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<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">David-<br>
<br>
Here is the .box file I used to generate the mesh. I noticed the CFL target number issue, it looks like nek resets it to 0.5 anyway.<br>
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<div style="font-family:Tahoma; font-size:13px"> -Jared<br>
<br>
CCS2/CNLS Postdoctoral Research Associate
<div>Los Alamos National Laboratory</div>
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<div style="direction: ltr;" id="divRpF328911"><font color="#000000" face="Tahoma" size="2"><b>From:</b> nek5000-users-bounces@lists.mcs.anl.gov [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> Monday, February 18, 2013 11:24 AM<br>
<b>To:</b> nek5000-users@lists.mcs.anl.gov<br>
<b>Subject:</b> Re: [Nek5000-users] Rayleigh Benard with symmetry BCs<br>
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<div dir="ltr">Hi Jared,<br>
<div>
<div class="gmail_extra"><br>
</div>
<div class="gmail_extra">If you send me your .box file, I will check that just in case.<br>
<br>
</div>
<div class="gmail_extra">Also, I see you are using variable time steps, so try reducing the target Courant number to 1/2.<br>
</div>
<div class="gmail_extra"><br>
Another thing to be aware of with variable time stepping: if the Rayleigh number is large and the simulation starts from a static state, the exponentially growing velocities might still cause the CFL condition to be violated. The solution to this is to decrease
the maximum allowed time step, DT. This is unlikely to be your problem at the current Rayleigh number, however.<br>
<br>
</div>
<div class="gmail_extra">-David<br>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Mon, Feb 18, 2013 at 11:53 AM, <span dir="ltr"><<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.gov</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex; border-left:1px solid rgb(204,204,204); padding-left:1ex">
<div>
<div style="direction:ltr; font-size:10pt; font-family:Tahoma">My apologies upfront for any simple misconceptions as I'm new to nek.<br>
<br>
I have successfully run the included 2d RB example and thought things looked reasonable. I then changed the mesh to an aspect ratio 2, 4x8 element mesh and modified the boundary conditions to be 'SYM' sidewalls and 'SYM' (free-slip) for the top and bottom
velocity (see attached rea and map file).<br>
<br>
Without changing anything else from the example (I did not modify SIZE) the velocities appear to blow up, and I get a series of errors like the following in the logfile:<br>
<br>
1 100 **ERROR**: Failed in HMHOLTZ: TEMP 1.4999E-02 3.7064E+01 2.4836E-03<br>
1 2.0000E-02 6.0370E-03 Heat done<br>
<br>
1 100 **ERROR**: Failed in HMHOLTZ: VELX 2.8743E-21 1.7086E-16 2.3416E-23<br>
0.000000000000000E+000 p22 1 1<br>
New CG1-tolerance (RINIT*epsm) = 1.010379228335448E-010<br>
2.341589846098494E-023<br>
<br>
<br>
1 100 **ERROR**: Failed in HMHOLTZ: VELY 1.0837E-01 1.0104E+03 1.0104E-10<br>
New CG2-tolerance (RINIT*10-5/10-10) = 2.795810823528297E-003<br>
3.472834773690102E-025<br>
<br>
<br>
<br>
Do I need to adjust the tolerances because the mesh/BCs are different?<br>
<br>
<br>
I don't think it matters, but I ran this on 16 procs (there are 16 per node on the machine I'm using).<br>
<br>
-Jared<br>
<div><br>
<div style="font-family:Tahoma; font-size:13px">CCS2/CNLS Postdoctoral Research Associate
<div>Los Alamos National Laboratory</div>
</div>
</div>
</div>
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<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Mon, Feb 18, 2013 at 11:53 AM, <span dir="ltr"><<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.gov</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex; border-left:1px #ccc solid; padding-left:1ex">
<div>
<div style="direction:ltr; font-size:10pt; font-family:Tahoma">My apologies upfront for any simple misconceptions as I'm new to nek.<br>
<br>
I have successfully run the included 2d RB example and thought things looked reasonable. I then changed the mesh to an aspect ratio 2, 4x8 element mesh and modified the boundary conditions to be 'SYM' sidewalls and 'SYM' (free-slip) for the top and bottom
velocity (see attached rea and map file).<br>
<br>
Without changing anything else from the example (I did not modify SIZE) the velocities appear to blow up, and I get a series of errors like the following in the logfile:<br>
<br>
1 100 **ERROR**: Failed in HMHOLTZ: TEMP 1.4999E-02 3.7064E+01 2.4836E-03<br>
1 2.0000E-02 6.0370E-03 Heat done<br>
<br>
1 100 **ERROR**: Failed in HMHOLTZ: VELX 2.8743E-21 1.7086E-16 2.3416E-23<br>
0.000000000000000E+000 p22 1 1<br>
New CG1-tolerance (RINIT*epsm) = 1.010379228335448E-010<br>
2.341589846098494E-023<br>
<br>
<br>
1 100 **ERROR**: Failed in HMHOLTZ: VELY 1.0837E-01 1.0104E+03 1.0104E-10<br>
New CG2-tolerance (RINIT*10-5/10-10) = 2.795810823528297E-003<br>
3.472834773690102E-025<br>
<br>
<br>
<br>
Do I need to adjust the tolerances because the mesh/BCs are different?<br>
<br>
<br>
I don't think it matters, but I ran this on 16 procs (there are 16 per node on the machine I'm using).<br>
<br>
-Jared<br>
<div><br>
<div style="font-family:Tahoma; font-size:13px">CCS2/CNLS Postdoctoral Research Associate
<div>Los Alamos National Laboratory</div>
</div>
</div>
</div>
</div>
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