Three-dimensional velocity measurement of complex interstitial flowsthrough water-saturated porous media by the tagging method in the MRItechnique

Abstract

Local velocity measurements of interstitial flow through porousmedia and observation of the local pore geometry, which strongly influencesthe flow field, are necessary in order to understand the transport mechanismin a porous system. In order to investigate the effect of pore geometry on theflow field in porous media, three-dimensional velocity measurements ofinterstitial flow through two porous samples with different pore geometrieshave been experimentally performed using magnetic resonance imaging (MRI). Theporous samples were made from cylindrical tubes in one case packed withcrushed glass particles and in the other spherical beads. Based on theobserved images of the porous samples, the porosity and pore sizedistributions as pore structure parameters were determined by image analysis.The two- and three-dimensional velocity vectors of the steady-state flow inthe void spaces of the crushed glass sample have been measured using aspin-echo sequence with tagging pulses. The obtained velocity maps show astrong non-uniform flow. In places, reversed flow is induced by the poregeometry. The effect of the mean flow velocity on the change in the flowpattern has been investigated in the mean flow velocity range from 3.84 to13.2 mm s-1. The frequency distribution of the axial velocity componentof the interstitial flows through the packed beads was broader than that ofthe crushed glass pack.