Sand can behave like water

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Washington, June 25 (ANI): A new study by researchers at the University of Chicago has shown that sand can behave like water, in the sense that both share similar properties.

The researchers showed that dry granular materials such as sands, seeds and grains have properties similar to liquid, forming water-like droplets when poured from a given source.

The finding could be important to a wide range of industries that use "fluidized" dry particles for oil refining, plastics manufacturing and pharmaceutical production.

In a first-time accomplishment, physicists from the Materials Research Science and Engineering Center at the University of Chicago, led by Professor Heinrich M. Jaeger, used high-speed photography to measure minute levels of surface tension and detect droplet formation in flows of dry granular materials.

Until recently, studies of so-called "free falling granular streams" tracked shape changes in flows of dry materials, but were unable to observe the full evolution of the forming droplets or the clustering mechanisms involved.

"Previous studies of granular streams were able to detect clustering by performing experiments in vacuum and were able to establish that the clustering was not caused by the drag from the ambient air," said Jaeger. "However, the cause of the clustering remained a mystery," he added.

But in this new experiment, researchers measured nanoscale forces that cause droplet formation using a special co-moving apparatus devised for a high-speed, 80,000 dollars camera that captures images much like a skydiver might photograph a fellow jumper in free fall.

They observed falling 100-micrometer-diameter glass beads, or streaming sand, and found that forces as much as 100,000 times smaller than those that produce surface tension in ordinary liquids could cause droplet formation in granular streams and cause these dry streams to behave like an ultra-low-surface-tension liquid.

John Royer, the graduate student in physics at the University of Chicago, who developed the apparatus, and his colleagues also directly measured grain-to-grain interactions with an atomic force microscope.

"At first we thought grain-grain interactions would be far too weak to influence the granular stream," said Royer.

"The atomic force microscopy surprised us by demonstrating that small changes in these interactions could have a large impact on the break up of the stream, conclusively showing that these interactions were actually controlling the droplet formation," he added.

According to researchers, understanding how dry materials coalesce could create greater efficiencies in their transportation and manipulation. (ANI)

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