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

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

This is impressive to me! 
the fact that filtering is not contributing too much to the dissipation rate and that both the trend/time evolution and numerical magnitude of the dissipation rate are accurately predicted throughout the simulation. 

Ammar

On Dec 12, 2012, at 5:02 AM, nek5000-users at lists.mcs.anl.gov wrote:

> 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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