Seminar | An experimental and numerical study of the rheology of cohesive granular materials

This seminar will be given by Adrien Gans, post-doctoral fellow at the Institut de Physique de Rennes (IPR).

Abstract :

Cohesive granular materials are encountered in many geophysical and industrial applications, such as fine sand, cement, pharmaceutical powders and flours. While much progress has been made in describing cohesionless granular flows in various configurations, the behaviour of cohesive powders remains elusive. In particular, one difficulty lies in understanding the cohesive force between particles. For very small particles (typically less than 10 µm in diameter), attractive forces such as Van der Walls or electrostatic forces dominate, whereas for larger particles, moisture provides the necessary amount of water to build solid liquid bridges between the particles and thus creates overall cohesion. As the concept of cohesion is very complex, it is necessary to have a simple definition and good control of cohesion in order to perform quantitative experiments. Several experimental studies have been carried out using wet granular materials where cohesion arises from capillary bonding. However, the main difficulty lies in the ability to control and reproduce the cohesive strength between particles. Recently, a new controlled cohesive granular material (CCGM) has been developed where the cohesion comes from a polyborosiloxane coating on the glass particles. This approach has proven to be very useful for developing experimental studies where global cohesion has to be implemented.
In this talk, I will present the results of our investigation of the effect of cohesion on the behaviour of granular media in benchmark experiments carried out with the CGPC. The experiments will be compared with continuous numerical simulations based on a cohesive µ(I) rheology performed with the Basilisk software (www.basilisk.fr).