Estimating error in wind speed measurements for experimental fires

2001 ◽  
Vol 31 (3) ◽  
pp. 401-409 ◽  
Author(s):  
A L Sullivan ◽  
I K Knight
Keyword(s):  
Wind Speed ◽  
Small Scale ◽  
Confidence Limits ◽  
Single Measure ◽  
Rate Of Spread ◽  
Scale Size ◽  
Fire Front ◽  
Scalar Measure ◽  
Eucalypt Forests ◽  
Measured Wind Speed

Most experimental fires, by nature, are small scale ([Formula: see text]100 m), and rate of spread measurements are taken over periods of several minutes. The aim of empirical fire modellers is to ascribe a single measure of rate of forward spread over a period to a single scalar measure of wind. The actual wind affecting the fire is unmeasurable; its value must be estimated from remote anemometry. Observation and consideration of the spatial and temporal statistics of the wind has allowed confidence limits to be placed upon the accuracy with which the measured wind reflects the wind acting on the fire front. Experimental data to verify these estimates was gathered during Project Vesta, a study into high-intensity fires in dry eucalypt forests. An equation that quantifies the accuracy of the estimate of wind affecting the fire front is given. The accuracy increases with time scale, size of the fire front, and density of anemometry. When applied to a measured wind speed taken some distance from the fire, it gives a useful estimate of the likely variation of the corresponding wind at the fire front.

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.

Simulation study of grass fire using a physics-based model: striving towards numerical rigour and the effect of grass height on the rate of spread

2018 ◽  
Vol 27 (12) ◽  
pp. 800 ◽  
Author(s):  
K. A. M. Moinuddin ◽  
D. Sutherland ◽  
W. Mell
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Heat Release ◽  
Bulk Density ◽  
Simulation Study ◽  
Release Rate ◽  
Rate Of Spread ◽  
Fire Front ◽  
Physics Based Simulation ◽  
Mode A

Grid-independent rate of spread results from a physics-based simulation are presented. Previously, such a numerical benchmark has been elusive owing to computational restrictions. The grid-converged results are used to systematically construct correlations between the rate of spread (RoS) and both wind speed and grass height, separately. The RoS obtained from the physics-based model is found to be linear with wind speed in the parameter range considered. When wind speed is varied, the physics-based model predicts faster RoS than the Mk III and V (McArthur) models (Noble et al. 1980) but slower than the CSIRO model (Cheney et al. 1998). When the grass height is varied keeping the bulk density constant, the fire front changes from a boundary layer flame mode to plume flame mode as the grass height increases. Once the fires are in plume mode, a higher grass height results in a larger heat release rate of the fire but a slower RoS.

A dimensionless correlation for the spread of wind-driven fires

1988 ◽  
Vol 18 (4) ◽  
pp. 391-397 ◽  
Author(s):  
Ralph M. Nelson Jr. ◽  
Carl W. Adkins
Keyword(s):  
Wind Speed ◽  
Residence Time ◽  
Fire Spread ◽  
Simple Expression ◽  
Small Scale ◽  
Strongly Correlated ◽  
Spread Rate ◽  
Ambient Wind ◽  
Rate Of Spread ◽  
Several Variables

Data for the behavior of 59 experimental wind-driven fires were extracted from the literature for use in determining a correlation among several variables known to influence the rate of forest fire spread. Also included in the correlation were unpublished data from six field fires. This information consisted of behavior measurements on small-scale burns of artificial fuels in the laboratory and measurements on field fires in diverse fuels such as grass and logging slash. Fire intensities ranged from about 40 to 4600 kW/m. Dimensional analysis was used to derive three variables governing the fire spread process. These variables, rearranged into a dimensionless rate of spread and a dimensionless wind speed, are strongly correlated and lead to a simple expression for fire spread rate in terms of fuel consumption, ambient wind speed, and flame residence time.

