Wildland-Urban Interface and Wildland Fires

AFTER APRIL 9th, 2011, THIS SITE WILL NO LONGER BE UPDATED
FOR FURTHER INFORMATION PLEASE REFER TO WUI RESEARCH AT THE
 NIST ENGINEERING LABORATORY WEBSITE
AND
THIS US FOREST WEBSITE
(this USFS website may take a few weeks to become fully functional)

This webpage contains an overview of ongoing work at the National Institute of Standards and Technology in the areas of wildland-urban interface (WUI) and wildland fires.

Post-doctoral opportunities within NIST WUI fire research and other fire research areas exist. See one page description.

For descriptions of the projects within NIST's WUI program go here.
last updated November, 2010
Disclaimer: Any links to non-Federal Government Web sites do not imply endorsement of any particular product, service, organization, company, information provider, or content.

Recent Activity ( within ~ the last year)
Articles in the pubic media
Defining exposure at the wildland urban interface Fire Protection Engineering, September 2009
'07 Wildfire Study Focuses on Devastated Community San Diego Union Tribune, June 21, 2009
Economics / Statiscal based research
Economic optimization of wildfire intervention activities Int'l J. Wildland Fire 19(5):659-672
Enticing arsonists with broken windows and social disaster to appear in Fire Technology
Fighting fire with fire: estimating the efficacy of wildfire mitigation programs using propensity scores Environ Ecol Stat 16:291-319 (2009)
Field Studies and Building Codes
A Case Study of a Community Affected by the Witch and Guejito Fires to appear in Fire Technolgoy and NIST TN 1635, April 2009
Development of rapidly deployable instrumentation packages for data aquisition in wildland-urban interface fires
 Fire Safety J. 45:327-336 (2010)
Fire behavior at the wildland-urban interface: Modifying  building codes to reduce losses Presentation to San Diego Chapter of the ICC
August 2009
Laboratory Studies
Comparison testing protocol for firebrand penetration through building vents: Summary of BRI/NIST fuel scale and NIST reduced scale results NIST TN 1659, January 2010
Quantifying the vulnerabilites of ceramic tile roofing assemblies to ignition during a firebrand attack Fire Safety J., 45, 35-43 (2010)
Investigation on the ability of glowing firebrands deposited
within crevices to ignite common building materials
 Fire Safety J., 44, 894-900 (2009)


Fire Behavior Modeling
Fire-front propagation using the level set method NIST TN 1611, March 2009
Numerical Simulation and Experiments of Burning Douglas Fir Trees Combustion & Flame 156 2023-2041 (2009)
A Simple Model for Wind Effects of Burning Structures and Topography
on WUI Surface-Fire Propagation		 Int'l J. Wildland Fire, 18, 290-301 (2009)
Other
Summary of Workshop on Research Needs for Full Scale Testing to Determine Vulnerabilities of Siding Treatments and Glazing Assemblies to Ignition by Firebrand Showers NIST Special Pub 1111 (2010)
The Wildland-Urban Interface Fire Problem Current Approaches and Research Needs Int'l J. Wildland Fire, 19, 238-251 (2010)

Postdoctoral opportunities

Contents

Contacts
  • Introduction
  • Fire  Behavior in Structural Fuels
    • Structure-to-structure fire spread
  • Fire Behavior in Vegetative Fuels
    • Burning single isolated trees (experiments and computer simulations)
    • Some grassland fire simulation results
    • Example of a grass fire spreading into a partially thinned forest with transition to crowning
    • WFDS simulation of a stand burn similar to the Intnl. Crown Fire Modeling Experiments (ICFME)
    • Example of a fire spreading through excelsior surface fuel under a 6 m tall tree
    • Enclosure effects in a laboratory experiment of fire spread in excelsior
  • Fire Behavior in the Intermix of Vegetative and Structural Fuels
    • Example of a grass fire spreading towards structures with different fuel treatments
  • Firebrand Experiments
  • Realistic Inputs for Modeling Wildland-Urban Interface Fires
  • Selected Presentations / Reports / 
  • Archival Publications
  • Other Publications
  • Links to databases of experimental results for model validation
    • Australian grassland data (partially completed)
  • Contacts and Collaborators
 1 page overview

pdf 218 kB




Introduction
The Building and Fire Research Laboratory at the National Institute of Standands and Technology is seeking to better understand, from a fire safety point of view, fire behavior and structure ignition in the Wildland-Urban Interface (WUI).   Fires in the WUI spread through both vegetative and structural fuels. Vegetative fuels can include those characteristic of wildlands (trees, grasses, understory growth, and ground litter) as well as those purchased at nurseries for home or community landscaping purposes (trees, mulch, grasses, and ornamental plants). Similary, a wide range of structural materials and designs are used in the construction of exterior walls, windows, soffits, eaves, decks, roofing assemblies, etc.

