{"id":5123,"date":"2015-07-09T06:32:32","date_gmt":"2015-07-09T06:32:32","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=5123"},"modified":"2015-07-09T06:32:32","modified_gmt":"2015-07-09T06:32:32","slug":"why-do-puddles-stop-spreading","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/why-do-puddles-stop-spreading\/","title":{"rendered":"Why do puddles stop spreading?"},"content":{"rendered":"

Simple everyday phenomenon was unexplained by physics \u2014 until now.<\/strong><\/em><\/span><\/p>\n

\"MIT-Puddles-1\"<\/a>
\u201cYou start with something very simple, like the spread of a puddle, but you get at something very fundamental about intermolecular forces,\u201d Ruben Juanes says. Image: Jose-Luis Olivares\/MIT and Amir Pahlavan<\/figcaption><\/figure>\n

CAMBRIDGE, Mass<\/strong>— When you spill a bit of water onto a tabletop, the puddle spreads \u2014 and then stops, leaving a well-defined area of water with a sharp boundary.<\/span><\/p>\n

There\u2019s just one problem: The formulas scientists use to describe such a fluid flow say that the water should just keep spreading endlessly. Everyone knows that\u2019s not the case \u2014 but why?<\/span><\/p>\n

This mystery has now been solved by researchers at MIT \u2014 and while this phenomenon might seem trivial, the finding\u2019s ramifications could be significant: Understanding such flowing fluids is essential for processes from the lubrication of gears and machinery to the potential sequestration of carbon dioxide emissions in porous underground formations.<\/span><\/p>\n

The new findings are reported in the journal\u00a0Physical Review Letters<\/em>\u00a0in a paper by Ruben Juanes, an associate professor of civil and environmental engineering, graduate student Amir Pahlavan, research associate Luis Cueto-Felgueroso, and mechanical engineering professor Gareth McKinley.<\/span><\/p>\n

\u201cThe classic thin-film model describes the spreading of a liquid film, but it doesn\u2019t predict it stopping,\u201d Pahlavan says. It turns out that the problem is one of scale, he says: It\u2019s only at the molecular level that the forces responsible for stopping the flow begin to show up. And even though these forces are minuscule, their effect changes how the liquid behaves in a way that is obvious at a much larger scale.<\/span><\/p>\n

\u201cWithin a macroscopic view of this problem, there\u2019s nothing that stops the puddle from spreading. There\u2019s something missing here,\u201d Pahlavan says.<\/span><\/p>\n

Classical descriptions of spreading have a number of inconsistencies: For example, they require an infinite force to get a puddle to start spreading. But close to a puddle\u2019s edge, \u201cthe liquid-solid and liquid-air interfaces start feeling each other,\u201d Pahlavan says. \u201cThese are the missing intermolecular forces in the macroscopic description.\u201d Properly accounting for these forces resolves the previous paradoxes, he says.<\/span><\/p>\n

\u201cWhat\u2019s striking here,\u201d Pahlavan adds, is that \u201cwhat\u2019s actually stopping the puddle is forces that only act at the nanoscale.\u201d This illustrates very nicely how nanoscale physics affect our daily experiences, he says.<\/span><\/p>\n

Whether someone\u2019s spilled milk stops on the tabletop or makes a mess all over the floor may seem like an issue of little importance, except to the person who might get soaked, or have to mop up the spill. But the principles involved affect a host of other situations where the ability to calculate how a fluid will behave can have important consequences. For example, understanding these effects can be essential to figuring out how much oil is needed to keep a gear train from running dry, or how much drilling \u201cmud\u201d is needed to keep an oil rig working smoothly. Both processes involve flows of thin films of liquid.<\/span><\/p>\n

Many more complex flows of fluids also come down to the same underlying principles, Juanes says \u2014 for example, carbon sequestration, the process of removing carbon dioxide from fossil-fuel emissions and injecting it into underground formations, such as porous rock. Understanding how the injected fluid will spread through pores in rock, perhaps displacing water, is essential in predicting how stable such injections may be.<\/span><\/p>\n

\u201cYou start with something very simple, like the spread of a puddle, but you get at something very fundamental about intermolecular forces,\u201d Juanes says. \u201cThe same process, the same physics, will be at play in many complex flows.\u201d<\/span><\/p>\n

Another area where the new findings could be important is in the design of microchips. As their features get smaller and smaller, controlling the buildup of heat has become a major engineering issue; some new system use liquids to dissipate that heat. Understanding how such cooling fluids will flow and spread across the chip could be important for designing such systems, Pahlavan says.<\/span><\/p>\n

This initial analysis dealt only with perfectly smooth surfaces. In pursuing the research, Juanes says, a next step will be to extend the analysis to include fluid flows over rough surfaces \u2014 which more closely approximate the conditions, for example, of fluids in underground porous formations. \u201cThis work puts us in a position to be able to better describe multiphase flows in complex geometries like rough fractures and porous media.\u201d<\/span><\/p>\n

The work was supported by the U.S. Department of Energy.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Simple everyday phenomenon was unexplained by physics \u2014 until now. CAMBRIDGE, Mass— When you spill a bit of water onto a tabletop, the puddle spreads \u2014 and then stops, leaving a well-defined area of water with a sharp boundary. There\u2019s just one problem: The formulas scientists use to describe such a fluid flow say that […]<\/p>\n","protected":false},"author":6,"featured_media":5124,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-5123","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",639,426,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",639,426,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",639,426,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",639,426,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",639,426,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",639,426,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",639,426,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",600,400,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",600,400,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",639,426,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",540,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",639,426,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/MIT-Puddles-1.jpg",150,100,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/5123","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=5123"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/5123\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/5124"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=5123"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=5123"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=5123"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}