I want to know how to use "user defined Subroutines" in fluent. Can I program my codes in the surface of Fluent directly?

if you understand programming in C, it's possible. for a better look, please try this website

for Dos/Windows: www.perkins-software.com.au/Fluent/udf_scalar_dos.c for Unix: www.perkins-software.com.au/Fluent/udf_scalar_unix.c

No, check the manuals, there's an overview on how tu use udf's in the solver.

Thanks for your answer on fluent forum. I am using fluent4.5 now while I can only find the simple explaination about "user defined subroutine" in Chapter20 "fluent user's guide". I want to know more information about the structure of subroutine and how to connect it with fluent.

You should check the files "uds_..._flu45.pdf" in the directory ".../Fluent.Inc/fluent4.5/info/". There You will find more information about the uds in fluent4.5.

After reading the manuals, also look in the srcu folder under your Fluent.Inc/fluent4.5 installation - here you will find two folders - user and include. In the user one are the fortran templates of all user defined subroutines available in 4.5. In these you simply add your equations to calculate sources of momentum, energy, species etc. etc. and user properties for viscosity, thermal conductivity etc. etc. You can also check out the include files in the include folder, from which its possible to determine other internal variables which are useful but which aren't documented in ch20 of the manual.

Also see many previous posts on this forum.

Greg

Thanks very much for your answers.I have read the pdf file and checked the file under user directory.But I have not the absoft Fortran compiler.