The likelihood of ignition of dry-eucalypt forest litter by firebrands

2015 ◽  
Vol 24 (2) ◽  
pp. 225 ◽  
Author(s):  
P. F. M. Ellis
Keyword(s):  
Wind Speed ◽  
Moisture Content ◽  
Eucalyptus Globulus ◽  
Forest Litter ◽  
Fuel Moisture ◽  
Ignition Probability ◽  
Moisture Contents ◽  
Eucalypt Forest ◽  
Fuel Moisture Content ◽  
Practical Measure

Ignition probability of litter of dry-eucalypt forest by standard flaming and glowing firebrand samples was tested in a wind tunnel. Standard flaming firebrands were sections of bamboo sate stick 50 mm long, and flamed for ~9 s in still air. Standard glowing samples were sections of shed bark of Eucalyptus globulus 50 mm long, 15 mm wide and ~2 mm in thickness. These were burnt at their terminal velocities and at deposition had a mean mass of 0.2 g and would remain glowing for 2.5 min in wind. Ignition was tested using air speeds of zero, 1 and 2 m s–1, and oven-dried fuel moisture contents between 4 and 21%. For flaming samples, ignition probability was insensitive to variation in fuel and airflow characteristics and was a function of wind (no wind or wind) and fuel moisture content. For glowing samples, ignition probability was a function of fuel moisture content and wind speed. The models confirm the dominating influence of fuel moisture, are consistent with expert observations in the field and provide a practical measure of ignition likelihood by firebrands. It is argued that airflow turbulence and relative humidity are potentially significant for ignition by glowing firebrands.

Modelling fine fuel moisture content and the likelihood of fire spread in blue gum (Eucalyptus globulus) litter

2014 ◽  
pp. 353-359
Author(s):  
Anita Pinto ◽  
Juncal Espinosa-Prieto ◽  
Carlos Rossa ◽  
Stuart Matthews ◽  
Carlos Loureiro ◽  
...  
Keyword(s):  
Moisture Content ◽  
Eucalyptus Globulus ◽  
Fire Spread ◽  
Fuel Moisture ◽  
Fuel Moisture Content ◽  
Blue Gum

Assessing ignition probability and moisture of extinction in a Mediterranean grass fuel

2010 ◽  
Vol 19 (1) ◽  
pp. 29 ◽  
Author(s):  
A. P. Dimitrakopoulos ◽  
I. D. Mitsopoulos ◽  
K. Gatoulas
Keyword(s):  
Moisture Content ◽  
Classification Tree ◽  
Weather Conditions ◽  
Stepwise Logistic Regression ◽  
Fuel Moisture ◽  
Ignition Probability ◽  
Plant Moisture ◽  
Plant Moisture Content ◽  
Fuel Moisture Content

The objective of this study was the assessment of the probability of ignition and moisture of extinction of the annual herbaceous species Slender Oat (Avena barbata Pott. ex Link) in Greece. Multiple ignition tests were conducted in situ with a drip torch during two fire seasons, with simultaneous monitoring of the weather conditions. Stepwise logistic regression was applied to assess the probability of ignition based on plant moisture content and meteorological parameters. Fuel moisture content was determined to be the only statistically significant (P < 0.0001) parameter and, therefore, it was the only variable kept in the analysis. The logistic model correctly predicted fire ignition in 93.6% of the tests and 50% ignition probability was determined at 38.5% oven-dried weight (ODW) plant moisture content. Moisture of extinction (i.e. probability of ignition at 1%) was calculated at 55.5% ODW. Furthermore, classification tree analysis was applied to determine the independent variables that explain the variability in ignition probability. Wind speed was found to have an effect on ignition probability only at relatively high (>30% ODW) fuel moisture contents. Assessment of the ignition potential and moisture of extinction of grass fuels is a prerequisite for reliable fire danger prediction.

Convective heat transfer in fire spread through fine fuel beds

2010 ◽  
Vol 19 (3) ◽  
pp. 284 ◽  
Author(s):  
W. R. Anderson ◽  
E. A. Catchpole ◽  
B. W. Butler
Keyword(s):  
Heat Transfer ◽  
Wind Speed ◽  
Moisture Content ◽  
Flame Front ◽  
Free Stream ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Fuel Moisture ◽  
Fire Front ◽  
Fuel Moisture Content

An extensive set of wind-tunnel fires was burned to investigate convective heat transfer ahead of a steadily progressing fire front moving across a porous fuel bed. The effects of fuel and environmental variables on the gas temperature profile and the ‘surface wind speed’ (gas velocity at the fuel bed surface) are reported. In non-zero winds, the temperature of the air near the fuel bed surface decays exponentially with distance from the fire front. In zero winds, the temperature decreases rapidly within a very short distance of the flame front, then decays slowly thereafter. The maximum air temperature decreases as the free stream wind speed, packing ratio and fuel moisture content increase. The characteristic distance of the exponential decay increases strongly with the free stream wind speed and decreases with the packing ratio and surface area-to-volume ratio of the fuel. The surface wind speed depends strongly on the free stream wind speed, and to a lesser extent on packing ratio, fuel bed depth and fuel moisture content. There are three general regimes for the surface flow: (1) a constant velocity flow of approximately half the free stream flow, far from the flame front; (2) an intermediate zone of minimum flow characterised by low or reversed flow; and (3) a region near the flame front where the velocity rises rapidly almost to the free stream velocity. The boundaries between the three regions move further from the flame front with increasing wind speed, in a way which is only slightly affected by fuel geometry.

