Research On Vortex Shedding And Vortex Induced Vibration Of Underwater Cable In Tension

Submerged buoy system is a kind of device mooring in the sea for signalcollection, so its interference rejection ability is of great importance to the reliabilityof the probe result. The dynamic characteristic of mooring cable plays a importantrole in the dynamics of the whole system. As the flow past cable cylinder wouldgenerate periodical vortex sheddding, which would induce the cable to vibrateemitting interference signal. Research on the vortex shedding and vortex inducedvibration of large flexible slender structure could forecast interference spectrum, aswell it is significant to understand the dynamics of slender structure such as risers,mooring ropes etc. in the ocean.This paper aims at building prediction method of VIV of large flexible slenderstructure basing on CFD-FEA two ways FSI method. The research contents includemodeling of vortex shedding in subcritical layer, flow past3-D right cylinder andinclined cylinder, dynamic meshing, VIV and lock-in problems of2-D cylinder,prediction of VIV of3-D full size mooring cable. The concrete research content is asfollows.1The modeling factors of vortex shedding in subcritical layer are studied,including geometric model, meshing, SGS model, boundary conditions and timestep. Finally a reasonable modeling parameters preference is presented.2The3-D models of flow past a cylinder are established, basing on which thethree dimensional effects and flow wake have been studied. The attitude of a kind ofsubmerged bouy system is calculated, basing on which the modeling of flow past3-D inclined cylinder is established. The related patterns of the flow wakes andhydroelasticity of flow past a inclined cylinder are studied.3The2-D vortex induced vibration of a cylinder with flexible support isstudied, whose results have been tested with real expriment data in order to validatethe model. Also the correlation between natural frequency of structure and sheddingfrequency is studied, and related conclusions are presented.4The prediction of3-D VIV of full size mooring cable in time domain isstudied basing on CFD-FEA two ways FSI method. The dynamic meshing methodfor large deformation is discussed. Finally, VIV analysis of a kind of real submergedbouy mooring cable is presented, and its fluid field, structure vibration, FSI modaletc. are discussed.This paper is devoted to study prediction model of VIV of3-D full size flexibleslender structure with large aspect ratio, which makes sense for the research on largedeformation FSI problems of low frequency structure in the ocean engineering.