[Nek5000-users] LES-wall

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

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> 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> 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> 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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