2.3.23 DEFINE_TRANS UDFs

The following DEFINE macros can be used to specify transition correlations for the Transition SST model in ANSYS FLUENT.

DEFINE_TRANS_FLENGTH

Description

You can use DEFINE_TRANS_FLENGTH to specify the transition length for the Transition SST turbulence model.

Usage

DEFINE_TRANS_FLENGTH( name, c, t)

Argument Type	Description
symbol name	UDF name.
cell_t c	Index of cell on which the transition length function is
	to be applied.
Thread *t	Pointer to cell thread.
Function returns
real

There are three arguments to DEFINE_TRANS_FLENGTH: name, c, and t. You supply name, the name of the UDF. c and t are variables that are passed by the ANSYS FLUENT solver to your UDF. Your UDF will need to return the real value for the transition length function to the solver.

Example

An example of a TRANS_FLENGTH UDF is provided at the end of this section.

Hooking a Transition Correlation UDF to ANSYS FLUENT

After the UDF that you have defined using DEFINE_TRANS_FLENGTH is interpreted (Chapter  4) or compiled (Chapter  5), the name of the argument that you supplied as the DEFINE macro argument (e.g., user_Flength) will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT. See Section  6.2.23 for details.

DEFINE_TRANS_RETHETA_C

Description

You can use DEFINE_TRANS_RETHETA_C to specify the critical momentum thickness Reynolds number for the Transition SST turbulence model.

Usage

DEFINE_TRANS_RETHETA_C( name, c, t)

Argument Type	Description
symbol name	UDF name.
cell_t c	Index that identifies the cell on which the critical momentum
	thickness Reynolds number is to be applied.
Thread *t	Pointer to cell thread.
Function returns
real

There are three arguments to DEFINE_TRANS_RETHETA_C: name, c, and t. You supply name, the name of the UDF. c and t are variables that are passed by the ANSYS FLUENT solver to your UDF. Your UDF will need to return the real value for the critical momentum thickness Reynolds number to the solver.

Example

An example of a TRANS_RETHETA_C UDF is provided at the end of this section.

Hooking a Transition Correlation UDF to ANSYS FLUENT

After the UDF that you have defined using DEFINE_TRANS_RETHETA_C is interpreted (Chapter  4) or compiled (Chapter  5), the name of the argument that you supplied as the DEFINE macro argument (e.g., user_Re_thetac) will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT. See Section  6.2.23 for details.

DEFINE_TRANS_RETHETA_T

Description

You can use DEFINE_TRANS_RETHETA_T to specify the transition onset momentum thickness Reynolds number for the Transition SST turbulence model.

Usage

DEFINE_TRANS_RETHETA_T( name, c, t)

Argument Type	Description
symbol name	UDF name.
cell_t c	Index that identifies the cell on which the transition onset momentum
	thickness Reynolds number is to be applied.
Thread *t	Pointer to cell thread.
Function returns
real

There are three arguments to DEFINE_TRANS_RETHETA_T: name, c, and t. You supply name, the name of the UDF. c and t are variables that are passed by the ANSYS FLUENT solver to your UDF. Your UDF will need to return the real value for the transition onset momentum thickness Reynolds number to the solver.

Example

The following functions (which are concatenated into a single C source code file) demonstrate this usage.

#include "udf.h"

DEFINE_TRANS_FLENGTH(user_Flength, c, t)
{
  real Flength = 31.468;

  return Flength;
}

DEFINE_TRANS_RETHETA_C(user_Re_thetac, c, t)
{
  real Re_thetac = 176.396;

  return Re_thetac;
}

DEFINE_TRANS_RETHETA_T(user_Re_thetat, c, t)
{
  real Re_thetat = 210;

  return Re_thetat;
}

Hooking a Transition Correlation UDF to ANSYS FLUENT

After the UDF that you have defined using DEFINE_TRANS is interpreted (Chapter  4) or compiled (Chapter  5), the name of the argument that you supplied as the DEFINE macro argument (e.g., user_Re_thetat) will become visible and selectable in the Viscous Model dialog box in ANSYS FLUENT. See Section  6.2.23 for details.