Based on their findings, the authors advocate pouring scorching water over your coffee grounds slowly to offer the beans extra time immersed in the water. But pour the water too slowly and the ensuing jet will persist with the spout (the “teapot impact”) and there will not be adequate mixing of the grounds; they will simply settle to the backside as a substitute, lowering extraction yield. “If you have a thin jet, then it tends to break up into droplets,” stated co-author Margot Young. “That’s what you want to avoid in these pour-overs, because that means the jet cannot mix the coffee grounds effectively.”
Smaller jet diameter influence on dynamics.
Credit:
E. Park et al., 2025
That’s the place rising the height from which you pour is available in. This imparts extra power from gravity, per the authors, rising the mixing of the granular coffee grounds. But once more, there’s such a factor as pouring from too great a height, inflicting the water jet to interrupt aside. The perfect height is not more than 50 centimeters (about 20 inches) above the filter. The traditional goosenecked tea kettle seems to be perfect for attaining that optimum height. Future analysis may discover the results of various the grain dimension of the coffee grounds.
Increasing extraction yields and, by extension, lowering how a lot coffee grounds one makes use of issues as a result of it’s changing into more and more tough to domesticate the commonest species of coffee due to ongoing local weather change. “Coffee is getting harder to grow, and so, because of that, prices for coffee will likely increase in coming years,” co-author Arnold Mathijssen advised New Scientist. “The idea for this research was really to see if we could help do something by reducing the amount of coffee beans that are needed while still keeping the same amount of extraction, so that you get the same strength of coffee.”
But the potential functions aren’t restricted to brewing coffee. The authors observe that this identical liquid jet/submerged granular mattress interaction can also be concerned in soil erosion from waterfalls, for instance, in addition to wastewater therapy—utilizing liquid jets to aerate wastewater to reinforce biodegradation of natural matter—and dam scouring, the place the strong floor behind a dam is slowly worn away by water jets. “Although dams function on a a lot bigger scale, they might endure related dynamics, and discovering methods to lower the jet height in dams might lower erosion and elongate dam well being,” they wrote.
Physics of Fluids, 2025. DOI: 10.1063/5.0257924 (About DOIs).