
[Sponsors] 
November 1, 2002, 07:08 
If the gas flows out of the inlet boundary,...

#1 
Guest
Posts: n/a

I'm doing some transient analysis of pipes. If the gas escape from the inlet boundary,what will happen? Can StarCD deal with this kind problem?


November 1, 2002, 07:39 
Re: If the gas flows out of the inlet boundary,...

#2 
Guest
Posts: n/a

If you have outflow you can use inlet or pressure boundary conditions.


November 1, 2002, 07:43 
Re: If the gas flows out of the inlet boundary,...

#3 
Guest
Posts: n/a

I've used inlet boundary conditions.It seems that Starcd hasn't processed the problem.


November 1, 2002, 09:20 
Re: If the gas flows out of the inlet boundary,...

#4 
Guest
Posts: n/a

Hi Miles, since upwind scheme has been used, inlet boundary as i see could not handle reverse flow. why not extrude the inlet for a distance.


November 1, 2002, 10:25 
Re: If the gas flows out of the inlet boundary,...

#5 
Guest
Posts: n/a

If you mean that you INTEND to use a velocity inlet as outlet boundary (i.e. apply a negative inlet flow  like a suction point) it should be alright. That is if you put a pressure boundary where the flow should enter, to be able to specify turbulent quantities.


November 6, 2002, 17:14 
Re: If the gas flows out of the inlet boundary,...

#6 
Guest
Posts: n/a

It seems that StarCD cannot deal with this problem.


November 7, 2002, 07:33 
Re: If the gas flows out of the inlet boundary,...

#7 
Guest
Posts: n/a

It seems to me that you are not able to describe your problem in a way that we know what you are doing and what you intend to do.


November 7, 2002, 09:48 
Re: If the gas flows out of the inlet boundary,...

#8 
Guest
Posts: n/a

I'm sorry. I'm trying to simulate the gas flow through pipes. And the boundary conditions is that the flow of the inlet boundary can be positive and negative.


November 7, 2002, 13:26 
Re: If the gas flows out of the inlet boundary,...

#9 
Guest
Posts: n/a

You have about 3 possibilities to do this.
1.) use a user defined subroutine and describe the velocity as a function of time 2) use a table with the values of the velocity 3) use the transient calculation with different load steps. For each load step you can select you boundary values and ramp between them. If you have an analytical function for the vel vs. time the subroutine should be the most straightforward way to go. Otherwise use the second or third way. 

November 7, 2002, 15:07 
Re: If the gas flows out of the inlet boundary,...

#10 
Guest
Posts: n/a

I'll use the first method. Thank you very much.


Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Inlet turbulent boundary condition: external flows  ROOZBEH  FLUENT  3  August 28, 2015 15:34 
Pressure inlet boundary conditions for open channel flows  jack2000  OpenFOAM Running, Solving & CFD  3  October 21, 2012 14:10 
Inlet turbulent boundary condition, external flows  ROOZBEH  Main CFD Forum  1  February 6, 2009 13:37 
Nonmatched Boundary Flows  Roger  CFX  7  April 6, 2006 07:27 
length scales at inlet for internal flows  AnneMarie Giroux  Main CFD Forum  3  July 5, 1999 21:28 