Metasurfaces and metagratings offers new platforms for electromagnetic wave
control with significant responses. However, metasurfaces based on abrupt phase
change and resonant structures suffer from the drawback of high loss and face
challenges when applied in water waves. Therefore, the application of
metasurfaces in water wave control is not ideal due to the limitations
associated with high loss and other challenges. We have discovered that
non-resonant metagratings exhibit promising effects in water wave control.
Leveraging the similarity between bridges and metagratings, we have
successfully developed a water wave metagrating model inspired by the Luoyang
Bridge in ancient China. We conducted theoretical calculations and simulations
on the metagrating and derived the equivalent anisotropic model of the
metagrating. This model provides evidence that the metagrating has the
capability to control water waves and achieve unidirectional surface water
wave. The accuracy of our theory is strongly supported by the clear observation
of the unidirectional propagation phenomenon during simulation and experiments
conducted using a reduced version of the metagrating. It is the first time that
the unidirectional propagation of water waves has been seen in water wave
metagrating experiment. Above all, we realize the water wave metagrating
experiment for the first time. By combining complex gratings with real bridges,
we explore the physics embedded in the ancient building-Luoyang Bridge, which
are of great significance for the water wave metagrating design, as well as the
development and preservation of ancient bridges.Comment: 25 pages, 13 figure