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Hydrodynamics of vertical surface-piercing cylinders

Potts, DA ORCID: 0000-0002-4534-3504 2019 , 'Hydrodynamics of vertical surface-piercing cylinders', Research Master thesis, University of Tasmania.

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The fluid flow around a long, slender circular cylinder, either in air or water, is a practical circumstance that has been long-studied in the field of fluid dynamics (both aerodynamics and hydrodynamics). The advent of the offshore oil and gas industry after World War II, employed platforms, risers and pipelines formed from steel tubular sections. These were subject to hydrodynamic loading under waves and currents where the need to reliably characterise the fluid loading conditions provided significant impetus to this field of investigation on the fully submerged and vertical surface-piercing cylinders under uniform and oscillatory flow conditions.
This thesis sets out a detailed investigation of the hydrodynamics of vertical surface-piercing cylinders. The aims of this thesis were to experimentally investigate: the effect of the end conditions on the Vortex-Induced Vibrations (VIV), the near field wake and the drag coefficient; the relationship between the depth of the ventilated pocket behind the cylinder with respect to the velocity and the Froude number; the typical hydrodynamic wake topology of a cylinder; and the finite aspect ratio at which the drag coefficient equals that of a typical fully submerged infinite cylinder.
The findings derived within this thesis may be summarised as follows:
1. The submerged free end-tip condition does not influence the hydrodynamic wake properties of the bow wave nor the ventilated pocket depth.
2. The difference in results from the alternate end conditions affect the VIV by an approximate 25%, which may then be further influenced by the occurrence of VIV lock-in.
3. Although there is some disparity between the end conditions with respect to the drag coefficient, the overall difference may be deemed negligible.
4. A relationship may be developed between the ventilated pocket depth with respect to the velocity squared and the diameter.
5. A relationship between the non-dimensional bow wave height with respect to the velocity squared and the diameter may also be developed.
6. A finite vertical surface-piercing cylinder may be deemed to be infinite in length when the aspect ratio ≥ 47.

Item Type: Thesis - Research Master
Authors/Creators:Potts, DA
Keywords: Aspect Ratio, Circular Cylinders, Drag Coefficient, Hydrodynamics, Surface-Piercing Cylinder, Tow Tank, Vortex-Induced Vibration
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Copyright 2019 the author

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