A power series formulation for two-dimensional wildfire shapes

2016 ◽  
Vol 25 (9) ◽  
pp. 970 ◽  
Author(s):  
J. E. Hilton ◽  
C. Miller ◽  
A. L. Sullivan
Keyword(s):  
Power Series ◽  
Small Scale ◽  
Two Dimensional ◽  
One Dimensional ◽  
Rate Of Spread ◽  
Mathematical Expressions ◽  
Fire Front ◽  
Small Set ◽  
Prediction Systems ◽  
The One

Computational simulations of wildfires require a model for the two-dimensional expansion of a fire perimeter. Although many expressions exist for the one-dimensional rate of spread of a fire front, there are currently no agreed mathematical expressions for the two-dimensional outward speed of a fire perimeter. Multiple two-dimensional shapes such as elliptical and oval-shaped perimeters have been observed and reported in the literature, and several studies have attempted to classify these shapes using geometric approximations. Here we show that a two-dimensional outward speed based on a power series results in a perimeter that can match many of these observed shapes. The power series is based on the dot product between the vector normal to the perimeter and a fixed wind vector. The formulation allows the evolution and shape of a fire perimeter to be expressed using a small set of scalar coefficients. The formulation is implemented using the level set method, and computed perimeters are shown to provide a good match to perimeters of small-scale experimental fires. The method could provide a framework for statistical matching of wildfire shapes or be used to improve current wildfire prediction systems.

Project Aquarius 4. Experimental Bushfires, Suppression Procedures, and Measurements

1997 ◽  
Vol 7 (2) ◽  
pp. 99 ◽  
Author(s):  
GM Budd ◽  
JR Brotherhood ◽  
AL Hendrie ◽  
SE Jeffery ◽  
FA Beasley ◽  
...  
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Air Temperature ◽  
Fire Intensity ◽  
Subjective Responses ◽  
Hand Tool ◽  
Infra Red ◽  
Fire Front ◽  
Forest Fire Danger ◽  
Eucalypt Forests

Experimental bushfires were lit over three summers in Australian eucalypt forests with fuel loads (mean and range) of 11.3 (8-14) tonnes per hectare, in air temperature 25 (17-33)° C, relative humidity 47 (14-81)%, and wind speed 4.4 (2-9) m s-1. The McArthur Forest Fire Danger Index (FFDI) ranged from 2 to 18 and was evenly distributed between 'low', 'moderate', and 'high' fire dangers. Fires were lit on a crosswind ignition line of 50-200 metres, and were allowed to develop for 10-50 minutes before a seven-man hand-tool crew commenced its attack. Airborne infra-red imagery showed that head-fire intensity (averaged over 6 minutes) of most fires exceeded 1000 kW per metre of fire front (kW m-1) at some stage and ranged as high as 3280 kW m-1, challenging the crew in much the same way as summer wildfires and evoking similar uncertainty and apprehension. Firefighters were generally unable to suppress headfires with an intensity of more than 1000 kW m-1. Comprehensive measurements were made of the stresses the firefighters and scientific observers experienced, their physiological and subjective responses, and the firefighters' productivity and efficiency. In all, 23 km of fireline were constructed and 238 man-days of measurements were obtained — 179 on the firefighters, 59 on the scientists.

scholarly journals Modeling surface fire rate of spread within a thinned Anatolian black pine stand in Turkey

2018 ◽  
Vol 27 (2) ◽  
pp. e007
Author(s):  
Omer Kucuk ◽  
Ertugrul Bilgili ◽  
Rifat Uzumcu
Keyword(s):  
Wind Speed ◽  
Weather Conditions ◽  
Fire Spread ◽  
Pinus Nigra ◽  
Small Scale ◽  
Black Pine ◽  
Fuel Loading ◽  
Surface Fire ◽  
Rate Of Spread ◽  
Northwestern Turkey

Aim of the study: To develop regression models for estimating the rate of surface fire spread in a thinned even-aged black pine stand (Pinus nigra J.F. Arnold subsp. nigra var. caramanica (Loudon) Rehder).Area of the study: The study was carried out within a thinned black pine forest located in the Kastamonu Forest District, northwestern Turkey. The study area is located at 546819, 4577880 UTM.Material and methods: A total of 33 small scale surface fires were ignited under varying weather and fuel conditions. Line ignition was used during the burnings. Surface fuels consisted generally of thinned material (needle+branches).Main results: Within the stand, surface fuel loading ranged from 3.0 to 10.2 kg/m2. Wind speed ranged from 0.3 to 8.4 km/h. Needle moisture content ranged from 8 to 15%. The rate of fire spread ranged from 0.47 to 6.92 m/min. Relationships between the rate of fire spread and fuel and weather conditions were determined through regression analyses.Research highlights: Wind speed was the most important factor on the rate of fire spread and explained 85% of the observed variation in the surface fire rate of spread within a stand.

