fix particletemplate/convexhull command

Syntax

fix ID group-ID particletemplate/convexhull seed keyword values file filename further_keyword further_values

• ID, group-ID are documented in fix command

• particletemplate/convexhull = style name of this fix command

• seed = random number generator seed (prime number greater 10000)

• zero or more keyword/value pairs can be appended

• keyword, values are documented in fix particletemplate/sphere command

• file = obligatory keyword

• filename = filename of stl file containing the particle template

• further_keyword = mass or inertia_tensor or center_of_mass

mass value = mass assigned to this particle template
    If used center_of_mass and inertia_tensor need to be specified.
center_of_mass values = xcm ycm zcm
    xcm ycm zcm = 3 values of center of mass
    If used mass and inertia_tensor need to be specified.
inertia_tensor values = Ixx Ixy Ixz Iyy Iyz Izz
    Ixx Ixy Ixz Iyy Iyz Izz = 6 independent components of the inertia tensor
    If used center_of_mass and mass need to be specified.

Examples

fix pts all particletemplate/convexhull 123457 atom_type 1 density constant 2500 file cube.stl
fix pts all particletemplate/convexhull 17903 atom_type 1 density constant 2500 file cube.stl &
    mass 10 center_of_mass 1.0 0.0 0.0 inertia_tensor 2.0 0. 0. 2. 0. 2.

Description

Define a convexhull particle template that is used as input for a fix_particledistribution_discrete command. The particle template defined by this fix is a convex non-spherical particle, defined by a stl file. The filename of this stl file is specified the file keyword.

After the convex hull mesh is read, an analytical formula is used to compute mass, center of mass and the inertia tensor including its eigensystem. The values calculated are written to the logfile. Note that this assumes a constant density inside the convex hull.

As an alternative, the body’s mass and inertia tensor can be specified directly via keywords mass, center_of_mass and inertia_tensor. Note that you can only use these keywords together, i.e. defining only only one or 2 of them will throw an error. In case of using coarsegrained particles, mass and inertia tensor of the original particle are expected. These values are then scaled appropriately with the coarsegraining factor specified.

Warning

As opposed to the number-based distributions, this fix uses the more common distribution based on mass-% for the radius distribution (as does fix_particledistribution_discrete).

This fix is used in the framework of CONVEX simulations. For more information see also the CONVEX guide.

Restart, fix_modify, output, run start/stop

Information about the random state in this fix is written to binary restart files so you can restart a simulation with the same particles being chosen for insertion. None of the fix_modify options are relevant to this fix. No global scalar or vector or per-atom quantities are stored by this fix for access by various output commands. No parameter of this fix can be used with the start/stop keywords of the run command.

Restrictions

none

Related commands

fix_particletemplate_sphere

Default

Not applicable, parameters need to be specified.