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.

scholarly journals Influence of Fuel Moisture Content, Packing Ratio and Wind Velocity on the Ignition Probability of Fuel Beds Composed of Mongolian Oak Leaves via Cigarette Butts

Forests ◽  
2018 ◽  
Vol 9 (9) ◽  
pp. 507 ◽  
Author(s):  
Ping Sun ◽  
Yunlin Zhang ◽  
Long Sun ◽  
Haiqing Hu ◽  
Futao Guo ◽  
...  
Keyword(s):  
Moisture Content ◽  
Prediction Model ◽  
Forest Fires ◽  
Logistic Model ◽  
Fuel Moisture ◽  
Ignition Probability ◽  
Cigarette Butts ◽  
Mongolian Oak ◽  
Fuel Moisture Content ◽  
Oak Leaves

Cigarette butts are an important human firebrand and account for a significant amount of man-made fires. To better address forest fires caused by cigarette butts, the influencing factors governing the ignition probability of cigarette butts can be used to establish a prediction model. This study obtains the influencing factors of the ignition probability of cigarette butts in order to establish a prediction model by constructing fuel beds composed of Mongolian oak leaves with varied fuel moisture content and packing ratios. A total of 2520 ignition experiments were then conducted by dropping cigarette butts on the fuel beds to test the burning probability of the fuels under varied wind speeds. Moisture content, wind speed, and their interaction significantly influenced ignition probability. In the absence of wind, the ignition probability is zero. The maximum moisture content of Mongolian oak leaves that could be ignited by cigarette butts was 15%. A logistic model and self-built model for predicting the ignition probability were established using these results; the mean absolute error values for the two models were 2.71% and 1.13%, respectively, and the prediction error of the self-built model was lower than that of the logistic model. This is important research to mitigate the threat of forest fires due to cigarette butts given the frequent occurrence of these events.

Evaluating models to predict daily fine fuel moisture content in eucalypt forest

2015 ◽  
Vol 335 ◽  
pp. 261-269 ◽  
Author(s):  
A. Slijepcevic ◽  
W.R. Anderson ◽  
S. Matthews ◽  
D.H. Anderson
Keyword(s):  
Moisture Content ◽  
Fuel Moisture ◽  
Eucalypt Forest ◽  
Fuel Moisture Content

scholarly journals ESTIMATING FINE DEAD FUEL MOISTURE CONTENT UNDER EQUATORIAL CLIMATE CONDITIONS

FLORESTA ◽  
2021 ◽  
Vol 51 (3) ◽  
pp. 696
Author(s):  
Benjamin Leonardo Alves White ◽  
Maria Flaviane Almeida Silva
Keyword(s):  
Moisture Content ◽  
Fire Behavior ◽  
Great Influence ◽  
Fuel Moisture ◽  
Statistical Parameters ◽  
Fire Weather Index ◽  
Ignition Probability ◽  
Climate Conditions ◽  
Equatorial Climate ◽  
Fuel Moisture Content

The measurement of the fine dead fuel moisture content (FDFMC) is extremely important for forest fire prevention and suppression activities, as it has a great influence on the ignition probability and fire behavior. The Fine Fuel Moisture Code (FFMC) from the Fire Weather Index (FWI), is one of the most used models to estimate the FDFMC. Nevertheless, studies that assess the efficiency of this model in Brazil or in low latitude regions are rare. The present study aimed to evaluate the efficiency of the FFMC in an equatorial climate area and to develop a new model capable of estimating the FDFMC with greater precision. For this purpose, 861 random samples of fine dead fuel had their moisture content determined through oven drying. The obtained values were compared with those estimated by the FFMC and correlated with meteorological parameters to build a regression model. The results obtained show that the FDFMC was overestimated by the FFMC. The independent variables with the greatest influence on the FDFMC were, in decreasing order of significance: air relative humidity, air temperature, amount of rainfall in the last 24 hours and number of days without rainfall. The developed model presented good statistical parameters (r2 = 0.86; p <0.0001; RMSE = 0.22) and can be used, in areas with similar characteristics of the study area, to estimate the daily fire risk and to determine ideal conditions for prescribed burns.

