From the authors of Phys. Rev. E 89, 023012, published 19 February:
Experiments show that features on the seafloor in shallow water can focus waves, just as glass lenses focus light waves.
Glass lenses can focus light at a focal point. Here we show that small features added to the
seafloor can result in a similar lens for overpassing oceanic waves. These
seafloor features are typically in the shape of curved sandbars, and the effect
is a result of a nonlinear interaction between surface waves and bottom
undulations which is known as “Bragg Resonance”. Wave lensing may substantially contribute to the efficiency
of ocean wave energy devices by providing localized high-energy wave zones.
Therefore instead of many small and low-efficiency wave energy devices
dispersed over a wide area, one (relatively large/high efficiency) device can
be placed at the focal point receiving the entire energy of the initial area.
This should be of interest of the environment and also the sea transportation
as the covered surface of the sea is significantly reduced. Wave lensing can also be used to create artificial surf
zones. It may have applications, by dispersing wave rays (a convex lens), in creating
localized safe havens for fishermen and sailors in open seas, or if implemented
in large scales to protect shores and harbors against strong storm waves. Quiet
beaches and open-sea water parks are other potential application of the gravity
wave lensing. The idea may be also used as a guideline for proper placement of
(nearshore) facilities particularly in the areas with substantial bottom
variations. The efficiency of the idea is particularly stronger over the
shallower waters of continental shelves.
Videos:
1- Surface Gravity Wave Lensing, direct simulation:
http://www.youtube.com/watch?v=0XcPOEaEFWg
2- Raw footage of the experiment at
Richmond Field Station (above):
http://www.youtube.com/watch?v=6dHG7jNC_nc
3- Comparison of Numerical Simulation and Experiment:
http://www.youtube.com/watch?v=3ArPkKMN7aE
