Magnetic resonance imaging of interstitial velocity distributions in porous media
In this article we report on a promising application of Magnetic Resonance Imaging (MRI), which can measure local interstitial velocity distributions inside fully-saturated porous media. We have extended the standard three-dimensional MRI sequence to include local velocity information. During flow, the moving spins of the fluid (in this case water) accumulate phase in the presence of magnetic field gradients. This phase is proportional to the local velocity. By repeating the measurement under the influence of different magnetic gradient strengths, we can reconstruct the velocity distribution in each volume element (voxel). Using this technique to study pressure-driven flow through a fully-saturated, cylindrical packed bed, we have observed flow channeling near the walls and an exponential distribution of velocities. (A)
