Academic journal article The Science Teacher

Foam Stops Sloshing Liquid

Academic journal article The Science Teacher

Foam Stops Sloshing Liquid

Article excerpt

Clinking your beverage glass often leaves its contents sloshing back and forth. Soon, though, the motion stops, your drink settles down, and you can take a sip without getting foam on your nose. It turns out that the foam helps stop the sloshing.


Now, physicists have figured out why. The analysis reveals a surprising effect on the surface of the water that contradicts conventional thought and deepens our understanding of the role of capillary forces.

Capillary forces describe everything from how ink fills up a fountain pen to how some insects can walk on water. They are the result of surface tension, which explains how droplets form and how the surface of a liquid adheres to the side of a container, forming a slope called a meniscus.

"Those capillary forces are small, but they're very important as soon as the sizes or motions get small," said Pierre-Thomas Brun of the Massachusetts Institute of Technology.

It's these effects, the researchers found, that dampen the sloshing of water covered by a layer of foam.

The new results, the researchers say, may eventually be used to prevent the sloshing of liquids in a container, such as fuel in a rocket tank or oil in a cargo ship, two situations in which sloshing could destabilize the vehicle. …

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