While the fire is one of the oldest human technologies, constructing a bonfire—and keeping it safe—is not always simple. After gathering dry wood or twigs from your campground, you must select how to arrange them for the best burn. Is placing them in a log cabin-like stack the best option? Or how about throwing them all together and seeing what happens?
There are several ways to organize your fuel source in theory, but according to Adrian Bejan, a professor of mechanical engineering at Duke University, there is only one sure-fire way: your fuel should be piled as high as it is broad, like a pyramid. It’s no accident that a pyre and a pyramid sound so similar, according to Bejan.
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Despite the fact that this ideal answer has been lurking in plain sight for millennia, Bejan published the mathematical formula for it in the journal Scientific Reports in 2015. Bejan explains, “I was able to sort it out as a homework issue for my kids.” “One evening, it took nearly two hours.”
Why Is Fire Like Swiss Cheese?
He claims that the answer begins with knowing what type of science governs how fires burn. This is a complex subject but ultimately boils down to two major contenders: thermodynamics and fluid dynamics.
Bejan tells Popular Mechanics, “Thermodynamics is the science of power, [in this instance] power from fire.” “Which is then utilized to move objects [such as air]… The airflow feeds the combustion process, while the heat created is convected away by the airflow.”
A fire can be compared to a slice of Swiss cheese. There are several holes or spaces that air may pass through between different pieces of fuel (whether coal, wood or another source). If your fire is packed too tightly, no air can pass through to cause combustion; if your fuel is packed too loosely, no air can travel swiftly. According to Bejan, the technical word for this type of hole-filled structure is “porous media.”
Bejan, on the other hand, claims that conical-shaped flames aren’t the sole useful form. He claims that as long as this width-to-height ratio is maintained, the form of the fire has no true limit.
A Firefighter’s Advice
According to Daniel Jimenez, a research engineer at the Missoula Fire Sciences Laboratory, understanding the mathematical concepts underlying fire building is simply the beginning. Understanding the arithmetic involved in keeping a fire safe—and properly extinguishing it—is critical not only for firemen but also for nature enthusiasts.
Jimenez’s employment requires him to assist facilitate an online course that teaches firefighters the mathematics underlying the fires they fight.
“Most of our course’s math is really simple geometry,” Jimenez tells Popular Mechanics. “However, when you start thinking about quantities and pressures and [water] distribution systems, it becomes a lot more complex.”
While some firemen enter the profession after college and have a background in physics and math, Jimenez notes that it is also usual for others to enter the profession right out of high school. This online course contributes to the development of a common ground of science- and math-based knowledge to keep firefighters safe and smart on the job.
Jimenez also creates mathematical modeling tools to assist firefighters in tracking the progress of wildfires. This app- and computer-based software can incorporate landscape and wind models, and they can replace what were once printed pocket-size guides. This allows firefighters to not only put out fires but also conduct safe, planned burns, which can help avoid uncontrolled blazes later in the season.
When it comes to keeping your mathematically-perfect campfire safe, Jimenez thinks the answer is simple: containment. Jimenez believes that ensuring your fire’s fuel supply is discontinuous, or that there is no stray fuel around the fire, is an effective strategy to guarantee it doesn’t mistakenly extend beyond its base.
A metal fire pit is one simple method to accomplish this, but you may also set your fire on dirt or near a fire blanket. And, before you leave your fire, make sure to turn off the thermodynamics by dousing it with water.
“If I had any advice for anyone with a campfire, I would tell them to drown,” Jimenez adds. “A campfire can never have too much water.”