On representativeness of the representative cells for the microstructure-based predictions of sound absorption in fibrous and porous media
Invited paper
Institute of Fundamental Technological Research
Wednesday 3 june, 2015, 14:20 - 14:40
0.7 Lisbon (47)
Abstract:
Realistic microstructure-based calculations have recently become an important tool
for a performance prediction of sound absorbing porous media, seemingly suitable
also for a design and optimization of novel acoustic materials. However, the
accuracy of such calculations strongly depends on a correct choice of the
representative microstructural geometry of porous media, and that choice is
constrained by some requirements, like, the periodicity, a relative simplicity, and
the size small enough to allow for the so-called separation of scales. This paper
discusses some issues concerning this important matter of the representativeness of
representative geometries (two-dimensional cells or three-dimensional volume
elements) for sound absorbing porous and fibrous media with rigid frame. To this
end, the accuracy of two- and three-dimensional cells for fibrous materials is
compared, and the microstructure-based predictions of sound absorption are
validated experimentally in case of a fibrous material made up of a copper wire.
Similarly, the numerical predictions of sound absorption obtained from some regular
Representative Volume Elements proposed for porous media made up of loosely-packed
identical rigid spheres are confronted with the corresponding analytical
estimations and experimental results. Finally, a method for controlled random
generation of representative microstructural geometries for sound absorbing open
foams with spherical pores is briefly presented.