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LES-Content of a Detached Eddy Simulation for OpenFOAM

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Old   March 6, 2013, 09:23
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  #21
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Anne Gerdes
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I have the same in my computation, meaning to use cubeRootVol for delta and IDDESDelta inside SpalartAllmaras model.
This works in any case.
Would be interesting to know if it is possible to set the general delta to "IDDESDelta".
So far, this does not work with OF-2.1.1.
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Old   March 6, 2013, 15:13
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It runs perfect! Thank you ingcorra.

But I might have spoken to fast. Anne has a point.

So to check if IDDESDelta is being used and not cubeRoot I simply added a line in the IDDESDelta.C file:

Info<<delta_.internalField()<<endl;

after the calculation of delta.

It prints the value of delta before the first iteration, but not in each iteration.

Does delta is something that is calculated once? (which will mean the IDDESDelta works fine) or it is calculated every iteration? (and there is something wrong in the code)

Last edited by MaryBau; March 6, 2013 at 15:48.
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Old   April 30, 2013, 09:56
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Sha Huang
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Quote:
Originally Posted by Anne Lincke View Post
Hey Foamers,

I started with OpenFOAM®+DES, SpalartAllmarasIDDES.
I would like to determine the LES-Content of my computation.
Does someone know an indicator or a way to determine the content?

It would be desirable to see the averaged LES content...

Thanks
Anne

Hello,
Anne, I notice that you are familar with IDDES, I am currently doing some simulation relating to this, but everytime it has errors like this:


request for RASModel RASProperties from objectRegistry region0 failed
available objects of type RASModel are
0
(
)

I attached the case file below(0,constant,system), could you please kindly help me with this, I will really appreciate that since I am suffering this now.
Attached Files
File Type: zip case.zip (4.1 KB, 23 views)
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Old   May 3, 2013, 09:02
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Håkon Bartnes Line
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Hi everyone! I was just wondering, what's the consensus on the delta for IDDES? The way I understand the issue is that in old releases of OpenFOAM (pre 2.1) it was possible to define the delta as "IDDESDelta" in the root of the "LESProperties" file (as per post #11), but that in the newer versions, the delta has to be defined as something else first (like in post #20).

Is this a bug in the new releases, or has it been done on purpose? If it's on purpose, is the first definition of delta just a "dummy definition" which isn't really used in the simulation?

I get the following output when I start an IDDES simulation, suggesting that the solver switches back and forth between different definitions of delta.

Code:
Selecting turbulence model type LESModel
Selecting LES turbulence model SpalartAllmarasIDDES
Selecting LES delta type maxDeltaxyz
Selecting LES delta type maxDeltaxyz
Selecting LES delta type IDDESDelta
Selecting LES delta type maxDeltaxyz
When I select a regular LES-model, there's no such switching back and forth:

Code:
Selecting turbulence model type LESModel
Selecting LES turbulence model oneEqEddy
Selecting LES delta type maxDeltaxyz
So is this a bug or a feature, and how do we find out?
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Old   May 6, 2013, 07:25
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Anne Gerdes
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The computation of IDDES delta is based on a general delta. You can find in IDDESDelta.C the formula of IDDESDelta

HTML Code:
delta_.internalField() =
            deltaCoeff_
           *min
            (
                max
                (
                    max(cw_*wallDist(mesh()).y(), cw_*hmax),
                    faceToFacenMax()
                ),
                hmax
            );
where "hmax" needs a general delta as you can see in SpalartAllmarasIDDES.C

HTML Code:
hmax_
    (
        LESdelta::New
        (
            "hmax",
            mesh_,
            *this
        )
    ),
The hmax equals to the maximum local grid spacing. When using structured meshes the defintion of maxDeltaxyz is fine, when using unstructured meshes the cubeRootVolDelta is more appropriate.
In the paper of Shur, Spalart, Strelets and Travin, International Jorunal of Heat and Fluid Flow 29 (2008) 1638-1649 you can read more.

Hope this helped.

Kind Regards,
Anne
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Old   May 7, 2013, 11:33
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Håkon Bartnes Line
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Hi Anne, and thanks for the thorough explanation! So in a structured grid, like one would make in blockMesh, all the cells are aligned with the principal axes of the domain, and the "maxDeltaxyz" definition is fine, but since this might not be the case for an unstructured grid, it would be safer to use the "cubeRootVol" definition..is this correct?

Shur et al. do talk a lot about how the "max"-definition is preferable to the cube root, but the choice of delta definition is maybe not as significant for DDES and IDDES, which have the shielding term?

cheers,
Håkon
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Old   May 8, 2013, 03:41
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Albrecht vBoetticher
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Hi Håkon,

The LeMoS extensions for OpenFOAM provide an URANS-LES Detatched Eddy approach where the regions of URANS and LES are decomposed dynamically in every timestep dependent on flow properties and local mesh resolution. They have very good validation results using ship hydrodynamic test cases. So if you want to use LES with an unstructured grid, this might be helpful.
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Old   May 8, 2013, 06:09
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Anne Gerdes
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Hey Ha°kon,

Quote:
So in a structured grid, like one would make in blockMesh, all the cells are aligned with the principal axes of the domain, and the "maxDeltaxyz" definition is fine, but since this might not be the case for an unstructured grid, it would be safer to use the "cubeRootVol" definition..is this correct?
Yes, this is correct.

Kind Regards
Anne
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Old   July 21, 2015, 11:41
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Anton
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Hi Anne,

Could you please post or attach the post-processing tool that you created, the one that writes \tilde{fd}*(1+fe) and 1-\tilde{fd} .

Many Thanks

Anton
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