Hi, all I have a question about ICALL in subroutine usrsrc. When I add source terms, I don¡¯t know clearly that I should use ICALL=1 or ICALL=2. Though the manual expands how to use it, I am puzzled. Someone know the principle to use ICALL=1 OR 2. Any suggestion is appreciated.

ICALL = 1 you will ADD your custom source term. When you set ICALL = 2 you'll OVERWRITE any existent source terms in your equation. If you take a look at the USRSRC subroutine on the manual, there's two examples using the energy equation. In one example (ICALL=1) there's a source of heat adding 100W/m3 in every cell, leaving the other source terms in the energy equation as they are. In the other example (ICALL=2) the source term is ONLY 100W/m3 in every cell of domain.
Regards, cfd guy