Civil Engineering Reference
In-Depth Information
Cells
|p|
2.32
2.17
X
2.03
1.88
1.73
1.58
1.44
1.29
1.14
0.995
0.848
Z
Figure 13.17
Illustration of the diffusion effect in the substrate material (Sgard
et al
.
2005). Reprinted from Sgard, F., Olny, X., Atalla, N. & Castel, F. On the use of perfora-
tions to improve the sound absorption of porous materials.
Applied acoustics
66
, 625-651
(2005) with permission from Elsevier.
etc
...
). Note that the numerical model is not restricted to the calculation of absorption
of single heterogeneous porous materials placed into a rectangular standing wave tube. It
can also deal with the computation of transmission performance of complex multilayered
systems involving plates, septum, air gaps, conventional and heterogeneous porous mate-
rials as illustrated in Figure 13.2. Several examples can be found in Sgard
et al
. (2005
and 2007).
13.9.6 Modelling of smart foams
This example, taken from Leroy (2008), illustrates the use of the
(
u
s
,p)
formulation for
modeling smart foams. A smart foam combines the passive dissipation capability of a
foam in the high frequency range and the active absorption ability of an actuator (gen-
erally piezoelectric PVDF) in the low-frequency range. This results in a passive/active
absorption control device that can efficiently operate over a broad range of frequen-
cies. The 3D finite element model of a smart foam prototype is presented here with its
experimental validation.
The configuration is made up of a half-cylinder of melamine foam covered with a
PVDF film (Figure 13.18a). The curved shape of the PVDF ensures coupling of in-plane
