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Master's Dissertation
DOI
10.11606/D.3.2013.tde-11072014-111759
Document
Author
Full name
Daniel Rodrigo Barreto Silva
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2013
Supervisor
Committee
Pesce, Celso Pupo (President)
Fernandes, Antonio Carlos
Saltara, Fábio
Title in Portuguese
O conceito de inércia adicional do escoamento em torno de cilindro circular em oscilação forçada.
Keywords in Portuguese
Equação de Morison
FreeFem++
Inércia adicional
Massa adicional
Oscilação forçada
Abstract in Portuguese
Um corpo imerso em movimento arbitrário interage com o fluido ao redor. As partículas fluidas próximas ao corpo exercem certa resistência inercial quando o corpo acelera ou desacelera, devido ao acoplamento dinâmico entre corpo e fluido. Este trabalho resolve as equações de Navier-Stokes, discretizadas pelo método dos elementos finitos, usando o programa de código aberto (LGPL) FreeFem++, e avalia as forças do escoamento que agem sobre um cilindro circular, o qual oscila harmonicamente em um fluido em repouso para números de Keulegan-Carpenter (KC) entre 0,5 e 10, mantendo o parâmetro da frequência constante e igual a 35. Os números de KC selecionados visam entender os conceitos de inércia adicional em fluido viscoso, desde em escoamentos simples até em escoamento mais complexos. O escoamento é bidimensional, laminar e não estacionário. A força em linha com o movimento é então decomposta, conforme equação de Morison, como a soma de uma força inercial e outra de arrasto. Os resultados possuem boa aderência com trabalhos analíticos, experimentais e numéricos anteriores disponíveis na literatura. A dinâmica do escoamento induzido pelo cilindro em movimento harmônico é rica. Para baixo KC, o escoamento é simétrico e estável. Para valores intermediários de KC, a camada limite descola da superfície do cilindro e vórtices são emitidos a cada meio-ciclo. Para elevado KC, certa assimetria se desenvolve e vórtices são emitidos obliquamente a cada meio-ciclo.
Title in English
The concept of added inertia of the flow around an oscillating cylinder in forced oscillation.
Keywords in English
Added mass
Forced oscillation
FreeFem++
Inertial force
Morison equation
Abstract in English
An immersed body in arbitrary motion interacts with the surrounding fluid. The fluid particles close to the body impart their inertial resistance when the body accelerates or decelerates, due to the dynamic coupling between body and fluid. This work solves the incompressible Navier-Stokes equation, discretized by the finite element method, using the open source (LGPL) software FreeFem++, and evaluates the flow forces that act on a circular cylinder which oscillates harmonically in a resting fluid for Keulegan- Carpenter (KC) number between 0.5 and 10, with a constant frequency parameter equal to 35. The selected KC numbers aims to understand the concepts of added inertia in viscous fluid, from simpler to more complex flows. The flow is two dimensional, laminar and unsteady. The in-line force is then decomposed, according to Morison equation, as a sum of an inertial force and a drag force. The results agree with former analytical, experimental and numerical works available in the literature. The dynamics of the flow induced by the harmonically moving cylinder is rich. For low KC, the flow is symmetric and stable. For intermediate KC, the boundary layer detaches from the cylinder surface and vortices are shed at each half cycle. For higher KC, certain asymmetry develops and vortices are shed obliquely at each half cycle.
 
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Publishing Date
2014-07-21
 
WARNING: The material described below relates to works resulting from this thesis or dissertation. The contents of these works are the author's responsibility.
  • Silva, Daniel R.B., and Pesce, Celso P. A FEM study on the added inertia of an oscillating cylinder in viscous flow. In COBEM2013, Ribeirão Preto, 2013. 22nd International Congress of Mechanical Engineering., 2013.
All rights of the thesis/dissertation are from the authors
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