<div dir="ltr">Hi Barak,<div><br></div><div>I am not aware of variable time stepping in nek5000. The time stepping used is BDFk/EXTk with CFL constraint for stability. You can change TORDER in .rea file to 2 or 3 to make the time stepping 2nd or third order accurate. There is a characteristic based time-stepping though... IFCHAR in .rea file.</div>
<div><br></div><div>However, if for a value ot DT you are getting convergence, essentially you should get the same for smaller value of DT. What is the error you are getting after the program aborts after 1200 iterations? It is still stored in your log file I suppose.</div>
<div><br></div><div>Thanks,</div><div>Tanmoy</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Sun, Dec 8, 2013 at 12:26 PM, <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">Hi Tanmoy,<br>
I have divided by 4 and again my run stopped at iteration 1200. My question is: does nek5000 have variable time-stepping?<br>
Thanks,<br>
Barak<div class="im"><br>
<br>
On 12/07/2013 08:37 PM, <a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.<u></u>gov</a> wrote:<br>
</div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="im">
Hi Barak,<br>
<br>
it is because of the fact that the generated file format is probably not<br></div>
readable in visit. In the *usrchk* subroutine in your .usr file write<div class="im"><br>
these 2 lines<br>
param(66) = 4<br>
param(67) = 4<br>
<br>
before the end of the routine<br>
<br>
Then compile and execute your program. Now you will get output files in<br>
the form of turbJet.fld001, turbJet.fld002, ...and so on.<br></div>
type in visnek turbJet in your terminal, and generate *turbJet.nek5000*.<div class="im"><br>
This .nek5000 file can be read by visit.<br>
<br>
Thanks,<br>
Tanmoy<br>
<br>
<br>
On Sat, Dec 7, 2013 at 10:33 AM, <<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.<u></u>gov</a><br></div><div class="im">
<mailto:<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.<u></u>mcs.anl.gov</a>>> wrote:<br>
<br>
Hi Tanmoy,<br>
Many thanks. It seems that after dividing by 4 (dt=0.005) it runs<br>
and I get output files in the form jet0.fxxxxx .<br>
Now I am trying to visualize them using the precompiled ubuntu11<br>
version of visit. Unfortunately, I get the following error:<br>
<br>
VisIt could not read from the file<br></div>
"/home/galanti/COMPUTATION/__<u></u>NEK5000/nek5_svn/TEST-__<u></u>examples/turbJet/jet0.f*<div class="im"><br>
database".<br>
<br>
The generated error message was:<br>
<br>
There was an error opening<br></div>
/home/galanti/COMPUTATION/__<u></u>NEK5000/nek5_svn/TEST-__<u></u>examples/turbJet/jet0.f*<div class="im"><br>
database. It may be an invalid file. VisIt tried using the<br>
following file format readers to open the file: Nek5000<br>
<br>
The following error(s) may be helpful in identifying the problem:<br>
When attempting to use "Nek", the file matched the general format<br>
expected by the reader but eventually encountered this error: "A tag<br>
called filetemplate: must be specified".<br>
<br>
What's wrong?<br>
Many thanks again,<br>
Barak<br>
<br>
<br>
<br></div>
On 12/07/2013 12:42 AM, nek5000-users@lists.mcs.anl.__<u></u>gov<div class="im"><br>
<mailto:<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.<u></u>mcs.anl.gov</a>> wrote:<br>
<br>
Hi Barak,<br>
<br>
It is a problem with numerical Stability. Decrease DT in your<br>
.rea file<br>
until the simulations become stable. You could start with 1/2 DT to<br>
check if simulation is stable, other wise go for 1/4 DT, and<br>
check with<br>
this simple test.<br>
<br>
Thanks,<br>
Tanmoy<br>
<br>
<br>
On Fri, Dec 6, 2013 at 3:31 PM,<br></div>
<nek5000-users@lists.mcs.anl._<u></u>_gov<br>
<mailto:<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.<u></u>mcs.anl.gov</a>><br>
<mailto:<a href="mailto:nek5000-users@lists." target="_blank">nek5000-users@lists.</a>__<a href="http://mcs.anl.gov" target="_blank"><u></u>mcs.anl.gov</a><div><div class="h5"><br>
<mailto:<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.<u></u>mcs.anl.gov</a>>>> wrote:<br>
<br>
Hello,<br>
I am testing the example turbJet, and it seems that I have some<br>
problem with output. This are the output files:<br>
jet0.f00001<br>
<br>
Moreover, the ran stops with emergency exit at time 5.64<br>
(CFL too<br>
large?):<br>
<br>
<br>
282 DNORM, DIVEX 6.2789891850172769E-004<br>
8.4967723454134898E-006<br>
282 5.6400E+00 1.1065E+01 Fluid done<br>
282 5.6400000E+00 1.1955953E-03 6.4269380E-04<br>
9.9999991E-01 e2<br>
t max/min: 0.0000000000000000 0.0000000000000000<br>
CFL, Ctarg! 22.504301079496056 2.0000000000000000<br>
call outfld: ifpsco: T<br>
<br>
283 5.6400E+00 Write checkpoint:<br>
0 283 OPEN: jet0.f00001<br>
<br>
283 5.6400E+00 done :: Write checkpoint<br>
file size = 55. MB<br>
avg data-throughput =<br>
572.1MB/s<br>
io-nodes = 1<br>
<br>
<br>
7 Emergency exit: 283 time =<br>
5.6399999999999677<br>
Latest solution and data are dumped for post-processing.<br>
*** STOP ***<br>
3 Emergency exit: 283 time =<br>
5.6399999999999677<br>
Latest solution and data are dumped for post-processing.<br>
*** STOP ***<br>
5 Emergency exit: 283 time =<br>
5.6399999999999677<br>
Latest solution and data are dumped for post-processing.<br>
*** STOP ***<br>
0 Emergency exit: 283 time =<br>
5.6399999999999677<br>
Latest solution and data are dumped for post-processing.<br>
*** STOP ***<br>
6 Emergency exit: 283 time =<br>
5.6399999999999677<br>
Latest solution and data are dumped for post-processing.<br>
*** STOP ***<br>
4 Emergency exit: 283 time =<br>
5.6399999999999677<br>
Latest solution and data are dumped for post-processing.<br>
*** STOP ***<br>
2 Emergency exit: 283 time =<br>
5.6399999999999677<br>
Latest solution and data are dumped for post-processing.<br>
*** STOP ***<br>
1 Emergency exit: 283 time =<br>
5.6399999999999677<br>
<br>
<br>
<br>
<br>
Thank you,<br>
Barak<br>
<br>
<br></div></div>
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