CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Phoenics

how to set inlet and outlet?

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   May 17, 2004, 23:44
Default how to set inlet and outlet?
  #1
green
Guest
 
Posts: n/a
Air is export from a pipe having special shape with a fun, the pipe is in a room. The volume rate of the fan is given. I want to konw the velocity and pressure in the pipe, how I should set the inlet and outlet? I have tried different ways. First, I set the velocity at outlet, but the pressure in the pipe is positive, but this is not right. Then I set the outlet to default, and before the outlet I set a fan with given volume rate, but it seems difficult to converge. Do you have any good idea? Thanks.
  Reply With Quote

Old   May 17, 2004, 23:53
Default Re: how to set inlet and outlet?
  #2
leon mills
Guest
 
Posts: n/a
Green,

If you are trying to look at the properties in the pipe only, then I suggest setting up the problem as follows.

Define the pipe, maybe using BFC. Define the fan as an inlet with a fixed m3/sec Define the outlet as an opening, with the correct coefficient. Check POLIS for this as it has some good examples.

Hope this helps.

Leon
  Reply With Quote

Old   May 18, 2004, 00:54
Default Re: how to set inlet and outlet?
  #3
green
Guest
 
Posts: n/a
I have done it in the way you told. But I also want to know if there is a smoke source at the inlet of the pipe, all the smoke will be export through the pipe or there will be some s,oke going into the room space. So I can't set an inlet at one end of the pipe, do you have any good idea? Thanks
  Reply With Quote

Old   May 18, 2004, 01:36
Default Re: how to set inlet and outlet?
  #4
leon mills
Guest
 
Posts: n/a
The big question is, does the pressure profile in the pipe matter.

If not, just model the smoke entering the room from the pipe.

You could work out from a 'pipe only' model the flow accross the outlet and ake the intel into the room, seperate model, be the same.

There maybe be a way of linking the two but I do not know how.

Otherwise to get suffcient resolution in the pipe region look at fine grid embedding.

  Reply With Quote

Old   May 18, 2004, 23:41
Default Re: how to set inlet and outlet?
  #5
green
Guest
 
Posts: n/a
The pressure in the pipe is what I want to know. I only know the velocity at the fan and the pressure at the room which is 1.0e5. I want to know the pressure and velocity in the pipe. I have tried to do it in such a way. Just before the outlet, I set a fan with the given velocity, but I don't know how to set the pressure in the outlet, because I don't know the pressure drop in the pipe. In fact, the pressure drop is what I want to konw.
  Reply With Quote

Old   May 18, 2004, 23:52
Default Re: how to set inlet and outlet?
  #6
leon mills
Guest
 
Posts: n/a
Green,

If all you are after is the pressure drop in the pipe.

Set up the geometry of the pipe. If there are bends or the like i recomend using BFC.

I find that with fans it is better to set the inlet pressure, to induce a velocity, or a flow rate. I have found this method to be more reliable when I want to find out velocities and pressures.

If you are talking about friction losses, have a look through POLIS and CHAM website, for examples on wall friction and surface roughness.

I would set the oulet pressure to be the ambien tpressure of the room. For this type of example it would seem fair.

Leon
  Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Without Inlet and outlet chetan FLUENT 4 February 11, 2008 13:45
Inlet-outlet BCs SUBHRA Main CFD Forum 0 June 3, 2004 20:15
one inlet and two outlet Fluenter FLUENT 2 March 28, 2004 23:23
use outlet as inlet Karin Phoenics 3 March 31, 2003 22:12
Outlet -> Inlet How? lego CFX 2 August 13, 2002 12:23


All times are GMT -4. The time now is 11:31.