The influence of boundary layer velocity gradients and bed proximity on vortex shedding from free spanning pipelines
The paper summarises the results of a laboratory study of the separate and combined effects of bed proximity and large velocity gradients on the frequency of vortex shedding from pipeline spans immersed in the thick boundary layers of tidal currents. Tests have been carried out using a rigid model pipeline cylinder in a water channel flow at subcritical Reynolds numbers. The measurements show that in the case of both sheared and uniform approach flows, with and without velocity gradients respectively, the Strouhal number defining the vortex shedding frequency progressively increases as the gap between the pipe base and the bed is reduced below two pipe diameters. The maximum increase in vortex shedding Strouhal number, recorded close to the bed in an approach flow with large velocity gradients, was of the order of 25 percent. A synthesis of these laboratory findings combined with the results of a linked full scale field investigation will be used to define threshold vibration criteria to be employed in assessing the stability of pipeline spans against vortex induced resonant oscillation.
- Research Organization:
- University College, London
- OSTI ID:
- 5363238
- Report Number(s):
- CONF-830514-
- Journal Information:
- Offshore Technol. Conf.; (United States), Journal Name: Offshore Technol. Conf.; (United States) Vol. 1; ISSN OSTCB
- Country of Publication:
- United States
- Language:
- English
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