The following fragment of udf comes from the Fluent UDF manual on using uds to calculate the derivative of temperature to the fourth power for post-processing. I want to do something like this to get the second order derivatives of the velocity (which I need only at the cell centers).

I am concerned about the face values. Can anybody tell me what line 11 is doing in this code? Thanks.

1. thread_loop_f (t,domain) 2. { 3. if (NULL != THREAD_STORAGE(t,SV_UDS_I(T4))) 4. { 5. begin_f_loop (f,t) 6. { 7. real T = 0.; 8. if (NULL != THREAD_STORAGE(t,SV_T)) 9. T = F_T(f,t); 10. else if (NULL != THREAD_STORAGE(t->t0,SV_T)) 11. T = C_T(F_C0(f,t),t->t0); 12. F_UDSI(f,t,T4) = pow(T,4.); 13. } 14. end_f_loop (f,t)

Hi !

Boundary face value to be equal to boundary cell value .

t-> t0 ;indicates to boundary cell thread "t0" adjacent with boundary face that it's thread is "t".