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-   -   Solving boundary layer with k-e model (http://www.cfd-online.com/Forums/openfoam-solving/73015-solving-boundary-layer-k-e-model.html)

Gearb0x February 24, 2010 09:41

Solving boundary layer with k-e model
 
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

cboss February 24, 2010 10:06

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

Gearb0x February 24, 2010 10:09

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!

alberto February 25, 2010 03:30

Quote:

Originally Posted by Gearb0x (Post 247223)
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,

Gearb0x February 25, 2010 07:39

At the walls, k and epsilon are set to something like 1e-06 and nut is set as calculated

-mAx- January 23, 2013 05:31

Hello Jérémy,
Did you manage to get what you wanted?
I also want to resolve the BL with y+ around1, (simpleFoam)

Aadhavan January 24, 2013 05:40

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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