The phenomenom of transversal vibrations to the main flow direction in deep water lines is of great interest. So far the structural mechanics of these lines is assessed by finite element numerical methods, that includes three dimensional effects and geometrical non-linearities. On the other hand, the fluid loading is evaluated usually through the Morison formula. In spite of being reliable under certain hypothesis, this treatment is simplified and do not represent the complex scenario that occurs in the wake. This approach, for instance, is not able to predict the transversal forces induced by vortex shedding. Therefore a numerical procedure is proposed to tackle this problem in 2D, based on the Galerkin finite element method in conjunction with the projection method to discretize spatially the field and an explicit finite difference method for the time derivative. The fluid-structure interaction is evaluated through an arbitrary Lagrangian-Eulerian method that enables cylinder forced and free motion within a moving grid. The main focus of the study, in this stage, is to validate the code verifying if it reproduces the behavior of vortex shedding experimental characteristics.
The vortex-induced vibration of risers is a subject that has been attracting a lot of attention through the years. Currently this subject has become even more important, once many production lines have reached up to 2000 meters of length, being attached to semi-submersibles, TLPs, SPARs, sb2p-shaped FPSOs and mono-buoys. These risers can be of different types and materials, like steel catenary risers, flexible risers and rigid tensioned vertical risers. No matter the type of platform or riser configuration, the assessment of transverse vibrations is important in order to avoid excessive motions and therefore a reduction in fatigue life.
