Study Of The Power Response Of Ships And Floating Offshore Platform Collision

Development of offshore petroleum resources has great potential in the world today, the current marine engineering gradually develop from offshore to the deep.China’s offshore / deep sea oil and gas resources are very rich,which is 24.6 billion tons, accounting for the total oil resources of almost quarter. Various ships on the job when the waters, semi-submersible offshore platform or oil drilling carried out at random complex marine environment, in addition to the role of environmental load by the time outside, passing ships, guard ships, supply vessels and other navigational operations due to negligence or stop by at the supply of the platform, the role of wind,wave and current loads, such as the environment, often inevitable collision occurred and platform, and may cause environmental pollution, structural damage, significant economic losses, casualties and some disastrous consequences. Especially in deepwater and ultra-deep waters, due to sea conditions are generally worse, the collision is more likely to occur.In this paper, in order to analyze the external dynamics of the random waves of ships and offshore platforms collision, using the explicit nonlinear finite element software ANSYS / LS-DYNA to establish a three-dimensional finite element model of semi-submersible platform and supply boat stern, calculated by DYNA the stern to2m/s speed vertical impact conditions semi-submersible offshore platform pillar,access to the timing results collision force. And then combined on the basis of external dynamics, the true impact force was introduced into the hydrodynamic software AQWA. The semi-submersible platform was in the flow waves and the impact force, under the combined effect of hydrodynamic coupling time domain calculation, obtained platform motion response results and the forces of different mooring. In summary, this article will do a detailed survey on the external dynamics of ship with semi-submersible offshore platform collisions.In this thesis include:(1)Conducted a modeling study of the supply ship stern and semi-submersible offshore platform, where semi-submersible offshore platform as a whole taking into account the finite element model for the location of the main pillars of injured area,carried out a detailed modeling of the column, and in order reduce the computation time model, simplified structure of the floating body and a lot of the casing, above thedeck and the deck by deck facilities, instead, the weight of those parts and their center of gravity, the structure can be LS-DYNA corresponding portion by controlling to adjust the density of the form. Stern to stern side is considering the relative stiffness of large offshore platforms column structure, so the model stern simplified rigid model, relatively conservative calculations. Eventually build three-dimensional model based on ANSYS software platform and stern and divide the finite element mesh, and on this basis, the explicit use of nonlinear finite element software LS-DYNA simulation collision.(2)Application of ANSYS / LS-DYNA explicit nonlinear dynamic analysis procedures, Cowper-Symonds constitutive model of a supply ship stern 5000 t to 2m /s speed vertical shock semi-submersible offshore platform uprights example with additional water quality numerical simulation methods, the focus of the analysis done on the part of the column, get the timing results collision force some important moments of stress cloud collisions, the collision force curve without any real loaded onto simplified hydrodynamic model of water dynamic analysis. Numerical simulation of hydrodynamic including frequency domain and time-domain calculations. In this paper, both the time domain analysis, frequency domain analysis and application of marine structures and mooring system performance analysis of hydrodynamic force in the collision.(3)Frequency domain characterization of marine structures, mainly in the added mass coefficient and additional damping at different frequencies, you can also get different waves down RAO, a first-order wave force, second-order wave forces and transfer function. When the paper will not make any impact force history curves simplified import into AQWA in, and with hydrodynamic software AQWA-Line,using three-dimensional potential flow theory, the collision of semi-submersible platform for numerical calculation, the hydrodynamic parameters.(4)Time-domain analysis method is mainly characterized by its motion response and mooring cables per roots force status under marine structures and mooring systems in the collision force marine environmental conditions must weigh whether they meet specifications. In this paper, AQWA-Drift hydrodynamic coupling time domain simulation software for the semi-submersible platform, motion simulation and collision force under the combined effects of the storm response of the platform,mooring different stress situations.(5)The results can be seen from the position due to the collision occurred in theback side of the platform on the port side of the column, there is the case under the force of the collision, swaying, rolling and yawing very large changes, in line with the reality of the situation, indicating the size of the force of the collision, direction and trends in response to a direct and significant impact on the movement of the platform,thereby affecting their operational efficiency and safety.