113 lines
4.0 KiB
ReStructuredText
113 lines
4.0 KiB
ReStructuredText
.. index:: fix add/heat
|
|
|
|
fix add/heat command
|
|
====================
|
|
|
|
Syntax
|
|
""""""
|
|
|
|
.. code-block:: LAMMPS
|
|
|
|
fix ID group-ID add/heat style args keyword values ...
|
|
|
|
* ID, group-ID are documented in :doc:`fix <fix>` command
|
|
* add/heat = style name of this fix command
|
|
* style = *constant* or *linear* or *quartic*
|
|
|
|
.. parsed-literal::
|
|
|
|
*constant* args = *rate*
|
|
*rate* = rate of heat flow (energy/time units)
|
|
*linear* args = *Ttarget* *k*
|
|
*Ttarget* = target temperature (temperature units)
|
|
*k* = prefactor (energy/(time*temperature) units)
|
|
*quartic* args = *Ttarget* *k*
|
|
*Ttarget* = target temperature (temperature units)
|
|
*k* = prefactor (energy/(time*temperature^4) units)
|
|
|
|
* zero or more keyword/value pairs may be appended to args
|
|
* keyword = *overwrite*
|
|
|
|
.. parsed-literal::
|
|
|
|
*overwrite* value = *yes* or *no*
|
|
*yes* = sets current heat flow of particle
|
|
*no* = adds to current heat flow of particle
|
|
|
|
Examples
|
|
""""""""
|
|
|
|
.. code-block:: LAMMPS
|
|
|
|
fix 1 all add/heat constant v_heat
|
|
fix 1 all add/heat linear 10.0 1.0 overwrite yes
|
|
|
|
Description
|
|
"""""""""""
|
|
|
|
This fix adds heat to particles with the temperature attribute every timestep
|
|
at a given rate. Note that this is an internal temperature of a particle intended
|
|
for use with non-atomistic models like the discrete element method.
|
|
|
|
For the *constant* style, heat is added at the specified rate. For the *linear* style,
|
|
heat is added at a rate of :math:`k (T_{target} - T)` where :math:`k` is the
|
|
specified prefactor, :math:`T_{target}` is the specified target temperature, and
|
|
:math:`T` is the temperature of the atom. This may be more representative of a
|
|
conductive process. For the *quartic* style, heat is added at a rate of
|
|
:math:`k (T_{target}^4 - T^4)`, akin to radiative heat transfer.
|
|
|
|
The rate or temperature can be can be specified as an equal-style or atom-style
|
|
:doc:`variable <variable>`. If the value is a variable, it should be
|
|
specified as v_name, where name is the variable name. In this case, the
|
|
variable will be evaluated each time step, and its value will be used to
|
|
determine the rate of heat added.
|
|
|
|
Equal-style variables can specify formulas with various mathematical
|
|
functions and include :doc:`thermo_style <thermo_style>` command
|
|
keywords for the simulation box parameters, time step, and elapsed time
|
|
to specify time-dependent heating.
|
|
|
|
Atom-style variables can specify the same formulas as equal-style
|
|
variables but can also include per-atom values, such as atom
|
|
coordinates to specify spatially-dependent heating.
|
|
|
|
If the *overwrite* keyword is set to *yes*, this fix will set the total
|
|
heat flow on a particle every timestep, overwriting contributions from pair
|
|
styles or other fixes. If *overwrite* is *no*, this fix will add heat on
|
|
top of other contributions.
|
|
|
|
----------
|
|
|
|
Restart, fix_modify, output, run start/stop, minimize info
|
|
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
|
|
|
|
No information about this fix is written to :doc:`binary restart files <restart>`.
|
|
None of the :doc:`fix_modify <fix_modify>` options are relevant to this fix.
|
|
No global or per-atom quantities are stored by this fix for access by various
|
|
:doc:`output commands <Howto_output>`. No parameter of this fix can be used
|
|
with the *start/stop* keywords of the :doc:`run <run>` command. This fix is
|
|
not invoked during :doc:`energy minimization <minimize>`.
|
|
|
|
Restrictions
|
|
""""""""""""
|
|
|
|
This pair style is part of the GRANULAR package. It is
|
|
only enabled if LAMMPS was built with that package.
|
|
See the :doc:`Build package <Build_package>` page for more info.
|
|
|
|
This fix requires that atoms store temperature and heat flow
|
|
as defined by the :doc:`fix property/atom <fix_property_atom>` command or
|
|
included in certain atom styles, such as atom_style rheo/thermal.
|
|
|
|
Related commands
|
|
""""""""""""""""
|
|
|
|
:doc:`fix heat/flow <fix_heat_flow>`,
|
|
:doc:`fix property/atom <fix_property_atom>`,
|
|
:doc:`fix rheo/thermal <fix_rheo_thermal>`
|
|
|
|
Default
|
|
"""""""
|
|
|
|
The default for the *overwrite* keyword is *no*
|