Gabriel de Lucas Garden

Abstract

Vortex-induced vibration (VIV) is a well-known problem in the offshore industry, especially when dealing with riser dynamics. This issue arises due to the nonlinear interaction between the fluid flow past cylindrical structures, which generate a von Karman vortex street. The flow of fluids around blunt objects creates a wake behind the geometry, which excites the structure, making it oscillate in the transverse and longitudinal directions of the flow. To accurately model the intricate dynamics of this phenomenon, this work employs the bidimensional incompressible Navier-Stokes equations within the arbitrary Lagrangian-Eulerian (ALE) framework. The finite element method (FEM) has been chosen to discretize the equations and the fivenoded quadrilateral was used to discretize the fluid domain, which automatically satisfies the Ladyzhenskaya-Babuˇ ska-Brezzi (LBB) condition. In order to stabilize the numerical code for higher Reynolds numbers, a first-order semi-Lagrangian (SL) scheme has been used. This method is unconditionally stable thus, large time steps may be used if necessary. The search-interpolation algorithm is remarkably efficient since it starts by inquiring about one of the node’s neighbouring elements. On the other hand, the solid structure was considered a rigid body therefore, its boundary was non-deformable. Several benchmark test cases have been investigated to confirm vii the accuracy of the proposed methodology. As for results, forced and free oscillation simulations were conducted to study cross-flow VIV. While the elastically supported cylinder was simulated under different Reynolds numbers to investigate both in-line and transverse vibrations of the rigid body

Advising

Advisors: Anjos, G. R.; Su, Jian