Investigation of Granular Flow Dynamics by Hyperpolarized-Gas and Pulsed-Field-Gradient NMR

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The goal of this proposal is to employ non-local nuclear magnetic resonance (NMR) to obtain particle displacement information on several granular systems for comparison with theoretical predictions. Systems will include a vertically oscillating container filled with granular solids, a fluidized bed, and a gravity driven granular flow down a vertical channel. The motion of the interstitial gas will be characterized using hyperpolarized nobel-gas NMR (PFG-NMR), and the microscopic motion of the grains will be monitored with pulsed-field gradient NMR. The PFG-NMR technique permits the measurement of the motion of molecules over distance scales of 100nm or greater and time scales of milliseconds to seconds. Detailed predictions exist for small scale fluctuations as well as for larger features such as shear layers at boundaries, one- and two-dimensional density waves, and the gas flow pattern in fluidized-bed bubbles. Because of the complexity of current models, simplifying assumptions must be made to obtain numerical results. The proposed experiments will test the validity of the model predictions. If successful, this work should lead to a better understanding of pattern formations and may be applied to important systems such as fluidized beds.