We designed and built experiments in which we measure the local porosity, local velocity and temperature pattern of water convecting in a porous medium using Magnetic Resonance Imaging (MRI). MRI is ideal for this application since, standard flow visualization techniques, like shadowgraph and laser velocimetry require that the media used be transparent. In a general porous medium, this condition is not met. Hence, non-invasive flow measurements in a porous medium are difficult to obtain through these standard methods. In particular convective flow patterns and local velocity information for general porous media are lacking in the literature. Using a pulse sequence developed during this project we measure the local porosity, local velocity and temperature pattern of water convecting in cells with several cross-sectional shapes (circular, rectangular, hexagonal) and with various packing arrangements of 3.125mm diameter acrylic spheres. The top and bottom plates of the cell are AlN, a ceramic with a thermal conductivity which is about 1/3 that of copper. These plates are held at constant temperatures with a system of water baths and circulators. Velocity data is obtained for various slices (typically 2mm thick) throughout the cell. The spatial resolution in the within a slice is typically 200 um, although significantly smaller resolution is possible.
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