Wave Slamming And Its Interaction Effects With Deepwater Semi-submersible Platforms Under Extreme Wave Conditions

The increasing importance of the sustainability challenge in ocean engineering has led to the development of floating structure of various configurations.The slamming and its interaction effects of extreme waves with deepwater semi-submersible platforms have been systematically investigated in the context of computational fluid dynamics (CFD) theory. The main objects of this dissertation such as offshore plate structure, offshore plate-column structure and a semi-submersible platform, is numerically simulated in a full range and then is verified by small-scale experiments.Based on the two different mechanisms of wave slamming problems, the effective simplified models including of offshore plate structure and offshore plate-column structure in view of the most severely deck areas are designed, and the slamming experiments of their different poses are conducted under regular wave and random wave conditions. According to the pitch response range of semi-submersible platform during the period of service, a comparison of the slamming pressure distribution of characteristic value with the model is acquired in-10°,5°,0°,5°and10°inclination. The dependence of the slamming pressure on the design parameters, such as the incident wave height, the inclination and the effect of the column, is systematically analyzed. The relationship between the slamming forces and wave forces is obtained from a lot of experimental results.The Characteristic Angle method (CAM) which aims at the nonlinear slamming problem, is effectively proposed and is applied for the wave slamming load forecast. As a result of the natural period far away the wave periods, the transient problem of slamming loads is simplified to the interaction between the incident wave and the fixed body. From a lot of experimental results, we refine and fitting out a formula with considering structure angle of wave slamming load forecast.The scale1:100model texts are carried out in view of the south China sea semi-submersible platform HYSY-981for anchoring positioning by one-way rule under the condition of wave slamming. Based on the selected wave parameters (the incident wave height H=10cm to20cm, incident wave period T=1.0s to1.6s, air gap height is14cm system), the slamming system of no chain constraint is designed. The paper shows the semi-submersible platform pressure peak value distribution on the basis of the statistical analysis of results. And the relationship between dimension slamming force and relative incident wave height H/relative column spacing of B/L is discussed by using dimensionless method.In this paper, we apply Newmark method to the solution of dynamic response of structure under slamming load. The semi-submersible platform model is built by using finite volume method, and the transient motion of the platform is simulated by using moving grid scheme. The numerical analysis results are verified in the context of three dimensional linear potential theory, and established a relatively perfect deepwater semi-submersible platform under extreme wave load slamming effect and fluid-structure coupling effect in the research and analysis.