It is widely known that a granular material flows out of a container at a constant speed. This is in contrast to the case of a liquid, where the flow rate decreases with fill height, i.e. the flow rate correlates with the pressure during the discharge process. Why do we have a constant flow rate for a granular material? Can we change this by changing the surface friction, the softness or the shape of the particles? In this seminar, we seek the answer to these questions.

T. Pongó, V. Stiga, J. Török, S. Lévay, B. Szabó, R. Stannarius, R.C. Hidalgo and T. Börzsönyi: Flow in an hourglass: particle friction and stiffness matter. New J. Phys. 23, 023001 (2021)

https://iopscience.iop.org/article/10.1088/1367-2630/abddf5/meta

T. Pongó, B. Fan, D. Hernández-Delfin, J. Török, R. Stannarius, R.C. Hidalgo and T. Börzsönyi: The role of the particle aspect ratio in the discharge of a narrow silo. New. J. Phys. 24, 103306 (2022)

https://iopscience.iop.org/article/10.1088/1367-2630/ac9923/meta