A NONLINEAR FLUID–STRUCTURE INTERACTION ANALYSIS OF A NEAR-BED SUBMARINE PIPELINE IN A CURRENT

A negative lift force (attraction) can be induced on a near-bed pipeline in a horizontal current due to asymmetric flow. This negative lift force has a significant influence on the behaviour of the near-bed pipeline, causing two remarkable failure patterns. One failure pattern is due to stability loss, and the pipeline fully rests on the seabed. The other is due to the excessive stress or deformation even if the pipeline is stable in a position between the original equilibrium position and the seabed. A quantitative method to assess these two failure patterns by combining boundary element and finite element methods is proposed in this paper. This is a nonlinear fluid–structure interaction problem, and an iteration procedure is used herein to solve it. Numerical examples reveal that there exists a critical current velocity, above which the pipeline fails. The relationship between the critical velocity and the distance from the pipeline to the seabed is given.