Nav: Home

Solving the riddle of the snow globe

May 25, 2017

If you've shaken a snow globe, you've enjoyed watching its tiny particles slowly sink to the bottom. But do all small objects drift the same way and at the same pace?

A new Tel Aviv University study finds the sedimentation of asymmetric objects in liquid is very different from that of symmetrical objects like spheres. The research solves a long-standing puzzle concerning the cause and the extent of "storminess" in sedimentation, and may be useful in improving water treatment and industrial processes that rely on suspensions, which are liquids that contain small solid particles. The research may also have use in the study of geological deposits, because variations in the concentration of particles from place to place affect the progress of sedimentation.

The research was led by Prof. Haim Diamant of TAU's School of Chemistry in collaboration with Prof. Thomas Witten of the University of Chicago, and conducted by TAU doctoral student Tomer Goldfriend. It was sponsored by the US-Israel Binational Science Foundation (BSF) and published in Physical Review Letters.

The calm and the storm

"Our research clarifies a common, complex phenomenon and offers ways of controlling it," Prof. Diamant said. "We have demonstrated that the 'storminess' of sedimentation is specific to symmetrical objects such as spheres and ellipsoids. It disappears in the more general case of asymmetric objects, which can have arbitrary shapes. Asymmetric objects render the sedimentation process more uniform and less chaotic."

Certain chemical reactors and water-treatment facilities rely on processes closely related to sedimentation, Prof. Diamant explained. "These are called 'fluidized beds,' where settling particles are made to hover in the liquid by an opposing upward flow of liquid, which facilitates their chemical activity. Fluidized beds are used in the production of polymers such as rubber and polyethylene. They are also used to improve the efficiency of water and waste treatment facilities. Our work might lead to improvements of such processes by controlling the uniformity of particles distributed in the liquid."

The team is currently studying the organizational properties of other kinds of materials. "We now intend to look for physical scenarios other than sedimentation that may show a similar kind of 'self-taming' -- that is, a tendency of the material's constituents to self-organize into extremely uniform configurations," Prof. Diamant said. "The basic question is whether the behavior that we have found is unique to the process of sedimentation or can be found in a much broader class of materials. We think -- we hope -- that the latter is true."
-end-
American Friends of Tel Aviv University (AFTAU) supports Israel's most influential, comprehensive and sought-after center of higher learning, Tel Aviv University (TAU). TAU is recognized and celebrated internationally for creating an innovative, entrepreneurial culture on campus that generates inventions, startups and economic development in Israel. For three years in a row, TAU ranked 9th in the world, and first in Israel, for alumni going on to become successful entrepreneurs backed by significant venture capital, a ranking that surpassed several Ivy League universities. To date, 2,400 patents have been filed out of the University, making TAU 29th in the world for patents among academic institutions.

American Friends of Tel Aviv University

Related Water Articles:

Source water key to bacterial water safety in remote Northern Australia
In the wet-dry topics of Australia, drinking water in remote communities is often sourced from groundwater bores.
Our water cycle diagrams give a false sense of water security
Pictures of the earth's water cycle used in education and research throughout the world are in urgent need of updating to show the effects of human interference, according to new analysis by an international team of hydrology experts.
Water management helped by mathematical model of fresh water lenses
In this paper, the homeostasis of water lenses was explained as an intricate interaction of the following physical factors: infiltration to the lens from occasional (sporadic) rains, permanent evaporation from the water table, buoyancy due to a density contrast of the fresh and saline water, and the force of resistance to water motion from the dune sand.
The age of water
Groundwater in Egypt's aquifers may be as much as 200,000 years old and that's important to know as officials in that country seek to increasing the use of groundwater, especially in the Eastern Desert, to mitigate growing water stress and allow for agricultural projects.
Water that never freezes
Can water reach minus 263 degrees Celsius without turning into ice?
More Water News and Water Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Erasing The Stigma
Many of us either cope with mental illness or know someone who does. But we still have a hard time talking about it. This hour, TED speakers explore ways to push past — and even erase — the stigma. Guests include musician and comedian Jordan Raskopoulos, neuroscientist and psychiatrist Thomas Insel, psychiatrist Dixon Chibanda, anxiety and depression researcher Olivia Remes, and entrepreneur Sangu Delle.
Now Playing: Science for the People

#537 Science Journalism, Hold the Hype
Everyone's seen a piece of science getting over-exaggerated in the media. Most people would be quick to blame journalists and big media for getting in wrong. In many cases, you'd be right. But there's other sources of hype in science journalism. and one of them can be found in the humble, and little-known press release. We're talking with Chris Chambers about doing science about science journalism, and where the hype creeps in. Related links: The association between exaggeration in health related science news and academic press releases: retrospective observational study Claims of causality in health news: a randomised trial This...