[GiannisgR]

Hi OpenFOAMers,

Could anyone, please, send me the paper for the compressible k-omega SST, Sandy, Henry?. Additionally, for which y+ does this model work, meaning the applicability of the used wall function.


Menter, F., Esch, T.
"Elements of Industrial Heat Transfer Prediction"
16th Brazilian Congress of Mechanical Engineering (COBEM),
Nov. 2001

Thanks,
giannis

i.asproulias@gmail.com

[bastil]

Originally Posted by Peter85

Hey @ all!
But, If I have a mehs y+<1(low-re), and I'd like to use the k-omega-sst modell, what boundary conditions for the walls do I have to take? Zerogradient for omega and k with very low values (10^-8), and calculated for alphat and mut (or other values?)? Or do I have to take a wall function (like mutlowrewallfunction) for one of those?

Peter, all,

I am also wondering about that. Henry mentioned in his posts above ( #54, #56) that one has to use mutLowReWallFunction in case you use a Low-Re model but you do not have y+<1 at this specific wall. Otherwise, if you have y+<1 you have to use "no" wall function - but howe to define this in 0/nut?. I am also wondering how to define the value sin k/epsilon/omega-Files.
Regarding k-omega SST it seems to me like you can not use this approach at all since it is a Hi-Re model...

[ivan_cozza]

Originally Posted by bastil

Peter, all,

I am also wondering about that. Henry mentioned in his posts above ( #54, #56) that one has to use mutLowReWallFunction in case you use a Low-Re model but you do not have y+<1 at this specific wall. Otherwise, if you have y+<1 you have to use "no" wall function - but howe to define this in 0/nut?. I am also wondering how to define the value sin k/epsilon/omega-Files.
Regarding k-omega SST it seems to me like you can not use this approach at all since it is a Hi-Re model...

If I understood SST, it works quite fine at all y+ conditions (this is the reason why using SST instead of k-Omega).

If you have y+ < 1, then
k -> fixedValue, very small (1e-9)
Omega -> omegaWallFunction (is not really a wall function, is the b.c. defined by Menter for Omega, it works at all y+ I suppose).
mut -> fixedValue, very small (1e-9)

If you have y+ > 30, then classical wall function setup

If you have 1 < y+ < 30, then
k -> zeroGradient
Omega -> omegaWallFunction
mut -> mutSpalartAllmarasWallFunction (is a kind of all y+ mut wall function, sometime ago Henry said that this should be renamed in mutSpaldingWallFunction...)

Hope this can help...

Btw, is someone working on transition model for SST?

[alex_rubel]

Hi everyone, this thread is very intersting. I just wonder one thing, I'm using OF1.6 and I use nut in my 0 file is it mut or nut ?

[GiannisgR]

Thanks guys for the replies. I was thinking to switch off the wall functions, which are used automatically for every turbulence model in 1.6v (I don't know about 1.7v) and apply manually the BC for the turbulent quantities. This is because I have y+<1 everywhere. Thanks again

Giannis

[Arnoldinho]

Originally Posted by ivan_cozza

If I understood SST, it works quite fine at all y+ conditions (this is the reason why using SST instead of k-Omega).

If you have y+ < 1, then
k -> fixedValue, very small (1e-9)
Omega -> omegaWallFunction (is not really a wall function, is the b.c. defined by Menter for Omega, it works at all y+ I suppose).
mut -> fixedValue, very small (1e-9)

If you have y+ > 30, then classical wall function setup

If you have 1 < y+ < 30, then
k -> zeroGradient
Omega -> omegaWallFunction
mut -> mutSpalartAllmarasWallFunction (is a kind of all y+ mut wall function, sometime ago Henry said that this should be renamed in mutSpaldingWallFunction...)

What about the case when I have a combination of both in one model domain due to different grid resolutions and changing flow regimes? Is there an automatic switch betweeen low-RE and high-RE implemented, e.g. by setting 'wall functions' for all quantities (e.g. omegaWallFunction, kqRWallFunction, nutRoughWallFunction in incompressible case)?
... I also posted this question here in more details.

Arne

[mai]

Originally Posted by ivan_cozza

If I understood SST, it works quite fine at all y+ conditions (this is the reason why using SST instead of k-Omega).

If you have y+ < 1, then
k -> fixedValue, very small (1e-9)
Omega -> omegaWallFunction (is not really a wall function, is the b.c. defined by Menter for Omega, it works at all y+ I suppose).
mut -> fixedValue, very small (1e-9)

If you have y+ > 30, then classical wall function setup

If you have 1 < y+ < 30, then
k -> zeroGradient
Omega -> omegaWallFunction
mut -> mutSpalartAllmarasWallFunction (is a kind of all y+ mut wall function, sometime ago Henry said that this should be renamed in mutSpaldingWallFunction...)

Hope this can help...

