Formulation of a finite element model for the study of vortex induced vibration in submarine pipelines

Résumé

Vortex induced vibrations (VIV) is a condition that submarines pipelines could suffer over important periods of time and that may reduce in a relevant way the structure fatigue life, particularly, when they are not appropriately considered during the design stages. An approach to study the behavior of VIV in pipelines, of practical applicability for the industry, consists on the use of van der Pol oscillators adjusted to produce a “wake oscillator” model that simulates the fluid flow and can be coupled to a one-dimensional structural numerical model of the pipeline. In the specialized literature, many VIV studies based on the wake oscillator models can be found, but most of them use finite difference (FD) models of the pipeline. In this paper, the development of a numerical model for studying the dynamics of submarine pipelines subjected to VIV regime, using wake oscillators coupled with a finite element (FE) model of the pipeline and applying a Newmark scheme for the time integration, is presented. The proposed model was validated by comparing the response of a pipeline under different conditions and considering different effects (e.g. buoyancy, variations in fluid velocity, fluid-added mass, fluid damping, etc.) against the results obtained by FD based models presented in the literature. Results show that the proposed FE based model produces similar predictions for all the studied cases, with differences lower than 5%. In addition, the FE based model presents many advantages over FD based models, that are especially important for industrial applications e.g. simplicity in the introduction of different boundary and other effects, possibility of meshing of 3D pipeline configurations, etc.