|
Numerical simulation of vibro-acoustic systems is usually done
by finite element or boundary element methods. Both deterministic
techniques are based on an element discretisation of the problem
domain or its boundary surface. The dynamic variables within each
element are expressed in terms of simple (polynomial) shape
functions, which do not satisfy the governing dynamic equations.
These element based methods are well suited for the dynamic
analysis of arbitrarily shaped (vibro-acoustic) systems, but their
use is practically restricted to low-frequency applications. At
higher frequencies, structural and acoustic wavelengths become so
small that a prohibitively large number of elements and
computational effort would be required to get reasonable prediction
accuracy.
In order to extend the applicability of numerical prediction
techniques towards vibro-acoustic analysis at higher frequencies,
the PMA division has developed a wave based method (WBM). The WBM
is a deterministic technique, based on the indirect Trefftz
approach. Instead of using locally defined element shape functions,
the WBM applies globally defined wave functions, which do satisfy
the governing dynamic equations. The vibro-acoustic response of the
system at a certain frequency is expressed as a summation of wave
function contributions, which result from an integral formulation
of the problem boundary conditions.
The WBM exhibits better convergence properties than the element
methods resulting in smaller model sizes and computational efforts.
However, the WBM is most efficient for systems of moderate
geometrical complexity. The WBM has been successfully applied for
the steady-state analysis of bounded and unbounded acoustic
problems, for the vibration analysis of flat plate assemblies and
for the study of vibro-acoustically coupled systems. Furthermore,
the applicability of the WBM has been extended to problems of
arbitrary geometry by the development of hybrid coupling schemes
with finite elements. These hybrid approaches aim at combining the
benefits of both techniques, namely the high computational
efficiency of the WBM and the geometrical flexibility of finite
element methods.
Currently, research activities focus on five items:
- optimisation of the hybrid schemes by making use of
state-of-the-art finite element technologies;
- investigation of a multi-level WB modelling approach for
efficient modelling of concave shapes;
- extension of the unbounded acoustic WB methodology towards
transmission and multi-fluid problems;
- investigations towards structural intensity and power flow
analysis with the WBM;
- and application of the WBM for the analysis of porous
materials.
 
|
Print
