In a new study published in the journal Physics of Fluids, a team of researchers has found that a few layers of foam can significantly dampen the sloshing motion of liquid.
Just a few layers of bubbles are enough to significantly decrease the height of the waves in a sloshing liquid. Image credit: Takeaway / CC BY-SA 3.0.
To test the damping power of foam systematically, the team, led by Prof Howard Stone of Princeton University, constructed a narrow rectangular container made of glass, which they filled with a solution of water, glycerol and the commercial dishwashing detergent Dawn.
By injecting air at a constant flow rate through a needle located at the bottom of the rectangular cell, the scientists created uniform layers of 3-mm-diameter bubbles.
“The dishwashing foam is very stable, which allowed us to conduct the experiments without the bubbles disappearing,” said co-author Dr François Boulogne, also from Princeton University.
The researchers experimented with two types of movements, either jolting the apparatus with a quick, side-to-side motion or rocking it steadily back and forth. They recorded the resulting waves with a high-speed camera.
They found that just five layers of foam were enough to decrease the height of the waves by a factor of ten.
Prof Stone and his colleagues believe that the foam dissipates the energy of the sloshing liquid through friction with the sides of the container.
More than five layers of bubbles did not add much additional damping, because the top layers of foam didn’t really move.
The scientists also found that bubbles that do not make contact with the walls of the container do not contribute much added damping.
They hope their research on foam may one day lead to cheap and easy ways to transport large amounts of fluids with minimal sloshing.
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A. Sauret et al. 2015. Damping of liquid sloshing by foams. Phys. Fluids 27, 022103; doi: 10.1063/1.4907048
