Physicists create water tractor beam
Complex waves generate flow patterns that could be used to manipulate floating objects or explain rips at the beach
VIDEO: Physicists at the Australian National University have created a tractor beam in water. Using a simple wave generator they can create water currents which could be used to confine oil...
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Physicists at The Australian National University (ANU) have created a tractor beam on water, providing a radical new technique that could confine oil spills, manipulate floating objects or explain rips at the beach.
The group, led by Professor Michael Shats discovered they can control water flow patterns with simple wave generators, enabling them to move floating objects at will.
"We have figured out a way of creating waves that can force a floating object to move against the direction of the wave," said Dr Horst Punzmann, from the Research School of Physics and Engineering, who led the project.
"No one could have guessed this result," he said.
The new technique gives scientists a way of controlling things adrift on water in a way they have never had before, resembling sci-fi tractor beams that draw in objects.
Using a ping-pong ball in a wave tank, the group worked out the size and frequency of the waves required to move the ball in whichever direction they want.
Advanced particle tracking tools, developed by team members Dr Nicolas Francois and Dr Hua Xia, revealed that the waves generate currents on the surface of the water.
"We found that above a certain height, these complex three-dimensional waves generate flow patterns on the surface of the water," Professor Shats said. "The tractor beam is just one of the patterns, they can be inward flows, outward flows or vortices."
The team also experimented with different shaped plungers to generate different swirling flow patterns.
As yet no mathematical theory can explain these experiments, Dr Punzmann said.
"It's one of the great unresolved problems, yet anyone in the bathtub can reproduce it. We were very surprised no one had described it before."
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Physicists at the Australian National University have created a tractor beam in water.

A research team from the  have generated complex  driven by three-dimensional s. Their results show possibility of remote manipulation of  objects and were published in  this Sunday.

As Dr Horst Punzmann told ABC, "A  is a popular term which, I think it captures quite well the basic principle. You put an object there and it propagates, it floats backwards to the source of the wave".  Professor Michael Shats clarified that "We found that above a certain height, these complex three-dimensional waves generate  on the surface of the . The tractor beam is just one of the patterns, they can be inward flows, outward flows or ".

Professor Michael Shats spoke about the s: "First I thought it was impossible and I thought that it was the effect of the boundaries nearby. So the first idea was to build a bigger tank. We did, and it worked". As Dr Horst Punzmann noted, "The ability to move films on the ocean, like oil films... would be an opportunity". Professor Michael Shats explained that "The power requirements for the wave maker are relatively small because we generate only the motion in the top layer".

To  visualise the three-dimensional flows and ,  was used and help was provided to the researchers by . To create a figure of , finite-time  analysis was used.

This study was supported by the , the  and the  (BSF).


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