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Thanks Tanmoy for the information you provided.<br>
<br>
I am currently working on a problem very like a flow over cylinder,
where the cylinder is located in a channel. However, there is no
span-wise homogeneity in this problem (as opposed to the flow over
2D cylinder) due to the specific channel shape. Therefore, there is
no need to averaging in spanwise planes. Beside planar averaging,
however, I couldn't find any thing else in the dynamic SGS model of
"turbchannel" example that needs to be modified for my case, as far
as I understand. <br>
<br>
Regards,<br>
Mohsen<br>
<br>
<br>
<div class="moz-cite-prefix">On 15-01-01 07:23 PM,
<a class="moz-txt-link-abbreviated" href="mailto:nek5000-users@lists.mcs.anl.gov">nek5000-users@lists.mcs.anl.gov</a> wrote:<br>
</div>
<blockquote
cite="mid:mailman.12786.1420158195.3424.nek5000-users@lists.mcs.anl.gov"
type="cite">
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charset=windows-1252">
<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 moz-do-not-send="true"
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 moz-do-not-send="true"
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
moz-do-not-send="true"
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 moz-do-not-send="true"
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
moz-do-not-send="true"
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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