Nonlinear Dynamic Analysis On Free Span Submarine Pipelines Considering Fluid-Structure Interaction

This paper mainly focuses on the Vortex-Induced Vibration(VIV.) of submarine pipeline. The reason of causing a free span to submarine pipeline is described. The generating mechanism, as well as properties of VIV are expressed. A physical model experiment of free span submarine pipeline is carried out. Dynamic response of free span conveying internal flow of different length, is investigated under different wave heights, current velocity and their combinations. Via analyzing of experimental data; some conclusions are obtained: The cross-flow resonant amplitude is larger than in-line resonant amplitude when the vortex shedding induced by ocean current appears, but the participation of waves will change this phenomenon sometimes. The response of a free span pipeline is affected much by its length, so the span length must be kept away from the length which can cause resonance of pipeline.Expression of nonlinear lift forces for VIV, considering fluid-structure interaction, is put forward via analyzing the experimental results. Nonlinear dynamic equation, considering fluid-structure interaction, of pipeline is put forward. Taking experimental model of pipeline, with and without fluid-structure interaction, is computed and compared by using the Finite Element method. The analysis shows that the response of pipeline unconsidering fluid-structure interaction is obviously less than that of pipeline considering fluid-structure interaction. The analysis shows that method considering fluid-structure interaction is more reasonable under high external steady velocity.