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<p style="margin-top:0;margin-bottom:0">The usual first step here is to restart with a lower value of dt.</p>
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<p style="margin-top:0;margin-bottom:0">In this case, I would recommend reducing dt by about a factor of 5 or</p>
<p style="margin-top:0;margin-bottom:0">10 and seeing if this survives with a reasonable Courant number.</p>
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<p style="margin-top:0;margin-bottom:0">hth,</p>
<p style="margin-top:0;margin-bottom:0">Paul</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> Wednesday, August 1, 2018 10:16:37 AM<br>
<b>To:</b> nek5000-users@lists.mcs.anl.gov<br>
<b>Subject:</b> [Nek5000-users] Restart using rea</font>
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<p class="x_MsoNormal">Dear Nek users,</p>
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<p class="x_MsoNormal">I ran into a problem when restarting using the .rea file. In the .rea file, I specified the name of the file (the file was renamed from the last time step of the previous simuiatlion)to restart with:</p>
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<p class="x_MsoNormal"> ***** NO THERMAL BOUNDARY CONDITIONS *****</p>
<p class="x_MsoNormal"> 1 PRESOLVE/RESTART OPTIONS *****</p>
<p class="x_MsoNormal">restart.fld</p>
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<p class="x_MsoNormal">Without changing the time step size, I restarted the simulation, but I received an error:</p>
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<p class="x_MsoNormal">Step 581, time= 3.0955000E+02, DT= 5.0000000E-02, C= 4.240 4.3486E+01 1.1724E-01</p>
<p class="x_MsoNormal"> Solving for fluid</p>
<p class="x_MsoNormal"> 581 Hmholtz VELX 12 1.5661E-12 7.4073E-01 5.0000E-12</p>
<p class="x_MsoNormal"> 581 Hmholtz VELY 11 9.6329E-13 3.3660E+00 5.0000E-12</p>
<p class="x_MsoNormal"> 581 Project PRES 5.5975E-05 1.6744E+00 2.9913E+04 13 20</p>
<p class="x_MsoNormal"> 581 U-PRES gmres 120 6.1973E-10 1.8658E-06 5.0000E-12 4.3239E-02 1.0688E-01</p>
<p class="x_MsoNormal"> 581 Fluid done 3.0955E+02 1.1453E-01</p>
<p class="x_MsoNormal"> 581 3.09550E+02 6.46747E+01 0.00000E+00 7.53982E+02 blasius: delta*</p>
<p class="x_MsoNormal">CFL, Ctarg! 7.39542251238818 0.500000000000000</p>
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<p class="x_MsoNormal">The original CFL was only 0.028 or so, after restart, it fluctuates significantly and eventually it quits for CFL being too large. Could anyone help me on this please?</p>
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<p class="x_MsoNormal">Many thanks </p>
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