Scientists believe vortices allow water to flow uphill |
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Melbourne, May 31 ANI: In a new study, scientists believe they've discovered a process that allows water to flow uphill. Professor Ernesto Althsuler and colleagues from the University of Havana in Cuba noticed the phenomenon while drinking the Argentinean tea-like beverage mate. Mate is consumed by slowly pouring hot water through a spout from a pot onto a brew of dried and finely chopped yerba mate leaves in a cup or hollow gourd, and then sipped through a metal straw. The leaves tend to float on the surface of the brew, but occasionally a few, somehow travel upstream, ending up contaminating the pot. According to Althsuler, they weren't splashed or poured in, so some other force must be at work. Althsuler and fellow researchers repeated the procedure with chalk power, and found that the same thing happened. As long as the distance from the lip of the spout to the surface of the water in the cup was less than one centimetre, some of the particles floating on the surface would eventually climb upstream. Scientists have previously noticed vortices developing in horizontal liquid flows, which cause a counter flow along the edge of channels, carrying small particles in the opposite direction. But, Altshuler and colleagues say what's new is the idea that the vortices can continue generating a counter flow even after the water has fallen off the end of the spout and into the cup below. They say this counter flow lifts particles out of the lower container and into the upper one. Altshuler and colleagues speculate, the upstream vortex is being reinforced by a Marangoni effect associated with a decrease of the surface tension in the lower reservoir caused by increasing the amount of floating chalk dust or mate leaves. In 1865, Carlo Marangoni wrote about the tears of wine effect on a glass where evaporation of alcohol changes the surface tension of the liquid, causing a film of fluid to travel up the side of the glass. Professor Geoff Stevens from the University of Melbourne's Department of Chemical and Biomolecular Engineering says while it's possible, he doesn't think Marangoni effects, or the normal diffusion of the chalk or leaf particles from areas of high to low density are involved. "The paper doesn't give enough data to draw a conclusion, but a vortex effect may be enough on its own," ABC Science quoted Stevens as saying. "If the spout is too long relative to its width, the vortex will die out and you end up with a laminar flow. "But if the size ratio of the spout is right, you could get the vortex formation which could entrain some of that downstream flow back upstream. "Is that what's happening here I can't tell, he doesn't give enough information. It's an interesting experiment, but there's just not enough data in the paper to draw any conclusions," he stated. The study has been reported on the pre-press physics blog arXiv.org. ANI Posted by aniin on Wednesday Jun 01 reply Comments |
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