DEM Framework for Soot Aggregate Mechanics

We have developed a Discrete Element Method (DEM) framework that includes contact models necessary to simulate the behavior of soot aggregates under mechanical loading and capillary forces.

Included modules

Aggregate deposition

The deposition module simulates deposition of a soot aggregate onto a square substrate. The aggregate is initialized with an initial velocity directed towards the substrate. All neighboring primary particles are bonded with rigid necks. The aggregate eventually collides with the substrate and adheres to it. The simulation progresses until most of the kinetic energy has been dissipated. The final state of a deposition simulation can be used as an input for an AFM indentation simulation.

AFM indentation

The Atomic Force Microscopy (AFM) module simulates indentation of an aggregate deposited onto a square substrate with a sharp solid tip. Some of the rigid bonds between primary particles are broken. One of the primary particles that is not hindered is selected and the tetrahedral tip is positioned above that particle. The tip approaches the particle until the particle adheres to the tip. The tip then reverses direction and starts stretching the aggregate. The aggregate unravels and, eventually, breaks. Force-displacement data is recorded.

Restructuring

The restructuring module simulates morphological evolution of a soot aggregate under a pair-wise capillary force between primary particles. An aggregate is initialized with some of the rigid bonds between primary particles broken and is allowed to evolve. The extent of restructuring that occurs depends of the fraction of rigid bonds, the magnitude and cutoff distance of the capillary force.

Available software

Windows binaries are currently available for internal use. Source code and documentation are pending release.