master
Vibroacustica de Barragens
Modelagens Numéricas pelo Métodos dos Elementos Finitos
em Problemas de Interação Fluido-Estrutura
Banca Examinadora da Dissertação de Mestrado em Estruturas
Lineu José PEDROSO Dr.Ing (UnB), Paul William PARTRIDGE PhD (UnB)
Luciano Mendes BEZERRA PhD (UnB), Renato PAVANELLO Dr.Ing (UNICAMP)
Departamento de Engenharia Civil - Faculdade de Tecnologia
Universidade de Brasilia
Data: 28 de junho de 2000 Local: Auditorio do EnM - FT/UnB
SUMMARY
The study of fluid-structure interaction in which the solid domain is in contact with the fluid, is necessary for many problems encountered in aeronautical, civil, mechanical, nuclear, naval and bioengineering. Such problems may be of different types: problems of vibrations caused by fluid flow, non-linear problems due to impact or explosions in closed systems and problems of vibrations in flexible structures connected to a linear acoustic medium are typical examples with direct application in nuclear reactors, dams, aircraft, offshore platforms, turbines and others. For this reason, the study of fluid-structure interaction has become an important area of international research.
do Aluno Marcus Vinicius Girão de Morais
Figura 1 - Scheme of gate-reservoir-column system: (a) gate-reservoir suite,
isolate gate scheme - (b) perspectif, and (c) floor plan -.
Figura 2 - Example of a dam with a group of gates (Léger e Tinawi,2000)
(P. Léger and R. Tinawi (2000) Structural safety evaluation of gravity dam for hidrodynamics loadings, Notes de Cours Sur: La securité et l'integrité structurale des barrages en beton, Chaire de barrage, University of Montreal, Civil Engineering Department, Montreal).
In this work, there 2D problems of fluid-structure interaction are considered using a Lagrangean formulation for the solid and an Eulerian formulation for the fluid using the finite elements method. The objective is to build a computational tool which will enable more complex studies to be carried out in the future. For this reason a mixed variational formulation was adopted with dissipation ($\vec{u}$, p, \pi, \eta$) using the formalism of Morse and Feshbach. The displacements $\vec{u}$ describe the behaviour of the solid, while the pressure p, the displacement potential $\pi$ and the surface elevation $\eta$ describe the behaviour of the fluid.
In this preliminary study, simple 2D problems are considered in which the structure is linear elastic and the fluid is compressible, irrotational and inviscid (acoustic problem). The computational formulation is tested for typical dynamic problems with uncoupled or coupled analytical solutions and with results obtained from the literature for both the time and frequency domain.
The formulation considered involves very sparse ill-conditioned matrices and as a consequence it was necessary to study the minimization of instabilities by balancing the matrices.
Finally, it is concluded that the formulation represents properly the class of problems considered and the numerical results obtained are in good agreement with the analytical results and with the results obtained from the literature.
Figure 3 - General Scheme of a coupled system dam-reservoir (a) and equivalent dam-reservoir system (b).
Figure 4 - First coupled mode of vibration (wC,1 = 813,86 rad/s).
Figure 5 - Transient reponse of adimensional pressure p to a senoidal loading F sin(0,8·wC,1t).
DOWNLOAD (PDF):
>[MUNB00] M.V.G. De Morais (2006) MODELAGENS NUMÉRICAS PELO MÉTODO DOS ELEMENTOS FINITOS EM PROBLEMAS DE INTERAÇÃO FLUIDO-ESTRUTURA(in portuguese), Master in Structures, University of Brasilia (UnB), Brasilia - BRAZIL;
BIBLIOGRAPHIE PRODUCTION:
INTERESTING PAPERS
>[GGG83] D. Guilbaud, F. Gantenbein, R.-J. Gibert (1983) A substructure method to compute the 3D fluid-structure interaction during blowdown. 7th SMiRT - Transaction on International Congress for Structural Mechanics in Reactor Technology, August 22-26, Chicago, (B1-06);
>[OhVa83] R. Ohayon, R. Valid (1983) Symmetric primal-dual variational formulations of coupled dynamic systems: Three-dimensional elasticity, shells, fluid-structure problems. 7th SMiRT - Transaction on International Congress for Structural Mechanics in Reactor Technology, August 22-26, Chicago, (B1-01);
>[BGG83] L. Brusa, A. Greco, A. Gurizzan (1983) Reduction Methods for Vibration Analysis of Fluid Structure Systems. 7th SMiRT - Transaction on International Congress for Structural Mechanics in Reactor Technology, August 22-26, Chicago, (B1-05);