Characterization models of poroelastic materials: A review - Research Paper Example

This paper reviews several characterization models of poroelastic materials. Both theoretical and numerical models such as empirical, phenomenological, finite element models, etc. are discussed. The aim is to provide a brief description and review of the various characterization models presently in existence. 3.2 Theoretical Modeling The determination of the sound absorption properties may be differentiated into three kinds, namely – empirical, microstructural and phenomenological models (Bo & Tianning 2009).

These are discussed as follows: 3.2.1 Empirical Models One of the first empirical models for determining properties of poroelastics is the one given by Delany and Bazley (1969). This model estimates the impedance of the material assuming that the material is a rigid skeleton (Sagartzazu, Hervella-Nieto, & Pagalday 2008). Other such models also exist that make the same rigid skeleton assumption, and they are also known as equivalent fluid models because according to them, the porous material has high stiffness towards the fluid medium (Sagartzazu, Hervella-Nieto, & Pagalday).

Other models also exist that take movements in both, the skeleton and the fluid, into account. These theoretical models are more complete and are based on many parameters belonging to both the fluid and the skeleton of the material. The empirical models are generally used for the estimation of the complex propagation constant and the impedance using the knowledge of the material’s secondary properties (Sagartzazu, Hervella-Nieto, & Pagalday). The Delany-Bazley model is the most representative model among the various empirical models for characterization of poroelastics.

This model is based on numerous impedance tube measurements and is good for determining the propagation constant and characteristic impedance at frequencies higher than 250 Hz but not at low frequencies (Rey et al. 2012; Fouladi, Ayub, & Nor 2011). This is a simple model based on the flow resistivity of the material (Kidner & Hansen 2008). The validity of this model for lower and higher frequencies was further extended by Bies and Hansen, to which further improvements were made by other investigators (Rey et al.). Bies and Hansen demonstrated that apart from flow resistivity, the linear relationship between bulk density and flow resistivity of the material is also important (Kidner & Hansen).

They combined the empirical formulae from the Delany and Bazley model with those of Morse in their theoretical predictions for porous materials. Other empirical models include those of Allard and Champoux (1992 cited in Sagartzazu, Hervella-Nieto, & Pagalday 2008). This model works on the assumption that the thermal effects are dependent on frequency. The model works well for low frequencies. The Mechel-Ver Model also works well at low frequencies, unlike the Delany-Bazley model (Sagartzazu, Hervella-Nieto, & Pagalday).

The Voronina model is another simple model that is based on the porosity of a material (Rey et al.). This model uses the average pore diameter, frequency and porosity of the material for defining the acoustical characteristics of the material. Voronina (1999 I) further extended the empirical model developed for porous materi