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November 26, 2007, 06:29 |
Dear Forum,
I forgot to ask
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#1 |
Member
Alessandro Spadoni
Join Date: Mar 2009
Location: Atlanta, GA
Posts: 65
Rep Power: 17 |
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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December 1, 2007, 21:21 |
Dear Forum,
I have produced
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#2 |
Member
Alessandro Spadoni
Join Date: Mar 2009
Location: Atlanta, GA
Posts: 65
Rep Power: 17 |
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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December 4, 2007, 12:36 |
Dear Forum,
Forgive me if I
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#3 |
Member
Alessandro Spadoni
Join Date: Mar 2009
Location: Atlanta, GA
Posts: 65
Rep Power: 17 |
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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December 4, 2007, 12:39 |
Dear Forum,
The jump in ini
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#4 |
Member
Alessandro Spadoni
Join Date: Mar 2009
Location: Atlanta, GA
Posts: 65
Rep Power: 17 |
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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