Exploring fire response to high wind speeds: fire rate of spread, energy release and flame residence time from fires burned in pine needle beds under winds up to 27 ms−1

2020 ◽  
Vol 29 (1) ◽  
pp. 81
Author(s):  
Bret Butler ◽  
Steve Quarles ◽  
Christine Standohar-Alfano ◽  
Murray Morrison ◽  
Daniel Jimenez ◽  
...  
Keyword(s):  
Wind Speed ◽  
Energy Release ◽  
Residence Time ◽  
Wildland Fire ◽  
Ground Level ◽  
Fire Spread ◽  
Convective Heating ◽  
Atmospheric Conditions ◽  
Wind Speeds ◽  
Rate Of Spread

The relationship between wildland fire spread rate and wind has been a topic of study for over a century, but few laboratory studies report measurements in controlled winds exceeding 5ms−1. In this study, measurements of fire rate of spread, flame residence time and energy release are reported for fires burning under controlled atmospheric conditions in shallow beds of pine needles subject to winds ranging from 0 to 27ms−1 (measured 5m above ground level). The data suggested that under constant flow conditions when winds are less than 10ms−1, fire rate of spread increases linearly at a rate of ~3% of the wind speed, which generally agrees with other laboratory-based models. When wind speed exceeds 10ms−1, the fire rate of spread response to wind remains linear but with a much stronger dependence, spreading at a rate of ~13% of the wind speed. Radiative and convective heating correlated directly to wind speed, with radiant heating increasing approximately three-fold as much as convective heating over the range of winds explored. The data suggested that residence time is inversely related to wind speed and appeared to approach a lower limit of ~20s as wind exceeded 15ms−1. Average flame residence time over the range of wind speeds was nominally 26s.

A cellular automata model to link surface fires to firebrand lift-off and dispersal

2013 ◽  
Vol 22 (4) ◽  
pp. 428 ◽  
Author(s):  
Holly A. Perryman ◽  
Christopher J. Dugaw ◽  
J. Morgan Varner ◽  
Diane L. Johnson
Keyword(s):  
Wind Speed ◽  
Wildland Fire ◽  
Fire Spread ◽  
Fuel Moisture ◽  
Fuel Loading ◽  
Cellular Automata Model ◽  
Rate Of Spread ◽  
Lift Off ◽  
Fuel Moisture Content ◽  
Spot Fires

In spite of considerable effort to predict wildland fire behaviour, the effects of firebrand lift-off, the ignition of resulting spot fires and their effects on fire spread, remain poorly understood. We developed a cellular automata model integrating key mathematical models governing current fire spread models with a recently developed model that estimates firebrand landing patterns. Using our model we simulated a wildfire in an idealised Pinus ponderosa ecosystem. Varying values of wind speed, surface fuel loading, surface fuel moisture content and canopy base height, we investigated two scenarios: (i) the probability of a spot fire igniting beyond fuelbreaks of various widths and (ii) how spot fires directly affect the overall surface fire’s rate of spread. Results were averages across 2500 stochastic simulations. In both scenarios, canopy base height and surface fuel loading had a greater influence than wind speed and surface fuel moisture content. The expected rate of spread with spot fires occurring approached a constant value over time, which ranged between 6 and 931% higher than the predicted surface fire rate of spread. Incorporation of the role of spot fires in wildland fire spread should be an important thrust of future decision-support technologies.

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.

Observations of energy transport and rate of spreads from low-intensity fires in longleaf pine habitat – RxCADRE 2012

2016 ◽  
Vol 25 (1) ◽  
pp. 76 ◽  
Author(s):  
B. Butler ◽  
C. Teske ◽  
D. Jimenez ◽  
J. O'Brien ◽  
P. Sopko ◽  
...  
Keyword(s):  
Total Energy ◽  
Energy Transport ◽  
Wildland Fire ◽  
Ground Level ◽  
Radiative Energy ◽  
Convective Heating ◽  
Emissive Power ◽  
Rate Of Spread ◽  
Heating And Cooling ◽  
Air Temperatures

