Abstract
The safety of mooring systems on offshore platforms seems more and more significant with the utilization of offshore space and resources, so the reduction of wave drift force is the key issue in this wave-body interaction problem. The wave drift force acting on the inner floating body surrounded by multiple small floating bodies can be reduced obviously with the occurrence of a phenomenon, which is called the Cloaking phenomenon. The Cloaking phenomenon refers to the reduction or complete elimination in amplitude of the scattered waves. In this paper, a real-coded genetic algorithm was used to optimize the parameters of outer floating bodies to minimize the scattered wave energy, and then the wave drift force acting on the inner body can be reduced. Furthermore, associated CFD simulations and experimental research were conducted with the above optimized parameters to investigate and verify the Cloaking phenomenon more systemically. It is shown that the wave drift force acting on the inner floating body in the Cloaking configuration can be reduced obviously both in numerical and experimental research, and the reduction of the wave drift force is closely related to the change of wave field around the structure.
Highlights
The offshore platform has got a wide range of application with the utilization of ocean energy and the development of large-scale marine structures, and the position system plays a significant role in the stability and safety of the platform
It is known that the wave drift force can be calculated by the amplitude of scattered outgoing waves according to the momentum conservation, so the reduction of wave drift force can be realized with the occurrence of the Cloaking phenomenon in water waves
It is shown that the wave drift force acting on the inner floating body can be reduced to very small in numerical results and in experimental measurements with the occurrence of Cloaking phenomenon and the reduction of the wave drift force is owing to the reduction of wave elevation difference between the weatherside and the leeside of the inner floating body
Summary
The offshore platform has got a wide range of application with the utilization of ocean energy and the development of large-scale marine structures, and the position system plays a significant role in the stability and safety of the platform. Following the work of Newman and Iida et al [7,8,9], the hydrodynamic forces on the inner floating body in Cloaking configurations and the spatial distribution of wave elevation are investigated in this paper; besides, the relationship between the reduction of wave drift force and the variety of wave surface distribution is systematically studied. In order to determine the optimal geometric dimensions of outer floating bodies at the certain frequency which corresponds to the minimal scattered wave energy, a genetic algorithm (GA) is adopted Both CFD numerical simulations and corresponding model experiments are conducted with the above determined geometric parameters at the certain frequency to investigate and verify the Cloaking phenomenon in water-wave field systematically. It is shown that the wave drift force acting on the inner floating body can be reduced to very small in numerical results and in experimental measurements with the occurrence of Cloaking phenomenon and the reduction of the wave drift force is owing to the reduction of wave elevation difference between the weatherside and the leeside of the inner floating body
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