Btw, is someone working on transition model for SST?

Hi Ivan,

what is the reason, that for the zeroGradient BC of k. Why is it not kRWallFunction?
Please see also the post under the following link:
http://www.openfoam.com/mantisbt/view.php?id=179
What is correct?

Martin

[arunraj]

Hi Guys,

First very sry to disturb u people...Bt I need some important help

I have a created a domain as Domain1 which is Fluid domain

Now I want to create a sub-domain for Domain1 which is a porous domain

Is it possible to create like this?

If so can u explain how?

[Aerospace]

Originally Posted by henry

If your near-wall y+<1 everywhere you can use a low-Re model; you don't need wall-functions at all.

H

In order to know the y+ when the grid is in the laminar region (Low-Re model, no wall function or nutLowReWallFunciton if y+>1), is it possible to employ the yPlusRAS utility provided by OpenFOAM? or it calculates the y*.

It is not cleary explained in other topics like this: y+ and u+ values with low-Re RANS turbulence models: utility + testcase

Thank you very much in advance

[1/153]

Originally Posted by ivan_cozza

If I understood SST, it works quite fine at all y+ conditions (this is the reason why using SST instead of k-Omega).

If you have y+ < 1, then
k -> fixedValue, very small (1e-9)
Omega -> omegaWallFunction (is not really a wall function, is the b.c. defined by Menter for Omega, it works at all y+ I suppose).
mut -> fixedValue, very small (1e-9)

If you have y+ > 30, then classical wall function setup

If you have 1 < y+ < 30, then
k -> zeroGradient
Omega -> omegaWallFunction
mut -> mutSpalartAllmarasWallFunction (is a kind of all y+ mut wall function, sometime ago Henry said that this should be renamed in mutSpaldingWallFunction...)

Hope this can help...

Btw, is someone working on transition model for SST?

Dear all,


I've been testing the "hybrid" or "enhanced" or "automatic" wall treatment. One thing I found nutSpaldingWallFunction is said to be a continuous WF, however, I cant get a good result with it. I am wondering anyone of you have success with nutSpaldingWallFunction?

Model: kwsst
Test cases: channelflow, periodic hills.

I set omega as omegaWallFunction, k as kqRwallFunction, nut as nutSpaldingWallFunction. And the results are not good. Separation and reattachments pts are all not good.



Another question is that, in Menter's paper of improved wall treatment, it is clear that omega is written as sqrt(sqr(omega_vis)+sqr(omega_log)). But in OF-2.0, the utau is calculated with sqrt(k), is this correct?

And also I am wondering why do we need a nut wall function, since the nut can be calculated simply by k and omega, once we have omega already set with certain wall function, then nut is calculated, why need nut wall function then?

Thanks!

[TengWU]

Originally Posted by GiannisgR

Hi OpenFOAMers,

Could anyone, please, send me the paper for the compressible k-omega SST, Sandy, Henry?. Additionally, for which y+ does this model work, meaning the applicability of the used wall function.


Menter, F., Esch, T.
"Elements of Industrial Heat Transfer Prediction"
16th Brazilian Congress of Mechanical Engineering (COBEM),
Nov. 2001

Thanks,
giannis

i.asproulias@gmail.com

Hey Giannis,

Have you got the paper "Elements of Industrial Heat Transfer Prediction"? If so, could you kindly send a copy to me?
tengwu86@gmail.com

Thanks,

[TengWU]

Originally Posted by henry

Here is a corrected version of kOmegaSST.C
kOmegaSST.C
to replace the file in OpenFOAM-1.4.1/src/turbulenceModels/compressible/kOmegaSST

I have tested the model runs and give sensible results but I have not performed a rigorous validation.

Hey Henry,

Could you kindly send a copy of the paper "Elements of Industrial Heat Transfer Prediction" to me?
tengwu86@gmail.com

Thanks,

[dogan]

Originally Posted by henry

I am referring to nutSpalartAllmarasWallFunction for incompressible flow and mutSpalartAllmarasWallFunction for compressible flow. Even though these were created for use with the Spalart-Allmaras model they are not dependent on this particular model in any way being generic implementations of the Spalding continuous wall-function using U rather than k as the controlling variable and can be used with other turbulence models.

We tested the kOmegaSST model with the nutSpalartAllmarasWallFunction wall-function and obtained good results, as good as others have obtained with adaptive/continuous wall-functions.

H

Dear Henry,
i would like to ask a question about the nutUSpaldingWallFunction. I have used this wall function in a diffusor test case with kOmegaSST turbulence model, and i also made the same simulation with CFX, then i compared the results. since i know, CFX is using the so called automatic wall treatment, i would like to be sure about that if nutUSpaldingWallFunction is also an automatic wall treatment, or in OpenFOAM is there anouther way to make an automatic wall treatment?
Thanks