delete_particles command

Purpose

This command deletes particles from a simulation.

Note

This command is supported by Aspherix GPU.

Syntax

delete_particles keyword value

General keywords:

Keyword

Description

every_time
once or time interval for deletion
units = [time]; default: once

mode
available options: all or rate
default: all

Setting-dependent keywords:

Setting

Option

Description

every_time once, mode all

no option-specific keywords

every_time once, mode rate

not available

every_time time interval, mode all

id

user-assigned name for the command call

reset_tags_after_deletion
available options: yes, no
sets whether particle tags are reassigned after deletion
default: no

every_time time interval, mode rate

massrate
obligatory, mass rate to be extracted from the domain
units: [mass/time]

target_mass
total mass to be removed
units: [mass]

shrink_before_deletion
available options: yes, no
shrink particles before deletion
default: no

delete_particles_below
radius below which particles are deleted; mandatory for
shrink_before_deletion yes
units: [length]

id

user-assigned name for the command call

seed

random number seed (prime number greater 10000)

reset_tags_after_deletion
available options: yes, no
sets whether particle tags are reassigned after deletion
default: no

General obligatory keywords:

To any of the above variants, any combination of the following keyword/value pairs can be appended to narrow down the choice of particles to be deleted.

every_time once requires at least one of the following keywords, every_time = time interval does not need any.

Keyword

Description

particle_group

ID of the group (see define_group) from which particles are deleted

region

ID of the region from which particles are deleted

material

ID of the material from which particles are deleted

Examples

delete_particles every_time 1e-2 mode rate massrate 100 target_mass 50 shrink_before_deletion yes delete_particles_below 0.001
delete_particles region delReg

Description

This command removes particles from the simulations. Removal can be either instantaneous (every_time once) or periodically (every_time = a positive scalar).

The three choice keywords region (see region), particle_group (see define_group) and material (see materials) can be used to specify which particles should be deleted. If multiple keywords are given, the particles to be deleted must fulfill all conditions (eg. be inside a region AND member of a group).

every_time once instantaneously removes particles meeting the criteria defined through the region, particle_group and material keywords. One of the three choice keywords has to be defined in this case.

every_time together with a time interval periodically removes particles from the simulation domain that match the criteria defined by the region, particle_group and material keywords. mode all removes all particles matching the criteria (in this case, at least one of the three choice keywords needs to be given). mode rate removes particles with a defined massrate (mass per time) set by the keyword massrate. Additionally, a target_mass can be set. If this mass has been removed, particle deletion will stop.

Please note that small deletion time intervals can lead to significant increases of the overall simulation time since every delete command triggers a rebuild of the neighbor lists. It is suggested to chose the interval as large as permitted by the application.

The keywords shrink_before_deletion and delete_below_radius will cause delete_particles to shrink particles, and delete them once they become smaller than the defined threshold radius. This is useful to smoothen the mass rate if there are only few, large particles to be deleted.

If reset_tags_after_deletion is set to yes, all particle tags will be reassigned every time delete_particles removes particles from the domain. This is helpful for either very long or very large simulations, since the total RAM required for a simulation depends on the maximum tag present in the simulation. Setting this to on will, however, remove the possibility to follow individual particles during postprocessing.

Restrictions