This summer has been hot. In fact, it has been so hot that my kids swimming pool started on fire! Well, to be honest, the fire wasn't by accident, I started it as an experiment to see if I could make a giant fire tornado using the kiddie pool, the fire pit, and some garden tools. Turns out, I was successful!
How did this happen? I was working on a video (BealsScience YouTube) to show the Desktop Fire Tornado Demonstration that I do in my classroom and at STEM Magic Shows to talk about fire science when I had an idea: I have been thinking about making a giant version of the fire tornado but was hung up on how to build it when I looked out in the back yard and saw a leaf floating in the kids swimming pool. Next to the pool was the fire pit. A light went on in my head and I realized that the fire pit bowl should float in the water. Because it would be buoyant and have very little friction, it should spin and it will remain in motion for some time. The rest is history!
What is a fire tornado?
A fire tornado can occur naturally during an intense fire because the immense heat rises very quickly away from the burning surface. As it rises it begins for form whirling eddies, spinning vortices of air, which pulls in more fuel and oxygen, thus causing the flame to reach even higher. Fire tornadoes that have occurred during wildfires have been known to reach a kilometer into the sky (a little more than half a mile)!
How does the fire tornado in the pool work?
In the video you will see the fire pit rotate with the bucket of fire but there is no fire tornado. This is because air is rushing in from all angles as the fire burns and pulls heated air upward. In order to get a firenado (fun name for fire tornado) the air must start to rotate into a vortex. The screen mesh allows air to move in toward the flame and up the column of fire. When the screen mesh is rotated, the air passing through the small holes from the outside begin to rotate as they move in toward the flame; the spinning causes all of the air to experience angular momentum (rotation). This rotation brings in more air and more flammable vapors from the white gas in the bucket forming...you guessed it...a fire tornado - in a kiddie pool!
Is the giant firenado in the kids pool is a little too extreme for your taste? If so, check out the tabletop version (click here). Now you can 'wow' your officemates with by creating a fire tornado on the bosses desk! Feel free to use that last "Performance Evaluation" your boss gave you as fuel...