Vortex-induced vibrations of a non-linearly supported rigid cylinder

Abstract

Vortex-Induced Vibrations (VIV) are a complex fluid-structure interaction problem.
VIV are particularly strong for low-mass structures subject to a low damping, as
encountered in the offshore industry, in which structures experiencing VIV can also
be subject to strong structural non-linearities.

In this project, investigation of the VIV of a low-mass low-damping rigid cylinder
subject to structural non-linearities is carried out first experimentally. Non-linearities
considered are the symmetric or asymmetric limitation of the amplitude of the
cylinder with soft or stiff stops placed at different offsets from the cylinder and
implying a non-smooth non-linearity of the system. Experimental results show that a
strong perturbation of the dynamics of the cylinder occurs when amplitude limitation
is strong, and flow visualisations displaying a modification of the vortex wake suggest
a change in the fluid-structure interaction affecting the vortex formation process.
Attention is also given to the impact velocities in the different cases of amplitude
limitation with stiff stops, as they are an important factor in the design of structures.

Two different wake oscillator models are then used to simulate the VIV of the same
rigid circular cylinder in the same conditions of non-linear structural restraints.
Results show that these simple models exhibit some features observed experimentally,
giving in some cases a good estimation of the experimental data.

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Identifiers

ORCID for John Chaplin: orcid.org/0000-0003-2814-747X

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