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

Density in icoFoam Densidad en icoFoam

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   August 23, 2006, 13:47
Default Hi, Thanks in advance . i
  #1
New Member
 
Manuel Felipe Mejia De Alba
Join Date: Mar 2009
Posts: 10
Rep Power: 17
manuel is on a distinguished road
Hi,
Thanks in advance .

i try to run a nozzle model, very simple, using icofoam. After try and try, and try ;-), run without problems. I run the same model in ANSYS and the result are not equal. In ansys, i need the density, but in IcoFoam No.

what equations solved icofoam, where not is necesary the density.??

My model is a modifid cavity, whit the nu 0.01.

thanks.
________________
Hola
Gracias por adelantado.

yo estoy tratando de correr un modelo de una tobera sencilla. Despues de tratat y tratar, logre que corriera sin problemas. Yo tratto de correr el mismo ejemplo en Ansys, pero el resultado no es el mismo. Ademas en ansys es necesario la densidad pero en icofoam no.

Que ecuaciones resuelve icofoam, donde no es necesario la densidad?

Mi modelo es como el modelo cavity pero modificado, con nu de 0.01

Gracias

Manuel F. Mejia De Alba
Universidad Nacional de Colombia.
manuel is offline   Reply With Quote

Old   August 23, 2006, 14:41
Default In icoFoam, the pressure being
  #2
Senior Member
 
Gavin Tabor
Join Date: Mar 2009
Posts: 181
Rep Power: 17
grtabor is on a distinguished road
In icoFoam, the pressure being solved is not the true pressure but is in fact p/rho. Thus the density cancels out throughout.

Gavin
grtabor is offline   Reply With Quote

Old   August 24, 2006, 17:50
Default Hi Ok, the press is equal.
  #3
New Member
 
Manuel Felipe Mejia De Alba
Join Date: Mar 2009
Posts: 10
Rep Power: 17
manuel is on a distinguished road
Hi

Ok, the press is equal. But, what happend whit the velocity, the graphics change, when change the density.

how i do, for make a model with the density of any value.

thanks
manuel is offline   Reply With Quote

Old   August 24, 2006, 18:00
Default Multiply the pressure field wi
  #4
Senior Member
 
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,904
Rep Power: 33
hjasak will become famous soon enough
Multiply the pressure field with the value of density. If you want to feel really good about it, you can also add it an offset, e.g. 101325 Pascal for air at atmospheric conditions.

This can all be done after the simulation and there's no need to change the solver. Look at the magU utility for examples - you will be manipulating the pressure instead.

Hrv
__________________
Hrvoje Jasak
Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk
hjasak is offline   Reply With Quote

Old   August 24, 2006, 18:37
Default ok, with the press, i not have
  #5
New Member
 
Manuel Felipe Mejia De Alba
Join Date: Mar 2009
Posts: 10
Rep Power: 17
manuel is on a distinguished road
ok, with the press, i not have problems

my doubts are with the velocity field:

this is independent of density??

thanks and sorry the insistence.

Manuel.
manuel is offline   Reply With Quote

Old   August 25, 2006, 08:26
Default Velocity is fine: remember, yo
  #6
Senior Member
 
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,904
Rep Power: 33
hjasak will become famous soon enough
Velocity is fine: remember, you only have grad p in the momentum equation and that does not change for arbitrary offset of p.

Enjoy,

Hrv
__________________
Hrvoje Jasak
Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk
hjasak is offline   Reply With Quote

Old   August 26, 2006, 13:35
Default Hi again, and I am sorry for i
  #7
New Member
 
Manuel Felipe Mejia De Alba
Join Date: Mar 2009
Posts: 10
Rep Power: 17
manuel is on a distinguished road
Hi again, and I am sorry for inconvenients for so many questions. One more, when I`m looking in the icofoam solver code, it appears a phi term (like a field Phi), that is multiply for velocity, and I`m not sure if that term is related with viscous loss term of generalized momentum equation. The problem is that changes in the kinematic viscosity produces big changes in the velocity field pattern, and not only in velocity field values.

Thanks again
manuel is offline   Reply With Quote

Old   August 26, 2006, 13:42
Default Hi again, and I am sorry for i
  #8
New Member
 
Manuel Felipe Mejia De Alba
Join Date: Mar 2009
Posts: 10
Rep Power: 17
manuel is on a distinguished road
Hi again, and I am sorry for inconvenients for so many questions. One more, when I`m looking in the icofoam solver code, it appears a phi term (like a field Phi), that is multiply for velocity, and I`m not sure if that term is related with viscous loss term of generalized momentum equation. The problem is that changes in the kinematic viscosity produces big changes in the velocity field pattern, and not only in velocity field values.
manuel is offline   Reply With Quote

Old   September 22, 2010, 05:10
Default
  #9
Senior Member
 
Pavan
Join Date: May 2009
Location: Melbourne
Posts: 101
Rep Power: 16
rieuk is on a distinguished road
Yeah but when you change viscosity you're changing Reynolds number so you should expect a change in flow field. Also if I'm not mistaken, Phi is a scaled flux per unit density per unit area...?
rieuk is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
IcoFoam aap OpenFOAM Running, Solving & CFD 15 May 28, 2012 09:30
About phi in icoFoam kar OpenFOAM Running, Solving & CFD 3 February 20, 2008 06:20
Possible bug in icoFoam msrinath80 OpenFOAM Bugs 6 November 19, 2007 18:35
Need help for a simple example with icoFOAM gruber2 OpenFOAM Running, Solving & CFD 3 April 3, 2007 07:26
IcoFoam on AIX 53 ds2taieb OpenFOAM Installation 1 March 24, 2006 04:22


All times are GMT -4. The time now is 16:14.