How fires spread: UK study brings new insight

Aug 23, 2013
Photos taken inside the wind tunnel show the "peak and valley" structure of flames, looking upwind. In the top image, flames are approximately 0.15 meters (6 inches) tall. In the bottom image, flames approximately 2 meters (6.5 feet) tall.

University of Kentucky researchers are helping to gain insight into how fire spreads, knowledge that could help forestry officials develop more effective strategies for containing wildfires.

Kozo Saito, director of UK's Institute of Research for Technology Development (IR4TD) and the Tennessee Valley Authority Professor in Mechanical Engineering, led the research effort, in collaboration with the U.S. Department of Agriculture's Missoula Fire Science Laboratory. Working alongside Saito at UK were mechanical engineering Professor Nelson Akafuah and graduate students Brittany Adam and Justin English.

The study suggests that the intensity of heat radiating from is not sufficient to ignite fine fuel particles, such as pine needles and grasses. Rather it is the intermittent convection of intense heat from the flames themselves that heats these particles to the ignition point.

Researchers also discovered that the ignition of wood depends on a critical rate of converting solid mass to combustible gas, and that ignition depends on and wind flow. Recent experiments also demonstrate that this critical rate is a function of the moisture content of the fuel.

The model fuel bed, made up of laser-cut cardboard strips arranged in rows of "combs."

The team constructed virtual "forests," made up of laser-cut cardboard strips arranged vertically at regular spacings into rows resembling large combs. The strips were created at different lengths and widths and arranged at different row spacings to achieve specific fuel bed properties. The size of the completed fuel beds ranged from 4-8 feet in width and 10-20 feet in length.

These cardboard forests were then burned in the wind tunnel at the Missoula Fire Sciences Laboratory, under varying . An array of 64 thermocouple sensors recorded temperatures throughout the fuel bed, taking 500 readings per second as the flames spread. The thermocouples recorded a fluctuating flame presence, creating a temperature that alternated from near-ambient temperature to more than 1,200 deg. C. (2,192 deg. F.) several times per second.

U.S. forestry officials say that, despite the advanced computer models used in fire management, the physical processes responsible for flame spread are poorly understood. This research suggests a completely new approach to understanding and modeling fire spread, and creates new opportunities for developing models that can be used for fire-management applications.

The team's findings were presented at the Seventh International Symposium on Scale Modeling, held Aug. 6-9, in Hirosaki, Japan.

Explore further: Dutch unveil big plan to fight rising tides

add to favorites email to friend print save as pdf

Related Stories

NASA image: Fires in eastern Russia—Urals and Siberia

Aug 16, 2013

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite detected dozens of fires burning in eastern Russia in this satellite image captured on August 15, 2013. The fires are outlined ...

NASA image: Fires in Idaho and Montana

Aug 21, 2013

Fires that started in July continue on in late August in Idaho and Montana. Actively burning areas, detected by the Moderate Resolution Imaging Spectroradiometer's (MODIS) thermal bands, are outlined in red.

FLEX-ible insight into flame behavior

Nov 30, 2011

(PhysOrg.com) -- Whether free-burning or smoldering, uncontrolled fire can threaten life and destroy property. On Earth, a little water, maybe some chemicals, and the fire is smothered.

Recommended for you

Red tide off northwest Florida could hit economy

47 minutes ago

It's like Florida's version of The Blob. Slow moving glops of toxic algae in the northeast Gulf of Mexico are killing sea turtles, sharks and fish, and threatening the waters and beaches that fuel the region's ...

Dutch unveil big plan to fight rising tides

11 hours ago

The Netherlands on Tuesday unveiled a multi-billion-euro, multi-decade plan to counter the biggest environmental threat to the low-lying European nation: surging seawater caused by global climate change.

Drought hits Brazil coffee harvest

14 hours ago

Coffee output in Brazil, the world's chief exporter, will slide this year after the worst drought in decades, agricultural agency Conab said Tuesday.

User comments : 0