Hydrodynamic Study Of Wave Evolution Characteristics Around Floating Platform In Shallow Water With Submerged Terrain Near Island By CFD Method

With the development of the resources of South China Sea,the strategic position of the island and reefs become increasingly prominent.It is an excellent choice to build a floating platform near the island to guarantee the construction of the islands.So that it is significant to investigate the wave condition and the hydrodynamic characteristics of the floating platform near the island and reefs.In this paper,a 3D viscous flow solver(naoe-FOAM-SJTU)is employed to simulate the wave evolution characteristics and hydrodynamic properties of semi-submersible platform in the corresponding wave environment in shallow water with submerged terrain near island.Firstly,a validation work was done.The comparison work was carried out between the natural period the free-decay motion of the computational results and experimental results which verifies the accuracy of the solver employed in this paper.In the validation work of the wave generation module,the waveform of this work was compared with the theoretical waveform which verifies the accuracy of the wave making module.Subsequently,the investigation about the hydrodynamic characteristics of the platform and the wave evolution phenomenon with the oblique bottom terrain were carried out.The response characteristic of the floating platform was firstly studied and the RAO(Response Amplitude Operator)results were compared with the experimental data to conduct a further verification of the solver and the calculation results.Meanwhile,a conclusion can be drawn that the response characteristic of the platform is better in high frequency waves.In the part of analysis about the wave evolution characteristics with oblique bottom terrain,the evolution characteristics of the regular waves with different wave condition were firstly analyzed,and then the research about the variation of the wave height and wave frequency components were mainly investigated.It is found that with the increase of the wave period,the wave height will increase obviously during the wave evolution process,and the high-order components of the wave will be more pronounced.In addition,the influence of different seabed terrain upon the wave evolution characteristics was studied,and the difference of the wave evolution characteristics between the flat bottom condition and slope bottom condition was explored.It can be found that the wave height decays steadily in the flat bottom condition and no obvious evolution characteristics such as the enlargement of wave height and non-linear component enhancement can be observed in this process.Thus it is verified that a series of strong nonlinear phenomenon that captured in the previous research are caused by the oblique bottom terrain exactly.Finally,the mechanism of wave overturning phenomenon was investigated deeply.In this paper,a two-dimensional wave pool was established in which the wave overturning problem was carried out.It is shown that with the increase of the wave steepness,the wave depth index,wave height index and the wave vertical asymmetry index reduced significantly,while the wave front asymmetry index,wave rear asymmetry index and the horizontal asymmetry index are not very sensitive to the wave steepness.