Investigation of a granular Bond number based rheological model for polydispersed particulate systems

Granular materials are used in many industrial processes among various fields, such as pharmaceutical, food, metallurgy or nuclear fuel production. However, compared to other commonly used media, such as liquids, powders are known to behave unpredictably, leading to uncontrolled process operations. Since the flow behavior of the powders originates from interparticle forces, we suggest a model, linking the macroscopic flowability of powder beds, and the properties of the microscopic particles constituting the powder. A population dependent granular Bond number (Capece et al., 2016), that takes into account the particles properties such as the particles' true density, surface energy, rugosity and the whole particle size distribution, is used. This non-dimensional number was found to correlate well with the flowability of polydispersed powder bed, which can be measured by shear testing with a Freeman FT4 (R) powder rheometer. The results found in previous studies (Bernard-Granger et al., 2019; Capece et al., 2016) are extended and discussed using five different oxide powders exhibiting various flow behaviors. In particular, a short sensitivity analysis of the model is carried out. The results show that the fraction of fine particles within a polydispersed powder is a critical parameter for the flowability of the powder bed. Finally, the Rumpfs theory is used to suggest a physical meaning for the model parameters. (author)