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

Simple axisymetric model for a fanturbine

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 6, 2005, 10:07
Default The simplest axisymetric model
  #1
New Member
 
Fran�ois Cauneau
Join Date: Mar 2009
Location: Sophia Antipolis, France
Posts: 8
Rep Power: 8
cauneau is on a distinguished road
The simplest axisymetric model for a fan/turbine consists in following the Froude theory: declare inside the fluid a couple of very close patches - e.g. forming a thin disk - and to set a fixed value for delta-P and a constant velocity+rho between up/downstream faces.

Doing so in openFOAM I encounter a deviation from the theory, i.e. the mass balance is slightly but progressively violated, resulting in mass injected by the disk inside the control volume. I think it comes from the fact I do not see how to actually set the up/downstream velocities to be identical.

Is there a way to merge the patches and then to set a mass conservation condition between the upstream patch and the downstream patch ?


Pr. Francois Cauneau
Ecole des Mines de Paris
cauneau is offline   Reply With Quote

Old   April 6, 2005, 10:36
Default Is your mesh one cell thick?
  #2
Senior Member
 
Join Date: Mar 2009
Posts: 854
Rep Power: 13
henry is on a distinguished road
Is your mesh one cell thick? If so it sounds like you are doing something similar to what boundaryFoam was designed for. If not it sounds like yo need cyclic conditions from front-to-back and drive the flow with a pressure-gradient body-force as in channelOodles.
henry is offline   Reply With Quote

Old   April 13, 2005, 11:44
Default Thanks Henry, indeed the ca
  #3
New Member
 
Fran�ois Cauneau
Join Date: Mar 2009
Location: Sophia Antipolis, France
Posts: 8
Rep Power: 8
cauneau is on a distinguished road
Thanks Henry,

indeed the case is 2D, but may extend it for 3D later. SO I was planning to test both of yoyr suggestions... but, shame on me I switched to new version 1.1 !!

bad Idea, I cannot further enter any data under FoamX. Trying any of 1.1 1,1 1.1d 1,1d to simply enter 1.1 gives "not a valid number".

So, before testing your suggestion, I scan the discussion list to seek for this very... basic trick :-)

Francois Cauneau
cauneau is offline   Reply With Quote

Old   November 26, 2005, 22:57
Default I will resolve the momentum eq
  #4
Member
 
olivier Petit
Join Date: Mar 2009
Location: Gteborg, Sweden
Posts: 67
Rep Power: 8
olivier is on a distinguished road
I will resolve the momentum equation for 2D axisymetric.
the equation is:
div(rho*vv)=-grad(p)+div(mu[grad(v)+Trans(grad(v))])
I implemented it like:

-------------------------
phi = fvc::interpolate(rho*U) & mesh.Sf();
tmp<fvvectormatrix> UEqn
(
fvm::div(phi, U)

- fvm::laplacian(mu,U)- fvc::div(mu*symm(fvc::grad(U)())) + fvc::div(mu*skew(fvc::grad(U)()))
);
UEqn().relax();

solve(UEqn() == -fvc::grad(p));
--------------------
When I run this equation with the case of pitzDaily I have the good result. but with the case (2D axisymetric) like nozzleFlow2D I have the bad result.
1. what's the probleme in my implementation ?
2. is there a method to rewrite this equation in cylindrical co-ordinates.
I wish to have a fast answer.
thanks a lot.
-----
Olivier
olivier 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
Gravity axisymetric Aminop FLUENT 2 May 5, 2008 04:12
axisymetric BB FLUENT 4 February 1, 2006 04:43
3d, 2d or axisymetric SAM Main CFD Forum 2 November 15, 2004 07:00
axisymetric jet mehdi icho FLUENT 2 March 31, 2002 23:03
meshing an axisymetric jet mehdi icho FLUENT 0 March 1, 2002 10:23


All times are GMT -4. The time now is 17:09.