Wave Pattern in Cloaking Phenomenon Around a Body Surrounded by Multiple Vertical Circular Cylinders

For a special arrangement of multiple floating bodies, it is known that the wave drift force acting on a body surrounded by a finite number of bodies becomes zero at a certain frequency because of hydrodynamic interactions; this is related to the "cloaking" phenomenon. To study this phenomenon in more detail and its application to engineering problems, we have developed an accurate computer code and an optimization scheme using a genetic algorithm and presented some preliminary results. In this paper, a study is made of the wave pattern in the cloaking phenomenon and its relationship with the wave drift force. Specifically, we conducted the measurement of not only hydrodynamic forces but also the wave pattern around vertical circular cylinders of finite draft arranged in a cloaking configuration. Comparison is made between the numerical and measured results, and it is shown that when the geometric parameters of surrounding circular cylinders are optimized such that the total scattered-wave energy becomes minimal, the wave drift force reduces to nearly zero not only on the central cylinder but also on the outer surrounding cylinders individually.