<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">This is impressive to me! <div><div>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. </div><div><br><div>Ammar</div><div><br><div><div>On Dec 12, 2012, at 5:02 AM, <a href="mailto:nek5000-users@lists.mcs.anl.gov">nek5000-users@lists.mcs.anl.gov</a> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">Hi<br><div class="gmail_quote"><div>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.</div>
<div>Thanks</div><div><span class="HOEnZb"><font color="#888888">praveen</font></span><div class="im"><br><br><div class="gmail_quote">On Sun, Dec 9, 2012 at 9:45 PM, <span dir="ltr"><<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.gov</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word">Hi Praveen<div><br><div>Filtering removes energy at the small scales (small length scales/high frequency components)</div>
<div>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)</div><div>then your simulation :</div><div><br></div><div>(1) May be considered DNS ; if the above ratio is small</div>
<div>(2) LES if it is relatively big</div><div><br></div><div>in (2) the hope is that subgrid scale motion does not affect the scales of interest in a given problem. </div><div><br></div><div>Filtering stabilizes simulations since it provides a way for removing energy at the small unresolved scales. I ran turbulent wake simulations in the past</div>
<div>where filtering was absolutely necessary and the argument was that it did not affect the scales of interest.</div><div><br></div><div>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</div>
<div>you see some comparisons in the paper for a given case with different values of the filtering parameter. </div><div><br></div><div>so let me know what happens when 32^3 is run with f=0 and also the comparison to Brachet et al. </div>
<div><br></div><div>Ammar</div></div></div></blockquote></div><br></div></div>
</div><br>
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