Convection and segregation in a horizontal mixer

Granular flow patterns were investigated in a horizontal cylinder stirred by series of long flat blades mounted on a centre shaft. Positron emission particle tracking (PEPT) enabled the agitation process within the bulk of 2-mm glass ballotini to be followed using a tracer identical to the bulk. The axial convective structure seen for a mixer with a single blade was again encountered. Comparisons were made with smaller and bigger tracers. The particles revealed a similar radial velocity structure whatever the tracer size, but axial motion decreased with increased tracer size. The studies aid the interpretation of the PEPT data and also develop insight into the onset of segregation in mixers.