you can use the following macro in the source definition:C_UDMI(c,t,phi_index).
You can use C_UDMI to access or store the value of the user-defined memory in a cell.
It can be used to allocate up to 500 memory locations in order to store and retrieve the values of cell field variables computed by UDFs.
For more details please refer to fluent customization manual: 3.2. Data Access Macros (ansys.com)
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