  This paper presents an experimental and numerical investigation of
solid-liquid fluidized beds consisting of bonded spheres in very narrow tubes,
i.e., when the ratio between the tube and grain diameters is small. In narrow
beds, high confinement effects have proved to induce crystallization, jamming
and different patterns, which can be intensified or modified if some grains are
bonded together. In order to investigate that, we produced duos and trios of
bonded aluminum spheres with diameter of 4.8 mm, and formed beds consisting
either of 150-300 duos or 100-200 trios in a 25.4 mm-ID pipe, which were
submitted to water velocities above those necessary for fluidization. For the
experiments, we filmed the bed with high-speed and conventional cameras and
processed the images, obtaining measurements at both the bed and grain scales.
For the numerical part, we computed the bed evolution for the same conditions
with a CFD-DEM (computational fluid dynamics - discrete element method) code.
Our results show distinct motions for individual duos and trios, and different
structures within the bed. We also found that jamming may occur suddenly for
trios, where even the microscopic motion (fluctuation at the grain scale)
stops, calling into question the fluidization conditions for those cases.
