[Nek5000-users] LES-wall

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

Hi Tanmoy,

I looked into the "turbchannel.usr" example and it seems that the 
spatial averaging of contractions, i.e., <MijLij>, needs to be modified 
for other geometries.  I Wondered if you have been using eddy-visc() 
routine for channel geometry or some other geometries.

Thanks,
Mohsen

On 14-12-30 11:29 AM, nek5000-users at lists.mcs.anl.gov wrote:
>
> Hi Mohsen,
>
> Yes the turbChannel case is a good point to start with. However, 
> explicit filtering as LES model only works when using wall-resolved 
> LES. My past experience shows, to use wall-model, one must have a good 
> eddy-viscosity model, to properly emulate wall layer physics. Explicit 
> filtering of LES, is way too bad in preserving the wall physics.
>
> Sincerely,
> Tanmoy
>
> Best Regards,
> Tanmoy
>
> On Tue, Dec 30, 2014 at 9:07 AM, <nek5000-users at lists.mcs.anl.gov 
> <mailto:nek5000-users at lists.mcs.anl.gov>> wrote:
>
>     Thanks Tanmoy for your suggestion.
>
>     You are right, for a eddy viscosity type of turbulent model, the
>     Channel example is a good starting point (though, I think it
>     should be considerably modified to be used in a case with a
>     different geometry compared to a channel). But I was thinking of
>     using sort of wall model when employing the explicit filtering of
>     velocity field as a LES model.
>
>     Thanks,
>     Mohsen
>
>     On 24-Dec-14, at 11:23 PM, <nek5000-users at lists.mcs.anl.gov
>     <mailto:nek5000-users at lists.mcs.anl.gov>> wrote:
>
>>     Hi Mohsen,
>>
>>     For LES with near wall modelling, you have to develop your own
>>     script in .usr file. There are no in-built routines except
>>     eddy_visc() in turbChannel example.  If you use eddy-viscosity
>>     type of near wall models in LES, you can modify the scripts and
>>     write your own eddy-viscosity routines in uservp.
>>
>>     Thanks,
>>     Tanmoy
>>
>>     Best Regards,
>>     Tanmoy
>>
>>     On Thu, Dec 25, 2014 at 12:47 AM,
>>     <nek5000-users at lists.mcs.anl.gov
>>     <mailto:nek5000-users at lists.mcs.anl.gov>> wrote:
>>
>>         Hello all,
>>
>>         I have a question regarding LES capability of Nek.
>>         I know that the explicit filtering introduced in Nek can be
>>         effective for velocity field to provide sort of eddy
>>         viscosity modeling. Nevertheless, there should be some form
>>         of modeling for the near wall regions, since it is almost
>>         infeasible to have DNS like resolution in such regions for
>>         problems with relatively high Reynolds number and large scale
>>         geometries. I have seen SFR assemblies example on the Nek web
>>         in which LES used, however, I am not sure if that was an LES
>>         with near-wall resolution or with near-wall modeling.
>>
>>         So I was wondering if anyone has any experience of using Nek
>>         LES with near wall models, or kind of hybrid RANS-LES approaches.
>>
>>         Thanks,
>>         Mohsen
>>
>>
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