Multiscale prediction of acoustic properties for glass wools: Computational study and experimental validation

Abstract

This work is concerned with the multiscale prediction of the transport and sound absorption properties associated with industrial glass wool samples. In the first step, an experimental characterization is performed on various products using optical granulometry and porosity measurements. A morphological analysis, based on scanning electron imaging, is further conducted to identify the probability density functions associated with the fiber angular orientation. The key morphological characterization parameters of the microstructure, which serve as input parameters of the model, include the porosity, the weighted volume diameter accounting for both lengths and diameters of the analyzed fibers (and therefore the specific surface area of the random fibrous material), and the preferred out-of-plane fiber orientation generated by the manufacturing process. A computational framework is subsequently proposed and allows for the reconstruction of an equivalent fibrous network. A fully stochastic microstructural model, parameterized by the probability laws inferred from the database, is also proposed herein. Multiscale simulations are carried out to estimate transport properties and sound absorption. With no adjustable parameter, the results accounting for ten different samples obtained with various processing parameters are finally compared with the experimental data and used to assess the relevance of the reconstruction procedures and the multiscale computations.

A self-consistent approach for the acoustical modeling of vegetal wools

“…So, using Mesurim c software, the measurements the SCM cyl modeling approach is based on an equivalent fiber radius value, in a first approach, we choose a single radius value corresponding to the mean of the fibre radii [3,8,13,48]. In [23,28] the fibre radius is weighted according (a) (b) to its corresponding fibre volume. This typically shifts the single fibre radius 280 towards larger values.…”

“…In [25,26] an hybrid approach is used on the basis of a numerical homogenization mixed with the JCAL model by numerical calculations related to the finite element method. This approach has been adapted to the case of porous media such as melamine foam in [27] and more recently to the special cases of a glass wool [28] and a vegetal fibrous materials (milkweed fibres) [29]. These methods have several advantages.…”

Benchmarks for microstructure-based modelling of sound absorbing rigid-frame porous media

“…This approach is less computationally intensive, since it uses the computed eight (or fewer) parameters as inputs to the semi-analytical formulas of the JCALP model (or its variations). Such a hybrid approach has been used to investigate the acoustical properties of fibrous materials [37][38][39][40][41][42][43], granular media [33,37,[44][45][46][47], various polymeric and open-cell foams [34,35,[48][49][50][51][52][53][54][55][56][57][58][59], ceramic foams with spherical pores [60], metallic foams [36], and syntactic hybrid foams, i.e. open-cell polyurethane foams with embedded hollow microbeads [61].…”

“…, where 43) and B 0 = γP 0 is the adiabatic bulk modulus of the pore fluid. Now, the effective speed of sound and characteristic impedance for the fluid acoustically equivalent to porous medium can be computed from the formulas involving the dynamic tortuosities α and α th (or instead of α th , the more convenient function β defined above), namely, c e (ω) = B e (ω)…”

Dynamic equations of a transversely isotropic, highly porous, fibrous material including oscillatory heat transfer effects

“…Recent work into the acoustic modelling of fibrous porous materials has increasingly focussed on microstructural aspects, i.e., the fibre diameter distributions, fibre orientation angles, and the distributions of fibre lengths [1][2][3] in order to predict the transport properties of the material. In practice, this means that a combination of numerical and experimental techniques is used to estimate the macroscopic transport properties of the fibrous material, such as static viscous and thermal permeabilities, viscous characteristic lengths, and tortuosity.…”