Numerical Simulation On The Dynamic Characteristics And Dynamic Responses Of Vortex-Induced Vibration Of Submarine Free Spanning Pipelines Conveying Fluid

Submarine pipelines are the lifelines of marine oil fields. The transportations of oil, gas and water in the marine oil field are almost accomplished by the submarine pipelines. So it is the submarine pipelines that make the marine oil field contact closely.This paper mainly focuses on the Vortex-Induced Vibration (VIV.) of submarine free spanning pipelines. The generating mechanism as well as properties and related parameters of VIV are expressed. The partial differential equation for the response of a marine pipeline considering the effect of the internal flowing fluid and the external marine environmental condition is derived. The dynamic characteristics without considering damping and considering damping are both analyzed, then using reduced velocity as a control parameter, derives the allowable span length of submarine pipelines. In order to find the dynamic response of the free span, combining Matteo Luca Facchinetti's wake oscillator model with the differential equation of the free span to get the coupling equations between pipe and fluid, the finite element method combined with the simple iteration is used to solve the system of equations. The results indicate that: in the same case, the allowable span length considering damping is a little small than that without considering damping, the allowable span length of the submarine pipelines decreases with an increment in the velocity of internal flow, compression and pressure , increases with an increment in tension ; the flowing of internal fluid may cause the resonant bands shift to the lower frequency as well as a slight decrease in the peak value, the effect will be more pronounced with the increase of the span length and can be weaken by the presence of the axial tension.