forked from lijiext/lammps
109 lines
4.4 KiB
Plaintext
109 lines
4.4 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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fix insert command :h3
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[Syntax:]
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fix ID group-ID insert N type seed keyword values ... :pre
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ID, group-ID are documented in "fix"_fix.html command :ulb,l
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insert = style name of this fix command :l
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N = # of atoms to insert :l
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type = atom type to assign to inserted atoms :l
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seed = random # seed :l
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one or more keyword/value pairs may be appended to args :l
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keyword = {region} or {diam} or {dens} or {vol} or {rate} or {vel} :l
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{region} value = region-ID
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region-ID = ID of region to use as insertion volume
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{diam} values = lo hi
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lo,hi = range of diameters for inserted particles (distance units)
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{dens} values = lo hi
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lo,hi = range of densities for inserted particles
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{vol} values = fraction Nattempt
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fraction = desired volume fraction for filling insertion volume
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Nattempt = max # of insertion attempts per atom
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{rate} value = V
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V = z velocity (3d) or y velocity (2d) at which
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insertion volume moves (velocity units)
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{vel} values (3d) = vxlo vxhi vylo vyhi vz
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{vel} values (2d) = vxlo vxhi vy
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vxlo,vxhi = range of x velocities for inserted particles (velocity units)
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vylo,vyhi = range of y velocities for inserted particles (velocity units)
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vz = z velocity (3d) assigned to inserted particles (velocity units)
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vy = y velocity (2d) assigned to inserted particles (velocity units) :pre
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:ule
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[Examples:]
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fix 3 all insert 1000 2 29494 region myblock
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fix 2 all insert 10000 1 19985583 region disk vol 0.33 100 rate 1.0 diam 0.9 1.1 :pre
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[Description:]
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Insert particles into a granular run every few timesteps within a
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specified region until N particles have been inserted. This is useful
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for simulating the pouring of particles into a container.
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Inserted particles are assigned the specified atom type and are
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assigned to two groups: the default group "all" and the group
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specified in the fix insert command (which can also be "all").
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This command must use the {region} keyword to define an insertion
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volume. The specified region must have been previously defined with a
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"region"_region.html command. It must be of type {block} or a z-axis
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{cylinder} and must be defined with side = {in}. The cylinder style
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of region can only be used with 3d simulations.
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Each timestep particles are inserted, they are placed randomly inside
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the insertion volume so as to mimic a stream of poured particles. The
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larger the volume, the more particles that can be inserted at any one
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timestep. Particles are inserted again after enough time has elapsed
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that the previously inserted particles fall out of the insertion
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volume under the influence of gravity. Insertions continue every so
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many timesteps until the desired # of particles has been inserted.
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All other keywords are optional with defaults as shown below. The
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{diam}, {dens}, and {vel} options enable inserted particles to have a
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range of diameters or densities or xy velocities. The specific values
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for a particular inserted particle will be chosen randomly and
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uniformly between the specified bounds. The {vz} or {vy} value for
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option {vel} assigns a z-velocity (3d) or y-velocity (2d) to each
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inserted particle.
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The {vol} option specifies what volume fraction of the insertion
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volume will be filled with particles. The higher the value, the more
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particles are inserted each timestep. Since inserted particles cannot
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overlap, the maximum volume fraction should be no higher than about
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0.6. Each timestep particles are inserted, LAMMPS will make up to a
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total of M tries to insert the new particles without overlaps, where M
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= # of inserted particles * Nattempt. If LAMMPS is unsuccessful at
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completing all insertions, it prints a warning.
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The {rate} option allows the insertion volume to move in the z
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direction (3d) or y direction (2d). This enables pouring particles
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from a successively higher height over time.
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[Restrictions:]
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Can only be used if LAMMPS was built with the "granular" package. Can
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only be used with atom_style granular.
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For 3d simulations, a gravity fix in the -z direction must be defined
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for use in conjunction with this fix. For 2d simulations, gravity
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must be defined in the -y direction.
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[Related commands:]
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"fix_gravity"_fix_gravity.html, "region"_region.html
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[Default:]
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The option defaults are diam = 1.0 1.0, dens = 1.0 1.0, vol = 0.25 50,
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rate = 0.0, vel = 0.0 0.0 0.0 0.0 0.0.
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