<div dir="ltr"><div>Hi Mohsen, <br><div><div><br></div>Yes you are partially right. The eddy_viscosity routines (dynamic Smagorinsky to be precise) used in "turbChannel.usr" is indeed specific for channel geometries, but they can be applied to geometries having small deviations from channels, like backward facing step, box (lid driven cavity), flat plates with very little modification. They wont work for very complex geometries. <br><br></div>It is important to note, that the spatial averaging done in "turbChannel.usr" case is to brute-force spatial homogeneity of the statistics in that direction. If some geometry does not have special homogeneity in one particular direction (e.g. other than periodic boundary conditions) we can comment out the planar average routines.<br><br></div>I am personally using 3D flat plate geometry.<br></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature"><div dir="ltr"><div>Best Regards,<br></div>Tanmoy<br></div></div></div>
<br><div class="gmail_quote">On Thu, Jan 1, 2015 at 5:08 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 bgcolor="#FFFFFF" text="#000000">
Hi Tanmoy,<br>
<br>
I looked into the "turbchannel.usr" example and it seems that the
spatial averaging of contractions, i.e., <MijLij>, needs to be
modified for other geometries. I Wondered if you have been using
eddy-visc() routine for channel geometry or some other geometries.<br>
<br>
Thanks,<br>
Mohsen<div><div class="h5"><br>
<br>
<div>On 14-12-30 11:29 AM,
<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.gov</a> wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div>
<div>
<div><br>
</div>
Hi Mohsen,<br>
<br>
</div>
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.<br>
<br>
</div>
Sincerely,<br>
Tanmoy<br>
</div>
<div class="gmail_extra"><br clear="all">
<div>
<div>
<div dir="ltr">
<div>Best Regards,<br>
</div>
Tanmoy<br>
</div>
</div>
</div>
<br>
<div class="gmail_quote">On Tue, Dec 30, 2014 at 9:07 AM, <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">
Thanks Tanmoy for your suggestion.
<div><br>
<div>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.</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Mohsen</div>
<div>
<div>
<div><br>
<div>
<div>On 24-Dec-14, at 11:23 PM, <<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.gov</a>>
wrote:</div>
<br>
<blockquote type="cite">
<div dir="ltr">
<div>Hi Mohsen,</div>
<div><br>
</div>
<div>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. </div>
<div><br>
</div>
<div>Thanks, </div>
<div>Tanmoy</div>
</div>
<div class="gmail_extra"><br clear="all">
<div>
<div>
<div dir="ltr">
<div>Best Regards,<br>
</div>
Tanmoy<br>
</div>
</div>
</div>
<br>
<div class="gmail_quote">On Thu, Dec 25,
2014 at 12:47 AM, <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">Hello all,<br>
<br>
I have a question regarding LES
capability of Nek.<br>
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.<br>
<br>
So I was wondering if anyone has any
experience of using Nek LES with near
wall models, or kind of hybrid RANS-LES
approaches.<br>
<br>
Thanks,<br>
Mohsen<br>
<br>
<br>
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