Wildland fire rate of spread (ROS) and intensity are determined by the mode and magnitude of energy transport from the flames to the unburned fuels. Measurements of radiant and convective heating and cooling from experimental fires are reported here. Sensors were located nominally 0.5 m above ground level. Flame heights varied from 0.3 to 1.8 m and flaming zone depth varied from 0.3 to 3.0 m. Fire ROS derived from observations of fire transit time between sensors was 0.10 to 0.48 m s–1. ROS derived from ocular estimates reached 0.51 m s–1 for heading fire and 0.25 m s–1 for backing fire. Measurements of peak radiant and total energy incident on the sensors during flame presence reached 18.8 and 36.7 kW m–2 respectively. Peak air temperatures reached 1159°C. Calculated fire radiative energy varied from 7 to 162 kJ m–2 and fire total energy varied from 3 to 261 kJ m–2. Measurements of flame emissive power peaked at 95 kW m–2. Average horizontal air flow in the direction of flame spread immediately before, during, and shortly after the flame arrival reached 8.8 m s–1, with reverse drafts of 1.5 m s–1; vertical velocities varied from 9.9 m s–1 upward flow to 4.5 m s–1 downward flow. The observations from these fires contribute to the overall understanding of energy transport in wildland fires.

Examination of the wind speed limit function in the Rothermel surface fire spread model

2013 ◽  
Vol 22 (7) ◽  
pp. 959 ◽  
Author(s):  
Patricia L. Andrews ◽  
Miguel G. Cruz ◽  
Richard C. Rothermel
Keyword(s):  
Wind Speed ◽  
Wildland Fire ◽  
Fire Spread ◽  
Speed Limit ◽  
Limit Function ◽  
Surface Fire ◽  
Rate Of Spread ◽  
Fire Modelling ◽  
Spread Model ◽  
Fire Spread Model

The Rothermel surface fire spread model includes a wind speed limit, above which predicted rate of spread is constant. Complete derivation of the wind limit as a function of reaction intensity is given, along with an alternate result based on a changed assumption. Evidence indicates that both the original and the revised wind limits are too restrictive. Wind limit is based in part on data collected on the 7 February 1967 Tasmanian grassland fires. A reanalysis of the data indicates that these fires might not have been spreading in fully cured continuous grasslands, as assumed. In addition, more recent grassfire data do not support the wind speed limit. The authors recommend that, in place of the current wind limit, rate of spread be limited to effective midflame wind speed. The Rothermel model is the foundation of many wildland fire modelling systems. Imposition of the wind limit can significantly affect results and potentially influence fire and fuel management decisions.

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 Atmospheric Circulation Effects on Wind Speed Variability at Turbine Height

2007 ◽  
Vol 46 (4) ◽  
pp. 445-456 ◽  
Author(s):  
Katherine Klink
Keyword(s):  
Wind Speed ◽  
Pressure Gradient ◽  
Large Scale ◽  
Ground Level ◽  
The Arctic ◽  
Circulation Index ◽  
Regression Equations ◽  
Change Models ◽  
Wind Speeds ◽  
The North

Abstract Mean monthly wind speed at 70 m above ground level is investigated for 11 sites in Minnesota for the period 1995–2003. Wind speeds at these sites show significant spatial and temporal coherence, with prolonged periods of above- and below-normal values that can persist for as long as 12 months. Monthly variation in wind speed primarily is determined by the north–south pressure gradient, which captures between 22% and 47% of the variability (depending on the site). Regression on wind speed residuals (pressure gradient effects removed) shows that an additional 6%–15% of the variation can be related to the Arctic Oscillation (AO) and Niño-3.4 sea surface temperature (SST) anomalies. Wind speeds showed little correspondence with variation in the Pacific–North American (PNA) circulation index. The effect of the strong El Niño of 1997/98 on the wind speed time series was investigated by recomputing the regression equations with this period excluded. The north–south pressure gradient remains the primary determinant of mean monthly 70-m wind speeds, but with 1997/98 removed the influence of the AO increases at nearly all stations while the importance of the Niño-3.4 SSTs generally decreases. Relationships with the PNA remain small. These results suggest that long-term patterns of low-frequency wind speed (and thus wind power) variability can be estimated using large-scale circulation features as represented by large-scale climatic datasets and by climate-change models.

scholarly journals Assessment of Resource and Forecast Modeling of Wind Speed through An Evolutionary Programming Approach for the North of Tehuantepec Isthmus (Cuauhtemotzin, Mexico)

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3197 ◽  
Author(s):  
Luis López-Manrique ◽  
E. Macias-Melo ◽  
O. May Tzuc ◽  
A. Bassam ◽  
K. Aguilar-Castro ◽  
...  
Keyword(s):  
Wind Speed ◽  
Computation Time ◽  
Ground Level ◽  
Bimodal Distribution ◽  
Programming Approach ◽  
Climatic Data ◽  
Wind Speeds ◽  
Availability Analysis ◽  
The North ◽  
Wind Resource

