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Dear Mohsen,
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<div>Years ago we did support internal walls, but that's no longer the case with the current workflow.</div>
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<div>The issue is that the gridpoints across the interface are identified as being one and the same if</div>
<div>they are physically adjacent. It would be possible to hack into your vertex numbering to make</div>
<div>these different (i.e., after they are generated by genmap), or to make a geometry in which they</div>
<div>are distinct by having a finite-thickness wall, but either way requires some application specific</div>
<div>coding in your usr file or modifications to your map file.</div>
<div><br>
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<div>Paul</div>
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<div id="divRpF512439" style="direction: ltr;"><font face="Tahoma" size="2" color="#000000"><b>From:</b> nek5000-users-bounces@lists.mcs.anl.gov [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> Monday, April 21, 2014 6:12 PM<br>
<b>To:</b> Nek 5000<br>
<b>Subject:</b> [Nek5000-users] Internal boundary condition<br>
</font><br>
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<div></div>
<div>Dear all,
<div>I have a question regarding the internal boundary condition in the code. </div>
<div>My problem consists of a fan-shaped nozzle, which parts of its walls are located within the flow domain (a cylindrical tank with inflow/outflow boundary conditions). The question is how to set the boundary conditions for such internal zero-thickness walls?</div>
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<div>I thought the walls could be defined as internal faces by creating a side-set (in the Cubit) and setting the velocity and the temperature fields of these faces to 'W ' and 'E ', respectively, similar to the solid-fluid interface in the conjugate heat
transfer example. Nevertheless, there is a fluid at both sides of the interface in this case.</div>
<div>Below is part of the boundary conditions in .rea file.</div>
<div>.....</div>
<div>.....</div>
<div>
<div>1 0 <span class="Apple-tab-span" style="white-space:pre"></span>! 1 fluid set, 0 other/solid sets</div>
<div>10<span class="Apple-tab-span" style="white-space:pre"> </span> <span class="Apple-tab-span" style="white-space:pre">
</span>! fluid set is 10</div>
<div>1<span class="Apple-tab-span" style="white-space:pre"> </span><span class="Apple-tab-span" style="white-space:pre"></span>! block 10 is material 1</div>
<div>10 <span class="Apple-tab-span" style="white-space:pre"> </span>! no. bc sets (side-sets); bc set id,</div>
<div>100 1 W , <span class="Apple-tab-span" style="white-space:pre"></span>(external walls)</div>
<div>100 2 I ,<span class="Apple-tab-span" style="white-space:pre"> </span>(external walls)</div>
<div>120 1 W ,<span class="Apple-tab-span" style="white-space:pre"> </span>(internal walls corresponding to the nozzle)</div>
<div><font class="Apple-style-span" face="Symbol">120 2 E ,</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Symbol">
</font></span>(internal walls corresponding to the nozzle)</div>
<div><span class="Apple-tab-span" style="white-space:pre"></span></div>
<div>200 1 v ,<span class="Apple-tab-span" style="white-space:pre"> </span>(inflow)</div>
<div>200 2 t ,<span class="Apple-tab-span" style="white-space:pre"> </span>(inflow)</div>
<div>300 1 O ,<span class="Apple-tab-span" style="white-space:pre"> </span>(outflow)</div>
<div>300 2 O ,<span class="Apple-tab-span" style="white-space:pre"> </span>(outflow)</div>
<div>400 1 SYM,</div>
<div>400 2 SYM,</div>
</div>
<div>.....</div>
<div>.....</div>
<div><br>
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<div>
<div>When I run this case, warning messages appear during assigning the sidesets to the element faces, saying that: "face shared by 2 Hexes (say) 2331 5227". It seems that this warning is only because I defined some faces as "internal", however, no "other solid/fluids"
has been defined in the input file.</div>
<div>Nevertheless, the issue with such definition is that, although, the velocity field is zero at the internal walls, there seems to be a pressure gradient across the wall, which is not physically consistent with internal walls, and drives a flow through the
walls.</div>
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<div><br>
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<div>It would be appreciated if anyone could help me on this problem.</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Mohsen</div>
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