G. Lu

Magnetic resonance imaging (MRI) study of jet height hysteresis in packed beds

The jet-spout transition in fluidized beds can show hysteretic behavior. In this study the jet-spout transition was studied as a function of orifice velocity for particles of different size and shape using Magnetic Resonance Imaging (MRI). The measurements showed that the particle shape primarily affect to the width of the hysteresis loop whereas particle size governs the position of the hysteresis loop with regards to the orifice velocity.

The formation of polygon-shaped patterns in vibrated, cylindrical granular beds

In this work particle image velocimetry (PIV) was employed to probe the motion of particles within a quasi-2D vibrated bed of circular cross-section. We have observed a polygon-shaped pattern for Γ = A(2π f)2/g greater than 10. It has been argued that the polygon pattern formed in 2D cylindrical beds is related to the arching structure encountered in squareshaped vibrated beds [G. Lu, J. R. Third, M. H. Kohl, and C. R. Muller, 2012. On the occurrence of polygon-shaped patterns in vibrated cylindrical granular beds. The European Physical Journal E 35, 90.]. However, using PIV a significant difference in the velocity profiles in the polygon and the arching patterns was observed. We found that in the arching structure the velocity profile around a node was highly symmetric, whereas this was not the case for the polygon structure. Using cylindrical beds of different diameters filled with a constant number of particles, we could confirm that the spatially varying filling height of cylindrical beds is the main ...