Modelling of coupled cross-flow and in-line vortex-induced vibrations of flexible cylindrical structures. Part I: model description and validation

This paper is first of the two papers dealing with nonlinear modelling and investigation coupled cross-flow in-line vortex-induced vibrations (VIVs) flexible cylindrical structures. As a continuation previous work (Qu Metrikine in Ocean Eng 196:106732, 2020) where new single wake oscillator model was proposed studied for VIVs rigid cylinders, present focuses on applying it to cylinders. In this paper, structure modelled as an extensible Euler–Bernoulli beam its 3D coupling motion described absolute coordinate system. The van der Pol structure, addition classic linear coupling, uniformly distributed along hydrodynamic force acting it. finite element method has been applied solve dynamics system, experiments VIV top-tensioned straight riser subjected step flow have taken validation model. shown be able capture most features good agreement between simulation results experimental measurements observed regard amplitude, frequency excited mode both vibrations, well mean deflection due amplified force. While conventionally expected that cylinder uniform dominated by frequency, multi-frequency response over range velocities through which transition dominant vibration occurs.