Water tractor beam could contain oil spills

Physicists from The Australian National University (ANU) have created a tractor beam on water, which they can use to manipulate floating objects at will.

The team found that they can control water flow patterns with simple wave generators. 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.

“Above a certain height, these complex three-dimensional waves generate flow patterns on the surface of the water,” explained group leader Professor Michael Shats.

Dr Horst Punzmann and Professor Michael Shats test their wave-generated tractor beam. Photo by Stuart Hay.

The 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. Dr Horst Punzmann, who led the project, said, “We have managed to manipulate floating objects to move towards the wave, to move in the direction of the wave or to keep them stationary.”

Writing in the journal Nature Physics, the researchers noted, “The ability to send a wave to fetch an object from a distance would find a broad range of applications.” Professor Shats stated that the technique could be used to collect floating objects or boats - or even to contain oil spills.

It also suggests “new ideas about how rips on the beach can occur in the presence of strong, very steep waves”, he said.

The team also experimented with different shaped plungers to generate different swirling flow patterns, with Professor Shats noting, “It’s not just a tractor beam we can generate - we can generate, and we can engineer, surface flows of practically any shape.

“These could be vortices, these could be outward and inward jets - it’s a variety of different flow configurations.”

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