Scientists discover why bubbles zig-zag as they rise through water

"The moment of inertia was completely ignored in the past, which explains the confusion and lack of understanding of the zig-zag," researchers wrote in a newly published study.
By Brooks Hays  |  Aug. 17, 2017 at 9:51 AM
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Aug. 17 (UPI) -- Until now, scientists have struggled to explain the zig-zagging motion of air bubbles rising through water. New research suggests patterns can be explained by the bubbles' rotation.

Scientists have known of the phenomenon since the 1600s, when Leonard Da Vinci first documented bubbles' nonlinear tendencies. But for four-plus centuries, researchers have failed to explain it.

Experiments by scientists at the researchers at the University of Twente in the Netherlands and Tsinghua University in Beijing, China, suggests the "moment of inertia" can explain the zig-zagging motion of rising bubbles.

The moment of inertia is a complex rotational measurement describing the ratio of an object or system's angular momentum to its angular velocity around an axis.

"The moment of inertia was completely ignored in the past, which explains the confusion and lack of understanding of the zig-zag and spiraling of buoyant particles," researchers wrote in their paper on the subject, published this week in the journal Physical Review Letters.

Scientists suggest a deeper exploration of the moment of inertia could help explain the movements of other spinning balls, especially sports balls -- the dip of a tennis ball on a top-spin serve, the swerve of a banana kick in soccer or the unpredictability of a knuckleball in baseball.

"Beyond the curiosity-driven part, the result will also be useful to a variety of physics and engineering communities," researchers explained in a news release. "In chemical engineering, the mixing induced by zig-zagging particles is very important."

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