CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

outflow boudary condition in SIMPLE algorithm

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

LinkBack Thread Tools Display Modes
Old   March 6, 2003, 12:55
Default outflow boudary condition in SIMPLE algorithm
Posts: n/a
Sponsored Links

I have a question about the outflow boudary condition in SIMPLE algorithm. I am implenmenting SIMPLE(H.K. Versteeg and W. Malalasekera book) in matlab.

Dealing with outflow BC, their book suggested using Unx,j=Unx-1,j*Min/Mout as mass conservation outflow BC. where Unx,j is outflow u velocity, Min is mass flux at inflow , Mout is mass flux at outflow.My question is how to implenment the boudary condition as we dont know Mout?

I am using SIMPLE algorithm. So first I need to get u* and v* through previous u,v and p results. When setting up u* matrix, I need to know Mout, which is unknown at that time(I cant using previous u to calculate Mout because Mass conservation should happen within each iteration).

My thought was:

1. still using Unx,j=Unx-1,j as outflow BC to obtain the u*, of course it doest obey mass conservation.

2. then calculate Mout using u*

3. apply Unx,j=Unx-1,j*Min/Mout back into the u* matrix, to calculate u* again.

I dont know if I am wrong or not. And I dont know if I should force the mass conservation after I correct u* with p'(i.e, corrected u).

Right now my result looks like ossillating at internal. The two ends(inflow and outflow velocity) are stable, but the internal u velocity are not stable at all, it is ossillating and gradully diverging.

Your advice will be of great help.
  Reply With Quote
Sponsored Links


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
SIMPLE algorithm SamR Main CFD Forum 14 June 17, 2017 06:00
Looking for simple, robust interface tracking algorithm ThomasTC Main CFD Forum 7 September 26, 2016 05:35
SIMPLE algorithm confusion lost.identity Main CFD Forum 1 October 7, 2010 11:48
What is advantage of SIMPLE algorithm? Geon-Hong Main CFD Forum 1 May 18, 2010 07:46
SIMPLE algorithm Jonathan Castro Main CFD Forum 3 December 10, 1999 05:59

Sponsored Links

All times are GMT -4. The time now is 01:55.