MAGNETIC-RESONANCE-IMAGING OF VIBRATING GRANULAR BEDS BY SPATIAL SCANNING

Nuclear magnetic resonance is becoming an important experimental techn ique to study the behavior of moving granular materials because of its unique ability to measure concentration, velocity, and dissipation wi thin the bulk granular materials rather than only on the surface. Of a ll the common motions of such assemblies of particles, the most diffic ult to measure is the vibrating bed because of the unsteady motion. Th is paper demonstrates a nuclear magnetic resonance imaging method to s tudy highly energetic vibrating granular beds by spatial scanning. In contrast to Fourier imaging, spatial scanning prevents scattering of i mage intensities caused by unsteady motion. Two-dimensional images of a vibrating bed undergoing period doubling were obtained. A band of hi gh shear was identified by reduced image intensity. It traveled back a nd forth across the bed with each cycle of up and down motion of the b ed. Further studies of vibrating beds with the sequence modified for v elocity encoding and velocity compensation should provide additional u seful information. (C) 1997 American Institute of Physics. [S0034-6748 (97)03411-4].