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Master's Dissertation
DOI
Document
Author
Full name
Aline Massabni Momenti
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2018
Supervisor
Committee
Fujarra, André Luís Condino (President)
Fiorentin, Thiago Antonio
Franzini, Guilherme Rosa
Title in Portuguese
Movimentos induzidos pelo escoamento ao redor de cilindros com alterações de geometria na extremidade livre.
Keywords in Portuguese
Baixa razão de aspecto
Cilindro de seção quadrada
Vibração Induzida por Vórtices (VIV)
Vibrações
Vórtices dos líquidos
Abstract in Portuguese
O desenvolvimento da indústria offshore fez com que a demanda por unidades flutuantes para operações em águas ultraprofundas aumentasse e, com isso, surgiu um maior interesse nos fenômenos decorrentes de vibrações induzidas pelo escoamento em plataformas do tipo spar, TLP e semissubmersível, além de torres para produção de energia eólica (instaladas no mar). Para ampliar o conhecimento nesta área, experimentos foram realizados com cilindros flutuantes com baixa razão de aspecto (L/D = 2) e com diferentes geometrias na extremidade livre . Experimentos com a vibração induzida pelo escoamento em cilindros de seção quadrada e cilindros de seção quadrada e arestas arredondadas com baixa razão de aspecto foram realizados em um tanque de reboque. Estas diferentes geometrias de cilindros foram testadas e suportadas elasticamente por um conjunto de molas lineares. Dois ângulos de incidência diferentes foram testados: 0 e 45 graus. Os resultados de amplitude na direção transversal para modelos submetidos à incidência de 0 graus mostraram ser maiores. Além disso, as oscilações em yaw se mostraram importantes em todos os caso analisados. O efeito das arestas se mostrou importante, particularmente na incidência de 45 graus, para velocidades reduzidas maiores que 8.
Title in English
Flow-induced motion around cylinders with geometry changes in the extremities.
Keywords in English
Low aspect ratio
Square-section cylinder
Vortex-Induced Vibration (VIV)
Abstract in English
The development of the offshore industry has meant that the demand for ultradeep water floating units has increased, and with this, a greater interest in the phenomena arising from FIV in spar, TLP and semi-submersible platforms has arisen. In order to increase the area knowledge, experiments were performed with floating cylinders with different geometries, with low aspect ratio (L/D = 2). Experiments of flow-induced vibration in cylinders with sharp aokokoknd rounded square section with low aspect ratio were performed in a towing tank. These geometries have been tested and elastically supported by a set of linear springs to provide low structural damping to the system. Two different incidence angles were tested: 0 and 45 degrees. The transverse response amplitudes for the 0-degree flow incidence were found to be larger. Moreover, yaw oscillations are important for all the cases analyzed. The rounded effect on the cylinders of square section were important, particularly for the the 45-degree incidence at reduced velocities higher than 8.
 
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Publishing Date
2019-07-23
 
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