Cloaking the coast

Mathematicians at Liverpool University, working with physicists at the Centre National de la Recherche Scientifique (CNRS) and Aix-Marseille Universite, have designed and tested a new structure that could reduce the risk of large water waves overtopping coastal defences.

The new structure is cylindrical and consists of rigid pillars that 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.

'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 property hidden behind them,' said Sebastien Guenneau, from Liverpool University’s Department of Mathematical Science.

What is unique about the new structure is its interaction 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.