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Hi Paul,
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<div class="">I simulate a synthetic jet that is produced by a membrane that I model with a moving boundary. The membrane vibrates inside a cavity that is connected to a nozzle and then to a box. The box has an outflow boundary condition and all other boundaries
are wall boundaries.</div>
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<div class="">Because of the moving membrane, the fluid enters and exits the nozzle, and the same fluid motions are observed in the box near the outflow boundary, i.e., I have reverse flow.</div>
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<div class="">Hope this helps to understand my problem.</div>
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<div class="">Thanks for your time,</div>
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<div class="">Marco</div>
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<div class="">On Aug 15, 2017, at 6:36 PM, <a href="mailto:nek5000-users@lists.mcs.anl.gov" class="">
nek5000-users@lists.mcs.anl.gov</a> wrote:</div>
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Hi Marco,</div>
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<div style="margin-top: 0px; margin-bottom: 0px;" class="">I'm not certain of your bcs... is flow leaving the domain? If so, is any flow</div>
<div style="margin-top: 0px; margin-bottom: 0px;" class="">coming in? How does this happen? Can you give a bit more of a description?</div>
<div style="margin-top: 0px; margin-bottom: 0px;" class="">Thanks.</div>
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<div style="margin-top: 0px; margin-bottom: 0px;" class="">Best,</div>
<div style="margin-top: 0px; margin-bottom: 0px;" class="">Paul</div>
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<div id="x_divRplyFwdMsg" dir="ltr" class=""><font face="Calibri, sans-serif" style="font-size: 11pt;" class=""><b class="">From:</b><span class="Apple-converted-space"> </span>Nek5000-users <<a href="mailto:nek5000-users-bounces@lists.mcs.anl.gov" class="">nek5000-users-bounces@lists.mcs.anl.gov</a>>
on behalf of <a href="mailto:nek5000-users@lists.mcs.anl.gov" class="">nek5000-users@lists.mcs.anl.gov</a> <<a href="mailto:nek5000-users@lists.mcs.anl.gov" class="">nek5000-users@lists.mcs.anl.gov</a>><br class="">
<b class="">Sent:</b><span class="Apple-converted-space"> </span>Tuesday, August 15, 2017 9:28:47 AM<br class="">
<b class="">To:</b><span class="Apple-converted-space"> </span><a href="mailto:nek5000-users@lists.mcs.anl.gov" class="">nek5000-users@lists.mcs.anl.gov</a><br class="">
<b class="">Subject:</b><span class="Apple-converted-space"> </span>[Nek5000-users] Synthetic jet with outflow boundary condition</font>
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<div class="PlainText">Hi,<br class="">
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I am working on a 3-D simulation of a synthetic jet. The synthetic jet exits a nozzle and expands in a box that has an outflow boundary condition. After one or two cycles, the solution returns NaN because of the reverse flow that occurs at the outflow boundary
condone. I am aware of the trick that consists in locally accelerating the fluid near the outflow but I am not sure this could be useful to me since I do not have an inlet condition.<br class="">
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My next step will be to increase the computational domain, i.e. the box where the jet expands, and hope that the jet does not reach the outflow boundary condition. The only drawback of this option is that it will require more CPU time.<br class="">
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Before I move forward, I would like to know if someone else has experienced the same problem and came up with a solution that could be useful to me. I also though of increasing the viscosity near the outflow boundary condition.<br class="">
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Any help will be appreciated.<br class="">
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Thanks,<br class="">
Marco<br class="">
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