For over a century, physicists such as Richard Feynman have been intrigued by a question concerning fluid dynamics: How would a sprinkler rotate if it was submerged underwater, drawing in water rather than expelling it? A team of researchers has finally provided an answer to this long-standing question.Alex Winter on the Most Important Modern Horror Movie While the concept was originally suggested in the 1880s, it gained attention again in the mid-20th century when Feynman discussed it, and became known as “Feynman’s sprinkler”. The issue at hand was whether a reverse sprinkler would rotate at all, as opposed to a regular sprinkler which expels water and spins to distribute water. Despite numerous attempts to address this question, it remained unanswered.Feynman explored this idea and even attempted to conduct an experiment as a graduate student at Princeton. However, the experiment came to an abrupt end when a large water-filled bottle exploded.A team of researchers at New York University revisited the idea with a new experimental setup. The reverse sprinkler setup involved a submerged sprinkler on an “ultra-low-friction” bearing to ensure smooth rotation, allowing for easy observation of water flow. The team also added dye and microparticles to the water, illuminated it with bright green lasers, and recorded the experiment using high-resolution, high-speed cameras. The resulting footage revealed the behavior of the water flow within the reverse sprinkler.Watch what happens when fluid is sucked into a sprinkler | Science NewsThe team’s findings, published in Physical Review Letters, confirmed that a reverse sprinkler does indeed rotate in the opposite direction to a regular sprinkler. Lead author of the study, Leif Ristroph, explained that while a regular sprinkler operates similar to a rocket by propelling itself through water ejection, the reverse sprinkler functions differently, with water jets inside the sprinkler explaining its motion. Despite rotating in reverse, the reverse sprinkler operates at only about 1/50th the speed of a regular sprinkler. The collision of the water jets inside the reverse sprinkler leads to its slow rotation.Co-author Brennan Sprinkle from the Colorado School of Mines suggested that the experimental methods used in this study could be beneficial for practical applications involving devices responding to flowing air or water.After 140 years, the mystery posed in the 1880s has finally been solved through precise testing and modeling that was not previously feasible. This discovery offers an intriguing topic to incorporate into discussions about fluid dynamics.More: Intruder-Blasting Sprinkler Is an AI-Powered Substitute for an Old Man Yelling at Kids to Get Off His Lawn
