Institut Fresnel

Water wave cloaking

Researchers at Institut Fresnel have designed and experimentally tested in collaboration with the group of Bernard Molin at IRPHE the first large scale water wave invisibility carpet in a 17m meter long water wave channel (see upper figure, with the photo of the metamaterial carpet and numerical simulations illustrating the reduced disturbance of reflected wavefronts in the channel thanks to the carpet). Researchers at IF have also tested a cylindrical invisibility cloak for microwaves (see lower figure with the photo of the metamaterial cloak and numerical simulations illustrating the reduced disturbance of wavefronts both in reflection and transmission)), as well as for water waves in collaboration with the group of Alexander Movchan at Liverpool University and sound waves in collaboration with the group of Nicholas Fang at MIT).

Since then this topic has given rise to many proposals, including an invisibility carpet for water waves in collaboration with the group of Bernard Molin and Olivier Kimmoun at IRPHE (PhD Thesis of Guillaume Dupont, see right photo and simulation).
An innovation project is currently funded by SATTSE on ocean wave protection, which is accompanied by two patents filed in 2015 and 2016, respectively on water wave cloaks and dikes. This research also benefits from a funding from European Research Council (ERC Grant ANAMORPHISM: 2011-2016).

Selected publications
Numerical and experimental study of an invisibility carpet in a water channel
Guillaume Dupont, Olivier Kimmoun, Bernard Molin, Sébastien Guenneau, Stefan Enoch
Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, American Physical Society, 2015, 91, pp.023010.
Molding acoustic, electromagnetic and water waves with a single cloak
Jun Xu, Xu Jiang, Nicholas Fang, Elodie Georget, Redha Abdeddaim, Jean Michel Geffrin, Pierre Sabouroux, Stefan Enoch, Sébastien Guenneau
Scientific Reports, Nature Publishing Group, 2015, 5, pp.10678.
Cloaking a vertical cylinder via homogenization in the mild-slope equation
G. Dupont, S. Guenneau, O. Kimmoun, B. Molin, S. Enoch
Journal of Fluid Mechanics, Cambridge University Press (CUP), 2016, 796, pp. R1-R12. 10.1017/jfm.2016.249

Contact: S. Guenneau, S. Enoch and G. Dupont

Seismic cloaking

Using analogies between transformational plasmonics to control surface electromagnetic waves propagating at structured metal-dielectric interfaces and transformational elastodynamics to control Rayleigh waves propagating at the surface structured soils, it has been proposed by Sébastien Guenneau and Stefan Enoch in 2009 (see artistic view of Rayleigh waves detoured around a building by concentric layers of soil of varying density and Young modulus, right image) that vulnerable buildings could someday be shielded from damaging earthquakes by surrounding them with seismic invisibility cloaks.

A first prototype of such a cloak has been tested experimentally in 2012 by the soil dynamic team of Stéphane Brûlé and Emmanuel Javelaud at the civil engineering Ménard company (see left image by Stéphane Brûlé that shows the regular mesh of boreholes, 30cm in diameter with a center-to-center spacing of 170cm and the velocimeters used to measure surface wave velocities that are generated by the crane, and reflected by the boreholes thanks to a stop band around 50Hz).

In principle, the concept of seismic cloak could be extended to create protective barriers that divert earthquake energy away from sensitive facilities such as nuclear power plants, with columns of concrete buried in soil, or even above the soil, notably in alluvium basin where seismic site effects can be observed, see insert in left figure.
This research benefits from a funding from European Research Council (ERC Grant ANAMORPHISM : 2011-2016).

Selected publications
Experiments on Seismic Metamaterials: Molding Surface Waves
Stéphane Brulé, Emmanuel Javelaud, Stefan Enoch, Sébastien Guenneau
Physical Review Letters, American Physical Society, 2014, 112, pp.133901.
Controlling solid elastic waves with spherical cloaks
Andre Diatta, Sebastien Guenneau
Applied Physics Letters, American Institute of Physics, 2014, 105, pp.021901.

Contact: S. Guenneau, S. Enoch and S. Brûlé (Ménard: http://fr.viadeo.com/fr/profile/stephane.brule)