Location of coordinate origin (UDF consideration)?

Frosn

For 2D cartesian simulation(H*D), the symmetry line should be placed on the postion of D/2 or 0.0. That is:

centerling Case 1: -D/2 --- 0.0 ----D/2 (involving negative value) Case 2: 0.0 --- D/2 ----D (completely positive)

Which one is better with considering that I will define a inlet velocity profile by UDF? Or both are the same for UDF internal treatment?

Thanks in advance for your help.