EXPERIMENTAL INVESTIGATION OF PORE-SCALE TRANSPORT IN AQUEOUS HETEROGENEOUS POROUS MEDIA

摘要

Chemical transport in aqueous heterogeneous poroussystems have been studied experimentally via novelnonintrusive fluorescence microscopic imaging (FMI)techniques. The techniques involve 3D visualization andquantification of flow fields within a refractive index-matchedtransparent porous column. The refractive index-matchingyields a transparent porous medium, free from any scatteringand refraction at the solid-liquid interfaces, as a resultallowing direct optical probing at any point within theporous system. By illuminating the porous regions withinthe column with a planar sheet of laser beam, flow processesthrough the porous medium can be observed microscopically,and qualitative and quantitative in-pore transport informationcan be obtained at a good resolution and a good accuracy. ACCD camera is used to record the fluorescent images at everyvertical plane location while sweeping back and forth acrossthe column. These digitized flow images are then analyzedand accumulated over a 3D volume within the column.Experiments have been performed at seven Reynolds (andPeclet) numbers covering a wide range of flow conditions.Microscopic values of velocity, concentration, and poregeometry have been obtained at a measurement resolution ofmore than 300,000 measurement points per given time. Thispaper reports on the values of concentration gradients andbreakthrough curves evaluated this way as a function of timeand axial position within the column.