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

SIMPLER Algorithm

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 22, 2006, 19:32
Default SIMPLER Algorithm
  #1
Bharath
Guest
 
Posts: n/a
Saturday, 22 April 2006

Hello everyone

I'm trying to solve 2D incompressible flow problem in a channel using SIMPLER algorithm on a staggered grid approach using Finite volume discretization using central differences. I have some issues with the proper implementation of boundary conditions. If you have some insight to the questions i have below, please reply to this message.

Problem setup: Flow is incompressible and is from left to right. The top and bottom are walls.

Boundary conditions: Left side: I specify a value of pressure and v-velocity at the inlet and allow u-velocity to float. Right side: I specify fully developed flow for u and v velocities and specify a value of pressure Top wall: No slip and normal pressure gradient is zero Bottom wall: No slip and normal pressure gradient is zero

1. If I'm right, one cannot simultaneously specify pressure and velocity at a boundary. In SIMPLER, since we need to solve the pressure equation using the estimated pseudo-velocities, we need to see the pressure equation as a boundary value problem. So, we need to specify pressures at the inlet and exit and apply the normal derivative of pressure at the top and bottom walls. This is fine. The question I have is- how can one consistently estimate the boundary velocities at the left side? Right now, I'm using a linearized form of NS equations like the Darcy's law to estimate the boundary velocities and then use the full blown NS equations for the interior volumes. The cell continuity is not satisfied and the pressure drop in the domain always stays linear. Is this right? Or, to be more accurate one can use Bernoulli equation to estimate the boundary velocities but again this prescription is not straight forward to implement and becomes too complex. Also, if I use the Darcy law kind of linear momentum equation connecting pressure gradient and velocity, the continuity is not satisfied.

In addition, I'm using Darcy law kind of linear momentum equation both in the u-pseudo-velocity routine to estimate the u-pseudo-velocities and in u-star-velocity routine to estimate the u-star-velocities. Is there any other consistent form of momentum equation to correctly estimate the boundary velocities? This special treatment of the boundary volumes is due to the fact that we need to specify a value of pressure (that has physical significance) in SIMPLER as against just specifying p' (mathematical artefact) in SIMPLE. Please let me know if you have any comments on this thought.

2. The over-specified and may be the inconsistent formulation would be to specify pressure and velocities at all sides. If this is the case, the continuity in each cell will not be satisfied.

In other words, what are the consistent? boundary conditions in SIMPLER algorithm?

Thanks

  Reply With Quote

Old   July 10, 2009, 10:17
Default
  #2
Member
 
Join Date: May 2009
Posts: 58
Rep Power: 8
amir2920 is on a distinguished road
Hello

could you please send me discretization of momentum and energy equation in cylindrical coordinate or a paper that contains this? Thank you in advance. my email is: amir2920@gmail.com
amir2920 is offline   Reply With Quote

Old   July 10, 2009, 10:53
Default
  #3
New Member
 
Join Date: Mar 2009
Posts: 11
Rep Power: 8
johndorian is on a distinguished road
Seriously is there any need to drag up three threads on the same thing for what basically amounts to begging?

Why is there such a rash of behaviour like this on the CFD Online forum these days? Do Masters and PhD students expect codes to be handed to them on a plate? The whole point of using CFD is to understand what your code is spitting out and learn as you go along, rather than just taking a black box and naively believeing everything that it spits out, or taking someone else's code and blindly using it.

Rant over.
johndorian 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
SIMPLER Algorithm David Main CFD Forum 1 July 13, 2008 12:18
Pressure BC in SIMPLER Algorithm? Mori Main CFD Forum 1 August 24, 2006 18:45
Interpolation algorithm in SIMPLER elisabet Main CFD Forum 0 December 7, 2005 05:54
SIMPLER Algorithm question Erik Main CFD Forum 1 May 23, 2004 03:57
SIMPLER ALGORITHM H.Setthapong Main CFD Forum 5 October 18, 2000 06:34


All times are GMT -4. The time now is 15:49.