Journal of Fluid Mechanics

Wave propagation in porous media containing a dilute gas–liquid mixture: theory and experiments

D. M. J. SMEULDERS a1 and M. E. H. VAN DONGEN a2
a1 Delft University of Technology, PO Box 5028, 2600 GA Delft, The Netherlands
a2 Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands


The influence of a small amount of gas within the saturating liquid of a porous medium on acoustic wave propagation is investigated. It is assumed that the gas volumes are spherical, homogeneously distributed, and that they are within a very narrow range of bubble sizes. It is shown that the compressibility of the saturating fluid is determined by viscous, thermal, and a newly introduced Biot-type damping of the oscillating gas bubbles, with mean gas bubble size and concentration as important parameters. Using a super-saturation technique, a homogeneous gas–liquid mixture within a porous test column is obtained. Gas bubble size and concentration are measured by means of compressibility experiments. Wave reflection and propagation experiments carried out in a vertical shock tube show pore pressure oscillations, which can be explained by incorporating a dynamic gas bubble behaviour in the linear Biot theory for plane wave propagation.

(Received May 13 1996)
(Revised March 11 1997)