Higher Order Frequency Component in VIV
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- Institutt for marin teknikk 
There are still quite a lot unknown and unexplainable territories in hydrodynamic field. VIV is one of them. In today s industry world, existence of uncertainty in VIV prediction program attracts much attention.In this thesis, two major questions are emphasized on. One is the relationship and correspondence between the trajectories figures and the strain curves. The other is the contribution of 3× component to the whole fatigue damage and the possible determinant reasons behind it. The experiments data comes from the MARINTEK 22 cases with varying current speed in shear flow are main target. During the analysis procedure, some obvious comparison results appear. The trend of 3× strain is highly similar to the motion phase angle, which lead to the idea for future work related to energy flow analysis. More importantly, with the increasing current speed, the 3× fatigue damage becomes more and more important in the total fatigue damage. The 3× component can cause extremely high fatigue in the stationary response time window than in the total time window. The occurrence of this high fatigue is often found in the place where witnesses high fatigue value in the original total time window. This can be interesting in revising corresponding VIV prediction program when dealing with high speed in stationary response time window.No detailed explanations in mathematical and physical level are done due to the limited time when it comes to the reasons behind the 3 × fatigue damage, which leave much space for future work.