# LES-Content of a Detached Eddy Simulation for OpenFOAM

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 March 6, 2013, 09:23 #21 Senior Member   Anne Gerdes Join Date: Aug 2010 Location: Hamburg Posts: 154 Rep Power: 7 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.

 March 6, 2013, 15:13 #22 Member   Join Date: Jul 2010 Posts: 37 Rep Power: 7 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<

April 30, 2013, 09:56
#23
New Member

Sha Huang
Join Date: Dec 2012
Posts: 22
Rep Power: 4
Quote:
 Originally Posted by Anne Lincke 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
 case.zip (4.1 KB, 23 views)

 May 3, 2013, 09:02 #24 New Member   Håkon Bartnes Line Join Date: Mar 2013 Posts: 27 Rep Power: 4 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?

 May 6, 2013, 07:25 #25 Senior Member   Anne Gerdes Join Date: Aug 2010 Location: Hamburg Posts: 154 Rep Power: 7 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 kiddmax and hakonbar like this.

 May 7, 2013, 11:33 #26 New Member   Håkon Bartnes Line Join Date: Mar 2013 Posts: 27 Rep Power: 4 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

 May 8, 2013, 03:41 #27 Senior Member   Albrecht vBoetticher Join Date: Aug 2010 Location: Zürich, Swizerland Posts: 191 Rep Power: 7 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. hakonbar likes this.

May 8, 2013, 06:09
#28
Senior Member

Anne Gerdes
Join Date: Aug 2010
Location: Hamburg
Posts: 154
Rep Power: 7
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

 July 21, 2015, 11:41 baklanton #29 New Member   Anton Join Date: Nov 2014 Posts: 2 Rep Power: 0 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

 October 12, 2015, 08:58 #30 Senior Member   Anne Gerdes Join Date: Aug 2010 Location: Hamburg Posts: 154 Rep Power: 7 Dear Anton, sorry for this late response. I found the tool which I implemented a while ago. If you are still interested, I could send it to you via e-mail. Kind Regards, Anne

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