Abstract
A set of two-dimensional analytical solutions considering the effects of diffraction and radiation are presented in this study to investigate the hydrodynamic interaction between an incident linear wave and a proposed floating breakwater system consisting of a rectangular-shaped body and two attached vertical side porous walls in an infinite fluid domain with finite water depth. The Matched Eigenfunction Expansion Method (MEEM) for multiple fluid domains is applied to derive theoretically the velocity potentials and associated unknown coefficients for wave diffraction and body motion induced radiation in each subdomain. Also, the exciting forces, as well as the added mass and damping coefficients for the floating breakwater system under the surge, heave, and pitching motions, are formulated. The displacements of breakwater motions are determined by solving the equation of motion. As a verification of the analytical model, the present solutions of the limiting cases in terms of exciting forces, moments, added masses, and damping coefficients are found to be well matched with other published numerical results. Additionally, the hydrodynamic performances and the dynamic responses in terms of Response Amplitude Operators (RAOs) of the proposed floating breakwater system are evaluated versus various dimensionless variables, such as wavelength and porous-effect parameter. The results show that the attached porous walls with selected porous properties are observed to have the advantages of reducing wave impacts on the floating breakwater system and at the same time its dynamic responses are also noticeably improved.
Highlights
The ocean-oriented activities, such as oil and gas extraction, aquacultural production, and recreations, have been identified to generate tremendous values to humans
A simplified analytical model to estimate the hydrodynamic performance of a long rectangular floating breakwater was developed under the assumption of a small gap condition [5]
The validation of the wave diffraction solutions in terms of reflection/transmission coefficients and hydrodynamic loads for a train of monochromatic wave propagating through the proposed floating breakwater system that consists of a partially submerged rectangular body and with or without the attached two porous side walls has been carried out in a previous study (Qiao et al [24])
Summary
The ocean-oriented activities, such as oil and gas extraction, aquacultural production, and recreations, have been identified to generate tremendous values to humans. The porous cylinder was employed to protect structure in Trafalgar offshore windfarm [28]; almost for the same purpose, a concentric two-cylinder system, involving an interior impermeable cylinder and external porous cylinder, was designed for Ekofisk gravity offshore structure in the North Sea [29]; the concept of single-layered porous cylinder was extended to doublelayered perforated cylinder by Xiao et al [30], and the experiments were conducted to investigate the hydrodynamic performances. Under the assumptions of linear incident waves and small translational and rotational motions of surge, heave, and pitch, this study focuses on the investigation of hydrodynamic coefficients, such as the added mass and damping coefficient, and the dynamic responses of the floating breakwater system through developing an analytical model with solutions of diffracted and radiated waves and the equation of motion which is formulated and solved. The effects of the incident wave parameters and porous walls conditions on the hydrodynamic coefficients and RAOs (Response Amplitude Operators) are examined and discussed
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