Doctoral Thesis
DOI
https://doi.org/10.11606/T.3.2009.tde-20072009-164347
Document
Author
Full name
Lauro Massao Yamada da Silveira
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2009
Supervisor
Committee
Martins, Clóvis de Arruda (President)
Aranha, José Augusto Penteado
Franciss, Ricardo
Morooka, Celso Kazuyuki
Pesce, Celso Pupo

Title in Portuguese
Modelo hidro-elástico para simular as vibrações induzidas por vórtices em cabos submersos.
Keywords in Portuguese
Cabos de amarração
Estruturas offshore semi-submersíveis
Vórtices dos fluídos (simulação numérica)
Abstract in Portuguese

Title in English
Hidro-elastic model to stimulate vortex-induced vibrations in submerged cables.
Keywords in English
Fluid vortices (numerical simulation)
Mooring lines
Semi-submersibles offshore structures
Abstract in English
The present work proposes a qualitative numerical study of a hydro-elastic model in order to simulate vortex-induced vibrations in submerged cables. The model is composed of a coupled system of equations describing the structure and the fluid. The structure is modeled through a classical elastic oscillator and discretized using a lumped mass approach. The fluid is modeled through discrete oscillators based on phenomenological models using Van der Pol or Ginzburg- Landau type equations. The coupling between these two oscillators is carried by the lift force. The study was carried in order to verify which response behavior can be obtained by using such phenomenological models and also, to evaluate their potential to be used in the offshore industry. In order to accomplish that, the model must provide reliable answers and must allow fast responses when it comes to simulation time. In this sense, a numerical model was developed to allow the time domain integration of this hydro-elastic model. The numerical integration is performed by a simple explicit Euler algorithm and allows dealing with non-linearities of both oscillators, elastic and fluid. A set of conditions was numerically simulated, including top tensioned risers and catenary. Simulations indicate a high level of coupling between the two oscillators and thus resonance is achieved in most part of the cases. With respect to the structural oscillator analysis, it was possible to observe interesting phenomena such as lock-in, travelling waves and also the third harmonic observed in some experiments and reported in the literature. Regarding the feasibility of the model usage in the daily offshore industry life, it seems possible once the model generally runs fast and some promising results were achieved.

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Publishing Date
2009-08-17

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