CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Pre-Processing

icoFoam >> density >> kinematic viscosity for air 20°C

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   November 30, 2009, 05:19
Default icoFoam >> density >> kinematic viscosity for air 20°C
  #1
New Member
 
Markus Golbs Hamm AG
Join Date: Nov 2009
Posts: 26
Rep Power: 16
mgolbs is on a distinguished road
Hello,

I want solve a problem whis air by 20°C in profile whis turbulent flow and icoFoam. Where can i set the density of air and the kinematic viscosity? Is the k/e-Modell in icoFoam use for turbulent flow?

Greeting Markus
mgolbs is offline   Reply With Quote

Old   December 1, 2009, 08:00
Default
  #2
Senior Member
 
Gijsbert Wierink
Join Date: Mar 2009
Posts: 383
Rep Power: 18
gwierink is on a distinguished road
Hi Markus,

You can set nu in constant/transportProperties.
__________________
Regards, Gijs
gwierink is offline   Reply With Quote

Old   December 1, 2009, 11:23
Default
  #3
New Member
 
Markus Golbs Hamm AG
Join Date: Nov 2009
Posts: 26
Rep Power: 16
mgolbs is on a distinguished road
Hello,

thank's! I have a problem, because icoPipe is only for laminar flow. I need turbulent flow. Also I must use simplefoam. The are any parameters to set:

# Field Patch Field Type
U ......................
p ......................
k ......................
epsilon ......................
R .....................
nuTilda .....................

Which physical properties to allocate U, p, k, epsilon, R, nuTilda and which physical quantity?

Greeting Markus
mgolbs is offline   Reply With Quote

Old   December 1, 2009, 14:50
Default
  #4
Senior Member
 
santos's Avatar
 
Jose Luis Santos
Join Date: Mar 2009
Location: Portugal
Posts: 215
Rep Power: 18
santos is on a distinguished road
Send a message via Skype™ to santos
Hi Markus,

Use simpleFoam if you want steady-state, or pisoFoam for transient flow.

I would recommend you to start by looking in the OpenFOAM user guide, there you have a couple of tutorials on setting up turbulent cases.

Good luck,
Jose Santos
santos is offline   Reply With Quote

Old   December 2, 2009, 11:52
Default
  #5
New Member
 
Markus Golbs Hamm AG
Join Date: Nov 2009
Posts: 26
Rep Power: 16
mgolbs is on a distinguished road
Hello,

thanks for the informations. In the openFoam userGuide are importent dokus. I have solve a modell whis icoFoam, linear flow. This works well. The same modell I would like the same mesh solve whis simpleFoam.

Is pisoFoam under 1.4.1 not available?

Where can I set the density of flow medium?

The definition of boundary in simpleFoam are likewise icoFoam.
# the wall surfaces are set to wall >> the paremeter from U, p...nuTilda are constants? When no, where can I manage this parameter, in asci File?
# the Flow input surfaces are set to inlet >> the paremeter from U, p...nuTilda are also constants?
# the flow output surfaces are set to outlet. >> the paremeter from U, p...nuTilda are also constants?

Under point Fields (simpleFoam) are the parameter U, p, k, epsillon, R, nuTilda.

# Is U the flow velocity in X,Y and Z direction?
# Is p the pressure in SI Unit?
# What is k - the thermal conductivity or k=1/2(Ux²...)?
# What is epsillon for a physical value epsillon=C...^0.75.../l?
# What is R for a physical value - Reynolds Stress?
# What is nuTilda for a physical value?

About informations I'm very happy!

Greeting Markus
mgolbs is offline   Reply With Quote

Old   December 2, 2009, 13:28
Default
  #6
Senior Member
 
santos's Avatar
 
Jose Luis Santos
Join Date: Mar 2009
Location: Portugal
Posts: 215
Rep Power: 18
santos is on a distinguished road
Send a message via Skype™ to santos
Hi,

In 1.4.1, pisoFoam=turbFoam.

You don't need to set the density for an incompressible fluid, you just set the kinematic viscosity=viscosity/density in the constant/transportProperties of your case.

Regarding the boundary conditions and initial fields, you can look in the tutorials available on how to set them (cd $FOAM_TUTORIALS && ls).

The answer to all your remaining questions are in the User Guide, I suggest you to study it in detail.