This work studies the characteristics of the wind resource for a location in the north zone of Tehuantepec isthmus. The study was conducted using climatic data from Cuauhtemotzin, Mexico, measured at different altitudes above the ground level. The measured data allowed establishing the profile of wind speeds as well as the analysis of its availability. Analysis results conclude that the behavior of the wind speed presents a bimodal distribution with dominant northeast wind direction (wind flow of sea–land). In addition, the area was identified as feasible for the use of low speed power wind turbines. On the other hand, the application of a new approach for very short-term wind speed forecast (10 min) applying multi-gene genetic programming and global sensitivity analysis is also presented. Using a computational methodology, an exogenous time series with fast computation time and good accuracy was developed for the forecast of the wind speed. The results presented in this work complement the panorama for the evaluation of the resource in an area recognized worldwide for its vast potential for wind power.

scholarly journals Evaluating Temperature Measurements of the iMET-XQ, in the Field, under Varying Atmospheric Conditions

Atmosphere ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 335 ◽  
Author(s):  
Sytske K. Kimball ◽  
Carlos J. Montalvo ◽  
Madhuri S. Mulekar
Keyword(s):  
Wind Speed ◽  
Solar Radiation ◽  
Aluminum Coating ◽  
Temperature Measurements ◽  
Atmospheric Conditions ◽  
Radiation Shield ◽  
Wind Speeds ◽  
Outdoor Setting ◽  
Accurate Temperature ◽  
Reference Sensor

Temperature measurements of InterMET Inc. aluminum-coated iMET-XQ sensors were tested in an outdoor setting under a variety of solar radiation and wind speed conditions. Twelve unshielded sensors were mounted side-by-side on the tower of a South Alabama Mesonet weather station next to a reference sensor on the tower. The iMET-XQ temperatures were most precise and accurate in solar radiation values that were close to zero, regardless of wind speed. Under overcast conditions, wind speeds of 2 m s−1 were sufficient to obtain precise and accurate temperature measurements. During the day-time, aspiration of wind speeds higher than or equal to 3 m s−1 is sufficient. An iMET-XQ was placed in a radiation shield next to the tower reference sensor to test the need for a radiation shield. A second iMET-XQ was placed unshielded on the tower. The iMET-XQ sensors with aluminum coating do not need to be shielded, but they do need to be aspirated. It is recommended that, when taking temperature measurements using unmanned aerial vehicles (UAV) with iMET-XQ sensors, the UAV either fly at 3 m s−1, be embedded in winds of those speeds, or to use the propeller wash of the UAV to aspirate the sensors.

scholarly journals Validation of Dual-Doppler Wind Profiles with in situ Anemometry

2015 ◽  
Vol 32 (5) ◽  
pp. 943-960 ◽  
Author(s):  
W. Scott Gunter ◽  
John L. Schroeder ◽  
Brian D. Hirth
Keyword(s):  
High Resolution ◽  
Wind Speed ◽  
Doppler Radar ◽  
Heavy Precipitation ◽  
Atmospheric Conditions ◽  
Wind Speeds ◽  
Time Histories ◽  
Mean Wind Speed ◽  
Wind Profiles

AbstractTypical methods used to acquire wind profiles from Doppler radar measurements rely on plan position indicator (PPI) scans being performed at multiple elevation angles to utilize the velocity–azimuth display technique or to construct dual-Doppler synthesis. These techniques, as well as those employed by wind profilers, often produce wind profiles that lack the spatial or temporal resolution to resolve finescale features. If two radars perform range–height indicator (RHI) scans (constant azimuth, multiple elevations) along azimuths separated by approximately 90°, then the intersection of the coordinated RHI planes represents a vertical set of points where dual-Doppler wind syntheses are possible and wind speed and direction profiles can be retrieved. This method also allows for the generation of high-resolution wind time histories that can be compared to anemometer time histories. This study focuses on the use of the coordinated RHI scanning strategy by two high-resolution mobile Doppler radars in close proximity to a 200-m instrumented tower. In one of the first high-resolution, long-duration comparisons of dual-Doppler wind synthesis with in situ anemometry, the mean and turbulence states of the wind measured by each platform were compared in varying atmospheric conditions. Examination of mean wind speed and direction profiles in both clear-air (nonprecipitating) and precipitating environments revealed excellent agreement above approximately 50 m. Below this level, dual-Doppler wind speeds were still good but slightly overestimated as compared to the anemometer-measured wind speeds in heavy precipitation. Bulk turbulence parameters were also slightly underestimated by the dual-Doppler syntheses.

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