Dynamic modelling of upslope fire growth

1999 ◽  
Vol 9 (4) ◽  
pp. 285 ◽  
Author(s):  
P.A. Santoni ◽  
J.H. Balbi ◽  
J.L. Dupuy
Keyword(s):  
Numerical Study ◽  
Dynamic Modelling ◽  
Fire Spread ◽  
Nous Obtenons ◽  
Rate Of Spread ◽  
Nous Permet ◽  
Modèle Bidimensionnel ◽  
Fire Front ◽  
Fire Spreading ◽  
Pin Maritime

A two-dimensional non-stationary model of fire spread including slope effects is proposed. The numerical study of this model allows us to predict the rate of spread, the fire front perimeter and the temperature distribution for a fire spreading across a fuel bed under slope conditions. The numerical results are compared with success to experimental data generated from two laboratory point-ignition fire experiments which were conducted on dehydrated Pinus pinaster litter with slopes of 20 and 30°. Résumé Nous proposons un modèle bidimensionnel évolutif de propagation de feu prenant en compte les effets de la pente. L’étude numérique du modèle présenté ici nous permet de prédire la vitesse de propagation, le perimètre du front de feu ainsi que la distribution de température pour un feu se propageant dans une litière en présence d’une pente. Les résultats numériques que nous obtenons sont comparés avec succés aux données expérimentales issues de deux expériences qui furent réaliseés dans une litière de pin maritime avec un allumage ponctuel pour des pentes de 20 et 30 degrés.

Dynamic modelling of fire spread across a fuel bed

1999 ◽  
Vol 9 (4) ◽  
pp. 275 ◽  
Author(s):  
J.H. Balbi ◽  
P.A. Santoni ◽  
J.L. Dupuy
Keyword(s):  
Numerical Study ◽  
Mathematical Problem ◽  
Dynamic Modelling ◽  
Reaction Diffusion ◽  
Fire Spread ◽  
Dynamic Features ◽  
Rate Of Spread ◽  
Reaction Diffusion Model ◽  
Initial Stage ◽  
Fire Front

The analysis of laboratory fire experiments led to the development of a reaction-diffusion model for the spread of fire across a fuel bed in windless and slopeless conditions. A method for the determination of coefficients in this model based on the dynamic features of a spreading fire is given. The numerical study of the mathematical problem proposed allows us to predict the rate of spread, the fire front perimeter and the temperature distribution for line-ignition and point-ignition fires. These results are compared with success to experimental data. Furthermore, the model allows us to estimate the acceleration of spread for a point-ignition fire in its initial stage and in the steady-state phase. Résumé Une analyse menée sur des expériences de laboratoires nous a permis de proposer un modèle de réaction-diffussion pour la propagation du feu sans vent et sans pente au travers d’une litière. Une méthode d’identification des coefficients du modèle, à partir des caractéristiques dynamiques de la propagation du feu, est donnée. L’étude numérique du problème mathématique nous permet de prédire la vitesse de propagation, le périmètre du front de feu et la température dans le domaine d’étude pour des allumages en ligne et pour des allumages ponctuels. Ces résultats sont comparés avec succés à des données expérimentales. De plus, nous sommes aussi en mesure de décrire l’accélération du front de feu dans les premiers instants suivant un allumage ponctuel.

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.

Laboratory fire spread analysis using visual and infrared images

2006 ◽  
Vol 15 (2) ◽  
pp. 179 ◽  
Author(s):  
J. Ramiro Martínez-de Dios ◽  
Jorge C. André ◽  
João C. Gonçalves ◽  
Begoña Ch. Arrue ◽  
Aníbal Ollero ◽  
...  
Keyword(s):  
Graphical Model ◽  
Fire Spread ◽  
Rate Of Spread ◽  
Virtual View ◽  
Fire Front ◽  
Computer Based ◽  
Front Shape ◽  
Processing Techniques ◽  
Spread Analysis ◽  
Base Width

This paper presents an experimental method using computer-based image processing techniques of visual and infrared movies of a propagating fire front, taken from one or more cameras, to supply the time evolutions of the fire front shape and position, flame inclination angle, height, and base width. As secondary outputs, it also provides the fire front rate of spread and a 3D graphical model of the fire front that can be rendered from any virtual view. The method is automatic and non-intrusive, has space–time resolution close to continuum and can be run in real-time or deferred modes. It is demonstrated in simple laboratory experiments in beds of pine needles set upon an inclinable burn table, with point and linear ignitions, but can be extended to open field situations.

