CFD Online Discussion Forums - SStkOmega Initial Condition problem??

Hi I really hope some kind soul will help me After 2 months i couldn't find the solution by my self and i decided to ask the community (Hoping that this time some one will answer me).

I'm studying the Backward facing step and i'm using the Makiola Data to validate the code. Here the checkMesh output:

Code:

Checking geometry...

    Overall domain bounding box (-1 -0.1 -0.0600333) (5 0.1 0.0600333)

    Mesh (non-empty, non-wedge) directions (1 1 0)

    Mesh (non-empty) directions (1 1 0)

    All edges aligned with or perpendicular to non-empty directions.

    Boundary openness (-9.79501e-18 6.68689e-16 9.46468e-20) OK.

    Max cell openness = 2.42701e-16 OK.

    Max aspect ratio = 180.003 OK.

    Minimum face area = 5.27601e-07. Maximum face area = 0.00749943.  Face area magnitudes OK.

    Min volume = 6.33473e-08. Max volume = 1.33007e-05.  Total volume = 0.130418.  Cell volumes OK.

    Mesh non-orthogonality Max: 20.1903 average: 6.51521

    Non-orthogonality check OK.

    Face pyramids OK.

    Max skewness = 0.444594 OK.

    Coupled point location match (average 0) OK.

My data are:

Code:

Reynold numbers: 15000, 64000

Aspect Ratio:2

Hinlet=Hstep=0.1 m

I%= sqrt(0.1) * 100 (as in the makiola paper)

nu=1.45e-5

U(Re1)=2.175

U(Re2)=9.28

l (mixing-length)= 10% Hstep

K, Omega calculated with the formulas in the wiki (the ones with the mixing length)

Omegawall= 60*nu/[ deltay^2 * Cmu]      (i found this relation in the wilcox)

I decided to use the SSTKomega model, after some problems with setting up the case (it's my first case using OpenFoam) i could run it and obtain some physically accepted results, but they were not experimentally correct. In particular the adimensionalised reattachment distance (Xr/Hstep) is higher than the experimental value (7.5 vs 6 more or less).

To solve i searched a lot in the forum and changed in every aspect the boundary condition and also the schemes with no effect, i tried using the KEpsilon and it gives as expected a lesser value.

Here some BC setting i've chosen for Re=15000:

Code:

Omega

Inlet: fixedValue 153.84

Outlet: zeroGradient

upperWall: fixedValue 9700

lowerWall: fixedValue 9700



K

Inlet: fixedValue 0.71

Outlet: zeroGradient

upperWall: fixedValue 1e-16

lowerWall: fixedValue 1e-16

Code:

Omega

Inlet: fixedValue 153.84

Outlet: zeroGradient

upperWall: omegaWallFunction

lowerWall: omegaWallFunction



K

Inlet: fixedValue 0.71

Outlet: zeroGradient

upperWall: kqRWallFunction

lowerWall: kqRWallFunction

And the last one with the zerogradient setting for the wall but from what i understood it is the same as the wall function.

If it is needed i can also upload my scheme file and everything that is needed.

P.S: I used the yPlusRAS to check the "yPlus" value and It is always less than the unit for the case Re=15000

Finally sorry for my bad English, i tried to write as correctly as i could.

Damn i didn't notice the mistake in the title sorry for that.