For a special arrangement of multiple floating bodies, it is known that body-generated waves will be confined inside of the bodies due to hydrodynamic interactions; which is referred to as ‘cloaking’ phenomenon. In order 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 GA (genetic algorithm) and presented some results for the diffraction problem. In the present paper, the floating body to be cloaked is assumed to be freely oscillating in regular waves and multiple bodies surrounding the central body are assumed to be controlled with an external dynamic system with damping and restoring forces. Study is made on the energy conservation relation and the scattered and radiation wave patterns when the cloaking is realized and also on the absorption of wave energy through the work done by the external force of damping installed in the surrounding cylinders.
In recent years, structures with complex shape or multiple floating bodies are increasing for the purpose of marine energy utilization. The wave drift force on these structures may increase by hydrodynamic interaction effects, and especially in the case of multiple floating bodies they may collide each other. Therefore the wave drift force should be calculated accurately and studied how to reduce it.
In general, the incident wave is disturbed by a floating body and thus the disturbance wave (consisting of scattered and radiation waves) is generated. In the cloaking phenomenon studied by Newman (2013), the disturbance wave could be zero and the incident wave was not disturbed by surrounding a central body with a finite number of smaller bodies and optimizing the location and size of those surrounding bodies. This phenomenon can be applied to reduce the wave drift force.
