[Nek5000-users] Dirichlet-Neumann BC

[nek5000-users at lists.mcs.anl.gov]

Indeed traction boundary conditions are suitable. However it is unclear 
which NEKUSE variable I should set. From bdry.f lines 1101 to 1103 :

             V1(IX,IY,IZ) = TRN
             V2(IX,IY,IZ) = TR1
             V3(IX,IY,IZ) = TR2

it seems that I should set TRN, TR1 and TR2 for (shear horizontal local) 
'shl' BC.

The end goal here is to compute a friction velocity locally for which 
loglaw - velocity at the first grid cell is zero.

For now whether I set 'shl' or 'SYM' I get the same results.


Le 18/07/2018 à 11:07, nek5000-users at lists.mcs.anl.gov a écrit :
> Hi,
>
> there are so-called traction boundary conditions (or mixed 
> traction-velocity boundary conditions), see the documentation 
> https://nek5000.github.io/NekDoc/theory.html
> (it is in the section about passive scalars, which is perhaps not 
> ideal). The conditions should work for both PnPn and PnPn-2, but for 
> some cases you need the stress formulation. I am not sure whether Nek 
> is properly catching all impossible (or unimplemented) combinations.
>
> There are some Nek examples that use these conditions, so you can get 
> some guidance from there.
>
> Hope this helps,
> Philipp
>
> On 2018-07-18 09:38, nek5000-users at lists.mcs.anl.gov wrote:
>> Dear Neks,
>>
>>
>> I have been looking into the different boundary conditions available 
>> by default in bdry.f. However, I haven't seen any mixed conditions. I 
>> would like to impose a no slip condition and specify the shear stress 
>> at the boundary. The boundary is flat and aligned with the mesh.
>>
>> Moreover it seems that shear stress boundary conditions are 
>> applicable only to the Pn-Pn-2 formulation. Is there a way I can 
>> specify the wall normal streamwise velocity gradient u_y as well ?
>>
>>
>> Best regards,
>>
>> Armand.
>>
>> -- 
>> *Armand Shams*
>> Master Thesis Intern
>> Département aérodynamique, aéroélasticité, acoustique
>> MSAT
>> Tél: +33 6 99 51 15 84
>>
>>
>> ONERA - The French Aerospace Lab - Centre de Meudon
>> 8, rue des Vertugadins - 92190 MEUDON
>>
>> Nous suivre sur : www.onera.fr <https://www.onera.fr> | Twitter 
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>>
>>
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-- 
*Armand Shams*
Master Thesis Intern
Département aérodynamique, aéroélasticité, acoustique
MSAT
Tél: +33 6 99 51 15 84


ONERA - The French Aerospace Lab - Centre de Meudon
8, rue des Vertugadins - 92190 MEUDON

Nous suivre sur : www.onera.fr <https://www.onera.fr> | Twitter 
<http://www.twitter.com/@onera_fr> | LinkedIn 
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