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Active control of
vortex-induced vibrations in offshore catenary risers: A
nonlinear normal mode approach
Carlos E. N. Mazzilli and César T. Sanches |
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Vol. 6 (2011), No. 7-8, 1079–1088
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Abstract |
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Offshore catenary risers are used in the exploitation of deep-water oil and gas fields. They are subjected to severe dynamical loads, such as high-pressure inside-flow of fluids, sea-current external flow, and sea-wave motion of the floating production platform. This paper addresses the dynamic instability caused by vortex-induced vibrations (VIV). For simplicity, the touchdown-point motion and the mooring compliance are neglected in this introductory study. The nonlinear normal modes of a finite element model of the riser are determined, following the invariant manifold procedure, and a mode that is particularly prone to be excited by VIV is selected. A reduced mathematical model that couples the structural response and the fluid dynamics is used to foresee the vibration amplitudes when the instability caused by VIV takes over. Active control is introduced and the linear quadratic regulator is employed to determine gain matrices for the system and the observer. Results are compared with those from a linear analysis. |
Keywords
catenary risers, VIV, nonlinear modes, finite element
method, active control
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Milestones
Received: 16 June 2010
Revised: 2 December 2010
Accepted: 17 January 2011
Published: 21 December 2011
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Authors |
| Carlos E. N. Mazzilli | |
| Department of Structural and
Geotechnical Engineering Polytechnic School University of São Paulo Av. Prof. Almeida Prado, trav. 2 n. 83 05508-900 São Paulo-SP Brasil |
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| César T. Sanches | |
| Department of Structural and
Geotechnical Engineering Polytechnic School University of São Paulo Av. Prof. Almeida Prado, trav. 2 n. 83 05508-900 São Paulo-SP Brasil |
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