mark_particles command

Purpose

Command for marking particles in a region as tracers.

Syntax

mark_particles region region-ID mark_time t mode mode_style keyword arg

  • region = obligatory keyword

  • region-ID = ID of the region where the particles will be marked

  • mark_time = obligatory keyword

  • t = time at which the particles are marked

  • mode = obligatory keyword

  • mode_style = once or continuous

  • zero or more keyword/arg pairs may be appended

  • keyword = id or particle_group or mark_every_time (obligatory if mode_style = continuous)

id value = command-ID
   command-ID = user-assigned name for the command call
particle_group value = group-id
   group-id = ID of a group of particles
mark_every_time value = dt
   dt = time interval between two consecutive markings (positive float)

Examples

mark_particles id marker region r1 mark_time 1e-3 mark_every_time 1e-4 mode continuous

Description

This command marks particles using either a Dirac delta impulse (mode_style once) or a Heaviside impulse (mode_style continuous). Particles are marked if they are inside the region specified by the region keyword. Using the Dirac impulse means that all the particles which are in the region at the time specified by the mark_time keyword are marked. Using the Heaviside impulse means that all the particles which pass by the specified region after the specified time are marked.

The keyword mark_every_time controls how often the region is checked and it must be used only when the mode_style continuous option is selected. Be careful not to choose time-intervals too large, as fast particles passing through the region might be skipped.

Additional information

This command can be used as an input for the calculate marked_particles command to evaluate the number and mass of the marked particles in a specific region.

Warning

The particles are un-marked after being counted by the calculate marked_particles command. This prevents counting the same particle multiple times in presence, for example, of a recirculation zone.

Information about this command is written to binary restart files.This command computes a per-particle scalar (the marker) which can be accessed by various output commands. This scalar is equal to one if a particle has been marked and zero otherwise. This command also computes a global scalar indicating how many particles were marked since the last time the global scalar was computed. This scalar can also be accessed by various output commands.

Restrictions

Currently, this feature does not support multi-sphere and concave particles.