CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Running, Solving & CFD

Stokes Flow Simulation

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

Reply
 
LinkBack Thread Tools Display Modes
Old   October 19, 2013, 17:11
Default Stokes Flow Simulation
  #1
New Member
 
Angus Hendrick
Join Date: Aug 2013
Posts: 4
Rep Power: 3
angushendrick is on a distinguished road
I am trying to find the steady-state velocity field for laminar flow transverse to a random array of parallel cylinders using simpleFoam in OpenFOAM 2.2.1. I am using empty boundary conditions on faces normal to the cylinder axes and cyclic boundary conditions for the other faces. The flow is supposed to be driven by gravity acting in one of the two cyclic directions.

The simulation does not work. It converges to a velocity that approaches 0, if seeded with non-zero velocities (as the attached case does). It appears that the gravitational term is ignored, though I have included "g" in the constants directory.

The case is zipped here. I'm sure I'm doing something stupid. Any help, especially if it wittily points out just how stupid I am, is much appreciated.
angushendrick is offline   Reply With Quote

Old   October 20, 2013, 23:58
Default
  #2
Member
 
mohsen kh
Join Date: Jan 2013
Location: Iran
Posts: 86
Rep Power: 5
m5m5kh is on a distinguished road
Quote:
Originally Posted by angushendrick View Post
I am trying to find the steady-state velocity field for laminar flow transverse to a random array of parallel cylinders using simpleFoam in OpenFOAM 2.2.1. I am using empty boundary conditions on faces normal to the cylinder axes and cyclic boundary conditions for the other faces. The flow is supposed to be driven by gravity acting in one of the two cyclic directions.

The simulation does not work. It converges to a velocity that approaches 0, if seeded with non-zero velocities (as the attached case does). It appears that the gravitational term is ignored, though I have included "g" in the constants directory.

The case is zipped here. I'm sure I'm doing something stupid. Any help, especially if it wittily points out just how stupid I am, is much appreciated.
Hi Angus and welcome to this forum
take a look to this project specially page 23 I think it would be helpful for your case

http://www.diva-portal.org/smash/get...T01.pdf‎

best regards
Mohsen
m5m5kh is offline   Reply With Quote

Old   October 21, 2013, 21:00
Default
  #3
New Member
 
Angus Hendrick
Join Date: Aug 2013
Posts: 4
Rep Power: 3
angushendrick is on a distinguished road
Thanks for the response to my question. I read the paper you linked, and while it is broadly related (i.e., flow around cylinders), I don't find a discussion of the problem I am having. That is, in my case I need to generate body-force (i.e., gravity) driven flow.
angushendrick is offline   Reply With Quote

Old   October 22, 2013, 01:56
Default
  #4
Senior Member
 
Bernhard
Join Date: Sep 2009
Location: Delft
Posts: 790
Rep Power: 12
Bernhard is on a distinguished road
There is something physically wrong with what you expect. You have a fluid with constant density. How would gravity act on it? E.g.: in a bottle of water there is no movement.
Bernhard is offline   Reply With Quote

Old   October 22, 2013, 20:21
Default
  #5
New Member
 
Angus Hendrick
Join Date: Aug 2013
Posts: 4
Rep Power: 3
angushendrick is on a distinguished road
The simulation is set up so that it has cyclic boundary conditions top and bottom. With gravity acting downward, I expect that all the fluid will fall, exiting the bottom and re-entering at the top. Because of the no-slip boundary conditions on the cylinders within the domain, I expect that it will eventually reach a steady state where the momentum added by gravity is equal to the momentum lost at the solid surfaces.

I recognize that if gravity is added as a modified pressure, then there will be no flow, and so an explicit body force term may be necessary. I don't know how to add this if it is.

Last edited by angushendrick; October 25, 2013 at 20:29.
angushendrick is offline   Reply With Quote

Old   November 3, 2013, 16:33
Default Solution using a vectorSemiImplicitSource
  #6
New Member
 
Angus Hendrick
Join Date: Aug 2013
Posts: 4
Rep Power: 3
angushendrick is on a distinguished road
Putting the following in system/fvOptions is my current approach. It seems to work.

momentumSource1
{
type vectorSemiImplicitSource;
active true;
selectionMode all;

vectorSemiImplicitSourceCoeffs
{
volumeMode absolute;
injectionRateSuSp
{
U ((1e-6 0 0) 0);
}
}
}
angushendrick 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
Domain format problem on airfoil flow simulation andrenonaka CFX 6 December 4, 2014 04:57
About Some Concepts:Laminar flow, turbulent flow, steady flow and time-dependent flow Jing Main CFD Forum 5 March 2, 2013 15:02
Query regarding temperature distribution in Solidworks flow simulation syarif FloEFD, FloWorks & FloTHERM 3 February 27, 2013 06:22
problems in synthetic jet flow simulation jackxu FLUENT 0 December 2, 2012 10:12
fluid flow fundas ram Main CFD Forum 5 June 17, 2000 21:31


All times are GMT -4. The time now is 00:34.