simulation.PyGranSim.dem¶

Python interface for running DEM engines

Created on April 25, 2016

Author: Andrew Abi-Mansour

This is the:

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DEM simulation and analysis toolkit http://www.pygran.org, support@pygran.org

Core developer and main author: Andrew Abi-Mansour, andrew.abi.mansour@pygran.org

PyGran is open-source, distributed under the terms of the GNU Public License, version 2 or later. It is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. You should have received a copy of the GNU General Public License along with PyGran. If not, see http://www.gnu.org/licenses . See also top-level README and LICENSE files.

Classes

DEM(**pargs)

A generic class that handles communication for a DEM object in a way that is independent of the engine used

class simulation.PyGranSim.dem.DEM(**pargs)[source]¶

Bases: object

A generic class that handles communication for a DEM object in a way that is independent of the engine used

Upon instantiation, this object initializes an MPI communicator and partitions proccesors based on user input

Parameters: model (model) – contact mechanical model (default SpringDashpot)

Todo

Provide a description of each arg in pargs

velocity(*args)[source]¶

Assigns velocity to selected particles.

Parameters: args (tuple) – group-ID style args keyword value
Note: See link for info on keywords and their associated values.

addViscous(**args)[source]¶

Adds a viscous damping force $F$ proportional to each particle’s velocity $v$ :

$F = - \gamma v$

Parameters

species (int) – species index (0, 1, …)
gamma (positive float) – viscosity coefficient ( $\gamma$ )
scale (tuple) – (species, ratio) tuple to scale gamma with

setupParticles()[source]¶: Internal function used to create particles in LIGGGHTS

createProperty(name, *args)[source]¶: Internal function used to create material and interaction properties

importMeshes(name=None)[source]¶

An internal function that is called during DEM initialization for importing meshes. Unless name is supplied, this function by default imports all meshes and sets them up as walls.

Parameters: name (str) – mesh name
Note: Can import only one mesh specified by the name keyword.

importMesh(name, file, mtype, **args)[source]¶

Imports a mesh file (STL or VTK)

Parameters

name (str) – define mesh name
file (str) – mesh file pathname
mtype (str) – mesh type (mesh/surface, mesh/surface/stress/deform, etc.)
args (dict) – mesh_keywords

Note

see link for further info on mtype and args.

setupWall(wtype, species=None, plane=None, peq=None)[source]¶

Creates a primitive (virtual) or surface (mesh) wall

Parameters

wtype (string) – type of the wall (primitive or mesh)
species (int) – species type or primitive (virtual) walls
plane (string) – x, y, or z plane for primitive (virtual) walls
peq (float) – plane equation for primitive (virtual) walls

Returns

wall name

Return type

string

Example

primitiveWall = setupWall(species=1, wtype=’primitive’, plane = ‘zplane’, peq = 0.0)

printSetup()[source]¶: Updates the print setup used to set which variables to write to file, and their format.

writeSetup(only_mesh=False, name=None)[source]¶

This creates dump files for particles and meshes in the system. In LIGGGHTS, all meshes must be declared once, so if a mesh is removed during the simulation, this function has to be called again, usually with only_mesh=True to keep the particle dump intact.

Parameters

only_mesh (bool) – controls if the particle dump is updated
name (str) – name of the particle dump

Returns

mesh dump ID(s)

Return type

str or list(str)

setupIntegrate(itype='nve/sphere', group='all')[source]¶

Controls how Newton’s eqs are integrated in time.

Parameters

itype (str) – integrator type (‘nve/sphere’ or ‘multisphere’)
group (str) – particle group ID to apply the integration for

integrate(steps, dt)[source]¶

Advance system in time.

Parameters

steps (int) – number of steps
dt (float) – timestep

remove(name)[source]¶

Delete variable/object by name.

Parameters: name (str) – name of variable/object to unfix

monitor(**args)[source]¶: Not yet documented

plot(fname, xlabel, ylabel, output=None, xscale=None)[source]¶: Not yet documented

moveMesh(name, **args)[source]¶: Not yet documented

saveas(name, fname)[source]¶: Not yet documented

command(cmd)[source]¶

Pass a command to DEM engine.

Parameters: cmd (str) – command specific to the DEM engine

close()[source]¶: Internal function that frees allocated memory and changes directory back to current working directory.