Thermoacoustic properties of fibrous materials

Abstract

The thermoacoustic properties of fibrous materials are studied using a computational fluid simulation as a test of proposed analytical models for propagation in porous materials with an ambient temperature gradient. The acoustic properties of porous materials have been understood in terms of microstructural models that approximate the material as an array of pores with empirical shape factors used to fit the pore theory to the material. An extension of these theories of acoustics to the thermoacoustic case with an ambient temperature gradient has been proposed by Roh et al. [J. Acoust. Soc. Am. 121, 1413-1422 (2007)] and a model based on Wilson's relaxation approximation for porous acoustics [J. Acoust. Soc. Am. 94, 1136-1145 (1993)] is proposed herein, but the predictions of these analytical models have not been tested successfully against measurements. Accurately characterizing the effects of the applied temperature gradient in a wide bandwidth laboratory setup have proven difficult; as a result, the authors conducted a numerical simulation of propagation within a fibrous geometry in order to test the predictions of the analytical models. The results for several fibrous samples show that the models yield a reliable prediction of thermoacoustic performance from the shape factors and relaxation times.

Three-dimensional reconstruction of a random fibrous medium: Geometry, transport, and sound absorbing properties

“…The reconstructed fibrous medium is used as a basis for the computation of its geometrical, transport, and sound absorbing properties. In discussing a range of experimental data on the microstructure of non-woven fibrous materials involving x-ray micro computed tomography and microscopy analysis, previous works had relied on ad hoc "fiber anisotropies" 7,8 or "volume weighted average radius." 9 Here it is shown that, in conjunction with the bulk porosity, these parameters: (1) Contribute to a precise description of the acoustical characteristics of fibrous absorbents.…”

Life-Cycle Assessment and Acoustic Simulation of Drywall Building Partitions with Bio-Based Materials

“…The airborne sound insulation of each solution has been computed using the simulation software Aisla 3 [ 13 ]. This software applies the mathematical model proposed by Ookura & Saito [ 14 ] and Chen & Jan [ 15 ], which uses the mechanical data of the materials to determine the coupling impedance (Z ij ) between layers. The simulation process is summarized in Figure 2 .…”

Influence of magnetic field on the periodically oscillating fluid inside a porous medium attached to a thick solid plate

“…Their theories included development of thermal and viscous functions, wave, and temperature distribution equation. Jensen and Raspet [27] [30] considered porous medium stack where Darcy momentum equation was used to model the flow field. The problem was formulated as a conjugate heat transfer problem with non-zero wall thickness.…”