| Wind energy,among types of renewable energy,has been focused by researchers from all over the world due to several advantages such as its abundant energy reserved,wide spreading and no need for transportation.It is considered to have the most promising future for large exploit and commercial development.The development tendency of wind field will be“from small to large,from land to sea,from shallow sea to deep sea,from fixed base to floating platform”.In this thesis,the study of offshore wind turbine Spar platform on its hydrodynamic time domain and frequency domain response was carried out.Apply the component design of offshore oil platform to 3rd generation Spar platform.The work carried out in the thesis is concluded below:1.The thesis symmetrically explains the motion equation of Spar platform and wind,wave and current load.The computation theory is also introduced in detail.Frequency and time domain response are calculated by numerical simulation.2.Compare Spar platform dynamic response in 200m and 320m depth of sea condition.Sea depth has no dramatically effect on wave load,diffraction force,F-K force,radiation damping and attached mass force.When the sea depth are keeps the same,load on Cell Spar is clearly smaller than other two types of Spar platform.By analyze the response RAO,it can be found that Classic Spar platform has the most server response while modified truss Spar and Cell Spar platform have better stability.The natural periods of modified platforms are all improved to be away from wave energy concentrated frequency.3.Apply heave plates on Cell Spar platform and analyze the effect of shapes,thickness,quantity and void ratio.Different shapes of heave plates have almost no effect on the wave force,diffraction force,F-K force,radiation damping and attached mass force on the structure.Heave plate shape doesn't affect structural load.Increase the number of edges of heave plates while keep the same equivalent diameter,the motion performance of Spar platform tends to be stable.4.Assume the thickness of heave plates varies from 1%to 5%of equivalent diameter of draught structure.Thicker heave plates have better motion performance until the thickness is 0.4m when the motion performance of platform is no longer affected.5.Install different number of heave plates in 42m long column structure and analyze the response.It can conclude that more heave plates lead to more stable structure.However,the increase of stability is not linear with heave plate number change.The surging and pitching response are more obvious with more heave plates.When there is more than 4 heave plates,the heaving motion is limited when surging and pitching motion are also acceptable.6.Void ratio affects heave plate performance.Keep the diameter of holes the same and analyze the dynamic response of Spar platform with different number of holes on heave plates,ie different void ratio.Void ratio doesn't affect surge motion.With the increase of void ratio,heave and pitching motion increase first and then decrease.The structure has best stability when void ratio is 10%.Attached mass reduces with the increase of void ratio. |
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