[Nek5000-users] 3-D Taylor-Green problem

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

Hi
I made the 28^3 computation without filter and all results are plotted
together. The KE is well predicted even on the coarse mesh. The dissipation
rate did not seem to change much with/without filtering on 28^3 mesh. I
will try with more elements to see if the results improve and compare with
Brachet et al.
Thanks
praveen


On Sun, Dec 9, 2012 at 9:45 PM, <nek5000-users at lists.mcs.anl.gov> wrote:

> Hi Praveen
>
> Filtering removes energy at the small scales (small length scales/high
> frequency components)
> If you estimate the turbulent kinetic energy removed by the filtering and
> compare it to the resolved kinetic energy or the total (resolved+subgrid
> scale)
> then your simulation :
>
> (1) May be considered DNS  ; if the above ratio is small
> (2) LES if it is relatively big
>
> in (2) the hope is that subgrid scale motion does not affect the scales of
> interest in a given problem.
>
> Filtering stabilizes simulations since it provides a way for removing
> energy at the small unresolved scales. I ran turbulent wake simulations in
> the past
> where filtering was absolutely necessary and the argument was that it did
> not affect the scales of interest.
>
> So the bottomline is you need to at least be aware of what scales are
> impacted by filtering and if indeed you are interested in such scales. That
> is why
> you see some comparisons in the paper for a given case with different
> values of the filtering parameter.
>
> so let me know  what happens when 32^3 is run with f=0 and also the
> comparison to Brachet et al.
>
> Ammar
>
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