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Solving boundary layer with k-e model

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Old   February 24, 2010, 09:41
Default Solving boundary layer with k-e model
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Jérémy Bulle
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Hello

In fluent, you can use "Enhanced wall treatment" to solve the boudary layer with the k-e turbulence model.

How can you do that with OpenFoam? Which boundary conditions to set instead of wall functions?

Thank you
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Old   February 24, 2010, 10:06
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Hi,

as far as I am understanding your question, you want to resolve the laminar sublayer with a fine mesh (with y-plus around 1) using the implemented k-epsilon turbulence model?

In literature it is often pointed out, that if the laminar sublayer should be resolved with the k-epsilon model, additional damping functions (to limit the k production) are needed.

In OF 1.6 one modified k-epsilon turbulence model for this usage is included. The Launder-Sharma low-Re k-epsilon model.
http://www.cfd-online.com/Wiki/Low-Re_k-epsilon_models

If you can manage provide small y-plus values to resolve the laminar sublayer, you can perhaps try this model. (Personally I have no experience with this model)

Regards
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Old   February 24, 2010, 10:09
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You totally understand and this is the model I was using but it gives me different results than fluent so I wanted to know if it was possible to stick as cloes as possible to the parameters in fluent by using the standard k-e model

Thanks for the answer!
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Old   February 25, 2010, 03:30
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Alberto Passalacqua
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Quote:
Originally Posted by Gearb0x View Post
You totally understand and this is the model I was using but it gives me different results than fluent so I wanted to know if it was possible to stick as cloes as possible to the parameters in fluent by using the standard k-e model

Thanks for the answer!
Well, if you want to actually resolve the boundary layer you need a low-Re model. For incompressible flows there are a few in OpenFOAM.

Now the question is how did you set the boundary conditions at the walls? If you use a low-Re model, you should not use the wall-functions but directly specify the conditions for k and epsilon.

Best,
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Last edited by alberto; February 25, 2010 at 03:31. Reason: corrected
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Old   February 25, 2010, 07:39
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At the walls, k and epsilon are set to something like 1e-06 and nut is set as calculated
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Old   January 23, 2013, 05:31
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Hello Jérémy,
Did you manage to get what you wanted?
I also want to resolve the BL with y+ around1, (simpleFoam)
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Old   January 24, 2013, 05:40
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Hi All,
I am using MRFSimpleFoam,
y+ value = 3, Growth factor = 1.2, layers = 15 and the whole domain has 6.3 Millions cells.

I am using kOmegaSST, the problem is, simulation not all getting converged.

my question is for kOmegaSST turb-model, is it right setting???
if not what should I change?

I have given the boundary conditions as follows

0/nut,

for all walls

top0
{
type nutkWallFunction;
value uniform 0;
}

top1
{
type nutkWallFunction;
value uniform 0;
}

top2
{
type nutkWallFunction;
value uniform 0;
}

0/k

top0
{
type kqRWallFunction;
value uniform 0.062424;
}

top1
{
type kqRWallFunction;
value uniform 0.062424;
}

top2
{
type kqRWallFunction;
value uniform 0.062424;
}


0/omega

top0
{
type omegaWallFunction;
value uniform 0.99;
}

top1
{
type omegaWallFunction;
value uniform 0.99;
}

top2
{
type omegaWallFunction;
value uniform 0.99;
}

0/U --> massFlowRate ---> 4m3/s inlet
0/p --> Gauge Pressure --> 0 Outlet

Thanks,
Aadhavan
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