Experimental study of tracer dispersion in sintered glass porous materials of variable compaction

Abstract

Experimental measurements of tracer dispersion in sintered glass samples of variable compaction are reported. The results are compared to measurements in nonconsolidated packings of the same glass beads used to prepare the sintered material. While normal ‘‘Gaussian’’ dispersion is obtained in nonconsolidated samples (37% porosity), clear-cut anomalies (such as dispersion ‘‘tails’’ at long times) are observed in sintered materials even with a very low degree of compaction (34% porosity). Experimental curves are analyzed with a ‘‘capacitance’’-type model. The effective dispersion coefficient increases by a factor of 60 when the porosity decreases from 37% to 14% at higher degrees of compaction. The characteristic exchange time between the low-velocity regions and the main flow varies linearly with the transit time through the sample. These results are interpreted by the presence of inhomogeneities with a size of several grain diameters.