Simulation of dilute and granular media
Granular materials are ubiquitous in nature, industrial processing and everyday life. Examples range from small scale particles in dust, graphite powder, cement or flour over medium-sized sand grains, plastic granulates and cornflakes to the planetary rings on the astrophysical scale. Similarly broad are the physical phenomena controlling their behavior in transport, storage and processing. However, despite their importance, continuum or other large-scale modeling still shows severe deficiencies and our understanding of the mesoscopic physics in these systems, as exemplified by fragmentation, dissipative effects, sound propagation, etc. is incomplete since many theoretical methods otherwise applicable to many-particle systems do not apply.
Often, large-scale computation is the only way to deepen our insight. One key problem is to understand the intermittent nature of the complex force network that keeps granulate packings stable. Breakdowns under load can give rise to silo failure, coffee powder spilling the kitchen floor and earthquakes.
In this metacomputing project, we use molecular dynamics techniques to compute the forces on every single grain in a large granular packing under uniaxial load. We study the probability of occurrence of strong forces and their spatial correlation, both being crucial to our understanding of failure phenomena. A precondition for this project are recent improvements of the execution speed of metacomputing applications by better latency hiding and optimized communication software in, e.g., the PACX-MPI package.