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Inlet boundary condition of turbulence

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Old   April 12, 2021, 08:05
Question Inlet boundary condition of turbulence
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Zhen ZHANG
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Hi all,
I am calculating film cooling problems using the incompressible NS solver with the S-A turbulence model. I am wondering whether I can specify the turbulence intensity at inlets. Could anyone give me some clues?
Thanks a lot!
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Old   April 12, 2021, 09:50
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yes, you can look in config_template.cfg for all available options, or in the example testcases to see how they are used. For SST, intensity i and viscosity ratio R are set using:

Code:
FREESTREAM_TURBULENCEINTENSITY= 0.05
FREESTREAM_TURB2LAMVISCRATIO= 10.0
For the SA model you use:

Code:
FREESTREAM_NU_FACTOR= 3.0
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Old   April 12, 2021, 10:26
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Thank you for your reply!
There are some related questions:
1. I find the FREESTREAM_TURBULENCEINTENSITY and FREESTREAM_TURB2LAMVISCRATIO in the module "COMPRESSIBLE FREE-STREAM DEFINITION", and similarly FREESTREAM_NU_FACTOR in module "ENGINE SIMULATION". Do these parameters work in other solvers, for instance, the incompressible NS solver here?
2. These parameters seem to be the only ones to control the turbulence level, so are these used in both initial and boundary conditions?
3. Is that possible to set different turbulence levels at different inlets?
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Old   April 13, 2021, 15:46
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Hi,
Yes the config options are used for compressible as well as incompressible, for instance FREESTREAM_TURBULENCEINTENSITY sets the variable TurbulenceIntensity_FreeStream, which is obtained with GetTurbulenceIntensity_Freestream and then used to initialize the field in CTurbSSTSolver


For boundary conditions it depends what the boundary is, but freestream conditions seem to be used for a number of boundary types. You can find the boundary implementations in CTurbSSTSolver.cpp for instance and have a look.



At the moment it is not possible to set different turbulence levels at different boundaries. So you would like to set a different turbulence intensity at each of your inlets for instance?
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Old   April 13, 2021, 22:51
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Thank you for your kind reply!
I checked the CTurbSSTSolver.cpp and found how FREESTREAM_TURBULENCEINTENSITY and FREESTREAM_TURB2LAMVISCRATIO worked for both initial and boundary conditions.
As for the inlets, I am calculating the film cooling problem, which is an internal flow and has multiple inlets typically with various flow conditions including the turbulence intensity and length scale. Ignoring these turbulence variations may introduce inaccuracy.
Could you please give me some clues? For example, is it a good way to add an "if statement" somewhere to set different turbulence conditions at different inlets?
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Old   April 14, 2021, 05:55
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Hi,


I see two possibilities to make su2 work with separate turbulence quantities at inlets in a more general fashion:

1. support for turbulence quantities in the inlet boundary file

2. define turbulence intensity and viscosity ratio for all inlets instead of globally from the free stream values
In BC_Inlet, we have the marker values available and we can get the marker tags as well from that. This can be used to set turbulence intensity for each of the inlets.
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Old   April 15, 2021, 07:25
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Hi, thanks for the kind reply!

The second method is convenient to set uniform inlet conditions at different inlets. That is good.

The first method seems able to set some distributions of the inlet velocity or turbulence. Is there any guide or tutorial about the inlet boundary file?

Thank you
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Old   April 15, 2021, 15:31
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The inlet boundary file has x,y,z as the first 3 columns and after that the order of the columns correspond to the order in marker_inlet, so if the first value in marker_inlet is for temperature, than that is also the first column after the coordinate columns.
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Old   April 16, 2021, 02:04
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Hi,
I see it. Thank you for the kind reply!
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Old   April 21, 2021, 15:41
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Based on this discussion, an additional 'comment' line is now added to each of the inlets in the inlet profile file when it is being created. This line contains the names of the variables in the columns. The line is ignored by the su2 reader and only meant for the user to make editing easier. The initialization is now also based on (turbulent) free stream and inlet values found in the config file. It is in the develop version now on github, will be in the newest release.

https://github.com/su2code/SU2/issues/1265
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