Analysis Of The Vortex-induced Vibrations Of The Tension Leg Platform For Offshore Wind Turbine

With the rapid development of the offshore wind turbine, one of the most suitablefoundation for deep sea, that is the tension leg platform, is becoming more and moreflexible, whose draw ratio is larger and larger. Vortex induced vibration is one branch ofthe fluid-structure interaction, which is a significant reason for the fatigue damage of thetension leg platform. With the changement of the structure, vortex induced vibration ismust be considered when a structure is designed.This paper is projected on the CFD, three dimension Vortex induced vibration ofthe tension leg platform is simulated with the help of ANSYS Workbench and CFX. Theuse of workbench is swapping the data between the fluid force which is the fluid act onthe structure and the displacement of the structure, which can assure the exchangementof the Coupling interface. Taking the simulating time and the accuracy of the results intocinsider, standard k-ε model is chosen for the simulation od the turbulence.There are three parts of the paper, firstly, in order to prove the method which isused in the paper is correct, a comparison of two dimension vortex induced vibration oftension leg platform is drawn with other literature,2S vortex are found in the case, afoundation is lain for the next simulation.Then, a new structural style of tension leg platform is proposed, that is variablecross-section tension leg platform. The simulation of vortex induced vibrationundergoing the uniform flow for the two kinds of tension leg platform is made, it isfound that though the two kinds of tension leg platform are at the same velocity and theaverage diameter, the frequency of the wake shedding and the amplitude of thestructural vibration for variable cross-section tension leg platform is smaller than thecylinder tension leg platform. In addition, the experimental data is compared with thesimulational results, which shows that the error is smaller than5%.At last, in consideration of the practical engineering, non-uniform flow is utilizedon the two kinds of tension leg platform, the results reveal that frequency of the wakeshedding and the amplitude of the structural vibration are the same with the uniformflow, but high frequency vibration is appeared for the variable cross-section tension legplatform, when the doameter of variable cross-section tension leg platform is magnifiedwith one time, it is found that the crosswise vibration is decreased, but there is still highfrequency, besides, in-linewise vibration is increased. So it is concluded that although variable cross-section tension leg platform performs better on vortex induced vibration,logical geometric dimensioning should be selected in order to avoid vortex inducedvibration.