Characteristics of VIV in multidegreeoffreedom

Authors: Dongho Jung Hyeonju Kim Seungho Shin

Publish Date: 2012/03/21

Volume: 17, Issue: 3, Pages: 349-359

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Abstract

The object of this study is to analyze the characteristics of vortexinduced vibration of a slender marine structure with the numerical method Applying a dynamic analysis method for a slender marine structure based on the 3D finite difference method we carried out case studies for a tensioned beam model at a constant flow speed The hydrodynamic forces in the direction of inline and crossflow created by vortex shedding are simultaneously considered based on Morison equation The frequency of force in the inline direction corresponding to the unstable zone is evaluated An eigenvalue analysis for different flow speeds of a tensioned beam considering the effect of the tension increase due to the inline and crossflow drag forces is performed We found that a revision of the eigenvalue should be considered if the tension along a riser or beam is significantly affected by an environmental or functional load From a trajectory on the XY plane it was shown that the riser did not move in an exact 8 shape for all flow conditions due to the phase angle difference between inline and crossflow displacement It is believed that the phase angles between inline and crossflow displacements in high modes are different among the nodes

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