Flame characteristics, temperature - time curves, and rate of spread in fires propagating in a bed of Pinus pinaster needles

2003 ◽  
Vol 12 (1) ◽  
pp. 67 ◽  
Author(s):  
José M. C. Mendes-Lopes ◽  
João M. P. Ventura ◽  
José M. P. Amaral
Keyword(s):  
Wind Speed ◽  
Moisture Content ◽  
Pinus Pinaster ◽  
Flame Height ◽  
Fuel Moisture ◽  
Propagation Models ◽  
Fire Propagation ◽  
Rate Of Spread ◽  
Fuel Moisture Content ◽  
Flame Angle

An extensive set of experiments was carried out in order to collect data to validate fire propagation models being developed in the context of an European research project. The experiments were performed in a dedicated burning tray (2.0 m × 0.70 m working section), where wind velocity, fuel moisture content and slope were varied to study fire propagation in beds of Pinus pinaster needles. All the runs were videotaped and, from the recordings, information on flame geometry (i.e. flame height, flame length and flame angle) and rate of spread was obtained. Temperature measurements were also carried out by a small tower of six thermocouples at different heights above the fuel bed. Results show that headfire rate of spread increases steeply with wind speed for wind-driven fires but does not depend on wind speed for backing fire spread rates. Rate of spread increases slightly with slope for up-hill propagation, and is not slope dependent for down-hill cases. Rate of spread decreases when fuel moisture content increases. Flame angle and flame height are also dependent on wind velocity, slope, and fuel moisture content. The importance of temperature for fire propagation is discussed, emphasizing the role of radiation heat transfer in the process. Correlations between temperature and other indicators of fire behaviour (namely the rate of spread) are presented. Results are discussed and compared. The results obtained provide a good database for the assessment of fire propagation models.

scholarly journals The Relevance of Current Hazard Stick Reading to the Moisture Content of Logging Slash

1969 ◽  
Vol 45 (2) ◽  
pp. 107-113
Author(s):  
Gy. Péch
Keyword(s):  
Moisture Content ◽  
Fuel Moisture ◽  
Daily Fluctuation ◽  
Individual Measurement ◽  
Moisture Contents ◽  
Red Cedar ◽  
Drying Rates ◽  
Fuel Moisture Content ◽  
Maximum Moisture Content ◽  
Composite Samples

Seven composite samples of western red cedar and western hemlock logging slash of 0.25 to 2 inches diameter were exposed on top of and within the bottom third of a fuel bed in the interior wet belt of British Columbia in August 1965. Their moisture contents were measured regularly 24 hours a day and compared with the moisture content of an exposed B.C. hazard stick on the basis of both the hourly drying rates on 1 clear day and the daily loss of moisture, relative to the morning maximum moisture content, for a period of 6 drying days after rain. The absolute moisture content values, the hourly rates of drying, and the daily fluctuation of the moisture content of the hazard stick differed from those of the fuel samples at all times. It was concluded that cedar-hemlock slash fuel moisture content cannot be predicted numerically from an individual measurement of the moisture content of freely exposed hazard sticks in those years when the slash retains a tight bark. Counting the number of drying days after rain proved to be of little practical value.

The initiation of fire spread in shrubland fuels recreated in the laboratory

2010 ◽  
Vol 19 (4) ◽  
pp. 512 ◽  
Author(s):  
Matt P. Plucinski ◽  
Wendy R. Anderson ◽  
Ross A. Bradstock ◽  
A. Malcolm Gill
Keyword(s):  
Moisture Content ◽  
Classification Tree ◽  
Fire Spread ◽  
Fuel Moisture ◽  
Shrub Layer ◽  
Moisture Contents ◽  
Layer Density ◽  
Live Fuel Moisture ◽  
Fuel Moisture Content ◽  
The Impact

Fire-prone shrub-dominated vegetation communities cover a considerable portion of Australia, including areas fringing urban development. Near urban interfaces, they are actively managed with prescribed fire to reduce the risk of wildfire (unplanned fire). Knowledge of the range of conditions that allow fires to spread or fail to do so is limited and can inconvenience fire managers when conducting prescribed burns. A series of experimental ignitions conducted in miniature shrublands reconstructed in the laboratory were used to investigate factors that influence ignition thresholds. The miniature shrublands were composed of foliage from the shrub Allocasuarina nana and were prepared over a range of moisture contents and densities. The impact of dead fuel within the aerial structure of the shrubs was also investigated, as was the presence and absence of wind and litter. The most important factors for spread initiation were identified using logistic regression analysis and classification tree modelling. The presence of litter, live fuel moisture content, shrub-layer density, presence of wind, and the amount and continuity of the dead elevated fuel were all found to influence spread sustainability. There was a negative interaction between shrub-layer density and live fuel moisture content, showing the effect of density to be less at higher moisture contents.

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