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<p style="margin-top:0;margin-bottom:0">Dear Dante,</p>
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<p style="margin-top:0;margin-bottom:0">I typically use the turb_outflow boundary condition that is in navier5.f (see below). It will guarantee no inflow.</p>
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<p style="margin-top:0;margin-bottom:0">Sometimes you need to set "uin" to get the correct scale if your inlet and outlet areas are disparate in one way or another, but I've rarely found a case where this does not work. Other groups use some form of convective
outflow treatment. There were comments on this just last week.</p>
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<p style="margin-top:0;margin-bottom:0">hth,</p>
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<p style="margin-top:0;margin-bottom:0">Paul</p>
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<span style="font-variant-ligatures: no-common-ligatures">c . Set div U > 0 in elements with 'O ' bc.</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c . rq is nominally the ratio of Qout/Qin and is typically 1.5</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c . uin is normally zero, unless your flow is zero everywhere</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c . d and m1 are work arrays of size (lx1,ly1,lz1,lelt), assumed persistant</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c This routine may or may not work with multiple outlets --- it has</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c not been tested for this case.</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c TYPICAL USAGE -- ADD THESE LINES TO userchk() in your .usr file:</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c (uncommented)</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c common /myoutflow/ d(lx1,ly1,lz1,lelt),m1(lx1*ly1*lz1,lelt)</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c real m1</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c rq = 2.</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c uin = 0.</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">c call turb_outflow(d,m1,rq,uin)</span></p>
<p></p>
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<span style="font-variant-ligatures: no-common-ligatures">c</span></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, March 6, 2018 1:33:29 AM<br>
<b>To:</b> nek5000-users@lists.mcs.anl.gov<br>
<b>Subject:</b> [Nek5000-users] Outflow boundary conditions</font>
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<div dir="ltr">Dear all,
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<div>are outflow advective boundary conditions available in nek5000? </div>
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<div>Or is there any work around in order to impose outflow boundary conditions</div>
<div>(for the velocity and the passive scalars) that can grantee that there is no flow coming </div>
<div>back from the outflow boundary?</div>
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<div>Thanks,</div>
<div>Dante</div>
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