Research On The Internal Multiphase Flow Induced Vibrations In Subsea Pipelines Based On The Fluid Structure Interaction Methods

Subsea pipelines are very important component in the offshore oiland gas development. According to the subsea pipelines design codes, thestatic design comes to the first place, while the dynamic design only takesthe vortex induced vibration into consideration at most time. The subseaoil and gas separation technology is technically difficult and costly, thusmultiphase mixing transportation technique is widely used. To improvethe productivity, high pressure and high flow rate are more commonly,which leads the subsea pipelines to be prone to FIV. The methodologycombining the Computational Fluid Dynamics of multiphase flow andtransient Computational Structural Dynamics take full advantage of CFDand FEA software. This technique is valid in analyzing the FIV problemsof subsea pipelines.The analysis of FIV of subsea pipelines is consisted of three mainparts. Firstly, the basic theory and principles are introduced here. A moredetailed introduction is carried out with the description of ANSYS FSIand MpCCI, and a comparison between different simulation environments.The multiphase flows are very different from single phase flow,particular parameters are introduced. Flow pattern is important inmultiphase flow analysis, typical flow patterns of horizontal and verticalpipes are introduced. Setting the multiphase pipe vibration equation, andthe natural frequencies are calculated. Taking the effect of pipeparameters and flow parameters.Finally, the CFD and CSD methods are used for the simulation ofsubsea horizontal pipeline and inverted U-shaped subsea jumper. The gasand liquid volume fractions are used for the flow pattern identification,simultaneously, the dynamic response of subsea pipelines can be gotten.When the natural frequency of the pipe is close to the slug frequency, theamplitude of the vibration will increase, which is a potential risk offailure of the pipe.