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-   -   Standard K-epsilon turbulence model with y~+1 (https://www.cfd-online.com/Forums/openfoam/218150-standard-k-epsilon-turbulence-model-y-1-a.html)

Evren Linda June 10, 2019 13:12

Standard K-epsilon turbulence model with y~+1
 
Hello,
I have a 2D mesh with y^+ = 1 of a computational domain around a cylinder with [inlet, outlet, top, bottom, cylinder].
I want to start two simulations: using the k-\omega SST and the standard k-\varepsilon turbulence models without changing the mesh.

As far as I know, for the k-\omega SST, the mesh is ok because y+ = 1. But for the k-\varepsilon model, it requires wall functions.

Can I use a mesh that has y+ = 1 with the standard k-\varepsilon model? if Yes which wall functions should I use at the wall (cylinder) for k (turbulent kinetic energy), and \varepsilon (turbulent dissipation)?

CFD_10 June 15, 2019 18:19

The standard k-epsilon turbulence model cannot be used with Low-Re formulation. However you can use a Low-Re implementation, LaunderSharmaKE (it uses damping functions)

sivakumar June 26, 2019 01:13

Hi Linda,
I dont know still you are looking for help regarding your Y+ and BCs.


It seems that you are clear about the wall function approach and resolving the boundary layers.


In your case, you are suppose to use Low Re k-Epsilon models.
for low Re k-Epsilon I have posted BCs long back (2013). I hope still you can use it (Please check it),


The boundary conditions are as follows (I used it for OF-2.1.1 Version),


Low Re model:

turbulence model : LaunderSharmaKE

nut ----> fixedValue (0)
k -----> fixedValue (1e-12)
epsilon -----> fixedValue (1e-8) it can be zeroGradient as well
nuTilda -----> fixedValue (0)

for high Re model:

nut ----> nutkWallFunction value (0)
k -------> kqRWallFunction value uniform (*******)
epsilon ----> epsilonWallFunction value uniform (*******)
nuTilda -----> zeroGradient

I hope it will be useful.


If there is any issue, please post it here,




Thanks,
Sivakumar


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