| Summary: | 碩士 === 國立中山大學 === 海洋環境及工程學系研究所 === 96 === This paper is to study the scattering problem and radiation problem between incident wave and a moored dual pontoon platform by using both a fully nonlinear numerical wave tank (NWT) and a physical tank. The nonlinear numerical wave tank is developed based on the velocity potential function and the boundary element method (BEM). In addition, a moored dual floating pontoon physical model is tested in an experimental wave tank to validate the numerical model for simulation of wave and structure interaction including mooring tension, structure translation and rotation. The phenomena of wave reflection and transmission due to a floating platform are also considered in the study.
The experimential results indicate that the platform surge-RAO decays as the wave frequency increases. Similarly, the platform heave-RAO decays first until at the vicinity of the resonance frequency happening where the vertical amplitude rises up and then decays again. The tension-RAO has two resonance frequencies, the lower resonance is resulted by the surge montion, while the higer resonance is caused by the heave motion. Both wave reflection and transmission coefficients decrease near the heave resonance frequency. This indicates that the platform has the best performance in wave shelter effect at heave resonance to protect costal zone.
In general, the comparisons of the numerical simulations and experimental results indicate the numerical horizontal motion have a good agreement, but for the vertical motion, the numerical predictions are larger than experiments especially near the heave resonance frequency. This may be due to the structure vertical velocity increases dramatically causing flow separation occurred below the structure sharp corner, thus the fluid viscous damping effect may play an important role in heave motion.
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