Featured Research

from universities, journals, and other organizations

Simulations Reveal Morphological Transition In Simple Foams

Date:
February 8, 2000
Source:
University Of Illinois At Urbana-Champaign
Summary:
By deriving an equation of state for compressible foam, and then simulating it numerically, University of Illinois researchers predict a dramatic morphological change that will occur as the surface tension is increased or, equivalently, the volume of the foam is greatly expanded. Foams are ubiquitous in nature and widely used in industry, from foamy foods such as bread and ice cream to foamy materials such as plant stems, bones, magma and foam rubber.

CHAMPAIGN, Ill. -- By deriving an equation of state for compressible foam, and then simulating it numerically, University of Illinois researchers predict a dramatic morphological change that will occur as the surface tension is increased or, equivalently, the volume of the foam is greatly expanded. Foams are ubiquitous in nature and widely used in industry, from foamy foods such as bread and ice cream to foamy materials such as plant stems, bones, magma and foam rubber. All foams have one characteristic in common: the bubble-delimiting films minimize surface energy by encapsulating the largest volume using the least amount of material.

"In a common liquid foam, like a soap froth, the elastic energy in the films is negligible compared to the work required to compress the air in the bubbles," said Hassan Aref, professor and head of the theoretical and applied mechanics department. "The individual bubbles, which are often of roughly comparable size, retain constant volumes, except for the slow redistribution of gas by diffusion or the rupturing of films between bubbles. If you imagine greatly enhancing the surface tension, however, the elastic energy in the films will compress most of the bubbles, leading to a very different structure." To investigate this phenomenon, Aref and graduate student Dmitri Vainchtein first derived the equation of state for compressible foam. "This equation shows that foam with a free boundary will expand to a maximum volume if the external pressure is lowered at constant temperature," Aref said. "The equation also suggests that the same foam -- when enclosed in a container -- can be expanded further, but will become unstable at a certain volume that we can predict."

Though difficult to explore experimentally, the nature of the instability was revealed in a series of numerical simulations. "We found that as the surface tension increased, the overall structure of the foam changed dramatically," Aref said. "We observed what may be described as two 'phases' of foam. In one phase we have a large number of small bubbles clustered together. In the other phase we must then have a small number of much larger bubbles that occupy most of the space in the container."

The increased surface tension appears to compress most of the bubbles, forcing the remaining bubbles to expand to fill the space, Aref said. This phenomenon might provide a model for the undesirable formation of large voids in solidifying foams, including those that form when baking bread. "As bread is baked, the bubble membranes begin to harden, which may roughly correspond to an increase in surface tension," Aref said. "The resulting segregation instability results in a loaf that contains clusters of tiny bubbles embedded in a background of a few much larger bubbles."

While of little consequence in bread, the formation of large voids can be a nuisance in products like foam rubber, where a homogeneous texture is desired. "A better understanding of this phenomenon could lead to more precise process control in the manufacturing environment," Aref said.

The researchers reported their findings in the December issue of Physics of Fluids.


Story Source:

The above story is based on materials provided by University Of Illinois At Urbana-Champaign. Note: Materials may be edited for content and length.


Cite This Page:

University Of Illinois At Urbana-Champaign. "Simulations Reveal Morphological Transition In Simple Foams." ScienceDaily. ScienceDaily, 8 February 2000. <www.sciencedaily.com/releases/2000/02/000208074838.htm>.
University Of Illinois At Urbana-Champaign. (2000, February 8). Simulations Reveal Morphological Transition In Simple Foams. ScienceDaily. Retrieved August 1, 2014 from www.sciencedaily.com/releases/2000/02/000208074838.htm
University Of Illinois At Urbana-Champaign. "Simulations Reveal Morphological Transition In Simple Foams." ScienceDaily. www.sciencedaily.com/releases/2000/02/000208074838.htm (accessed August 1, 2014).

Share This




More Matter & Energy News

Friday, August 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Tesla, Panasonic Ink Deal To Make Huge Battery 'Gigafactory'

Tesla, Panasonic Ink Deal To Make Huge Battery 'Gigafactory'

Newsy (July 31, 2014) The deal will help build a massive battery factory that Tesla says will produce 500,000 lithium batteries by 2020. Video provided by Newsy
Powered by NewsLook.com
Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
7 Ways to Use Toothpaste: Howdini Hacks

7 Ways to Use Toothpaste: Howdini Hacks

Howdini (July 30, 2014) Fresh breath and clean teeth are great, but have you ever thought, "my toothpaste could be doing more". Well, it can! Lots of things! Howdini has 7 new uses for this household staple. Video provided by Howdini
Powered by NewsLook.com
Smoked: 2015 Ducati Diavel Vs 2014 Chevy Corvette Stingray Drag Race

Smoked: 2015 Ducati Diavel Vs 2014 Chevy Corvette Stingray Drag Race

Cycle World (July 30, 2014) The Bonnier Motorcycle Group presents Smoked; a three part video series. In this episode the 2015 Ducati Diavel takes on the 2014 Chevy Corvette Stingray Video provided by Cycle World
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins