Strongly Nonlinear Analysis On The Hydrodynamic Resonance Of Free Double-floating Bodies With Gap

With the development of human society, more and more attention has been payed on the abundant biological and mineral resources contained in the vast oceans. Collection, transportation and processing are the necessary parts of utilizing marine resources. During these activities the strong nonlinear hydrodynamic resonance phenomena, such as wave breaking and splashing, may appear in the gap between floating production storage and offloading(FPSO) equipment and liquefied natural gas(LNG) ship due to excitation of incident wave. When the resonance happens, tremendous wave force on storage equipments and transport ships would occur with the wave elevation rapidly increased. This paper aims to study this phenomenon and to reveal the mechanism of the resonance in the gap between two bodies, then to guide the practical engineering application.In this paper a two-dimensional incompressible viscous flow numerical wave tank based on the CIP(Cubic interpolation polynomial) method is established, by using the THINC(Tangent of hyperbola for interface capturing) method and the virtual particle method. Then the characteristics of mass conservation and wave dissipation performance of the numerical wave tank are verified, and the wave-height meters are setted to get the free liquid surface wave form to verify that the numerical wave tank can simulate the generation and propagation of linear wave. A slope is setted in the numerical wave tank. The results which are illustrated by Tecplot animation validate that strongly nonlinear phenomena can be simulated.By changing the gap width and the floating body draft separately, t he fixed double floating body model is simulated and caculated in the numerical wave tank which is established based on the above self programming technique, and the results are compared to the experimental results and the numerical simulation results. The results show that under the influence of the incident wave, there will be wave resonance phenomenon appearing in the gap of the fixed double floating body model. The resonance frequency will be affected by gap width and floating body draft. When the resonance occurs, wave surface in the gap elevates sharply and forces acted on the double floating body both in horizontal direction and vertical direction change dramatically.The motion free double floating-body model is established and calculated, by changing the gap width between the double floating body, and the results are compared to the fixed double floating body model. The results show that under the influence of the incident wave, there will be wave resonance phenomenon appearing in the gap of the motion free double floating body model. The resonance frequency will be affected by gap width. When the resonance occurs, wave surface in the gap elevates sharply and forces acted on the double floating body both in horizontal direction and vertical direction change dramatically, which is smaller than that in the fixed double floating body model.