Most recent study: Leaves can burn even with 50 percent of their moisture present
- The BYU team was asked by the U.S. Forest Service to help improve the computer programs used to predict wildfire behavior.
- The lab uses a special device to simulate an approaching flame front.
- The researchers record how moisture, wind, and vegetation type affect burning.
A Brigham Young University professor and his students have been tapped by the U.S. Forest Service to fight wildfires, but not with axes and hoses. Instead, they use experimental fires in their lab to beef up and speed up the computer programs that predict where wildfires spread.
After nine years, seven peer-reviewed articles, dozens of presentations and lots of charred leaves and twigs, Thomas Fletcher, professor of chemical engineering, and his team are adding several components to the Forest Service’s existing models.
“This interaction of temperature and flow and chemistry has a real application that can help save lives and property,” Fletcher said. “Every time we run more experiments we learn new things that we hadn’t known before, things that nobody has ever seen.”
Because of the danger of studying real wildfires, Fletcher and his team created a simulated fire front in the lab—the only arrangement of its kind.
Students run the simulation by pumping a gas mixture (a combination of methane, hydrogen and oxygen) into what looks like a small lunar rover. The top of the rover is covered with a square foot of porous material that steadily allows gas to escape, creating a very uniform, 1,800-degree flame when lit.
A small pulley brings the flame-on-wheels toward different types of leaves and bushes to simulate an approaching wildfire. Students can also apply environmental effects such as wind to the flame and take measurements using, infrared cameras, oxygen sensors and – after the burn – moisture analyzers to safely predict how a fire will behave in the wild.
Most recently, Fletcher published an article in the International Journal of Wildland Fire detailing how a leaf can burn even with up to 50 percent of its moisture present. This previously unknown fact has serious ramifications for existing models, which often mistakenly factor in the additional time it takes for a leaf’s moisture to evaporate.
“Once a fire gets going, it doesn’t matter if you have wet leaves or bone-dry plants,” Fletcher said. “A big enough fire can ignite the leaves even though there still may be some moisture in the vegetation.”
Over the years, Fletcher and his team have focused on improving three aspects of fire models: the impact of moisture on fires, how wind affects flame and how flame spreads through shrubs.
Yes, Fletcher acknowledged with a chuckle, that last part means that BYU is in fact modeling “the burning bush.”
But this type of information is crucial to a fire boss, an individual who usually directs the efforts of firefighters and rescue personnel during large fires. The fire boss relies on available fire models to make quick and significant decisions about deploying resources.
“The model the fire boss usually runs on his laptop doesn’t have a lot of physics in it,” Fletcher said. “It runs fast and predicts something, but it’s not as good as it can be. We’re trying to improve that model so he can better understand where the fire is, where it’s going, which houses can be saved and where he can safely place firefighters.”
David Weise, supervisory research forester at the USDA Forest Service lab in Riverside, Calif., said Fletcher’s team complements others across the country working to improve the fire models.
“Tom’s fundamental work is providing us with information that can be used in our next generation of models,” Weise said. “The live fuels he’s working on are something we’ve found is important for us to look at, because our current models are dominated by dead fuels.”
McKaye Dennis, a senior chemical engineering major, worked in the lab for 18 months running experiments on how leaves burn under windy conditions.
“It’s rewarding and interesting to look at something that is so big on so small of a scale,” she said. “It’s great to stretch my capacity and learn about things I hadn’t had an opportunity to learn about before.”
Dallan Prince, a chemical engineering Ph.D. candidate and head of the wildland fire lab, has worked on a wide range of the projects done in the lab.
“In some labs you just do experiments all the time or program all the time, and that can get old,” he said. “In this lab we get a chance to do experiments and work with computers as well as share ideas with a larger group.”
That hands-on experience has given students who worked in the lab a leg up after graduation, leading some students to jobs with the Air Force Research Laboratory and several oil companies.
Fletcher and his team of five students, four of whom are undergraduates, hope to finish their improvements to existing models within the next year or two.
Writer: Jordon Trebas
