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<p style="margin-top:0;margin-bottom:0">Dear Sijo,</p>
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<p 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">your problem if you have element sizes at positions that have order unity magnitude and 1.e-6 size.</p>
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<p 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">First, I wonder why you would need elements of that size (when there will</p>
<p 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">points interior to these very small elements).</p>
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<p 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">It will generate the correct periodicity and you can output the mesh file</p>
<p 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">in 64-bit floating point.</p>
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<p style="margin-top:0;margin-bottom:0">Best,</p>
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<p style="margin-top:0;margin-bottom:0">Paul</p>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" 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)</font>
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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>
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<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>
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<div>Hi Neks,<br>
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<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>
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<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>
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<div>When I use prex for simple gemetries like cube and cylinder, the periodic conditions are set well.</div>
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<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>
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<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>
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<div>I saw that some elements are not set with Periodic bcs. </div>
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<div>I understand that the loop helps to make the BC consitent.<br>
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<div>But could you please tell me why it happens to NACA and not for simple gemoteries.</div>
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<div>I am really stuck here..<br>
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<div>Thank you<br>
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<div>Sijo GEORGE<br>
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