compute gas/collision/tally command

Syntax:

compute ID gas/collision/tally group-ID mix-ID value1 value2 ... 

• ID is documented in compute command
• gas/collision/tally = style name of this compute command
• group-ID = group ID for which grid cells to perform calculation on
• mix-ID = mixture ID to perform calculation on
• one or more values can be appended
• value = id/cell or id1 or id2 or type1 or type2 or vx1/pre or vy1/pre or vz1/pre or vx2/pre or vy2/pre or vz2/pre or vx1/post or vy1/post or vz1/post or vx2/post or vy2/post or vz2/post

    id/cell = grid cell ID
    id1, id2 = particle IDs of two particles
    type1, type2 = particle species of two particles
    vx1/pre, vy1/pre, vz1/pre = velocity components of first particle before collision
    vx2/pre, vy2/pre, vz2/pre = velocity components of second particle before collision
    vx1/post, vy1/post, vz1/post = velocity components of first particle after collision
    vx2/post, vy2/post, vz2/post = velocity components of second particle after collision 
  

Examples:

compute 1 gas/collision/tally all all id id/cell time xc yc zc 

This command will dump the tallies in the previous command to a dump file every 10 steps:

dump 1 tally all 10 tmp.tally c_1[*] 

Description:

Tally various values for each gas-phase collision of two particles during the current timestep. Only gas collisions which do not result in chemical reactions are tallied by this command. See the related compute gas/reaction/tally command to tally collisions which induce reactions. It provides different tally value options than this compute.

Only collisions within grid cells in the grid group specified by group-ID and pairs of particles with both species in the mixture specified by mix-ID are included. See the group grid command for info on how grid cells can be assigned to grid groups.

The results of this compute can be used by different commands in different ways. The values for a single timestep can be output by the dump tally command. Currently this is the only option for accessing the tallied values.

The id/cell value is the ID of the grid cell in which the collision takes place.

The id1 and id2 values are the IDs of the colliding particles. Note that particle IDs are generated randomly. Thus multiple particles in the system can potentially have the same ID. See Section 6.17 for more details on particle IDs.

The type1 and type2 values are the integer index for the particle species of the colliding particles. They are values from 1 to Nspecies. The values corresponds to the order in which species were defined via the species command. See Section 6.17 for more details on particle types.

The vx1/pre, vy1/pre, vz1/pre, vx2/pre, vy2/pre, vz2/pre values are the velocity components of the two particles before the collision.

The vx1/post, vy1/post, vz1/post, vx2/post, vy2/post, vz2/post values are the velocity components of the two particles after the collision.

Output info:

This compute calculates a per-tally array, with the number of columns equal to the number of values.

The array can be accessed by any command that uses per-tally values from a compute as input. See Section 6.4 for an overview of SPARTA output options.

The per-tally array values will be in the units appropriate to the individual values as described above. All the velocity keywords are in velocity units.

Restrictions: none

Related commands:

compute gas/reaction/tally, compute surf/collision/tally, dump tally

Default: none