Gas flow patterns in a granular fluidized bed

Here we demonstrate the use of magnetic resonance imaging for monitoring a laser-polarized xenon ( \(^{129}\) ${}^{129}$ Xe) gas working as a fluidizing phase for a glass bead pack, inside a straight circular tube, simulating a granular gas-fluidized bed. The imaging method enabled encoding spatially resolved velocity and diffusion 2D-axial maps of the gas vertical upflow at variable flow regimes. From these maps one could identify gas flow transitions, hysteresis loops, regions of stagnation, and reversed flow, all of which associated, as well as complementary, to reported flow dynamics probing the particles inside the bed. In particular, we focused on the initial stage of bubbling where quantitative data on gas flow spatial maps and their potential correlation with the granular particles dynamics are scarce.