scale_particles mix-ID factor
scale_particles air 0.5 scale_particles air 4.0
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 run command is issued, as if the global fnum 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 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.