DIRECT MEASUREMENT OF INTERSTITIAL VELOCITY-FIELD VARIATIONS IN A POROUS-MEDIUM USING FLUORESCENT-PARTICLE IMAGE VELOCIMETRY

Fluorescent-particle image velocimetry (FPIV) is used in conjunction with refractive-index matching to measure flow velocities in the interstitial regions of a porous medium. Adaptations that allow the use of conventional PIV methodology in index-matched systems are discussed, and the results of flow field measurements in a porous test bed under saturated flow conditions are presented. Preliminary analysis of these data, in which the horizontal and vertical components of the interstitial velocity vectors were averaged over a specified region within the medium, are also presented and compared with the vertical velocity component calculated from the total volumetric flow rate. The magnitude of the macroscopically derived and FPIV-measured values are found to be very similar. In general, our results demonstrate the utility of the FPIV technique to determine both the point velocity and the local volume-averaged velocity within porous media.