Physical modelling of forest fire spreading through heterogeneous fuel beds

2011 ◽  
Vol 20 (5) ◽  
pp. 625 ◽  
Author(s):  
Albert Simeoni ◽  
Pierre Salinesi ◽  
Frédéric Morandini
Keyword(s):  
Field Experiments ◽  
Heterogeneous Medium ◽  
Reaction Diffusion ◽  
Physical Modelling ◽  
Fire Spread ◽  
Physical Models ◽  
Fire Intensity ◽  
Fire Behaviour ◽  
Fire Front ◽  
Fire Spreading

Vegetation cover is a heterogeneous medium composed of different kinds of fuels and non-combustible parts. Some properties of real fires arise from this heterogeneity. Creating heterogeneous fuel areas may be useful both in land management and in firefighting by reducing fire intensity and fire rate of spread. The spreading of a fire through a heterogeneous medium was studied with a two-dimensional reaction–diffusion physical model of fire spread. Randomly distributed combustible and non-combustible square elements constituted the heterogeneous fuel. Two main characteristics of the fire were directly computed by the model: the size of the zone influenced by the heat transferred from the fire front and the ignition condition of vegetation. The model was able to provide rate of fire spread, temperature distribution and energy transfers. The influence on the fire properties of the ratio between the amount of combustible elements and the total amount of elements was studied. The results provided the same critical fire behaviour as described in both percolation theory and laboratory experiments but the results were quantitatively different because the neighbourhood computed by the model varied in time and space with the geometry of the fire front. The simulations also qualitatively reproduced fire behaviour for heterogeneous fuel layers as observed in field experiments. This study shows that physical models can be used to study fire spreading through heterogeneous fuels, and some potential applications are proposed about the use of heterogeneity as a complementary tool for fuel management and firefighting.

scholarly journals Georeferencing Oblique Aerial Wildfire Photographs: An Untapped Source of Fire Behaviour Data

Fire ◽  
2021 ◽  
Vol 4 (4) ◽  
pp. 81
Author(s):  
Henry Hart ◽  
Daniel D. B. Perrakis ◽  
Stephen W. Taylor ◽  
Christopher Bone ◽  
Claudio Bozzini
Keyword(s):  
Fire Behavior ◽  
Fire Spread ◽  
Behavior Prediction ◽  
Empirical Relationships ◽  
Rate Of Spread ◽  
Front Position ◽  
Fire Front ◽  
Initial Work ◽  
The Mean ◽  
Behaviour Data

In this study, we investigate a novel application of the photogrammetric monoplotting technique for assessing wildfires. We demonstrate the use of the software program WSL Monoplotting Tool (MPT) to georeference operational oblique aerial wildfire photographs taken during airtanker response in the early stages of fire growth. We located the position of the fire front in georeferenced pairs of photos from five fires taken 31–118 min apart, and calculated the head fire spread distance and head fire rate of spread (HROS). Our example photos were taken 0.7 to 4.7 km from fire fronts, with camera angles of incidence from −19 to −50° to image centre. Using high quality images with detailed landscape features, it is possible to identify fire front positions with high precision; in our example data, the mean 3D error was 0.533 m and the maximum 3D error for individual fire runs was less than 3 m. This resulted in a maximum HROS error due to monoplotting of only ~0.5%. We then compared HROS estimates with predictions from the Canadian Fire Behavior Prediction System, with differences mainly attributed to model error or uncertainty in weather and fuel inputs. This method can be used to obtain observations to validate fire spread models or create new empirical relationships where databases of such wildfire photos exist. Our initial work suggests that monophotogrammetry can provide reproducible estimates of fire front position, spread distance and rate of spread with high accuracy, and could potentially be used to characterize other fire features such as flame and smoke plume dimensions and spotting.

Analysis of the physical processes associated with junction fires at laboratory and field scales

2018 ◽  
Vol 27 (1) ◽  
pp. 52 ◽  
Author(s):  
J. R. Raposo ◽  
D. X. Viegas ◽  
X. Xie ◽  
M. Almeida ◽  
A. R. Figueiredo ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Large Scale ◽  
Symmetry Plane ◽  
Initial Boundary ◽  
Fire Spread ◽  
Intersection Point ◽  
Deceleration Phase ◽  
Rate Of Spread ◽  
Wide Range ◽  
Fire Front

Junction fires, which involve the merging of two linear fire fronts intersecting at a small angle, are associated with very intense fire behaviour. The dynamic displacement of the intersection point of the two lines and the flow along the symmetry plane of the fire are analysed for symmetric boundary conditions. It is observed that the velocity of displacement of this point increases very rapidly owing to strong convective effects created by the fire that are similar to those of an eruptive fire. The change of fire geometry and of its associated flow gradually blocks the rate of spread increase and creates a strong deceleration of the fire, which ends up behaving like a linear fire front. Results from laboratory and field-scale experiments, using various fuel beds and slope angles and from a large-scale fire show that the processes are similar at a wide range of scales with little dependence on the initial boundary conditions. Numerical simulation of the heat flux from two flame surfaces to an element of the fuel bed show that radiation can be considered as the main mechanism of fire spread only during the deceleration phase of the fire.

