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Checks for multi-phase variables available on ANSYS Fluent UDFs

We use a lot of different approaches to consult the case multi-phase configuration and multi-phase setup details. Here I show and test a few more direct options available at the sg_mphase.h header file.

The main entrance point to these new variables is the sg_mphase variable, its value is defined by an enumeration defined at the sg_mphase.h header file as:

typedef enum
{
  MP_OFF = 0,       /* same as FALSE */
  MP_VOF,           /* corresponds to boolean mp_vof    */
  MP_HOMOGENEOUS,   /*                        mp_hom    */
  MP_DRIFT_FLUX,    /*                        mp_drift  */
  MP_MULTI_FLUID,   /*                        mp_mfluid */
  MP_MODEL_MAX
} MP_Model;

extern FLUENT_EXPORT MP_Model sg_mphase;

So, the sg_mphase variable indicates the current case multi-phase approach being used.

Additional variables listed on the same file (not in this order, but all are defined at the same block) are:

extern FLUENT_EXPORT cxboolean mp_vof;
extern FLUENT_EXPORT cxboolean mp_mixture;
extern FLUENT_EXPORT cxboolean mp_hom;
extern FLUENT_EXPORT cxboolean mp_drift;
extern FLUENT_EXPORT cxboolean mp_mfluid;

All these variables are (threated as) Boolean flags for:

  • mp_vof - Volume of Fluid
  • mp_mixture - multiphase approach with a mixture (main) velocity field being used
  • mp_hom - mixture model without slip-velocity
  • mp_drift - mixture with slip-velocity
  • mp_mfluid - Eulerian multi-fluid

Another interesting variable is the mp_n defined at the same header file. This variable has an integer value and is used to store the number of phases being used in the current setup.

extern FLUENT_EXPORT int mp_n;

Below are the outputs of the test UDF showing the usage and contents of these variables.

Single-phase

...multi-phase option via the `sg_mphase` variable:
     ...single-phase setup.

...multi-phase Boolean variables:
     ...`mp_vof` variable = 0
     ...`mp_mixture` variable = 0
     ...`mp_hom` variable = 0
     ...`mp_drift` variable = 0
     ...`mp_mfluid` variable = 0
     ...`mp_n` variable = 0

VOF (volume-of-fluid)

...multi-phase option via the `sg_mphase` variable:
    ...VOF multi-phase setup.

...multi-phase Boolean variables:
    ...`mp_vof` variable = 1
    ...`mp_mixture` variable = 1
    ...`mp_hom` variable = 0
    ...`mp_drift` variable = 0
    ...`mp_mfluid` variable = 0
    ...`mp_n` variable = 2

Eulerian

...multi-phase option via the `sg_mphase` variable:
    ...Eulerian multi-fluid multi-phase setup.

...multi-phase Boolean variables:
    ...`mp_vof` variable = 0
    ...`mp_mixture` variable = 0
    ...`mp_hom` variable = 0
    ...`mp_drift` variable = 0
    ...`mp_mfluid` variable = 1
    ...`mp_n` variable = 3

Mixture

...multi-phase option via the `sg_mphase` variable;
    ...Mixture homogeneous multi-phase setup.

...multi-phase Boolean variables;
    ...`mp_vof` variable = 0
    ...`mp_mixture` variable = 1
    ...`mp_hom` variable = 1
    ...`mp_drift` variable = 0
    ...`mp_mfluid` variable = 0
    ...`mp_n` variable = 4

Mixture + slip velocity

...multi-phase option via the `sg_mphase` variable:
    ...Mixture drift-flux multi-phase setup.

...multi-phase Boolean variables:
    ...`mp_vof` variable = 0
    ...`mp_mixture` variable = 1
    ...`mp_hom` variable = 0
    ...`mp_drift` variable = 1
    ...`mp_mfluid` variable = 0
    ...`mp_n` variable = 4

So we can use these variables and the enumeration with confidence that they will contain the expected (correct) values.