### 16.3.1. Particle Track Variables

Particle track variables are particle variables that are defined directly on each track. These variables are defined on the particle positions for which track information is written to the results file. Direct access to the particle track variables outside of CFD-Post is possible only if the raw track file is kept after a particle run.

You can do the following with particle track variables:

- Export them from particle tracks in CFD-Post

- Use them to color particle tracks in CFD-Post

- Use them in particle histograms

- Use them as input to Particle User Fortran

Particle track variables are not available for use in CEL expressions and general User Fortran. In addition, they cannot be monitored during a simulation.

The following table lists particle track variables that are available in general, including in CFD-Post:

Long Variable Name | Short Variable Name | Units | Description | Availability
--- | --- | --- | --- | ---
<Particle Type>.Mean Particle Diameter | mean particle diameter | [m] | Particle diameter | 3 PR
<Particle Type>.<Particle Component>.Mass Fraction |  | [-] | Note: Only available for multi-component particles. Fraction of mass of a particular particle component |
<Particle Type>.Particle Number Rate | particle number rate | [s^-1] | Particle number rate | 3 PR
<Particle Type>.Particle Time | pttime | [s] | Simulation time | 2 PR
<Particle Type>.Particle Traveling Distance | ptdist | [m] | Distance along the particle track measured from the injection point | 2 PR
<Particle Type>.Particle Traveling Time |  | [s] | Time measured from the time of injection of the particle. For steady-state simulations only, this time is identical to <Particle Type>.Particle Time. | 2 PR
<Particle Type>.Particle Weber Number |  | [-] | Note: Only available if a secondary droplet breakup model is active. Particle Weber number along track where |
<Particle Type>.Temperature | T | [K] | Particle temperature | 1 PR
<Particle Type>.Total Particle Mass | ptmasst | [kg] | Particle total mass | 2 PR
<Particle Type>.Velocity |  | [m s^-1] | Particle velocity | 1 PR
<Particle Type>.Velocity u <Particle Type>.Velocity v <Particle Type>.Velocity w | u v w | [m s^-1] | Particle velocity components in X, Y, and Z direction | 1 PR

For Particle User Fortran, these additional track variables, which are not available in CFD-Post, can be specified in the argument list for the user routine:

Long Variable Name | Short Variable Name | Units | Definition | Availability
--- | --- | --- | --- | ---
Particle Eotvos Number | pteo | [ ] |  | 2 PR
Particle Morton Number | ptmo | [ ] |  | 2 PR
Particle Nusselt Number | ptnu | [ ] |  | 2 PR
Particle Ohnesorge Number | pton | [ ] |  | 2 PR
Particle Reynolds Number | ptre | [ ] |  | 2 PR
Particle Slip Velocity | ptslipvel | [m s^-1] |  | 2 PR
Particle Position | ptpos | [m] | Cartesian coordinates of current particle position | 2 PR
Particle Impact Angle [a] | particle impact angle | [radian] |  | 3 PR
[a] Note: The impact angle is measured from the wall.

The following particle variables are available only in particle histograms:

Long Variable Name | Short Variable Name | Units | Description | Availability
--- | --- | --- | --- | ---
<Particle Type>.Particle Mass Flow Rate |  | [kg s^-1] | Particle mass flow rate = Particle Total Mass * Particle Number Rate | 3 PR
<Particle Type>.Velocity Magnitude |  | [m s^-1] | Particle Speed | 2 PR

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