scholarly journals An Empirical Model for the Effect of Wind on Fire Spread Rate

Fire ◽  
2018 ◽  
Vol 1 (2) ◽  
pp. 31 ◽  
Author(s):  
Carlos Rossa ◽  
Paulo Fernandes
Keyword(s):  
Empirical Model ◽  
Vegetation Type ◽  
Fire Spread ◽  
Fuel Load ◽  
Wind Effect ◽  
High Moisture ◽  
Independent Laboratory ◽  
Live Fuels ◽  
Released Energy ◽  
Good Agreement

Predicting wind-driven rate of fire spread (RoS) has been the aim of many studies. Still, a field-tested model for general use, regardless of vegetation type, is currently lacking. We develop an empirical model for wind-aided RoS from laboratory fires (n = 216), assuming that it depends mainly on fire-released energy and on the extension of flame over the fuel bed in still air, and that it can be obtained by multiplying RoS in no-wind and no-slope conditions by a factor quantifying the wind effect. Testing against independent laboratory and field data (n = 461) shows good agreement between observations and predictions. Our results suggest that the fuel bed density effect detected by other work may be a surrogate for the amount of fuel involved in combustion, which depends on fuel load. Because RoS under windless conditions is unaffected by fuel load, the involved mechanisms differ from wind-aided propagation. Compared to shallow fuel beds, the wind effect is usually modest in deep vegetation, because tall fuel complexes are dominated by live fuels (high moisture content) and flames extend less above the vegetation when fuel moisture is high. The present work warrants further inspection in a broader range of field conditions.

Characterisation of the fuel and fire environment in southern Ontario’s tallgrass prairie

2015 ◽  
Vol 24 (8) ◽  
pp. 1118 ◽  
Author(s):  
Susan Kidnie ◽  
B. Mike Wotton
Keyword(s):  
Moisture Content ◽  
Tallgrass Prairie ◽  
Prescribed Burning ◽  
Fire Spread ◽  
Fuel Load ◽  
Prairie Restoration ◽  
Prescribed Burn ◽  
Spread Rate ◽  
Prescribed Burns ◽  
Tallgrass Prairie Restoration

Prescribed burning can be an integral part of tallgrass prairie restoration and management. Understanding fire behaviour in this fuel is critical to conducting safe and effective prescribed burns. Our goal was to quantify important physical characteristics of southern Ontario’s tallgrass fuel complex prior to and during prescribed burns and synthesise our findings into useful applications for the prescribed fire community. We found that the average fuel load in tallgrass communities was 0.70 kg m–2. Fuel loads varied from 0.38 to 0.96 kg m–2. Average heat of combustion did not vary by species and was 17 334 kJ kg–1. A moisture content model was developed for fully cured, matted field grass, which was found to successfully predict moisture content of the surface layers of cured tallgrass in spring. We observed 25 head fires in spring-season prescribed burns with spread rates ranging from 4 to 55 m min–1. Flame front residence time averaged 27 s, varying significantly with fuel load but not fire spread rate. A grassland spread rate model from Australia showed the closest agreement with observed spread rates. These results provide prescribed-burn practitioners in Ontario better information to plan and deliver successful burns.

Determinants of spatial variation in fire return period in a semiarid African savanna

2011 ◽  
Vol 20 (4) ◽  
pp. 540 ◽  
Author(s):  
T. G. O'Connor ◽  
C. M. Mulqueeny ◽  
P. S. Goodman
Keyword(s):  
Spatial Variation ◽  
Return Period ◽  
Vegetation Type ◽  
Fire Frequency ◽  
Fuel Load ◽  
Annual Rainfall ◽  
Vegetation Types ◽  
Terrestrial Vegetation ◽  
African Savanna ◽  
Data Set

Fire pattern is predicted to vary across an African savanna in accordance with spatial variation in rainfall through its effects on fuel production, vegetation type (on account of differences in fuel load and in flammability), and distribution of herbivores (because of their effects on fuel load). These predictions were examined for the 23 651-ha Mkuzi Game Reserve, KwaZulu-Natal, based on a 37-year data set. Fire return period varied from no occurrence to a fire every 1.76 years. Approximately 75% of the reserve experienced a fire approximately every 5 years, 25% every 4.1–2.2 years and less than 1% every 2 years on average. Fire return period decreased in relation to an increase in mean annual rainfall. For terrestrial vegetation types, median fire return periods decreased with increasing herbaceous biomass, from forest that did not burn to grasslands that burnt every 2.64 years. Fire was absent from some permanent wetlands but seasonal wetlands burnt every 5.29 years. Grazer biomass above 0.5 animal units ha–1 had a limiting influence on the maximum fire frequency of fire-prone vegetation types. The primary determinant of long-term spatial fire patterns is thus fuel load as determined by mean rainfall, vegetation type, and the effects of grazing herbivores.

