<html><body><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; color: #000000"><div><style style="display: none;" data-mce-style="display: none;"><!-- P {margin-top:0;margin-bottom:0;} --></style></div><div>Thanks Paul.</div><div><br data-mce-bogus="1"></div><div>Yes you were right in your first thought.</div><div><br data-mce-bogus="1"></div><div>I was just debugging the problem. So I just tried some meshes. In reality I would be using bigger mesh. And then I will refine with GLL points.</div><div><br data-mce-bogus="1"></div><div>Thanks for your replay and it will help me to move on the right way.</div><div><br data-mce-bogus="1"></div><div>For the second thing, I use mshconvert.py to convert meshes from ICEM and this script only works for HEXA8 elements. So I prefer to use prenek</div><div> for periodic bc.</div><div><br data-mce-bogus="1"></div><div>And for my final objective, my domain can not be extruded in that way. </div><div><br data-mce-bogus="1"></div><div>Regards</div><div><br data-mce-bogus="1"></div><div>Sijo GEORGE</div><hr id="zwchr" data-marker="__DIVIDER__"><div data-marker="__HEADERS__"><b>De: </b>"nek5000-users" <nek5000-users@lists.mcs.anl.gov><br><b>À: </b>"nek5000-users" <nek5000-users@lists.mcs.anl.gov><br><b>Envoyé: </b>Mardi 19 Juin 2018 21:21:59<br><b>Objet: </b>Re: [Nek5000-users] In consistent periodic BC after prex (CAUSE TO THE PROBLEM FOUND)<br></div><div><br></div><div data-marker="__QUOTED_TEXT__">
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<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;">Dear Sijo,</p>
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<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;">Prenek is a 32-bit code, so it would be difficult to resolve</p>
<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;">your problem if you have element sizes at positions that have order unity magnitude and 1.e-6 size.</p>
<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;"><br>
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<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;">I have two thoughts about this.</p>
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<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;">First, I wonder why you would need elements of that size (when there will</p>
<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;">be yet another order of magnitude reduction in spacing coming from the GLL</p>
<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;">points interior to these very small elements).</p>
<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;"><br>
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<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;">Second, assuming you can represent the 2D mesh, I would use n2to3.</p>
<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;">It will generate the correct periodicity and you can output the mesh file</p>
<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;">in the binary .re2 format, which I believe actually stores all coordinates</p>
<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;">in 64-bit floating point.</p>
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<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;">Best,</p>
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<p style="margin-top: 0; margin-bottom: 0;" data-mce-style="margin-top: 0; margin-bottom: 0;">Paul</p>
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<div id="divRplyFwdMsg" dir="ltr"><span face="Calibri, sans-serif" data-mce-style="font-size: 11pt; color: #000000; font-family: Calibri, sans-serif;" style="font-size: 11pt; color: #000000; font-family: Calibri, sans-serif;" color="#000000"><b>From:</b> Nek5000-users <nek5000-users-bounces@lists.mcs.anl.gov> on behalf of nek5000-users@lists.mcs.anl.gov <nek5000-users@lists.mcs.anl.gov><br>
<b>Sent:</b> Tuesday, June 19, 2018 12:50:48 PM<br>
<b>To:</b> nek5000-users<br>
<b>Subject:</b> Re: [Nek5000-users] In consistent periodic BC after prex (CAUSE TO THE PROBLEM FOUND)</span>
<div> </div>
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Hello Neks,</div>
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I think I found the exact problem.</div>
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I made two meshes for NACA0012 from same block in ICEM.</div>
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1. Mesh with very fine refinement close to the wall. (The distance between the wall to first element in the order of -1 x 1e6 or lets say the distance between the element faces is too small)</div>
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2. Mesh with uniform distribution.(Mesh with uniform distance between faces and in the order of -1 x 1e2)</div>
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The mesh 1 throws the errror (when I give Auto periodic option in Prenek, the number of NFAIL is greater than zero and it never comes to zero)<span class="x_Apple-converted-space"> </span></div>
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and Mesh 2 works fine.</div>
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So I think in prenek they have set some limits to take care of this because I have seen some variables called tol. (tolerences).</div>
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Is there anything that I can change in Prenek to take care of this problem?</div>
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br,</div>
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Sijo GEORGE</div>
</div>
<div><br>
</div>
<hr id="x_zwchr">
<div><b>De: </b>"Sijo George" <sijo.george@eleves.ec-nantes.fr><br>
<b>À: </b>"nek5000-users" <nek5000-users@lists.mcs.anl.gov><br>
<b>Envoyé: </b>Lundi 18 Juin 2018 18:25:43<br>
<b>Objet: </b>In consistent periodic BC after prex<br>
</div>
<br>
<div>
<div style="font-family: arial,helvetica,sans-serif; font-size: 12pt; color: #000000;" data-mce-style="font-family: arial,helvetica,sans-serif; font-size: 12pt; color: #000000;">
<div>Hi Neks,<br>
</div>
<br>
<div>I did a mesh conversion from ICEM to NEK with ' ' (3 spaces) as boundary conditions instead of periodic. (It is a 3D naca profile). I tried n2to3 method for extrusion but I am not confident with that method since I already have a 3D mesh and my future
works will be like that.<br>
</div>
<br>
<div>So my problem is, I am trying to set periodic boundary conditions on both sides of the naca wing. I use prex for that.<br>
</div>
<br>
<div>When I use prex for simple gemetries like cube and cylinder, the periodic conditions are set well.</div>
<br>
<div>But when I try on NACA the periodic BCs become in consistent and it runs a loop to check the consistency and not generating rea file anymore.</div>
<br>
<div>I commented some lines in source code (tools/prenek/bound.f) and tried to figure whats going on, then I generated an rea file and checked inside.<br>
</div>
<br>
<div>I saw that some elements are not set with Periodic bcs. </div>
<br>
<div>I understand that the loop helps to make the BC consitent.<br>
</div>
<br>
<div>But could you please tell me why it happens to NACA and not for simple gemoteries.</div>
<br>
<div>I am really stuck here..<br>
</div>
<br>
<div>Thank you<br>
</div>
<br>
<div>Sijo GEORGE<br>
</div>
<div> <br>
</div>
</div>
<br>
</div>
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