Preliminary Study Of Hydrodynamic Performance Of SEMI

As the world's population increasing, the demand of oil also increases fast, so people have to search resources from the ocean. Ocean is rich in all kinds of natural resources including oil resources, mineral resources, chemical resources, foods. The ocean is hope of the 21st century. People should pay more attention to it.This paper based on the 3d potential theory including the theory of radiation and diffraction, using frequency-domain Green function method for solving the equations of motion in frequency-domain to get dynamic parameters. In the numerical calculation, we use SESAM to calculate the performances of the semi-submersible. Comparing the results, we can draw the following conclusions:1. In semi-submersible platform hydrodynamic analysis, we more concerned about its pitch, roll and heave performance. From the numerical results we can see response of pitch and roll in the operational and survival condition are great different .Survival sea state is chosen as the Gulf of Mexico hundred-year sea conditions which is not easy to encounter in actual production. But as a long-term operation and marine structures, their design and production must consider extreme environments, in the survival of sea conditions in the platform can reach the largest roll over 10 degree and 4 degree in pitch, 10 meters in heave. To ensure survive of the platform, we should make it strength and stable.2. In this paper, there is a comparative analysis of some parameters such as draft, different center of gravity, heave plate set. By comparing numerical results of different parameters we know: Increasing the draft of platform can improve the performance of pitch, roll and heave. And the platform set up a high center of gravity is not sensitive to a certain extent. The center of gravity height of the platform movement has little effect. Add heave plate can made further reduce the movement direction, but should choose certain depth to avoid the wave impact, the platform heave become larger, when the plate is set to 20m. So set of height must have a minimum value. Because of cost and the water depth is not a linear relationship, with the water depth increases, the cost of heave plate will increase significantly, and the connected truss strength and stability is hard to ensure, so the height of heave plate must be controlled at a reasonable height, both for the performance optimized and in economy.