Investigation of binary granular mixing in a rotating drum

Motivations

Mixing of granular solids is found in diverse industrial applications, such as pharmaceuticals, food and concrete processing. While the aim is to produce a spatially homogeneous blend, differences in particle properties, such as size, density or shape, result in spontaneous particle segregation during the granular flow. In the case of a binary granular system in a rotating drum, as is the case here, rapid segregation dynamics in the radial direction.

In-situ and high-speed visualization of particle detachment

State-of-the art techniques allow the study of segregation dynamics at the end walls of a drum, as well as the observation of slow axial dynamics and the steady state of radial mixing inside the drum bulk. They do not allow, however, continuous observation of the transient radial mixing in the bulk. Using the ultrafast X-ray computer tomography it is possible to take cross-sectional images through the opaque granular systems at 1000 frames per second. The high-speed image sequences from intermediate planes of the drum can reveal the segregation dynamics in the bulk. Here we present experimental results from the transient state of radial mixing for a binary granular system with density difference (density ratio 2.8) and equal size (4 mm) spherical beads in a half-filled drum.

Measurements with camera and simulations with the discrete element methods are also performed (Figure 1). We discovered that, at low filling degree, the particles in the passive layer do not stick to the drum, as it rotates. Instead, they slip. Because of the lower granular mass above the first particle layer, friction is reduced, allowing the spheres in contact with the wall to roll or slide.

Funding

This work is funded by a Scholarship provided by the Free State of Saxony.

Publications

Papapetrou, T.N., Bieberle,M., Barthel, F., Hampel, U. Lecrivain, G. (2025), Effect of filling degree on particle segregation in a rotating drum - an experimental and numerical study, Under Review

Papapetrou, T.N., Bieberle,M., Barthel, F., Hampel, U. Lecrivain, G. (2024), Investigating binary granular mixing in a rotating drum using ultrafast X-ray computed tomography, Powder Technology 443, 119964

Bieberle, M., Papapetrou, T. N., Lecrivain, G., Windisch, D., Bieberle, A., Wagner, M., & Hampel, U. (2024). Simplified beam hardening correction for ultrafast X-ray CT imaging of binary granular mixtures. Sensors, 24, 2964

Papapetrou, T. N., Lecrivain, G., Bieberle, M., Boudouvis, A., Hampel, U. (2021). An improved contact method for quantifying the mixing of a binary granular mixture. Granular Matter, 23, 1-13.