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Old   February 11, 2016, 11:55
Default Solving Boundary Layer
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Alessandro Cinciripini
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Hi everybody,
I'm setting a low-Re stady-state case using simpleFoam. I'd like to use KOmegaSST turbulent model solving directly the BL because I set y+ lower than 1. I guess I have to set k=0, but how can I set omega at the wall, if I don't want to use any wall-functions?
Thank you in advance.
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Old   February 11, 2016, 14:40
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Hi,

http://www.cfd-online.com/Wiki/Turbu...ary_conditions
here you can find the initial values you want to calculate.
Setting k=0 means, that the fluctuating part of the velocity is zero. Does that make sense in your case?

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Old   Yesterday, 08:47
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Alessandro Cinciripini
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I think that k have to be 0 beacuse the velocity fluctuactions at the wall are 0. I think that with that formulas I can compute omega=0 at the walls but I don't know if it is correct.
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Old   Yesterday, 08:55
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Hi,

well good question.
The way I did this for "k" was normally to use the kqRWallFunction at walls:

Code:
                type            kqRWallFunction;
                value           uniform 0.1;
and the turbulentIntensityKineticEnergyInlet function at inlet:

Code:
        type            turbulentIntensityKineticEnergyInlet;
        intensity       0.005;       // 0.05% turbulent intensity
        value           $internalField;
I am not very concern about the actual meaning of "value" this time. kqRWallFunction should "know" that at the wall is no velocity and thereby no turbulence. I think sometimes OF simply needs the "value XXX;" line although it does not use it in the end (If I am not correct about this, I am of course happy to be enlightened as well :-) )

By the way: I found these lines in some tutorial files and used them for my simulations. If you search in the tutorials you mostly find what you need.

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Old   Yesterday, 09:20
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Alessandro Cinciripini
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I set exactly this function at the inlet patch, in fact I know the initial conditions at the inlet. Actually I'm talking about walls (it is a flat plate placed in the middle of the domain). I don't know if using the omegaWallFuction it automatically will avoid the WallF hence calculate the BL.
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komega, komega sst model, wallfunction, yplus

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