Broadband Waveguide Cloak for Water Waves

Inspired by electromagnetic waveguide cloaks with gradient index metamaterials, we fabricated a broadband cloak with simply a gradient depth profile on the bottom and without any other structures on the top to confine water waves in a certain area for cloaking regions. The new physics of mode conversion for water waves is first found. The experimental and numerical simulation results are in good agreement and show that the presented device has a nice performance for various situations and is feasible over a broadband of working frequencies. Being easy to construct, this design is potentially of significance for port applications.

Figure 1

The concept of a broadband cloak for water waves: (a) The schematic plot of the top view of the cloak device and three-dimensional sketch of GIMs. (b) The side view of the waveguide cloak with GIMs. (c) The experimental photographs of the real cloak device with two GIMs in the water tank.

Figure 2

Field patterns of water waves: (a) The numerically simulated results for $f=0.7\mathrm{Hz}$ and $h=0.15\mathrm{m}$. (b) The numerically simulated results for $f=0.7\mathrm{Hz}$ and $h=0.16\mathrm{m}$. (c) The measured results at the condition of $f=0.7\mathrm{Hz}$ and $h=0.16\mathrm{m}$.

Figure 3

Comparison between the experimental results and simulation results for various working frequencies, water depths, and incident amplitude: (a) working frequency response for $h=0.15\mathrm{m}$ and $A_a=1\mathrm{mm}$; (b) working frequency response for $h=0.16\mathrm{m}$ and $A_a=1\mathrm{mm}$; (c) water depth influence for $f=0.7\mathrm{Hz}$ and $A_a=1.2\mathrm{mm}$; (d) incident amplitude influence for $h=0.16\mathrm{m}$ and $f=0.7\mathrm{Hz}$.

Figure 4

The simulated field pattern and field amplitude of the designed wharf for the case of $f=0.9\mathrm{Hz}$ and $h=0.16\mathrm{m}$ for (a) a plane wave incidence and (b) a point source.