<html>
<head>
<meta content="text/html; charset=windows-1252"
http-equiv="Content-Type">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<div class="moz-cite-prefix">Hi<br>
<br>
For full_restart you should have four velocity fields and you
could use nek5000 as a preprocessing tool. You can simply load all
4 fields in userchk, perform some kind of interpolation in time
and finally write down new restart files. The question is how to
deal with pressure. One solution would be simply interpolate
pressure saved in the files. The other would be to run modified
version of pressure solver with uzawa turned on to get pressure
corresponding to interpolated velocity field. We've played with
uzawa for pn-pn-2 and we use our version of full_restart, but we
haven't done this kind of modified restart, so I don't know what
is better. On the other hand you could restart nek with your
current checkpoints and dt corresponding to the old simulation,
and later (after 4th step) gradually decrease time step. I guess
this would be the simplest and probably best solution. If time
resolution in old simulation was insufficient, your restart files
do not give correct evolution of the field and interpolation in
time would not remove it. Anyhow you introduce some initial error
to simulation. In this case I probably would simply play with dt
keeping it constant during first 4 steps and gradually decreasing
later.<br>
Regards<br>
Adam<br>
<br>
On 2015-11-16 20:19, <a class="moz-txt-link-abbreviated" href="mailto:nek5000-users@lists.mcs.anl.gov">nek5000-users@lists.mcs.anl.gov</a> wrote:<br>
</div>
<blockquote
cite="mid:mailman.10777.1447701586.24727.nek5000-users@lists.mcs.anl.gov"
type="cite">
<meta http-equiv="Content-Type" content="text/html;
charset=windows-1252">
<style type="text/css" style="display:none;"><!-- P {margin-top:0;margin-bottom:0;} --></style>
<div id="divtagdefaultwrapper"
style="font-size:12pt;color:#000000;background-color:#FFFFFF;font-family:Calibri,Arial,Helvetica,sans-serif;">
<p>Dear Neks,</p>
<p><br>
</p>
<p>I use full_restart option for my current simulations. One
simulation crashed after restarting for some time with the
Courant number going crazy. I suppose I will need to reduce
the time step size.</p>
<p><br>
</p>
<p>Basically, I want to continue my simulation using
full_restart option but with a smaller time step size. Somehow
I remember I saw one post saying one shouldn't change the time
step size when using the full_restart option. I'm just
thinking of a way to work around the problem.</p>
<p><br>
</p>
<p>So does anyone have ideas on how I can interpolate the flow
fields between two time steps or any other ways to fully
restart a simulation with a different time step size?<br>
</p>
<p><br>
</p>
<p>Thank you very much in advance for any suggestions or
comments.</p>
<p><br>
</p>
<p>Best regards,</p>
<p>Tony<br>
</p>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
Nek5000-users mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Nek5000-users@lists.mcs.anl.gov">Nek5000-users@lists.mcs.anl.gov</a>
<a class="moz-txt-link-freetext" href="https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users">https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users</a>
</pre>
</blockquote>
<br>
</body>
</html>