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Scientists Create Water ‘Tractor Beam’



Australian scientists designed a wave generator aimed at manipulating floating objects.

The so-called “tractor beam” was able to control the movement of a ping-pong ball in a water tank by producing a specific pattern of waves, including the movement against the direction of the waves. It owes its name to science fiction, where it was a device used to manipulate objects from a distance.

Scientists of the Australian National University in Canberra, who published the results of their research in the Nature magazine, think that their tractor beam has the potential to find a number of different practical applications. In particular, the invention could help find new ways to solve some marine pollution problems, such as oil spills or floating debris. It could also be used in manipulating small boats and rescuing ships from sea accidents.

Dr. Horst Punzmann, who led the study, and his research team used a fast video camera to track the water movements in a water tank, and found the necessary frequency, speed and extent of the waves to keep a ping-pong ball floating and to control the direction of its movement. At the same time, the surface was covered with floating tracer particles aimed at tracking the direction of currents on the water surface and distinguishing them from the patterns of the waves themselves.

“We can engineer surface flows of practically any shape,” said Prof Michael Shats, the study’s senior author. “These could be vortices, these could be outward and inward jets – it’s a variety of different flow configurations.”

At the same time, there is still no mathematical model to explain this phenomenon, despite the fact that it is quite easy to reproduce. “It’s one of the great unresolved problems, yet anyone in the bathtub can reproduce it,” Punzmann said in a press release. “We were very surprised no one had described it before.” 

“We have figured out a way of creating waves that can force a floating object to move against the direction of the wave.”

We realized that particle motion on the surface, determined by waves, is far too complex to handle by any existing theory,” added Prof Shats.

Research link:

Featured image credit: Australian National University

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