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Old   November 26, 2007, 07:29
Default Dear Forum, I forgot to ask
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Alessandro Spadoni
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Dear Forum,

I forgot to ask about z-dimension in LES:

What would be the extent of the z-dimension for the airfoil model described above?
How many cells would you recommend in the z-direction?

Thank you,

Alessandro Spadoni
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Old   December 1, 2007, 22:21
Default Dear Forum, I have produced
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Alessandro Spadoni
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Dear Forum,

I have produced a new mesh whereby the inlet region touches the outlet region, similarly to the tutorial sonicTurbFoam/nacaairfoil.

I was wondering if it is ok to have my inlet touch the outlet. If this is ok, what are the approriate boundary conditions to facilitate convergence?

At the moment, I use

inlet:
U fixed value
p zeroGradient

otlet:
U zeroGradient
p fixedvalue 0

Would it be better to use inletOutlet?
or alternaltively, set p zeroGradient at the outlet?

Thank you,

Alessandro
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Old   December 4, 2007, 13:36
Default Dear Forum, Forgive me if I
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Alessandro Spadoni
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Dear Forum,

Forgive me if I ask some questions that may be answered by looking at references. I am really trying to get a grasp of how turbulence modeling is done in OpenFOAM, and I am having some problems.

I am struggling with getting convergence with fine grids. By fine I mean Fluent converges and tells me that the resulting y+ ~ 1 (used k-w SST with transient flow option turned on, meaning low Re version).

As posted in

http://www.cfd-online.com/OpenFOAM_D...tml?1196717652

I get good convergence using the kOmegaSST model with a y+ of about 7 in OpenFOAM. I now refined the grid to prepare good initial conditions for a LES case, and I get very poor or no convergence.

This is the initial residual for pressure:




I understand the implementation of kOmegaSST in OpenFOAM always uses wall functions (do I undestand this correctly?), and thus the boundary file should have:

myWallPatch
{
type wall;
physicalType wallFunctions;
...
}

What happens if I do not declare physicalType?
Does the model still uses wallFunctions by default?

Is there an a lowRe k-w SST model in OpenFOAM?

If I were to use one of the low Re models supplied with OpenFOAM, say LRR, how would I define by wall patches?

myWallPatch
{
type pach;
...
}
would this be correct?

I did search through the postings, but I could not find any information about the boundary file specifications for low Re models, and most questions about wallFunctions refer to the k-e model.

Thank you for your help,

Alessandro
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Old   December 4, 2007, 13:39
Default Dear Forum, The jump in ini
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Alessandro Spadoni
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Dear Forum,

The jump in initial pressure residual at about iteration number 1000 happened spontaneously. I did not change fvSchemes or anything else.

Thank you,

alessandro
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