Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.807986
Title: On the free vibration of an array of elastically mounted cylinders
Author: Lee, Kunhee
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2020
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Abstract:
With growing demand of petrochemicals, offshore oil exploration is encouraged to reach deeper water and further offshore. Offshore platforms are characterised by multiple riser pipes. One of the main logistical challenges is of riser pipe failure caused by vibration induced by surface currents. In this thesis, a fundamental study of the free vibration of an array of elastically mounted cylinders is performed. The Reynolds number of the array was fixed at 2100 and the cylinder mass ratios m ∗ = 7.7883 with 2D fluid and 1D solid models. A novel RBF method was developed to accommodate repeated cylinder movement on mesh deformation. A new collision algorithm with conservation of fluid and solid momentum and energy has been developed. Data diagnostic tools were developed to better highlight vibration features of interest to this study has been developed. A companion experimental study was developed. Due to difficulty replicating the long, thin cylindrical pipes, cantilever cylinders are used for their practicality. The computational results show that the response of an array depends on reduced velocity Vr and blocking ratio φ. When Vr = 0, the response corresponds to Nicolle & Eames (2011), where three flow regimes were identified. The intermediate steady state regime is lost when Vr > 0. Lower values of φ resembles findings of literature. For φ & 0.2, the group of bodies significantly affects the local mean flow direction and magnitude, especially at the sides of the array, generates a GIV. A detailed analysis of cylinder response force displacement and trajectories was performed, enabling the key response of the array to Vr to be parametrised and understood. The collated computational and experimental work provides insight in choosing geometry of risers. Failure scenarios are simplified to two cases, fatigue and fracture. These results are explored and then framed within a practical context.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.807986  DOI: Not available
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