A granular material sheared in a split-bottom Couette cell, wherein a section of the base (blue) moves with velocity Vw relative to the stationary walls (grey), exhibits a dilation-driven secondary flow: (a) primary velocity (z direction), (b) secondary velocity in the x-y plane.
The flow and handling of granular materials, such as foodgrains, ores and pharmaceutical powders, is important part of numerous industrial processes, yet fundamental understanding of their mechanics is lacking. To help develop such an understanding, Prof. Prabhu Nott’s lab in Chemical Engineering department of IISc have studied the kinematics and rheology of granular materials by Discrete Element Method simulations. Additionally, such simulations have helped understand certain topological features of grain clusters, called “force chains”, that are the agents of stress transmission.
This involved the use of the Cray system and the visualization engine in SahasraT. In 2017, 2.1 million core hours of SahasraT were used. Open source molecular dynamics package Large Atomic Molecular Massively Parallel Simulator (LAMMPS) was used. The Message Passing Interface (MPI) was implemented using open source OPEN-MPI package.
“The simulations in the Cray system executes in approximately 24 hours, which would otherwise take 5-7 days with resources available in our lab.”, says Prof Nott.
- K. P. Krishnaraj and P. R. Nott, “A dilation-driven vortex flow in sheared granular materials explains a rheometric anomaly”, Nature Commun. 7, 10630 (2016).
- P. V. Dsouza, K. P. Krishnaraj and P. R. Nott, Secondary flows in slow granular flows, Powders and Grains (2017).