<div dir="ltr"><div><div><div>Hi Paul, <br><br></div>Thank you for your reply. </div><div>Yes, if i increase Reynolds number, the outlet profile become much close to the inlet one. But in my simulations the Reynolds number is between 300 and 1200. <br>Can you recommend me what kind of boundary conditions i can utilise for ensure for ensure the flow physics<font color="#000000" face="tahoma, arial, verdana, sans-serif, Lucida Sans"><span style="font-size:11px;line-height:16.5px"> ?</span></font> I would implement these one in code. <br><br></div>Thanks,<br></div>Andrew<br><div><div><br></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">2015-12-05 3:37 GMT+01:00 <span dir="ltr"><<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.gov</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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Hi Andrew,
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<div>I checked into this... I think what is happening is that the 'O ' bc for the stress formulation</div>
<div>means stress-free, which is not guaranteed to yield a parabolic profile at the outlet.</div>
<div><br>
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<div>If you increase your Reynolds number I'm guessing that you'll recover the parabolic</div>
<div>profile because the viscous stresses will diminish -- this is what I observed.</div>
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<div>From my perspective, the outlet boundary is not a region where I would count on accurate</div>
<div>physics --- it is, after all, a truncated domain, so I don't generally worry too much about</div>
<div>the behavior there.</div>
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<div>Paul</div>
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<div style="direction:ltr"><font face="Tahoma" size="2" color="#000000"><b>From:</b> <a href="mailto:nek5000-users-bounces@lists.mcs.anl.gov" target="_blank">nek5000-users-bounces@lists.mcs.anl.gov</a> [<a href="mailto:nek5000-users-bounces@lists.mcs.anl.gov" target="_blank">nek5000-users-bounces@lists.mcs.anl.gov</a>] on behalf of <a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.gov</a> [<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.gov</a>]<br>
<b>Sent:</b> Tuesday, December 01, 2015 2:44 AM<br>
<b>To:</b> <a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.gov</a><br>
<b>Subject:</b> [Nek5000-users] Stress formulation<br>
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<div><span lang="en"><span title="Andrew"></span></span>Hi Neks,<br>
<br>
I have one question about stress formulation in NEK5000.<br>
I tried to make a simulation for Poiseuil flow with stress formulation. In inlet boundary condition use was made of parabolic profile. If IFSTRS=false the outlet profile is exactly the same as inlet one but in case of IFSTRS=true the outlet profile changes
significantly (both the maximum value and profile shape). Could you tell me how I can get the parabolic profile at outlet, please?<br>
The same thing occurs with pressure values. The maximum pressure value with IFSTRS=true is three times higher then the one with IFSTRS=false.<br>
<br>
I found that the difference comes from subroutines where the stiffness matrix is calculated (axehlm for IFSTRS = false and axhmsf for IFSTRS = true) but I don't undestand what is happening exactly.<br>
<br>
Thanks in advance for your help,<br>
Best regards,<br>
Andrew<br>
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