### 16.2.9. Variables Relevant for Multiphase Calculations

The following table contains a list of variables (with both long and short variable names) that can be used when working with multiphase calculations. For an explanation of the column headings, see List of Field Variables.

Note: Variables with names shown in bold text are not output to CFD-Post. However, some of these variables can be output to CFD-Post by selecting them from the Extra Output Variables List on the Results tab of the Solver > Output Control details view of CFX-Pre.

Long Variable Name | Short Variable Name | Units | Availability | Definition
--- | --- | --- | --- | ---
Interfacial Area Density | area density | [m^-1] | 3 C | Interface area per unit volume for Eulerian multiphase fluid pairs.
Interphase Mass Transfer Rate | ipmt rate | [ ] | 3 C | Interface mass transfer rate for Eulerian multiphase fluid pairs.
Mean Particle Diameter | mean particle diameter | [m] | 3 A, C, M | Mean particle diameter for an Eulerian dispersed phase (including Polydispersed Fluids).
Volume Fraction | vf | [ ] | 1 A, C, M, P, R, TS | For details, see Volume Fraction in the CFX-Solver Modeling Guide.
Conservative Volume Fraction | vfc | [ ] | 2 A, C, M, R, TS | For details, see Volume Fraction in the CFX-Solver Modeling Guide.
Drift Velocity | drift velocity | [ ] | 2 C, M, R, TS | Velocity of an algebraic slip component relative to the mixture.
Slip Reynolds Number | slip Re | [ ] | 3 C | Reynolds number for Eulerian multiphase fluid pairs.
Slip Velocity | slipvel | [ ] | 1 C, M, R, TS | Velocity of an algebraic slip component relative to the continuous component.
Surface Tension Coefficient | surface tension coefficient | [N m^-1] | 2 C | Surface tension coefficient between fluids in a fluid pair.
Unclipped Interfacial Area Density | unclipped area density | [m^-1] | 3 C | Similar to area density, but values are not clipped to be non-zero.
Superficial Velocity | volflx | [m s^-1] | 1 A, C, M, R, TS | The Fluid.Volume Fraction multiplied by the Fluid.Velocity.

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