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

Vortex-Induced Vibrations (VIV) are a complex fluid-structure interaction problem.<br/>VIV are particularly strong for low-mass structures subject to a low damping, as<br/>encountered in the offshore industry, in which structures experiencing VIV can also<br/>be subject to strong structural non-linearities.<br/><br/>In this project, investigation of the VIV of a low-mass low-damping rigid cylinder<br/>subject to structural non-linearities is carried out first experimentally. Non-linearities<br/>considered are the symmetric or asymmetric limitation of the amplitude of the<br/>cylinder with soft or stiff stops placed at different offsets from the cylinder and<br/>implying a non-smooth non-linearity of the system. Experimental results show that a<br/>strong perturbation of the dynamics of the cylinder occurs when amplitude limitation<br/>is strong, and flow visualisations displaying a modification of the vortex wake suggest<br/>a change in the fluid-structure interaction affecting the vortex formation process.<br/>Attention is also given to the impact velocities in the different cases of amplitude<br/>limitation with stiff stops, as they are an important factor in the design of structures.<br/><br/>Two different wake oscillator models are then used to simulate the VIV of the same<br/>rigid circular cylinder in the same conditions of non-linear structural restraints.<br/>Results show that these simple models exhibit some features observed experimentally,<br/>giving in some cases a good estimation of the experimental data.

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2008

Author dc:creator

• Bourdier, Sylvain

Advisor dc:contributor.advisor

• Chaplin, John