The Speed of a Fire Front and Its Dependence on Wind-Speed

1993 ◽  
Vol 3 (4) ◽  
pp. 193 ◽  
Author(s):  
T Beer
Keyword(s):  
Wind Speed ◽  
Laboratory Tests ◽  
Field Data ◽  
Fire Spread ◽  
Measured Data ◽  
Rate Of Spread ◽  
Wind Rate ◽  
Fire Front ◽  
Analytical Formulae ◽  
Definition Of

The results of a number of laboratory tests of wind-driven fires indicate the existence of a characteristic wind speed, U'. The form of the fire spread (V) as a function of mid-flame wind speed (U) differs above and below this characteristic speed. The scatter in field data is so great that it is difficult to confirm this result for field data. However, expressions of the form: V/V0 -1 = α(U/U')0.5 U/U' < 1 and V/V0 -1 = α(U/U')3 U/U' > 1 with U' = 2.5 m s-1 perform in a similar manner to existing models. For many fuel types α = 15. A difficulty with existing fire spread models is the measurement and definition of V0, the no-wind rate of spread. It can hardly ever be measured in the field and has to be inferred from analytical formulae, or by extrapolating measured data. The value of a depends on the method used estimate V0.

scholarly journals Evaluation of WRF-SFIRE performance with field observations from the FireFlux experiment

2013 ◽  
Vol 6 (4) ◽  
pp. 1109-1126 ◽  
Author(s):  
A. K. Kochanski ◽  
M. A. Jenkins ◽  
J. Mandel ◽  
J. D. Beezley ◽  
C. B. Clements ◽  
...  
Keyword(s):  
Wind Speed ◽  
Ground Level ◽  
Surface Flow ◽  
Horizontal Wind ◽  
Temperature Structure ◽  
Fire Plume ◽  
Arrival Times ◽  
Wind Speeds ◽  
Rate Of Spread ◽  
Fire Front

Abstract. This study uses in situ measurements collected during the FireFlux field experiment to evaluate and improve the performance of the coupled atmosphere–fire model WRF-SFIRE. The simulation by WRF-SFIRE of the experimental burn shows that WRF-SFIRE is capable of providing realistic head-fire rate of spread and vertical temperature structure of the fire plume, and fire-induced surface flow and vertical velocities within the plume up to 10 m above ground level. The simulation captured the changes in wind speed and direction before, during, and after fire front passage, along with the arrival times of wind speed, temperature, and updraft maxima, at the two instrumented flux towers used in FireFlux. The model overestimated vertical wind speeds and underestimated horizontal wind speeds measured at tower heights above 10 m. It is hypothesized that the limited model spatial resolution led to overestimates of the fire front depth, heat release rate, and updraft speed. However, on the whole, WRF-SFIRE simulated fire plume behavior that is consistent with FireFlux observations. The study suggests optimal experimental pre-planning, design, and execution strategies for future field campaigns that are intended to evaluate and develop further coupled atmosphere–fire models.

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.

scholarly journals Dynamic Loads and Response of a Spar Buoy Wind Turbine with Pitch-Controlled Rotating Blades: An Experimental Study

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3598
Author(s):  
Sara Russo ◽  
Pasquale Contestabile ◽  
Andrea Bardazzi ◽  
Elisa Leone ◽  
Gregorio Iglesias ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Laboratory Data ◽  
Nonlinear Behavior ◽  
Offshore Wind ◽  
Small Scale ◽  
Wave Steepness ◽  
Design Factor

New large-scale laboratory data are presented on a physical model of a spar buoy wind turbine with angular motion of control surfaces implemented (pitch control). The peculiarity of this type of rotating blade represents an essential aspect when studying floating offshore wind structures. Experiments were designed specifically to compare different operational environmental conditions in terms of wave steepness and wind speed. Results discussed here were derived from an analysis of only a part of the whole dataset. Consistent with recent small-scale experiments, data clearly show that the waves contributed to most of the model motions and mooring loads. A significant nonlinear behavior for sway, roll and yaw has been detected, whereas an increase in the wave period makes the wind speed less influential for surge, heave and pitch. In general, as the steepness increases, the oscillations decrease. However, higher wind speed does not mean greater platform motions. Data also indicate a significant role of the blade rotation in the turbine thrust, nacelle dynamic forces and power in six degrees of freedom. Certain pairs of wind speed-wave steepness are particularly unfavorable, since the first harmonic of the rotor (coupled to the first wave harmonic) causes the thrust force to be larger than that in more energetic sea states. The experiments suggest that the inclusion of pitch-controlled, variable-speed blades in physical (and numerical) tests on such types of structures is crucial, highlighting the importance of pitch motion as an important design factor.

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