<div dir="ltr">Thanks so much for your reply.<div><br></div><div>Is it possible for you to elaborate on the specific way to interpolate using the nek5000 built in routine? Say I have run a simulation already and have a number of outputs in ASCII format how would I go about interpolating all the outputs onto this new mesh. </div><div><br></div><div>Would it be possible, once I have interpolated onto this new mesh to convert back to the old one such that I can restart the simulation using it?</div><div><br></div><div>Once again, I appreciate your patience as I am still quite new to CFD in general and these questions might seem too basic.</div><div><br></div><div>Cheers,</div><div>William</div></div><div class="gmail_extra"><br><div class="gmail_quote">On 20 August 2018 at 17:33, <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">Hi,<br>
<br>
how to exactly do it depends on your case. For a channel (or pipe), we typically map the mesh onto a normal rectilinear mesh which is equidistant in the wall-parallel (streamwise/spanwise or axial/azimuthal) directions. This is done via the nek-built-in interpolation routines. however, one needs to check carefully that the new mesh does not lead to interpolation errors close to element boundaries (for curved elements). Once you have everything on a regular mesh, then you just go ahead and to FFTs in the language of choice.<br>
<br>
Philipp<span class=""><br>
<br>
On 2018-08-20 05:22, <a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.go<wbr>v</a> wrote:<br>
</span><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">
Hi Philipp,<br>
<br>
Thanks for the reply. So you are saying that I would map the output to a simpler mesh then do the fourier transforms for the spectras? Would you be able to give me a basic idea behind how the spectra could be computed using a simpler mesh?<br>
<br>
Thanks,<br>
William<br>
<br></span><span class="">
On 20 August 2018 at 02:42, <<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.g<wbr>ov</a> <mailto:<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mc<wbr>s.anl.gov</a>>> wrote:<br>
<br>
Hi,<br>
For most cases, we typically do all these things (statistics,<br>
spectra, budgets) outside of Nek5000, on simpler meshes (equidistant<br>
or polar meshes for instance). For instance in our paper on pipe<br>
flow, we show exactly those 1D and 2D energy spectra.<br>
<br>
<a href="https://link.springer.com/article/10.1007/s10494-013-9482-8" rel="noreferrer" target="_blank">https://link.springer.com/arti<wbr>cle/10.1007/s10494-013-9482-8</a><br>
<<a href="https://link.springer.com/article/10.1007/s10494-013-9482-8" rel="noreferrer" target="_blank">https://link.springer.com/art<wbr>icle/10.1007/s10494-013-9482-8</a><wbr>><br>
<br>
For your purpose however, I would suggest some physical space filter<br>
with specific transfer function. That might be the easiest way.<br>
<br>
Best regards,<br>
Philipp<br>
<br>
<br>
On 2018-08-19 07:54, <a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.go<wbr>v</a><br></span><span class="">
<mailto:<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mc<wbr>s.anl.gov</a>> wrote:<br>
<br>
Hi Nek Users,<br>
<br>
I am a new user to Nek5000 and I have been playing around with<br>
the channel flow example. I have set up an example similar to<br>
Kim and Moin. The mean velocity profile seems to agree quite<br>
well so I have set up the initial case correctly. Now, my goal<br>
is to try and recreate the energy spectra as in the paper above.<br>
I am confused as to the best way to go about this, would it be<br>
best to obtain output files then do the post processing outside<br>
of Nek or can it be done inside Nek as well?<br>
<br>
My ultimate goal is to be able to cut off some of the higher<br>
energy modes and transform it back and feed it at the start of<br>
the simulation. Any advice on this would be appreciated as I<br>
have been struggling as to how I should proceed in Nek5000.<br>
<br>
Thanks in advance,<br>
David<br>
<br>
<br>
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