Testing the Effect of Fuel Consumption on Fire Spread Rate

1995 ◽  
Vol 5 (3) ◽  
pp. 143 ◽  
Author(s):  
RS McAlpine
Keyword(s):  
Fuel Consumption ◽  
Fire Behavior ◽  
Fire Spread ◽  
Data Sets ◽  
Behavior Prediction ◽  
Spread Rate ◽  
Data Set ◽  
Weak Relationship ◽  
Rate Of Spread ◽  
Fire Front

It has been theorized that the amount of fuel involved in a fire front can influence the rate of spread of the fire. Three data sets are examined in an attempt to prove this relationship. The first, a Canadian Forest Service database of over 400 experimental, wild, and prescribed fires showed a weak relationship in some fuel complexes. The second, a series of field experimental fires conducted to isolate the relationship, showed a small effect. The final data set, from a series of 47 small plots (3m x 3m) burned with a variety of fuel loadings, also show a weak relationship. While a relationship was shown to exist, it is debatable whether it should be included in a fire behavior prediction system. Inherent errors associated with predicting fuel consumption can be compounded, causing additional, more critical, errors with the derived fire spread rate.

scholarly journals Resolving vorticity-driven lateral fire spread using the WRF-Fire coupled atmosphere–fire numerical model

2014 ◽  
Vol 14 (9) ◽  
pp. 2359-2371 ◽  
Author(s):  
C. C. Simpson ◽  
J. J. Sharples ◽  
J. P. Evans
Keyword(s):  
High Spatial Resolution ◽  
Wildland Fire ◽  
Fire Spread ◽  
Weather Research And Forecasting ◽  
Grid Spacing ◽  
Fire Behaviour ◽  
Model Framework ◽  
Rate Of Spread ◽  
Fire Front ◽  
Vertical Grid

Abstract. Vorticity-driven lateral fire spread (VLS) is a form of dynamic fire behaviour, during which a wildland fire spreads rapidly across a steep leeward slope in a direction approximately transverse to the background winds. VLS is often accompanied by a downwind extension of the active flaming region and intense pyro-convection. In this study, the WRF-Fire (WRF stands for Weather Research and Forecasting) coupled atmosphere–fire model is used to examine the sensitivity of resolving VLS to both the horizontal and vertical grid spacing, and the fire-to-atmosphere coupling from within the model framework. The atmospheric horizontal and vertical grid spacing are varied between 25 and 90 m, and the fire-to-atmosphere coupling is either enabled or disabled. At high spatial resolutions, the inclusion of fire-to-atmosphere coupling increases the upslope and lateral rate of spread by factors of up to 2.7 and 9.5, respectively. This increase in the upslope and lateral rate of spread diminishes at coarser spatial resolutions, and VLS is not modelled for a horizontal and vertical grid spacing of 90 m. The lateral fire spread is driven by fire whirls formed due to an interaction between the background winds and the vertical circulation generated at the flank of the fire front as part of the pyro-convective updraft. The laterally advancing fire fronts become the dominant contributors to the extreme pyro-convection. The results presented in this study demonstrate that both high spatial resolution and two-way atmosphere–fire coupling are required to model VLS with WRF-Fire.

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.

Fire spread in canyons

2004 ◽  
Vol 13 (3) ◽  
pp. 253 ◽  
Author(s):  
Domingos Xavier Viegas ◽  
Luis Paulo Pita
Keyword(s):  
Forest Fires ◽  
Numerical Study ◽  
Fire Spread ◽  
Laboratory Scale ◽  
Experimental Program ◽  
Small Scale ◽  
Geometrical Parameters ◽  
Fire Behaviour ◽  
Fatal Accidents ◽  
Rate Of Spread

Canyons or ridges are associated with a large number of fatal accidents produced during forest fires all over the world. A contribution to the understanding of fire behaviour in these terrain conditions is given in this paper. The basic geometrical parameters of the canyon configuration are described. An analytical model assuming elliptical growth of point ignition fires and constant values of rate of spread is proposed. A non-dimensional formulation to transfer results from analytical, numerical, laboratory or field simulations to other situations is proposed. An experimental study at laboratory scale on a special test rig is described. A wide set of canyon configurations were covered in the experimental program. In spite of the relatively small scale of the experiments they were able to put in evidence some of the main features found in fires spreading in this type of terrain. They show that in practically all cases the rate of spread of the fire front is non-constant. On the contrary, the fire has a dynamic behaviour and its properties depend not only on the canyon geometry but on the history of fire development as well. The convection induced by the fire is enhanced by terrain curvature and the fire accelerates causing the well-known blow-up that is associated with canyon fires. The rate of spread of the head fire increases continuously even in the absence of wind or any other special feature or change of boundary conditions that are sometimes invoked to justify such fire behaviour. The results of the present study confirm the predictions of a previous numerical study of the flow and fire spread in canyons that showed the important feedback effect of the fire on the atmospheric flow and how this affects fire behaviour in canyons. Results from a field experiment carried out in a canyon-shaped plot covered by tall shrubs were used to validate the laboratory scale experiments. Case studies related to fatal accidents that occurred in canyon-shaped configurations are analysed and recommendations to deal with this problem are made. It is shown that these accidents may occur even in the absence of special fuel or atmospheric conditions as they are intrinsically related to terrain configuration.

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