[romant]

Originally Posted by meihua

I think the above thinking is correct. But I have a question, how to apply the wall shear stress into the momentum equation discretizations as a boundary condition?

Hi meihua,


The wall shear stress is implemented through the turbulent viscosity on the wall, since it is 0 on the wall, it can be re-used for other purposes.


You can find the implementation and derivation in the thread and post nutWallFunction


Cheers,
Roman

[meihua]

Hi Roman,

Thanks for your quick reply. I want to apply the LES wall model in OpenFoam. Now by the log law, I have calculated the wall shear stress. Then I would like to use this wall shear stress as a boundary condition for the LES. Now I am stuck in this step. Do you think this is possible? Could you show me some ideas or hints how to do it?

Thanks!
Meihua

Originally Posted by romant

Hi meihua,


The wall shear stress is implemented through the turbulent viscosity on the wall, since it is 0 on the wall, it can be re-used for other purposes.


You can find the implementation and derivation in the thread and post nutWallFunction


Cheers,
Roman

[romant]

Hi Meihua,


It should work the same as for the nut. I think what you have to do is take the nuSGSWallFunction instead of the nutWallFunction and use a similar approach. The nuSGS is 0 at the wall.


By taking a look at the nutWallFunction's implementation in the file, you might get an idea of how to do it in a modified nuSGSWallFunction



Best regards,
Roman

[esha]

Hi, I am trying to simulate viscoelastic fluid over a bluff body. I have udf for voscoelasticity (addition of polymers) also applying shear stress at wall. but now I want to apply on a bluff body having slip boundary.Can anyone please help me to write udf for Navier slip boundary.

[qi.yang@polimi.it]

Originally Posted by AlmostSurelyRob

The expression you give
k = utau²/sqrt(Cmu)
has been established for logarithmic subregion only (300>y+>30). This is also called constant shear layer (correct me if I am wrong!). Experiments show that it is an okay approximation for log region.

Hi, k = utau²/sqrt(Cmu) this expression should be right in the near wall cell. However, I checked the k value in the near wall cell, which is not consistent with that formula. In Spalding wall function, k is calculated by the own transport equation even in the near wall cell. Thus, how can we keep the expression k = utau²/sqrt(Cmu). Anybody know this issue?