Fire Spread  Mechanisms in the WUI
vegetation-to-vegetation fire spread vegetation-to-structure


Fire spreading within vegetative fuels approaches a community.
 Fire spreading through vegetation in the upper part of the photo ignited a single structure.
structure-to-structure

(John Gibbons)
Fire spread occured without significant particpation from burning vegetation or significant flame contact from adjacent structures.

Fire spread between structures due to direct flame contact.


Currently our effort is divided into three catagories:
  1. Fire behavior in structural fuels
  2. Fire behavior in vegetative fuels
  3. Fire behavior in the intermix of vegetative and structural fuels
The sections below contain examples of ongoing work in each of these areas.

Large Fire Laboratory (LFL) Experimental Facility
Experiments are conducted in the Large Fire Laboratory at NIST which consists of  a 9 m x 37 m test area containing a 6 m x 6 m and a 9 m x 12 m hood for oxygen consumption calorimentry measurements (heat release rates). A description of some of the measurement capabilities in the LFL in "The NIST 3 Megawatt Quantitative Heat Release Rate Facility."

Computer Simulations
Fire simulations are performed by a modified version of the structural fire code the Fire Dynamics Simulator (FDS) and visualized by Smokeview (a one page handout on Smokeview is here). The version of FDS used here in being modified to simulate firespread through vegetative fuels. This version of FDS is call WFDS (Wildland-urban-interface Fire Dynamics Simulator). WFDS is a physics based numerical modeling approach which includes all modes of heat transfer (convection, conduction, and radiation). Smokeview uses OpenGL to interactively render WFDS outputs (temperature, heat release rates, smoke, heat and mass fluxes, etc.) on animated color contour slices, isosurfaces, and solid surfaces. Both WFDS and Smokeview run on a variety of computer systems including Windows, Linux, and OSX. WFDS can be run on on single or multiple processor computers.

Fire Behavior in Structural Fuels

Structural fuels: Experiment on structure-to-structure fire spread
The separation distance between structures and the materials used in their construction are both important factors in structure-to-structure fire spread.  For exampe, as seen in the above photograph from a 2003 WUI fire in San Diego, CA (USA Today),   Experiments have been conducted to investigate the likelihood that fire can spread from one structure to another. The materials and design used in the structures were either typical of current building practices or included a fire barrier. In these experiments a fire was started and allowed to burn in a typically furnished room. Eventually the fire exited a window and an adjacent structure either ignited (in the case of typical construction, shown below) or did not  ignite (when a fire barrier was included in the wall construction). In these experiments the structures were separated by 6 feet (1.8 m) which is currently allowed in some local building codes.





Downloads:
  • movie (150 MB) of experiments with and without a fire barrier in the wall construction
  • factsheet (pdf) of experiment





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In the above photographs a structural fire exits an enclosure through a window and ignites an adjacent wall.

Structural fuels: Simulations of structure-to-structure fire spread


Downloads:
  • avi movie from Smokeview (22 MB)






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The snapshots above are from preliminary simulations of the structure seperation experiments discussed above. These simulations were conducted on 4 processors using measured heat release information from the room fire in the experiments. Further work is required in the modeling of the target wall which has been assumed to be spruce in the simulation.

Fire Behavior in Vegetative Fuels

Vegetative fuels: Single, isolated, tree burns (experiments and simulations)
Experiments of burning trees have been conducted in order to validate heat fluxes and heat release predictions of simulated trees using WFDS and other modeling approaches.


The sequence of snapshots are of a 2.4 m tall Douglas fir; top row are the experimental burn, bottom row are Smokeview rendered WFDS predictions.
Movies of experimental burns:
- mpeg movie (12 MB) of a 1.5 m, 3 m, and 3.8 m tall Douglas fir trees burning
- quicktime movie (5 MB) of 5 m Douglas fire
Comparison of experimental and computer simulated tree burn:
-  mpeg movie (17 MB) or avi movie (60MB) of a 2.9 m (10 ft) tall Douglas tree burning, mass loss rate, net radiation flux 
Additional information is available in the NIST technical report:  "Physics-Based Modeling for WUI Fire Spread - Simplified Model Algorithm for Ignition of Structures by Burning Vegetation"



Vegetative fuels: Grassland fire simulation results


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The homogeneous fuel and lack of terrain variation in the grassland fires of Australia and Brazil make these fires good candidates for use in model validation.  The figures below are some examples of simulation results of Australian grassland fires from a current validation study.

