽  
Fire Spread ◽  
Personal Safety ◽  
Fire Behaviour ◽  
Ecological Processes ◽  
Rate Of Spread ◽  
Turbulent Diffusion Flames ◽  
Wildfire Suppression ◽  
The Impact

Grassfires: Fuel, Weather and Fire Behaviour presents information from CSIRO on the behaviour and spread of fires in grasslands. This second edition follows over 10 years of research aimed at improving the understanding of the fundamental processes involved in the behaviour of grassfires. The book covers all aspects of fire behaviour and spread in the major types of grasses in Australia. It examines the factors that affect fire behaviour in continuous grassy fuels; fire in spinifex fuels; the effect of weather and topography on fire spread; wildfire suppression strategies; and how to reconstruct grassfire spread after the fact. The three meters designed by CSIRO for the prediction of fire danger and rate of spread of grassfires are explained and their use and limitations discussed. This new edition expands the discussion of historical fires including Aboriginal burning practices, the chemistry of combustion, and the structure of turbulent diffusion flames. It also examines fire safety, including the difficulty of predicting wind strength and direction and the impact of threshold wind speed on safe fire suppression. Myths and fallacies about fire behaviour are explained in relation to their impact on personal safety and survival. Grassfires will be a valuable reference for rural fire brigade members, landholders, fire authorities, researchers and those studying landscape and ecological processes.

Towards improving wildland firefighter situational awareness through daily fire behaviour risk assessments in the US Northern Rockies and Northern Great Basin

2017 ◽  
Vol 26 (7) ◽  
pp. 574 ◽  
Author(s):  
W. Matt Jolly ◽  
Patrick H. Freeborn
Keyword(s):  
Great Basin ◽  
Situational Awareness ◽  
Wildland Fire ◽  
Weather Conditions ◽  
Fire Spread ◽  
Fire Danger ◽  
Fire Behaviour ◽  
Radiative Power ◽  
In Fire ◽  
Fire Danger Indices

Wildland firefighters must assess potential fire behaviour in order to develop appropriate strategies and tactics that will safely meet objectives. Fire danger indices integrate surface weather conditions to quantify potential variations in fire spread rates and intensities and therefore should closely relate to observed fire behaviour. These indices could better inform fire management decisions if they were linked directly to observed fire behaviour. Here, we present a simple framework for relating fire danger indices to observed categorical wildland fire behaviour. Ordinal logistic regressions are used to model the probabilities of five distinct fire behaviour categories that are then combined with a safety-based weight function to calculate a Fire Behaviour Risk rating that can plotted over time and spatially mapped. We demonstrate its development and use across three adjacent US National Forests. Finally, we compare predicted fire behaviour risk ratings with observed variations in satellite-measured fire radiative power and we link these models with spatial fire danger maps to demonstrate the utility of this approach for landscape-scale fire behaviour risk assessment. This approach transforms fire weather conditions into simple and actionable fire behaviour risk metrics that wildland firefighters can use to support decisions that meet required objectives and keep people safe.

scholarly journals Defining fire spread event days for fire-growth modelling

2011 ◽  
Vol 20 (4) ◽  
pp. 497 ◽  
Author(s):  
Justin Podur ◽  
B. Mike Wotton
Keyword(s):  
Forest Fire ◽  
Growth Models ◽  
Fire Spread ◽  
Fire Growth ◽  
Fire Behaviour ◽  
Area Burned ◽  
Rate Of Spread ◽  
Definition Of ◽  
Intensity Spread

Forest fire managers have long understood that most of a fire’s growth typically occurs on a small number of days when burning conditions are conducive for spread. Fires either grow very slowly at low intensity or burn considerable area in a ‘run’. A simple classification of days into ‘spread events’ and ‘non-spread events’ can greatly improve estimates of area burned. Studies with fire-growth models suggest that the Canadian Forest Fire Behaviour Prediction System (FBP System) seems to predict growth well during high-intensity ‘spread events’ but tends to overpredict rate of spread for non-spread events. In this study, we provide an objective weather-based definition of ‘spread events’, making it possible to assess the probability of having a spread event on any particular day. We demonstrate the benefit of incorporating this ‘spread event’ day concept into a fire-growth model based on the Canadian FBP System.

Curvature effects in the dynamic propagation of wildfires

2016 ◽  
Vol 25 (12) ◽  
pp. 1238 ◽  
Author(s):  
J. E. Hilton ◽  
C. Miller ◽  
J. J. Sharples ◽  
A. L. Sullivan
Keyword(s):  
Propagation Model ◽  
Computationally Efficient ◽  
Local Curvature ◽  
Fire Propagation ◽  
Curvature Effects ◽  
Dynamic Propagation ◽  
Rate Of Spread ◽  
Complex Interactions ◽  
Curvature Parameter ◽  
Curvature Dependence

The behaviour and spread of a wildfire are driven by a range of processes including convection, radiation and the transport of burning material. The combination of these processes and their interactions with environmental conditions govern the evolution of a fire’s perimeter, which can include dynamic variation in the shape and the rate of spread of the fire. It is difficult to fully parametrise the complex interactions between these processes in order to predict a fire’s behaviour. We investigate whether the local curvature of a fire perimeter, defined as the interface between burnt and unburnt regions, can be used to model the dynamic evolution of a wildfire’s progression. We find that incorporation of curvature dependence in an empirical fire propagation model provides closer agreement with the observed evolution of field-based experimental fires than without curvature dependence. The local curvature parameter may represent compounded radiation and convective effects near the flame zone of a fire. Our findings provide a means to incorporate these effects in a computationally efficient way and may lead to improved prediction capability for empirical models of rate of spread and other fire behaviour characteristics.

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