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icoFoam >> density >> kinematic viscosity for air 20°C |
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November 30, 2009, 05:19 |
icoFoam >> density >> kinematic viscosity for air 20°C
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#1 |
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Markus Golbs Hamm AG
Join Date: Nov 2009
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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 |
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December 1, 2009, 08:00 |
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#2 |
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Gijsbert Wierink
Join Date: Mar 2009
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Hi Markus,
You can set nu in constant/transportProperties.
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Regards, Gijs |
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December 1, 2009, 11:23 |
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#3 |
New Member
Markus Golbs Hamm AG
Join Date: Nov 2009
Posts: 26
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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 |
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December 1, 2009, 14:50 |
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#4 |
Senior Member
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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 |
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December 2, 2009, 11:52 |
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#5 |
New Member
Markus Golbs Hamm AG
Join Date: Nov 2009
Posts: 26
Rep Power: 16 |
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 |
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December 2, 2009, 13:28 |
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#6 |
Senior Member
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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 |
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December 2, 2009, 13:37 |
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#7 |
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Gijsbert Wierink
Join Date: Mar 2009
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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!
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Regards, Gijs |
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December 2, 2009, 13:39 |
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#8 |
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Gijsbert Wierink
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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) ...
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Regards, Gijs |
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December 4, 2009, 03:25 |
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#9 |
New Member
Markus Golbs Hamm AG
Join Date: Nov 2009
Posts: 26
Rep Power: 16 |
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 |
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February 11, 2010, 06:00 |
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#10 |
New Member
Markus Golbs Hamm AG
Join Date: Nov 2009
Posts: 26
Rep Power: 16 |
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 |
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February 13, 2010, 03:50 |
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#11 |
Senior Member
Gijsbert Wierink
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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).
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Regards, Gijs Last edited by gwierink; February 13, 2010 at 03:51. Reason: typo |
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February 15, 2010, 11:09 |
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#12 |
New Member
Markus Golbs Hamm AG
Join Date: Nov 2009
Posts: 26
Rep Power: 16 |
Hello,
thanks for the informations. My mistake was setting "0" in the internal field of k and epsilon. Greeting Markus |
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