The purpose of this study was to investigate the effect of the porosity of a submerged breakwater on wave fields, including snapshots of the wave, velocity profiles of the water over the structure, and the kinetic energy of the wave. Two-dimensional experiments were conducted for submerged trapezoidal breakwaters with impermeable and permeable layers in a two-dimensional wave tank. The flow fields obtained by the particle image velocimetry (PIV) technique are presented to understand the flow characteristics due to the waves' interactions with the submerged impermeable and permeable breakwaters, and these characteristics showed that the vertical velocity dominant flow occurred under the crest of the wave. In addition, the kinetic energies were compared for different porosities and wave conditions. The comparisons of the wave flow fields and kinetic energy distributions showed that the different pattern of the dissipated kinetic energy was dependent on the porosity. The dissipation of kinetic energy also was observed to increase as the wave period increased. The comparisons indicated that greater amounts of energy were dissipated for longer wave periods.
Ikeda et al.(1977)는 이론 및 실험적 방법을 사용하여 횡동 요 추정과 함께 2차원 물체의 횡동요의 와류감쇄 (Eddy making damping)항이 주파수의 제곱에 비례함을 제시하였 다. Chakrabarti(2001)는 횡동요 감쇄현상을 선체표면의 마찰감쇄 (Skin friction damping), 와류감쇄(Eddy making damping), 조파감쇄 (Wave damping), 부가물 부착으로 인한 감쇄(Bilge keel damping) 로 구분하였다.
which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.In this study, hydrodynamic and mooring analysis for LNG FSRU moored by an internal turret with 9 mooring lines are numerically performed using commercial softwares, Hydrostar and Ariane. Met-ocean combinations for screening method are taken from wave governed condition(BV Rule Note NR 493) with relative heading between wave and wind between -45° and +45° and relative heading between wind and current between -30° and +30°. Extreme mooring analysis and sensitivity analysis are performed for intact and damaged (=one line missing) conditions and the parameters for sensitivity analysis are wave peak period, peak enhancement factor and line pretension. In the viewpoint of the design tension in mooring line, chain diameter is designed to satisfy safety factor for each conditions. As the chain diameter is increased from 152mm to 171mm, the designtension is reduced while the minimum breaking load is increased.
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