Determination of the viscous characteristic length in air-filled porous materials by ultrasonic attenuation measurements

Philippe Leclaire (1) , Luc Kelders (1) , Walter Lauriks (1) , Christ Glorieux (1) , Jean Thoen

1 LATF - Laboratorium voor Akoestiek en Thermische Fysica

The concept of viscous characteristic length is used to describe the acoustical behavior of fluid-saturated porous media in the high-frequency regime. A method to determine this parameter consists of measuring the wave attenuation in the high-frequency limit. This method has already been used for porous materials saturated by superfluid ²He. It is tested in the case of air-filled absorbent materials in a frequency range of [50-600 kHz]. The thermal characteristic length is assumed to be known or measured independently. Two examples are presented. In the first one the method is usable and the viscous characteristic length A is deduced from the high-frequency behavior of the attenuation per cycle. In the second example, an additional attenuation occurs at high frequencies and only an estimate of A can be given. Nevertheless, the estimation appears to be rather accurate. The values obtained by this method are compared to those determined by a nonlinear fit of the dispersion curves.

Domaines: Matériaux

Philippe Leclaire, Luc Kelders, Walter Lauriks, Christ Glorieux, Jean Thoen. Determination of the viscous characteristic length in air-filled porous materials by ultrasonic attenuation measurements. Journal of the Acoustical Society of America, 1996, ⟨10.1121/1.415378⟩. ⟨hal-01330321⟩