scholarly journals Computer Simulation of the King's Cross Fire: Effect of Radiative Heat Transfer on Fire Spread

1991 ◽  
Vol 205 (3) ◽  
pp. 201-208 ◽  
Author(s):  
W M G Malalasekera ◽  
F Lockwood
Keyword(s):  
Mathematical Model ◽  
Radiative Heat ◽  
Health And Safety ◽  
Fire Spread ◽  
Future Research ◽  
Full Description ◽  
Department Of Health ◽  
Underground Fire ◽  
The Mathematical Model ◽  
Good Agreement

A mathematical model has been applied to simulate model experiments of the 1987 King's Cross underground fire by the Department of Health and Safety Executive. The predicted growth of the fire is compared with the experimental data and in particular the predicted and measured times to ‘flashover’ are compared. The comparisons show exceptional agreement which, in part, may be fortuitous due to the need to facilitate the prediction of the early stages of the growth with the aid of an experimentally estimated fire strength. The good agreement nonetheless is also due to the full description of the radiation transfer which is a feature of the mathematical model. It is concluded that the flashover phenomenon that occurred at King's Cross was thermal radiation driven and that future research should be devoted to modelling the details of fire spread across a combustible surface.

scholarly journals Determining Firebrand Generation Rate Using Physics-Based Modelling from Experimental Studies through Inverse Analysis

Fire ◽  
2022 ◽  
Vol 5 (1) ◽  
pp. 6
Author(s):  
Amila Wickramasinghe ◽  
Nazmul Khan ◽  
Khalid Moinuddin
Keyword(s):  
Wind Velocity ◽  
Forest Fire ◽  
Inverse Analysis ◽  
Vegetation Type ◽  
Experimental Studies ◽  
Generation Rate ◽  
Fuel Load ◽  
Potential Threat ◽  
Collection Data ◽  
Vegetation Species

Firebrand spotting is a potential threat to people and infrastructure, which is difficult to predict and becomes more significant when the size of a fire and intensity increases. To conduct realistic physics-based modeling with firebrand transport, the firebrand generation data such as numbers, size, and shape of the firebrands are needed. Broadly, the firebrand generation depends on atmospheric conditions, wind velocity and vegetation species. However, there is no experimental study that has considered all these factors although they are available separately in some experimental studies. Moreover, the experimental studies have firebrand collection data, not generation data. In this study, we have conducted a series of physics-based simulations on a trial-and-error basis to reproduce the experimental collection data, which is called an inverse analysis. Once the generation data was determined from the simulation, we applied the interpolation technique to calibrate the effects of wind velocity, relative humidity, and vegetation species. First, we simulated Douglas-fir (Pseudotsuga menziesii) tree-burning and quantified firebrand generation against the tree burning experiment conducted at the National Institute of Standards and Technology (NIST). Then, we applied the same technique to a prescribed forest fire experiment conducted in the Pinelands National Reserve (PNR) of New Jersey, the USA. The simulations were conducted with the experimental data of fuel load, humidity, temperature, and wind velocity to ensure that the field conditions are replicated in the experiments. The firebrand generation rate was found to be 3.22 pcs/MW/s (pcs-number of firebrands pieces) from the single tree burning and 4.18 pcs/MW/s in the forest fire model. This finding was complemented with the effects of wind, vegetation type, and fuel moisture content to quantify the firebrand generation rate.