Australian grassland experiment
200 m x 200 m plot; 5 m/s wind left to right
Ignition: over 56 s two field workers walked in opposite directions starting from the center of the left-hand-side fire break.





WFDS computer simulation of the experiment
Ignition procedure was simulated. Grass fuel is modeled as a subgrid fuel along the base of the gas phase. Convective and radiative heat transfer is accounted for. See here for preprint of paper in the Intnl. J. Wildland Fire.

Animation of WFDS simulation: mpeg (17MB) or avi (38MB)

Note: simulation domain extends ~ 700 m in all directions. Only the 200 m x 200 m grassland plot in the WFDS simulation is shown here.








The figure at left shows the steady state spread rate from the grassland simulations (symbols), BEHAVE (solid line), and from Eq. 4 in Cheney et al. (Prediction of Fire Spread in Grasslands, Int. J. Wildland Fire, 8: 1-13, 1998).  BEHAVE is the most commonly used fire spread prediction model in the U.S.


Vegetative fuels: Intermix of vegetative fuels leading transition to crown fire.
Many of today's forests have historically dense accumulations of dead fallen material which pose a fire threat to the overall ecology of the forest and nearby communities. An important question in forest management is, therefore, how much of this material should be removed to reduce the fire threat to acceptable levels. In the example below WFDS is used to simulate a surface fire spreading through a forested region part of which has underbrush.
Plan View
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Side View of Vegetative Fuel
In the above figures grass and pine needle fuel are colored green and black, respectively; the underbrush, tree trunks and tree crowns are colored blue. In the movies (see links below) this blue color changes according to the temperature of the fuel (red is hottest).

Fuel/Wind Specifications:
- grass fuel loading is NFFL 3 (tall grass, 0.674 kg/m^2)
- pine needles: 5 cm depth, 20 kg/m^3 bulk density
- underbrush: 0.5 m - 2.0 m height, 1 kg/m^3 bulk density
- tree crown: 7 m - 14 m height, 0.24 kg/m^3 bulk density (160 trees in 80 m x 80 m area)
- wind is 6 m/s from left to right

 Computational Specification:
- domain is 320 m x 320 m x 80 m (160x160x20 grid cells)
- horizontal grid resolution is 2 m, vertical is 2 m near ground and stretches to 8 m at top.

Animations from Smokeview:
- plan view quicktime movie (1.3 MB) showing fire spread
- tour view avi movie (15 MB) showing fire spread and smoke)

The animations clearly show the loss of tree crowns in areas where the underbrush was present and provided a ladder fuel for fire spread from the pine needles to the crowns. Additional information is in a talk given at the March 2004 Core Fire Science Caucas meeting in Reno, NV.



WFDS Simulation of a Stand Burn Similar to the International Crown Fire Experiment
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Two wall assemblies are placed 10 m and 20 m down spread of the stand. This mimics similar experiments performed during the International Crown Fire Experiments conducted in the Northwest Territories of Canada. The simulated stand is approximately 1/4 the size of the experimental stand. A movie of the simulation is here. Time histories of the radiant fluxes on the walls are shown in the movie. The magnitudes and duration of the rise to maximum value of the fluxes are similar to the experiment. 


Vegetative fuels: Simulation of surface fire spreading under tree

wfds_one_tree_movie.avi (8.5 MB)
Example of a fire spreading through an excelsior surface fuel under a 6 m tall conifer.



Vegetative fuels: Simulation of enclosure effects: excelsior fuel bed burning in a wind tunnel

Two different simulations were conducted. The two lower images in the figure above show a side view (on the left) of the wind tunnel and an end view looking downwind (on the right). The wind tunnel on the bottom row of the figure has the same cross-section (3 m x 3 m) dimensions as the experimental facility used by the USDA Foreset Service in their Missoula, Montana laboratory. The wind tunnel in the upper row has crossection dimensions which have been doubled (6 m x 6 m). Both wind tunnels are 16 m long. A fuel bed of excelsior 1 m wide, 8 m long and 20 cm tall is placed in the center of the wind tunnel floor. A 1.8 m/s wind blow from left to right. The fuel properties of the excelsior are from an experiment conducted by Catchepole et al. (Rate of Spread of Free-Burning Fires of Woody Fuels in a Wind Tunnel, Comb. Sci. Tech., 131, 1-37, 1998). The

As can be seen in the figure above and the movies (links are below) the walls and ceiling of the wind tunnel sufficiently confine the buoyant plume that the plume itself it acts as a barrier to the incoming flow.

Links to movies:
- fuel_bed_wind_tunnel.mpg (4.6 MB)
- fuel_bed_wind_tunnel.avi (12 MB)


Fire Behavior in the Intermix of Vegetative and Structural Fuels


Related searches:
spread wildland structure behavior burning
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