Numerical Simulation of Vortex-Induced Vibrations of Riser-Conductor Systems Including Soil-Structure Interactions

Abstract

A fully three-dimensional numerical approach for analyzing deepwater drilling riser-conductor system vortex-induced vibrations (VIV) including soil-structure interactions (SSI) is presented. The drilling riser-conductor system is modeled as a tensioned beam with linearly distributed tension and is solved by a fully implicit discretization scheme. The fluid field around the riser-conductor system is obtained by Finite-Analytic Navier-Stokes (FANS) code, which numerically solves the unsteady Navier-Stokes equations. The SSI is taken into account by modeling the lateral soil resistance force according to p-y curves. Overset grid method is adopted to mesh the fluid domain with approximately 0.86 million computational points in total. Meshes are much finer in regions close to the pipe outer boundary and coarser in the far-field regions. A partitioned Fluid-Structure Interaction (FSI) method is achieved by communication between the fluid solver and pipe motion solver.

A pipe VIV simulation without SSI is firstly presented and served as a benchmark case for following simulations. Two SSI models based on a popular p-y curve are then applied to the VIV simulations. Results from those simulations are compared and analyzed. The effects of two key soil properties on the VIV simulations of riser-conductor systems are then studied. Conclusions are made and suggestions are given for VIV analysis of riser-conductor systems and future research