Radial segregation driven by axial convection
ABSTRACT We experimentally study the mixing of binary granular systems in a horizontal rotating cylinder. When materials have the same size and differ by dynamic angle of repose only, we observe an axial transport of matter that generates transient radial segregation. The system then evolves towards homogeneity. If materials differ by density also radial segregation becomes steady. A mechanism is suggested where radial segregation is promoted by axial differences of dynamic angle of repose. This differs from the free surface segregation suggested so far to explain radial segregation.
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ABSTRACT: Composition quantification in granular mixtures through colorimetric imaging is addressed. Digital images of binary mixtures have been analysed with three different colour spaces: gray scale, L⁎a⁎b⁎ and HSV. Experiments have been carried out on a small scale drum mixer. After blending, the mixtures have been impregnated with a binder, solidified and sliced. The colorimetric analysis has been carried out on the interior of the granular bed. Results obtained using the three colour-spaces have been performed and compared. The HSV colour space yields better results in terms of accuracy and computational effort. Effectiveness of HSV relies on its independence from shadows that are a distinctive feature of pictures of the three-dimensional granular surface. Very important, HSV does not require a calibration curve to convert colour information into composition, differently from the other colour spaces.Powder Technology - POWDER TECHNOL. 01/2008; 187(3):205-213.