Simulation Control

The Simulation Control subsection of DEM simulations is identical to the CFD in Lethe.

Note

A constant time step must be defined in the DEM solver. Lethe-DEM does not support adaptative time step scaling method.

Note

time step in DEM simulations is generally in the range of 1e-7 to 1e-5 seconds. With this small time step, the DEM simulation can capture a single collision in several iterations, which leads to the high accuracy of the simulation.

Note

Lethe-DEM compares the selected time step to Rayleigh time-step and prints a warning if the selected time step is too small or too large. Users should modify the time step if they see this warning.

The Rayleigh time-step is defined as:

\[{\Delta}t_{Ra}=\frac{\pi}{2}{d_p}\sqrt{\frac{\rho_p}{G}}(\frac{1}{0.1631\nu+0.8766})\]

where \({d_p}\), \({\rho_p}\), \({G}\), \({\nu}\) denote particle diameter, particle density, shear modulus, and Poisson’s ratio.

Note

If the output path is specified in the parameter handler file, a folder with the specified name should be created before starting simulation in the working directory.

subsection simulation control
  # DEM time-step
  set time step         = 1e-5

  # Simulation end time
  set time end          = 0.2

  # File output prefix
  set output path       = ./

  # Log frequency
  set log frequency     = 1000

  # Output frequency
  set output frequency  = 10000

  # Output boundary
  set output boundaries = true
end