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

pipe

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

Reply
 
LinkBack Thread Tools Display Modes
Old   June 29, 2011, 05:16
Default pipe
  #1
Senior Member
 
hamid
Join Date: Nov 2010
Posts: 184
Rep Power: 6
hamid1 is on a distinguished road
Hi Guys

in pipe with pressure boundary condition is it needed to have long domain? or any arbitrary length of pipe is fine for numerical calculation,
hamid1 is offline   Reply With Quote

Old   June 29, 2011, 08:17
Default
  #2
New Member
 
eddy
Join Date: Apr 2011
Posts: 8
Rep Power: 5
shimmyya is on a distinguished road
as far as i know u dont need any specific length for solve ur problem, but if u want to see the full developed flow u need a certain length
shimmyya is offline   Reply With Quote

Old   June 29, 2011, 09:55
Default
  #3
Senior Member
 
hamid
Join Date: Nov 2010
Posts: 184
Rep Power: 6
hamid1 is on a distinguished road
In modeling fluid flow in a pipe, when do I need to see the fully developed flow? (either of laminar or turbulent regime)
Do I need specific length in inlet or outlet?
What is the criterion for that?
I was thinking that if after any modeling there wouldn’t be any circulation (which cause back flow) in openings the length is enough (either of inlet or outlet), is it true?
hamid1 is offline   Reply With Quote

Old   June 29, 2011, 10:53
Default
  #4
New Member
 
eddy
Join Date: Apr 2011
Posts: 8
Rep Power: 5
shimmyya is on a distinguished road
hi,
1. it depends on you if u want to see any full developed flow. For example u have something in ur pipe and want to see how ur fluid pass it and how turbulent it will be.
2. still as far as i know in fluent u dont need any specific length, the solver will give u same results so if u solve ur modell with 10m length and anothertime with 1m length, this first meter should allways have same values.
3. ur last sentence i dont get
shimmyya is offline   Reply With Quote

Old   June 29, 2011, 11:07
Default
  #5
Senior Member
 
hamid
Join Date: Nov 2010
Posts: 184
Rep Power: 6
hamid1 is on a distinguished road
Thank u very much for reply, I think the main issue is if flow passing through opposite direction in openings or not, say, in inlet flow coming from inside the domain to outside and in case of outlet if flow coming from outside of the domain to inside … if it dosent happen then the simulation is correct from this point of view (regardless of whatever the length of the pipe is), u may correct me please if I am wrong,
Thanks in advance
Hamid
hamid1 is offline   Reply With Quote

Old   June 29, 2011, 11:45
Default
  #6
New Member
 
eddy
Join Date: Apr 2011
Posts: 8
Rep Power: 5
shimmyya is on a distinguished road
hi,
thats right, the flow dont come back from outside. but i guess if u have backflow in ur pipe, its possible that flow left pipe through inlet.
Because i dont know it 100%,i guess i will try to simulate it in next time

edit: hmm seems i was on wrong way ... if u look at image u see that there is a little bit diffrence
Attached Images
File Type: jpg yytest-1-3.jpg (85.2 KB, 5 views)

Last edited by shimmyya; June 29, 2011 at 12:26.
shimmyya is offline   Reply With Quote

Old   June 29, 2011, 13:16
Default
  #7
Senior Member
 
hamid
Join Date: Nov 2010
Posts: 184
Rep Power: 6
hamid1 is on a distinguished road
So.. u mean at same cross section there are different results for longer and shorter length of the pipe, ... if so how long do u use for a domain to get rid of this issue?

and what if u have only the boundary condition of short length ? (though this is not my case but just asking)
hamid1 is offline   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
[DesignModeler] DesignModeler Pipe within pipe shields ANSYS Meshing & Geometry 8 March 7, 2011 13:24
pipe in pipe heat exchanger JohannV FLUENT 3 December 3, 2009 03:53
CYCLIC BC in pipe flows matthias OpenFOAM 0 November 5, 2009 11:52
My Revised "Time Vs Energy" Article For Review Abhi Main CFD Forum 2 July 9, 2002 10:08
Terrible Mistake In Fluid Dynamics History Abhi Main CFD Forum 12 July 8, 2002 10:11


All times are GMT -4. The time now is 20:47.