“…At low frequencies, the flow is dominated by viscous forces whereas, at high frequencies, the inertial forces are more important (AURIAULT et al, 1985;JOHNSON et al, 1987). A striking feature uncovered by recent theoretical, experimental and numerical studies, is that all examined porous materials have the same behavior in these two domains (JOHNSON et al, 1987;SHENG and ZHOU, 1988;CHARLAIX et al, 1988;ZHOU and SHENG, 1989;JOHNSON, 1989;YAVARI and BEDFORD, 1990;SMEULDERS et al, 1992;CHAPMAN and HIGDON, 1992;ACHDOU and AVELLANEDA, 1992;PRIDE et al, 1993). Namely, for decreasing to zero, the real part of k() asymptotically approaches the steady-state value k 0 while the imaginary part decreases as .…”