Vortex-induced vibration (VIV)

Causes and consequences
Vortex shedding is a periodic instability that occurs in the wake behind bluff bodies, most notably cylinders.

At lower flow velocities, the vortices are shed symmetrically from top and bottom of the pipe, giving an in-line oscillation mode (oscillations in-line with the direction of current flow). 

At increased velocity, the vortices are shed asymmetrically, giving initially a further mode of in-line oscillation and then a cross-flow mode (oscillations across the flow direction).

One consequence of vortex-induced vibrations is fatigue damage to the pipeline or riser. It can also cause large-amplitude vibrations, leading to riser clashing.

Jee technology and experience
We have been working in this field for many years and have accumulated experience and developed technological solutions in the following areas:

• Screening: span length, environmental conditions and pipe properties.
• Fatigue analysis: based on DNV RP F105 and similar.
• FE analysis: for calculation of natural frequencies.
• Span monitoring: development of systems and analysis tools for on site monitoring of vibration and environmental conditions.
• CFD: to model VIV and design VIV suppression systems.

• FEED: screening of pipeline systems to determine likely susceptibility to VIV fatigue damage. Propose suitable methods for eliminating susceptible spans.
• Technical support: assessment of fatigue damage due to VIV based on DNV RP F105. Recommendations for remedial action to suppress VIV.
• R&D: assessment of alternative VIV suppression devices.