:orphan:

.. index:: scale_particles

.. _scale-particles:

.. _scale-particles-command:

#######################
scale_particles command
#######################

.. _scale-particles-syntax:

*******
Syntax:
*******

::

   scale_particles mix-ID factor

   - mix-ID = ID of mixture to use when scaling particles
   - factor = scale factor

.. _scale-particles-examples:

*********
Examples:
*********

::

   scale_particles air 0.5
   scale_particles air 4.0

.. _scale-particles-descriptio:

************
Description:
************

Scale the number of particles in the simulation by cloning or deleting
individual particles.  This can be useful between runs, or after
reading a restart file, to increase or decrease the particle count
before a new :ref:`run<run>` command is issued, as if the :ref:`global fnum<global>` value had been changed.  For example, an initial
coarse simulation can be performed, followed by a simulation at
higher resolution.

Only particles of species in the specified mixture are considered for
cloning/deleting.  See the :ref:`mixture<mixture>` command for how it
defines a collection of species.

The specified *factor* can be any value >= 0.0.

If *factor* < 1.0, then for each particle, a random number *R* is
generated.  If R > factor, the particle is deleted.

If *factor* > 1.0, then for each particle additional particles may be
created, by cloning all attributes of the original particle, except
for a new random particle ID assigned to each new particle.  E.g. if
*factor* = 3.4, then two extra particles are created, and a 3rd is
created with probability 0.4.

.. _scale-particles-restrictio:

*************
Restrictions:
*************

none

.. _scale-particles-related-commands:

*****************
Related commands:
*****************

:ref:`create_particles<create-particles>`

.. _scale-particles-default:

********
Default:
********

none