On Figure 5 are presented the average changes of sand concentration during silo discharging
process (taken directly from the measurements capacitance) in function of time for
two different initially sand packing density (loose and dense). The most interesting part of
silo discharging process is between 700 and 2500 frame number for initially loose packing
density of sand and between 825 and 3250 for dense sand. The interpretation of average
changes of sand concentration allows to conclude, that these changes are more noticeable
for dense sand, where volume changes in sand characterizes more differential in sand packing
densities for funnel area and area close to the wall silo. The changes (decreasing) of
concentration for loose sand in funnel are reached about 3–5= initially level during stabilized
flow. In case of dense sand this changes (increasing) is about 12–15=. The next different,
between the sand behaviour for these two cases, is visible in silo discharging time,
where in the case of dense sand time is longer for silo discharging.
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