“Fire” and “tornado” are probably two of the scariest terms you can stick together. And yet fire tornados, alternatively known as “fire whirls,” exist. They typically happen during wildfires and can last a few minutes, though that’s long enough to do significant damage.
But a giant, uncontrollable firenado isn’t all bad, a team at the University of Maryland has discovered. Or at least not the newly observed version of the phenomenon that they recently described in the Proceedings of the National Academy of Sciences.
Dubbed the “blue whirl,” this smaller, more stable flame could have practical applications. “A fire tornado has long been seen as this incredibly scary, destructive thing,” co-author Michael Gollner, assistant professor of fire protection engineering at the University of Maryland says in a press release. “But, like electricity, can you harness it for good? If we can understand it, then maybe we can control and use it.”
Traditional fire whirls produced in forest fires or urban fires burn with a yellow color, which occurs when the fire is not able to completely consume its fuel and produces soot. Blue whirls, however, have access to more oxygen and completely combust their fuel, burning quickly and much more cleanly.
According to their paper, the researchers discovered the whirl while investigating the possibility of using fire whirls to clean up oil spills. As they produced the whirls using a stream of heptane gas pumped through a tray of water, they watched as the yellow swirl stabilized and settled into the stable blue phase. They believe that the stable blue whirl forms because of the water barrier.
Whirls over land, they explain, reach all the way down to the ground, but over the water the blue whirl sits above the liquid's surface. This is likely created by a layer of evaporated fuel mixed with air, giving the flame a nice supply of stable premixed fuel which the spinning vortex sucks up.
According to Nicole Orttung at The Christian Science Monitor, one of the current techniques for dealing with ocean oil spills is using booms to collect the oil before burning it off. The researchers believe that if they could produce a blue whirl it could burn up the oil without producing sooty emissions in the atmosphere or leaving a mess in the water.
Orrtung reports that the researchers were able to create a stable blue whirl in the lab for about eight minutes, though they believe they could sustain it much longer. Until they can produce giant oil-eating blue whirls, however, the technique for creating the flames in the lab is still useful, and will help researchers study vortexes and other elements of fluid mechanics.