(748e) X-Ray Measurements of Voidage in a Flat-Bottomed 2-D Silo with a Central Discharge

As part of an investigation of residence time distribution in discharging silos, we have constructed apparatus compatible with the dimensions and beam intensity of a Philips Allura Xper FD X-ray machine, to which we have access at a local hospital. The imaging area is 250 mm x 350 mm, and the beam intensity constrains the thickness of the silo to approximately 15 mm for silica based materials, glass ballotini in the work reported here. The X-ray machine can record 15 images per second. Raw data is available as a grey-scale intensity, and is interpreted by interpolation between intensities for prepared cartridges of known voidage located in the field of view in all experiments. Results on work in progress are reported for the transient period immediately after the start of discharge, and also for steady state flows for narrow slots spanning the full 15 mm width of the silo.