time dependent velocity input by user subroutine
 

Hi Everybody I am struggling with a simple transient model. I have a 2-D rectangular channel with one inlet, one outlet, and two walls. At the inlet, V and W velocity are zero. Only U velocity is time dependent. For example, U=U0*sin(2*pi*f*time) where, U0, f, and time are velocity amplitude, frequency, and time or iteration number. How can I set this boundary condition in starcd user subroutine? The existing subrutine only accept spatial variation not temporal.

any help will be greatly appreciated

shohel

university of waterloo

Re: time dependent velocity input by user subrouti
 

The user subroutine bcdefi.f supports time dependant velocity boundary conditions.

Another option is to use a table.

Re: time dependent velocity input by user subrouti
 

Thanks Pauli I don't know how to implement time in the bcdefi.f suroutine. Specially, no idea about variable time or time step. Below I copied a portion of the bcdefi.f subroutine and show an example of time variation of U. lots of question mark, I don't know what to put to consider the time or time step or iteration. Do I need to "include" any new inc file or add new EQUIVALENCE. Your help will be greatly appreciated.

IF(IREG.EQ.2) THEN

TURINT=.FALSE.

U=2.3*sin(2*22/7*??????)

V=0.0

W=0.0

TE=0.0

ED=0.0

T=0

V22=0.0

F22=0.0

SCALAR(1)=0.0

DEN=0

ENDIF

RETURN

END C

Re: time dependent velocity input by user subrouti
 

If you look in nom.inc the variable time should be available (it comes through a common block not the call list)

Re: time dependent velocity input by user subrouti
 

The bcdefi.f template should include the line:

INCLUDE 'usrdat.inc'

This gives you access to a parameter "TIME". So for your example:

U=2.3*sin(2*22/7*TIME)

When you tell Star to write the usubs, it should put usrdat.inc into the ufile subdirectory.

On my system I have to create the ufile subdirectory manually. Otherwise when I try to write the usubs, Star reports the directory doesn't exist.