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

SIMPLE scheme and Boundary conditions

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 1, 2009, 17:13
Default SIMPLE scheme and Boundary conditions
  #1
New Member
 
Hoarau Yannick
Join Date: Mar 2009
Posts: 21
Rep Power: 8
yhoarau is on a distinguished road
Hi,

I've written a multi-bloc incompressible scheme on collocated grids (Rhie and Chow correction) and i have some problems.
1) I have fixed the pressure at the outlet : it's working for steady flows but for not for unsteady (cylinder at Reynolds 100). I've seen that some use zero second derivative of the pressure but in this case the the pressure deviates. Is there a trick?
2) Concerning the pressure correction on multibloc, what is the condition on the interface? I've tried dp'/dn=0 but in this case i have discontinuities on the pressure at the interfaces so i use p'=0. Is that correct?
3) Finally i have some difficulties with the SIMPLEC scheme, the correction is : (Ap)e minus the sum of Ap of the neighbors. (Ap)e is an averaged value. What is used for the neighbors? I explain myself : we have AP + AN + AS + AE + AW = 0 in 2D so in SIMPLEC does the correction resume to the under-relaxation?

Many thanks.
yhoarau is offline   Reply With Quote

Old   April 5, 2009, 14:17
Default
  #2
New Member
 
Hoarau Yannick
Join Date: Mar 2009
Posts: 21
Rep Power: 8
yhoarau is on a distinguished road
Nobody have any ideas?
yhoarau is offline   Reply With Quote

Old   April 5, 2009, 19:45
Default
  #3
Member
 
Newton KF
Join Date: Mar 2009
Posts: 36
Rep Power: 8
NewtonKF is on a distinguished road
What are the other BCs??? Have you used Neumann or Dirichlet??? What about the inlet??? You should not have problems when changing from steady to unsteady cases... in this kind of analysis... Good luck...
NewtonKF is offline   Reply With Quote

Old   April 6, 2009, 03:06
Default
  #4
New Member
 
Hoarau Yannick
Join Date: Mar 2009
Posts: 21
Rep Power: 8
yhoarau is on a distinguished road
The other BC are :
- for the inlet Dirichlet for the velocities and Neumann for the pressure and pressure correction
- Block connection ; Dirichlet for velocitie, P and p'
- Outlet : Neumann for velocities, dirichlet for P and p'
yhoarau is offline   Reply With Quote

Old   April 6, 2009, 09:32
Default
  #5
Member
 
Newton KF
Join Date: Mar 2009
Posts: 36
Rep Power: 8
NewtonKF is on a distinguished road
Have you ever tried with only one block???? like a poiseuille flow??? does it works??? what about the lateral bcs??? neumann also??? like the outlet???
NewtonKF is offline   Reply With Quote

Old   November 24, 2011, 00:11
Default
  #6
Senior Member
 
Mehdi
Join Date: Jan 2011
Location: Iran
Posts: 130
Rep Power: 6
mb.pejvak is on a distinguished road
Hi
I see you apply dirichlet boundary condition for pressure in outlet for collocated arrangment. iI have problem with applying that. In simpler method we don't need amount of pressure for faces but in applying this boundary condition we have constant pressure for face of boundary cell. I don't know how to make it. can you please tell me what should I do?
thanks a lot
mb.pejvak 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
Fluent accuracy and boundary conditions Paolo Lampitella FLUENT 0 June 12, 2008 06:25
Convective Heat Transfer - Heat Exchanger Mark CFX 6 November 15, 2004 16:55
New topic on same subject - Flow around race car Tudor Miron CFX 15 April 2, 2004 06:18
Please help with flow around car modelling! Tudor Miron CFX 17 March 19, 2004 20:23
SIMPLE Boundary Conditions Kunal Jain Main CFD Forum 3 August 20, 2001 09:58


All times are GMT -4. The time now is 05:34.