<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">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><div><br></div><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></div><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></div><div><br></div><div>It would be appreciated if anyone could help me on this problem.</div><div><br></div><div>Thanks,</div><div>Mohsen</div><div><br></div></body></html>