Simulation and thermal imaging of the 2006 Esperanza Wildfire in southern California: application of a coupled weather–wildland fire model

2014 ◽  
Vol 23 (6) ◽  
pp. 755 ◽  
Author(s):  
Janice L. Coen ◽  
Philip J. Riggan
Keyword(s):  
Thermal Imaging ◽  
Large Scale ◽  
Transient Flow ◽  
Wildland Fire ◽  
Fire Spread ◽  
Early Morning ◽  
Fuel Load ◽  
Dynamic Interactions ◽  
Riverside County ◽  
Layer Flow

The 2006 Esperanza Fire in Riverside County, California, was simulated with the Coupled Atmosphere–Wildland Fire Environment (CAWFE) model to examine how dynamic interactions of the atmosphere with large-scale fire spread and energy release may affect observed patterns of fire behaviour as mapped using the FireMapper thermal-imaging radiometer. CAWFE simulated the meteorological flow in and near the fire, the fire’s growth as influenced by gusty Santa Ana winds and interactions between the fire and weather through fire-induced winds during the first day of burning. The airflow was characterised by thermally stratified, two-layer flow channelled between the San Bernardino and San Jacinto mountain ranges with transient flow accelerations driving the fire in Cabazon Peak’s lee. The simulation reproduced distinguishing features of the fire including its overall direction and width, rapid spread west-south-westward across canyons, spread up canyons crossing its southern flank, splitting into two heading regions and feathering of the fire line. The simulation correctly depicted the fire’s location at the time of an early-morning incident involving firefighter fatalities. It also depicted periods of deep plume growth, but anomalously described downhill spread of the head of the fire under weak winds that was less rapid than observed. Although capturing the meteorological flow was essential to reproducing the fire’s evolution, fuel factors including fuel load appeared to play a secondary role.

Bare soil and rill formation following wildfires, fuel reduction treatments, and pine plantations in the southern Sierra Nevada, California, USA

2010 ◽  
Vol 19 (4) ◽  
pp. 478 ◽  
Author(s):  
Neil H. Berg ◽  
David L. Azuma
Keyword(s):  
Sierra Nevada ◽  
Vegetation Type ◽  
Fire Severity ◽  
Reference Conditions ◽  
Bare Soil ◽  
Fuel Load ◽  
Load Reduction ◽  
Fuel Reduction ◽  
Management Options ◽  
Burned Areas

Accelerated erosion commonly occurs after wildfires on forested lands. As burned areas recover, erosion returns towards prefire rates depending on many site-specific characteristics, including fire severity, vegetation type, soil type and climate. In some areas, erosion recovery can be rapid, particularly where revegetation is quick. Erosion recovery is less well understood for many fuel load reduction treatments. The rate of post-disturbance erosion recovery affects management options for forested lands, particularly when considering the combined ramifications of multiple disturbances on resource recovery rates (i.e. cumulative watershed effects). Measurements of percentage bare soil and rilling on over 600 plots in the southern Sierra Nevada with slopes less than 75% and within 1 km of roads were made between 2004 and 2006. Results suggest that after high-, moderate- or low-severity wildfire, rilling was seldom evident more than 4 years after fire. Percentage bare soil generally did not differ significantly between reference plots and wildfire plots greater than 6 years old. Little rilling was evident after treatment with a variety of fuel reduction techniques, including burning of machine- and hand-piled fuel, thinning, mastication, and crushing. Percentage bare soil at the fuel load reduction treatment plots also did not differ significantly from reference conditions. Percentage bare soil at pine plantation plots was noticeably higher than at reference sites.

Combustion and Nutrient Losses During Laboratory Burns

1995 ◽  
Vol 5 (1) ◽  
pp. 1 ◽  
Author(s):  
D Gillon ◽  
V Gomendy ◽  
C Houssard ◽  
J Marechal ◽  
JC Valette
Keyword(s):  
Moisture Content ◽  
Fuel Consumption ◽  
Fire Spread ◽  
Fuel Load ◽  
Maximum Temperature ◽  
Fuel Moisture ◽  
Nutrient Losses ◽  
Constant Moisture Content ◽  
Fuel Moisture Content ◽  
Experimental Burns

