Determination of transport parameters in air-saturated porous materials via reflected ultrasonic waves

Abstract

An ultrasonic reflectivity method of evaluating the acoustic parameters of porous materials saturated by air (or any other gas) is discussed. The method is based on experimental detection of waves reflected at normal incidence by the first and second interface of the material. This method is based on a temporal model of direct and inverse scattering problems for the propagation of transient ultrasonic waves in a homogeneous isotropic slab of porous material with a rigid frame [Fellah et al., J. Acoust. Soc. Am. 113, 61-73 (2003)]. Generally, the conventional ultrasonic approach can be used to determine tortuosity, and viscous and thermal characteristic lengths via transmitted waves. Porosity cannot be estimated in transmitted mode because of its very weak sensitivity. First interface use of the reflected wave at oblique incidence leads to the determination of porosity and tortuosity [Fellah et al., J. Acoust. Soc. Am. 113, 2424-2433 (2003)] but this is not possible at normal incidence. Using experimental data of reflected waves by the first and second interface at normal incidence simultaneously leads to the determination of porosity, tortuosity, viscous and thermal characteristic lengths. As with the classic ultrasonic approach for characterizing porous material saturated with one gas, both characteristic lengths are estimated individually by assuming a given ratio between them. Tests are performed using weakly resistive industrial plastic foams. Experimental and numerical results, and prospects are discussed.

Transient Acoustic Wave Propagation in Porous Media

“…The propagation equation can be easily obtained from (24,25). The propagation equation obtained has exactly the same form as the equation (13), the only difference appears at the…”

Ultrasonic non destructive characterization of trabecular bone: estimation of the propagation velocity and attenuation

“…The Biot theory was developed to predict the acoustical properties of fluid saturated porous rocks in the context of geophysical testing but has been used extensively to describe the wave motion in trabecular (cancellous) bone [10]. Biot model describes the acoustic wave propagation in the porous medium.…”

“…This theory has been developed and adapted to the description of the ultrasonic waves propagation in bone (trabecular bone) by several authors, in particular Hosokawa and Otani [7,8], Hair and Langton [9], Fellah and al. [10]. Biot theory predicts the existence of two longitudinal waves (the slow wave and the fast wave) and a transverse wave.…”

A time-domain model of transient acoustic wave propagation in double-layered porous media

“…[5][6][7][8][9][10][11][12][13] In the frequency domain, measurements of the attenuation coefficient may be more robust than measurements of phase velocity. In these situations, the application of the Kramers-Kronig [11][12][13] dispersion relations may allow the determination of the phase velocity from the measured attenuation coefficient.…”

“…3,4,[8][9][10][11] When a broadband ultrasound pulse passes through a layer of a medium, the pulse waveform changes as a result of attenuation and dispersion of the medium. The classic method for predicting a change in the waveform of a signal passing through a medium relies on the system's impulse response.…”