Regards,
Jose Santos
santos is offline   Reply With Quote

Old   December 2, 2009, 13:37
Default
  #7
Senior Member
 
Gijsbert Wierink
Join Date: Mar 2009
Posts: 383
Rep Power: 18
gwierink is on a distinguished road
Hi Markus,

Here some short answers. I think pisoFoam in OF-1.6 is like turbFoam in OF-1.4.1, an incompressible transient solver.

You can set U, p, etc in 0/.

k is the turbulent kinetic energy k = 1/2 (u')^2

epsilon is the dissipation rate epsilon = C_mu^0.75 * k^1.5 / L, where C_mu is usually 0.09 and L is, say, 20% of channel width.
This stuff is explained in section 2.1.8.1 of the user guide.

The dimensions of p depend on the solver, but they are SI anyways: [kg m s T n A cd], so [0 1 -2 0 0 0 0] means m/s^2.

Hope this helps!
__________________
Regards, Gijs
gwierink is offline   Reply With Quote

Old   December 2, 2009, 13:39
Default
  #8
Senior Member
 
Gijsbert Wierink
Join Date: Mar 2009
Posts: 383
Rep Power: 18
gwierink is on a distinguished road
Oh yeah, forgot, you can set the density in constant/transportProperties by changing the kinematic viscosity nu (which is the dynamic viscosity mu divide by density) ...
__________________
Regards, Gijs
gwierink is offline   Reply With Quote

Old   December 4, 2009, 03:25
Default
  #9
New Member
 
Markus Golbs Hamm AG
Join Date: Nov 2009
Posts: 26
Rep Power: 16
mgolbs is on a distinguished road
Hello,

thanks for the many Informations. I have a look in the userGuide.. but not all my questions are answered.

When I create a modell "90° pipe" -turbulent air, whis wall, one input 10m/s y-Direction, and 100 Pa relativ, one output whis 0 Pa relativ medium air 20°C and I searching "distribution of pressure" and "distribution of velocity" in the "90°pipe" what must I set leastwise in turbFoam?

The output after solving "pressure" are "static pressure" or "velocity head" or "velocity head and static pressure"?

Greeting Markus
mgolbs is offline   Reply With Quote

Old   February 11, 2010, 06:00
Default
  #10
New Member
 
Markus Golbs Hamm AG
Join Date: Nov 2009
Posts: 26
Rep Power: 16
mgolbs is on a distinguished road
Hello,

....k is the turbulent kinetic energy k = 1/2 (u')^2

epsilon is the dissipation rate epsilon = C_mu^0.75 * k^1.5 / L, where C_mu is usually 0.09 and L is, say, 20% of channel width....

Is k and epsilon only to set in internalField, or also in inlet and outlet faces?

Greeting Markus
mgolbs is offline   Reply With Quote

Old   February 13, 2010, 03:50
Default
  #11
Senior Member
 
Gijsbert Wierink
Join Date: Mar 2009
Posts: 383
Rep Power: 18
gwierink is on a distinguished road
Hi Markus,

You need to set k and epsilon at the inlet, outlet, as well as for the internalField. You could set k and epsilon according to the equations above and then the internal field to 0 or something small (e.g. 1% of inlet value).
__________________
Regards, Gijs

Last edited by gwierink; February 13, 2010 at 03:51. Reason: typo
gwierink is offline   Reply With Quote

Old   February 15, 2010, 11:09
Default
  #12
New Member
 
Markus Golbs Hamm AG
Join Date: Nov 2009
Posts: 26
Rep Power: 16
mgolbs is on a distinguished road
Hello,

thanks for the informations. My mistake was setting "0" in the internal field of k and epsilon.

Greeting Markus
mgolbs 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
Density in icoFoam Densidad en icoFoam manuel OpenFOAM Running, Solving & CFD 8 September 22, 2010 05:10
User-defined turbulent viscosity - kinematic or dynamic? tstorm FLUENT 0 August 13, 2009 17:49
REAL GAS UDF brian FLUENT 6 September 11, 2006 09:23
kinematic viscosity at diff temperatures,pressures Mecobio Main CFD Forum 0 November 7, 2005 13:55
Warning 097- AB Siemens 6 November 15, 2004 05:41


All times are GMT -4. The time now is 12:55.