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Possible to account for surface roughness with SST model?

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Old   June 19, 2009, 03:34
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Hi Timon,

I suspect that the version which I am using is an academic version which does not have the beta feature. If the beta features are incorporated, how do I go about enabling it? I read that the option is at the Launcher under EDIT>>OPTION menu but I don't see any in it..
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Old   June 19, 2009, 03:37
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It is not a feature that becomes visible in cfx-pre when you enable beta-features. You just need to modify the ccl manually. One way to do this is by means of the method described in my previous post.
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Old   June 19, 2009, 04:03
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Hi Timon,

which means that chances are the beta features are already incorporated in the V11 fully released version just that we might need to edit the CCL manually right?
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Old   June 19, 2009, 04:12
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Hi Timon,

I found the beta features! Many many thanks for your help. Will try out the roughness feature.
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Old   June 19, 2009, 04:15
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The beta-tag does not refer to the cfx-version but to the specific feature (in this case rough wall treatment for k-omega models). It means that the feature can be used but has not yet gone through extensive testing and validation. In cfx v12 rough wall treatment for k-omega models is no longer a beta feature, but a fully released feature, as it has gone through the testing procedures and been found to function properly. CFX mentions that rough wall treatment for k-omega models has been improved in v12, but what exactly has been changed I do not know.
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Old   June 19, 2009, 04:26
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Hi Timon,

thanks for providing further insights. I am actually an undergrad working on my final year project and this is the first time I am being exposed to CFD. Since it is a beta feature, I am thinking it would be good that I test out these features and until when my school got V12 where my peers will do a comparison then.
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Old   June 20, 2009, 02:47
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Hi,

how to I relate the equivalent sand roughness height to the Transition roughness height (which can be found under the transition model)?
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Old   June 20, 2009, 07:07
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Hi,

You will need the documentation on this to understand what all the terms mean. That's one disadvantage with the beta software - no documentation. That's why you should push for your school to go to V12 ASAP. If that is not possible you should get your hands on the V12 documentation as that should explain how this feature works.

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Old   June 20, 2009, 08:21
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Hi Glenn,

think it would be hard lay my hands on V12 and my project due in August (time is running out!) anyway. I'll see if I can get hold of the documentations. Once again, many thanks for all your inputs. I managed to get reasonably good predictions for the clean aerofoil data. Now will go into accounting for roughness effects which is what my project is all about.
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Old   June 21, 2009, 07:54
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Hi,

Well, if you can't get your hands on the full V12 then at least get the documentation. You can download it from the customer portal on the ANSYS website. You will need a login to get onto the site but once there you will be able to download the V12 documentation.

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Old   June 23, 2009, 23:27
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Hi,

for the beta feature that was mentioned earlier about adding roughness using SST model, can transition model be turned on and predict as well?
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Old   June 23, 2009, 23:53
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Quote:
Originally Posted by Tom View Post
Ok i get what you mean i placed it in the wrong tree of the command line.

I have corrected it. How do i activate it. I tried importing the the CCL file with those few lines but when i run the solver it does not appear there. How do i start it or will it be shown in the GUI.
Hi Tom,

I managed to add roughness using SST model. I faced the same problem as you and found out that it works (solver has the roughness and SST model appeared) when you disable the auto physics update checkbox which is located at the option menu. Running the simulations now and fingers crossed!
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Old   June 23, 2009, 23:56
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Hi

just to check, when i start the solver and the roughness and SST appears in the CCL does that mean roughness has indeed been added?
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Old   June 24, 2009, 01:40
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Hi,

The CCL reported at the start of the output file is the exact CCL used in the simulation. CFX-Pre does not support all the CCL available so some stuff has to be added manually.

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Old   June 24, 2009, 01:49
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Hi Glenn,

I started with selecting RNG k-e model with roughness added on the wall boundary condition. Subsequently I export the CCL first and change the turbulence model to SST using Notepad and import back to cfx-pre. I disabled the auto update physics and save it to the def file. When I run the solver, I did a check on the CCL and indeed the roughness and SST command is there. Is this correct? Anyway I have run two simulations with roughness and without roughness using SST model with the rest of the parameters kept at constant. There is a huge difference..
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Old   June 24, 2009, 08:03
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Hi,

Don't import your CCL modifications to CFX-Pre. As I said, Pre does not support the the full CCL. You should use the command line "cfx5cmds -write -def Run1.def -text MyCCL.ccl" to put the CCL into the definition file. You can also add CCL statements from the command line option -ccl or the equivalent in soler manager but I prefer to have the full CCL as a file so the cfx5cmds method is better.

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Old   June 24, 2009, 12:51
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Glen,

What is the procedure to import CCL modifications (CCL modified file) to put the CCL into the definition file?

I am not sure how i can do this: you should use the command line "cfx5cmds -write -def Run1.def -text MyCCL.ccl" to put the CCL into the definition file

Thanks
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Old   June 24, 2009, 13:18
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from the cfx launcher use tools>command line

to read CCL from the definition file
cfx5cmds -def file1.def -text file1.ccl -read

to write the modified CCL to the definition file:
cfx5cmds -def file1.def -text file1.ccl -write

if you do this for first time backup your files until you are comfortable of using the command prompt
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Old   June 14, 2014, 05:55
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I am using fluent.. By default, the surface roughness is disabled.. how do i enable it ? and is adding values for surface roughness in fluent enough for computing results ?
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Old   June 14, 2014, 06:11
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Try the fluent forum.
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