mesh_module contact

Purpose

Command for calculating particle-wall contact area.

Syntax

mesh_module contact id module-ID keywords values

id = obligatory keyword
module-ID = user-defined name for the mesh module
zero or more contact_keyword/value pairs may be appended
contact_keyword = area_correction or start_step

area_correction value = yes or no
start_step values = step
  step = time-step where evaluation starts

Examples

mesh_module contact id my_contact area_correction no start_step 20000

Description

This mesh module evaluates particle-wall contact area and four per-element properties are created:

contact_area
contact_area_abs
contact_area_step
contact_area_step_abs

All of these four properties can be can be dumped into VTK format using output_settings. Property contact_area is the relative area (in %) for every mesh element that is in contact with particles (overlap area). It is averaged over time. Property contact_area_abs is the absolute area (length*length) for every mesh element that is in contact with particles (overlap area). It is averaged over time. Property contact_area_step is the relative area (in %) for every mesh element that is in contact with particles (overlap area) at a certain time-step. Property contact_area_step_abs is the absolute area (length*length) for every mesh element that is in contact with particles (overlap area) at a certain time-step.

With the optional start_step keyword, the time-step where the averaging starts can be set. This is especially helpful to wait until a process has reached a steady-state condition before starting the averaging.

An area correction can additionally be performed using keyword area_correction to account for the fact that the Young’s modulus might have been decreased in order to speed-up the simulation, thus artificially increasing the overlap. In this case, you have to specify the original Young’s modulus of each material by means of a material_properties command:

material_properties steel density 8000 youngsModulus 5e6 youngsModulusOriginal 200e9 keywords values

where keyword/value denotes additional material properties (e.g., poissonsRatio, coefficientRestitution, etc.). The area correction is performed by scaling the contact area with $({Y}/{Y_{orig}})^a$ , where $Y$ and $Y_{orig}$ are respectively the Young’s modulus employed in the DEM (see youngsModulus keyword) and the original Young’s modulus of the material (see youngsModulusOriginal keyword). The scaling factor $a$ is equal to 1 for Hooke interactions and 2/3 for Hertz interactions.