Eventos Anais de eventos
DINAME2019
DINAME2019
Modeling and fatigue analysis of an hybrid riser system submitted to vortex-induced motion
Submission Author:
Leandro Gonçalves , RJ
Co-Authors:
Leandro Gonçalves, Bruno Cesar Cayres, Julien Mauprivez
Presenter: Leandro Gonçalves
doi://10.26678/ABCM.DINAME2019.DIN2019-0158
Abstract
As a structure responsible to connect the platform to the wellhead in offshore operations, the riser is subject to weathering. The fluid flow interacts with the structure and provides the vortex shedding behind the riser which may lead to the vortex-induced motion (VIM) and the vortex-induced vibration (VIV) phenomena. The VIM occurs usually in larger diameter structures such as the float support of the hybrid riser and the VIV occurs in slender structures such as the riser itself. When the frequency of vortex shedding approximates to the natural frequency of the riser, such phenomena appears increasing the motion amplitudes. This latter is known as lock-in and can have a significant contribution in decreasing of the life time of the riser. To analyze the fluid flow influence on the life time of the riser, this work uses a two degrees of freedom mathematical model which describes the dynamics of the system coupled to the vortex shedding given by Van der Pol oscillators. The main objective of this work is to investigate the parameters which influence the life time of the riser and provide a knowledge of the phenomena involved. The float support diameter presented great influence on the fatigue of the riser mainly at the lock-in state, the length of the riser changes the whole dynamics due to the imposed changes to the mass, stiffness and damping of the system. Also, the Strouhal number changes directly the band of the lock-in and the life time. These study used a well-known model in literature to provide a better understand about the dynamics and life time of the riser structures.
Keywords
fatigue, vortex-induced motion, Vortex-Induced Vibration, riser dynamics
