Measurements of Water-Wave Cloaking by an Array of Circular Cylinders

An experiment is performed to demonstrate water-wave cloaking of a surface-piercing cylinder by an array of eightsurrounding cylinders. The objective is to confirm cloaking for one wave number (5 rad m−1) and steepness (305%) bymeasuring the second-order mean drift force on the inner cylinder and the far-field surface elevation. The influences ofthe tank walls and viscous forces are explored, and uncertainties in the measured quantities are evaluated. A geometry isselected using a linear potential-flow solver coupled with an optimizer, and an apparatus is built for tank testing. For theconfiguration tested, tank-wall effects are important, but viscous forces and load-cell cross talk effects are small. Eliminationof the measured second-order mean drift force is observed with the addition of the outer cylinders. Experimental waveamplitudes are in agreement with numerical predictions at almost all measurement points.