Calculating Second Derivative of a Flow Variable in UDF

How to calculate second derivative of a flow variable in a UDF?

To calculate the second derivative of a flow variable in a UDF within Ansys Fluent, you would first store the gradient of the variable, such as `C_T_G`, into a user-defined scalar, which is denoted as `C_USDI`. After this, you can compute the gradient of `C_USDI` by using `C_USDI_G`.

This process will provide you with the data for the second derivative. It is crucial to allocate temporary memory before you start manipulating gradient macros to ensure proper calculation and to avoid any errors