Coastlines could be protected by 'invisibility cloak'

Scientists at the University of Liverpool have tested an 'invisibility cloak' that could reduce the risk of large water waves overtopping coastal defences.

Mathematicians at Liverpool, working with physicists at the Centre National de la Recherche Scientifique (CNRS) and Aix-Marseille Universite have found that coastal defences could be made 'invisible' when water is guided through a special structure called metamaterial.

Metamaterial was first invented by Sir John Pendry at Imperial College London where scientists discovered that this unique structure could bend electromagnetic radiation – such as visible light, radar or microwaves – around a spherical space, making an object within this region appear invisible.

The new structure is cylindrical and consists of rigid pillars that help guide water along concentric corridors. The pillars interact with the water, guiding it in different directions along the corridors and increasing its speed as it nears the centre of the structure - similar to a whirlpool. The water waves, however, are never broken-up and exit the structure as though they had never been disturbed.

Dr Sebastien Guenneau, from the University's Department of Mathematical Science, explains: "Defending land against flooding and tidal waves is a big issue for scientists and engineers all over the world. Coastal defences have to withstand great forces and there is always a risk of water overtopping or penetrating these structures. Water crashes against these defences, breaking the wave and causing a lot of damage to roads and property hidden behind them.

"What is unique about this new structure is that it interacts with the water, guiding it to a particular destination rather than breaking it up and sending it everywhere. It is as though the defences are invisible to the wave and as such it does not recognise the structure as an obstacle. This makes it easier to manipulate water waves.

"We now need to investigate how to replicate this effect in a 'real' life situation to protect land from natural disasters such as tsunamis, and defend other structures such as oil rigs in the ocean."

The research is published in Physical Review Letters.

Source: University of Liverpool

   

• bearly - Oct 02, 2008
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  This sounds like it would also work as a "Star Trek" shield to protect anything.
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• Modernmystic - Oct 02, 2008
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  A bit off topic here but yes the principles might have implications for directed energy weapon deployment. This may be one area where the defense against a new weapon system is actually there before the weapon.
  
  However I believe at present the cloaks/shields they're using for EM radiation are generally only effective against a narrow frequency.
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• mattytheory - Oct 02, 2008
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  To my knowledge, current "cloaking" technologies are limited to the microwave wavelengths of the EM spectrum. However, this limitation is more probably due to the fact that optical wavelengths are a great deal shorter than those in the microwave range and therefore require a finer resolution - than current technology can account for - to create. The fact that the researchers in this study were able to extend the "cloaking" concept to waves of much larger wavelengths is on a level I would compare with Newton when he realized the same force pulling the apple to the ground kept the moon in orbit - pure genius.
  
  Though, from my own reflections on this subject, it may also be beneficial to develop a way to fully dissipate a wave, instead of allowing it to pass "around" a coastal defense structure. In the case of Hurricane Katrina, the levies that protected the people failed due to stress. By dissipating the waves, the overall stresses introduced to the levy structures are greatly reduced, thereby increasing their lifetime and overall efficacy. Maybe the answer is as simple as cement pillars placed in the water in an alternating "diamond" pattern.
  
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• vlam67 - Oct 02, 2008
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  I wonder where those monstrous waves typical of hurricanes are allowed to go after passing around the protected areas as if they are not there? As logic suggests the protected valuable properties are on the shoreline, to guide the waves away from it the water edge and beyond are going to be populated by meta-material structures. It's going to be quite popular to the beach side residents, I hope!
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• Arikin - Oct 03, 2008
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  Tokyo has major rivers that flow into the ocean. When a tsunami hits the excess water flowing up into the rivers is directed into a system of under ground over-flow rooms. Except these rooms are like the size of stadiums. Afterward, the water is released back into the rivers slowly.
  
  Working with nature instead of against it is always the best course.
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• Rick69 - Oct 03, 2008
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  If they are going to construct these structures anyway for this "cloaking" effect, they might as well also top them off with wind turbines or otherwise use them to capture wave energy or tidal energy.
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• flashgordon - Oct 03, 2008
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  I'm not sure I understand what they've done here; it almost sounds as if they've actually wormholed it . . . ?!
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