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 October 21, 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 October 21, 2014).

Share This



More Matter & Energy News

Tuesday, October 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Thanks, Marty McFly! Hoverboards Could Be Coming In 2015

Thanks, Marty McFly! Hoverboards Could Be Coming In 2015

Newsy (Oct. 21, 2014) If you've ever watched "Back to the Future Part II" and wanted to get your hands on a hoverboard, well, you might soon be in luck. Video provided by Newsy
Powered by NewsLook.com
Robots to Fly Planes Where Humans Can't

Robots to Fly Planes Where Humans Can't

Reuters - Innovations Video Online (Oct. 21, 2014) Researchers in South Korea are developing a robotic pilot that could potentially replace humans in the cockpit. Unlike drones and autopilot programs which are configured for specific aircraft, the robots' humanoid design will allow it to fly any type of plane with no additional sensors. Ben Gruber reports. Video provided by Reuters
Powered by NewsLook.com
Graphene Paint Offers Rust-Free Future

Graphene Paint Offers Rust-Free Future

Reuters - Innovations Video Online (Oct. 21, 2014) British scientists have developed a prototype graphene paint that can make coatings which are resistant to liquids, gases, and chemicals. The team says the paint could have a variety of uses, from stopping ships rusting to keeping food fresher for longer. Jim Drury reports. Video provided by Reuters
Powered by NewsLook.com
China Airlines Swanky New Plane

China Airlines Swanky New Plane

Buzz60 (Oct. 21, 2014) China Airlines debuted their new Boeing 777, and it's more like a swanky hotel bar than an airplane. Enjoy high-tea, a coffee bar, and a full service bar with cocktails and spirits, and lie-flat in your reclining seats. Sean Dowling (@SeanDowlingTV) has the details. Video provided by Buzz60
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:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

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