2.3.2 DEFINE_CPHI

Description

You can use DEFINE_CPHI to set the value of the mixing constant $C_{\phi}$ (see this equation and this equation in the separate Theory Guide for details). It is useful for modeling flows where $C_{\phi}$ departs substantially from its default value of $2$, which occurs at low Reynolds and/or high Schmidt numbers.

Usage

DEFINE_CPHI( name, c, t)

Argument Type	Description
symbol name	UDF name.
cell_t c	Cell index.
Thread *t	Pointer to cell thread.
Function returns
real

There are three arguments to DEFINE_CPHI: name, c, and t. You supply name, the name of the UDF. c and t are passed by the ANSYS FLUENT solver to your UDF. Your UDF will need to compute the real value of the mixing constant ( $C_{\phi}$) and return it to the solver.

Hooking a Mixing Constant UDF to ANSYS FLUENT

After the UDF that you have defined using DEFINE_CPHI is interpreted (Chapter  4) or compiled (Chapter  5), the name of the argument that you supplied as the first DEFINE macro argument will become visible and selectable in the User-Defined Function Hooks dialog box in ANSYS FLUENT whenever the Composition PDF Transport model is enabled. See Section  6.2.2 for details.