The aim of this study was to assess the effects on combustion characteristics, and their consequences on nutrient losses, of (1) the change in load and packing ratio of the fuel bed, and (2) the change in fuel moisture content. Eighty-one experimental burns were carried out, on a test bench in the laboratory; the fuel was composed of needles and twigs of Pinus pinaster. Two levels of fuel load an dpacking ratio (8t ha-1 needles, packing ratio of 0.040; and 16t ha-1 twigs and needles, packing ratio of 0.066) were compared at constant moisture content (6%); and four levels of moisture content(6%, 12%, 24% and 30% dry weight) were compared at constant fuel load (8t ha-1 needles). At constant moisture content, an increase in the load and packing ratio of the fuel bed led to an increase in the height of flames and in the maximum temperature 25 cm above the fuel bed, in the duration of the rise in temperatures within the fuel, and in the fireline intensity. Conversely, the rate of fire spread decreased. At constant fuel load, an increase in the moisture content of the fuel led to a decrease in the rate of fire spread, in the flame height and the maximum temperature 25 cm above the fuel bed, and in the fireline intensity. In contrast, the maximum temperatures reached within the fuel, when the flaming front was continuous, did not significantly change with varying fuel loads or fuel moisture contents. The percentage fuel consumption was always high, more than 80%, but it significantly decreased with increasing fuel load and packing ratio and with increasing moisture content. Total losses of N, S, and K significantly decreased with increasing fuel load and packing ratio, with increasing moisture content and with decreasing percentage fuel consumption. Losses in P only significantly decreased with increasing fuel load and packing ratio. Losses in Mg and Ca were not significantly affected by fuel load, moisture content. or percentage consumption. An attempt was made to separate volatile from particulate losses, based on the assumption that all the losses of Ca were in particulate form. Whereas losses in particulate form remained relatively constant, losses of nutrients in volatile form seem to have been related to the percentage fuel consumption. Even if these experimental burns were of low intensity (40 to 56 kW m-1), their impact, in terms of lethal temperatures and nutrient losses, was not negligible, particularly for N and P. The increasing fireline intensity with increasing fuel load was not accompanied by an enhancement in the proportion of nutrient losses. In the same way, the strong decrease in fireline intensity with increasing fuel moisture content led only to a slight decrease in some nutrient losses. It was through their effect on the percentage fuel consumption that fuel load or moisture content modified the nutrient losses, particularly volatile losses.

On the Game Method for the forest fire spread modelling with considering the wind effect

2012 ◽  
Author(s):  
Emiliya Velizarova ◽  
Evdokia Sotirova ◽  
Krassimir Atanassov ◽  
Peter Vassilev ◽  
Stefka Fidanova
Keyword(s):  
Forest Fire ◽  
Fire Spread ◽  
Wind Effect

Analysis of Screw-Expander Performance

1989 ◽  
Vol 203 (1) ◽  
pp. 15-20 ◽  
Author(s):  
K C Ng ◽  
T B Lim ◽  
T Y Bong
Keyword(s):  
Experimental Data ◽  
Experimental Work ◽  
Empirical Model ◽  
Saturated Steam ◽  
Polytropic Index ◽  
Work Output ◽  
Predicted Values ◽  
Good Agreement ◽  
Thermodynamic Processes

The paper examines the thermodynamic processes of a helical screw-expander that operates with dry saturated steam at its inlet. The work output of the screw-expander is analysed using a simple ‘pseudo-polytropic’ index. Using the available experimental data from the literature, an empirical model for the prediction of work using the ‘pseudo-polytropic’ indices is formulated. The expansion indices are expressed in terms of built-in volumetric and pressure ratios; how they are formulated is usually given in an expander specification. Based on the empirical model, there is a good agreement between the experimental work and the predicted values.

Untersuchung der Temperatur und der Expansion von Funkenkanälen in H2 bei variabler Energiezufuhr

1970 ◽  
Vol 25 (3) ◽  
pp. 430-439 ◽  
Author(s):  
H. Martinen ◽  
H. Tholl
Keyword(s):  
Energy Dissipation ◽  
Energy Input ◽  
Temporal Development ◽  
Channel Axis ◽  
Temporal Behaviour ◽  
Released Energy ◽  
Expansion Energy ◽  
Good Agreement

Measurements were carried out in order to investigate the temporal behaviour of temperatures in the channel axis of sparks in hydrogen in which different amounts of energy were released. It was found that with increasing energy input the temperature rises to approximately 60 000 °K . A further enhancement of temperature above this value could not be observed in spite of increasing energy dissipation. This effect can be explained by the fact that an increasing amount of the released energy is converted into expansion energy.The temporal development of the channel radii was measured and was compared with calculated values using Drabkina's and Braginskii's theories. Good agreement between measured and calculated radii was found

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