University of Chicago researchers recently 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.
Researchers previously thought dry particles lacked sufficient surface tension to form droplets like ordinary liquids. But, 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.
The science journal Nature reports the finding in its June 25 issue. The materials research center at the University of Chicago is supported by the National Science Foundation.
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.
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."
Source: National Science Foundation. http://www.nsf.gov/news/news_summ.jsp?cntn_id=114907&org=NSF&from=news
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