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©2012 Civil-Comp Ltd |
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M. Mansouri1,2, B. Radi1 and A. El Hami2
1LM, FST Settat, Morocco
2LMR, INSA de Rouen, St Etienne de Rouvray, France
Keywords: fluid-structure interaction, vibro-acoustic, numerical simulation, finite element method, reliability based design optimization.
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reference
In this paper focuses on problems of fluid-structure
interaction and specifically the vibro-acoustic coupling which is
generally defined as the contact between bodies interacting
according to the principles of continuum mechanics. The
comprehension of the mechanisms of interactions between a fluid and
an elastic solid are of prime importance in several industrial
applications ( in the aerospace, automotive and civil engineering areas as
well as in biomechanics). When a structure vibrates in the
presence of a fluid, there is an interaction between the natural waves
of each media: the fluid flow generates a structural deformation
and, or the movement of a solid causes the displacement of the fluid.
These applications require an effective coupling. In addition, the
dynamic analysis of the industrial systems is often expensive from
the numerical point of view. For the coupling in the fluid-structure finite
element models, the importance of the size reduction becomes
obvious because the fluid freedom degrees will be added to those of
the structure. A method of condensation will be used to reduce the
size of the matrices.
One of the principal hypotheses in the use of
component mode synthesis method is that the model is deterministic;
it is to say that parameters used in the model have a defined and
fixed value. In fact, all aspects of an analysis model are
uncertain, and uncertainty is either ignored or accounted for using
conservative assumptions. However, the fluctuations in the input
parameters generate significant degradation of the quality of the
deterministic solution. The volatility of the parameters and the other
difficulties require consideration of
variability in the formulation of the coupling problem. So it is
neither financially feasible nor physically possible to eliminate
the dispersion of the input parameters.
The reduction of the dispersion is generally associated with higher costs,
either by
production methods more efficient and accurate processes and
increased efforts in quality control, hence, by accepting the
existence of these uncertainties, the problem must be considered with
uncertainty. Furthermore, the knowledge of the variation response of a
structure involving uncertain materials, geometrical parameters,
boundary conditions, tolerances of manufactures and loading
conditions is essential in the global process of conception. In order to
do that, the modal condensation method is extended to reliability
analysis for coupled fluid-structure finite element models.
A numerical vibratory study is based on a three-dimensional structure
immersed in
water taking into account the acoustic aspect. In this context, the study is focused
very
specifically on a deterministic, stochastic and reliability analysis
through numerical simulations in three-dimensional dynamic fluid-structure
interaction problems. In the case of this problem, the presence of
several parameters to random characters namely the Young's modulus
of the structure and structure density and fluid density, which
often show a great variability, which inevitably leads to a loss
of precision important. Better control of these parameters is thus
based on the use of stochastic methods whose main objective is to
improve the quality and the reinterpretation of results from
simulations. To do this, a good understanding and formulation of the
main phenomena involved in the coupling problem are required.
The results of the reliability based design optimisation study
shows the effectiveness of the steps followed
to condense the system and to take into account the uncertain parameters.
The numerical results are compared with some experimental ones.
The results obtained show the potential of the proposed
methodology and encourage improvement of this procedure for use in
complex coupled fluid-structure systems.
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