Time-resolved measurements of the shape and position of a
spout were done with a high speed X-ray CT scanner. This system contains 3
X-ray sources and detector arrays, which makes it possible to scan the whole
cross section of spouted bed of 24cm diameter simultaneously. We
reconstructed the images of the spout in several cross sections. The spout size
and position is found from the raw data with a temporal resolution of 2500 fps
and spatial resolution of 1 mm.
The time averaged spout size is validated with McNab's prediction. From the spout data we estimated the
particle circulation in the bed. It shows good agreement with theoretical predictions.
When U/Ums = 0.96 ~ 1.44 (with Ums the minimum spout
velocity), there is very small fluctuation of the spout diameter, with an
amplitude less than 10% of the spout diameter. We analyzed the fluctuation using
the Power Spectrum Density. It is shown that the spouts are most stable when
U/Ums = 1.20~1.27. We also analyze the movement of the center of the
spouts, and find that there is an oscillation of the spout position when it is
close to surface of the bed.
Figure 1. Experiment
setup: (a) Overall; (b) 3 D view; (c) Top view.
Figure 2. The time-averaged profile of
the spouts.
Figure 3. The stability of the spouts' size
indicated with average Power Spectrum Density (Red -> Blue: Instable ->
Stable).