A typical lawn sprinkler has various nozzles placed at an angle on a rotating wheel. When water is pumped, a jet is released, causing the wheel to rotate. But what happens if the water is sucked into the sprinkler instead? In which direction does the wheel then turn, or does it even turn at all? That’s the essence of “.”reverse sprinkler“This is a problem that physicists, especially Richard Feynman, have been working on since the 1940s. Now, applied mathematicians at New York University think they have solved the puzzle.” recent papers The answer called into question conventional wisdom on the subject.
“Our research solved the problem by combining precise laboratory experiments with mathematical modeling that explains how reverse sprinklers work.” Co-author Leif Ristlov said: from the Courant Institute, New York University. “We found that reverse sprinklers rotate in ‘reverse’ or opposite directions when taking in water and when discharging water. The reasons for this are subtle and surprising.”
Ristoroff’s lab frequently tackles these kinds of colorful real-world puzzles.For example, back in 2018, Risttroph and his colleagues Tweak A perfect lather recipe based on experiments using a thin soapy film. (Requires a circular cane with a circumference of 1.5 inches and a constant he blow slowly at 6.9 cm/s.) In 2021, Risttroph lab Examined The formation process underlying the so-called “stone forests” common in certain regions of China and Madagascar. These sharp rock formations are like the famous rocks. stone forest Located in China’s Yunnan province, this material is the result of the dissolution of solids into liquids in the presence of gravity, resulting in natural convection.
In 2021, his lab will I made a moving Tesla valve, measured the flow of water in both directions through the valve at different pressures according to the inventor’s design. They found that water flows about twice as slowly in the unfavorable direction. And he was in 2022, Listorov studied. Extremely complex aerodynamics We will discuss what makes a good paper airplane, especially what is needed for smooth glide. They discovered that the aerodynamics of paper airplanes are very different from traditional aircraft, which rely on their airfoils to generate lift.
The reverse sprinkler problem is associated with Feynman because he popularized the concept, but it actually dates back to a chapter in Ernst Mach’s 1883 textbook. science of mechanics (“Die Mechanik” in “Ihrer Entwicklung Historisch-Kritisch Dargerstelt”). Mach’s thought experiment remained relatively unknown until a group of physicists at Princeton University began discussing the problem with him in the 1940s.
Feynman was a graduate student there at the time, enthusiastically participating in discussions and even devising an experiment in the cyclotron laboratory to test his hypothesis. (In true Feynman style, the experiment culminated in an explosion due to the high internal pressure of the glass carboy used within the device.)
Some people may intuit that reverse sprinklers work just like regular sprinklers, only playing in the opposite direction, so to speak. But the physics turned out to be more complicated. “The answer is self-explanatory,” Feynman wrote. You must be kidding, Mr. Feynman. (1985). “The problem is that some people think it’s perfectly obvious [that the rotation would be] In one direction, another guy will think it’s completely obvious in another direction. ”