compute surf/collision/tally command

Syntax:

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

• ID is documented in compute command
• surf/collision/tally = style name of this compute command
• group-ID = group ID for which surface elements to perform calculation on
• mix-ID = mixture ID to perform calculation on
• one or more values can be appended
• value = id/surf or id or type or time or xc or yc or zc or vx/pre or vy/pre or vz/pre or vx/post or vy/post or vz/post

    id/surf = surface element ID
    id = particle ID
    type = particle species
    time = time of collision (within timestep, see below)
    xc, yc, zc = coordinates of collision point
    vx/pre, vy/pre, vz/pre = velocity components before collision
    vx/post, vy/post, vz/post = velocity components after collision 
  

Examples:

compute 1 surf/collision/tally all all id id/surf 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 collision of a particle with a surface element during the current timestep. Only surface collisions which do not result in chemical reactions are tallied by this command. See the related compute surf/reaction/tally command to tally collisions which induce reactions. It provides different tally value options than this compute.

Only surface elements in the surface group specified by group-ID and particles with species in the mixture specified by mix-ID are included. See the group grid command for info on how surface elements can be assigned to surface groups.

This compute can be used for simulations with either explicit or implicit surface elements. See Section 6.13 for more discussion of explicit and implicit surfaces.

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/surf value is the ID of the surface element. For explicit surfaces, surface element IDs are unique. For implicit surfaces, the surface ID of all the surface elements within a grid cell are the grid cell ID. See Section 6.13 for more discussion of explicit and implicit surfaces.

The id value is the ID of the particle. 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 type value is an integer index for the particle species. It is a value from 1 to Nspecies. The value corresponds to the order in which species were defined via the species command. See Section 6.17 for more details on particle types.

The time value is the point in time within the timestep when the collision occured. Thus if the timestep size is DT, as set by the timestep command, the time values will all be within the range of 0.0 to DT, for all collisions tallied by this compute on each timestep it is invoked.

The xc, yc, and zc are the coordinates of the collision point between the particle and the surface element.

The vx/pre, vy/pre, vz/pre values are the velocity components of the incident particle before it collides with the surface element.

The vx/post, vy/post, vz/post values are the velocity components of the particle after it collides with the surface element.

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. Time is in time units; see above for details. Xc, yc, and zc are in distance units. Vx/pre, vy/pre, vz/pre are in velocity units, as are vx/post, vy/post, vz/post.

Restrictions: none

Related commands:

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

Default: none