Direct measurement of surface granular temperature in a high shear granulator

High speed images of the bulk motion in a flat disc high shear granulator have been analysed using particle image velocimetry (PIV) to obtain surface velocity fields. The fluctuations in the temporal surface velocity field are found to exhibit a Gaussian distribution, allowing direct measurement of the granular temperature from the velocity field. The spatial correlation of fluctuations is examined, indicating a high level of correlation at the length scale of granule diameter, which then decreases rapidly with increasing distance. This spatial correlation profile is shown to be consistent with the expected profile for uncorrelated motion, confirming that individual granules exhibit random fluctuations during bulk motion.