Mixtures In A Rotating Drum
We look at mixtures of different sized particles in a rotating drum. We expand upon previous work and look at polydisperse mixtures. For 3 and 4 different sizes of glasses beads we find a band within band (within band) pattern. For 3 sizes the bands oscillate in time with a period of about 45 minutes. For more than 4 sizes, we do not see any band formation.
Ternary Band Oscillation Movie.
We also image the mixture with a high speed high resolution camera (1000 fps) and track particles on the surface. We find interesting patterns in the average velocities of the particles. The small particles flow with a higher velocity then the large particles.
We also simultaneously shake and rotate the drum. We use the response of the flowing layer to measure its fluidity and compare for different particle sizes.