[Nek5000-users] turbJet problem
nek5000-users at lists.mcs.anl.gov
nek5000-users at lists.mcs.anl.gov
Mon Dec 9 16:59:44 CST 2013
Hi Tanmoy,
It is the 4th time that the program stops (probably because of two big
dt). See the end of the log of the run. The time step is dt=1e-3. The
first test it was 0.02. It seems that the time step has to be reduced
when the jet develops considerably.
Perhaps, the best thing to do is to simulate till the time limit when
the time step becomes not enough small, to stop, and then restart with
the next time step (decreased) till the next stage and so on.
Now I have further questions:
1. I noticed that there is a parameter to control the error of
divergence. If I choose smaller value, how it ncrease the simulation time?
2. I am interested in the Lagrangian properties of the flow, i.e.
calculating velocity, vorticity or other velocity derivatives at the
Lagrangian orbit. Is it possible and which are the available tools?
Barak
On 12/09/2013 02:56 AM, nek5000-users at lists.mcs.anl.gov wrote:
> Hi Barak,
>
> 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.
>
> 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.
>
> Thanks,
> Tanmoy
>
>
> On Sun, Dec 8, 2013 at 12:26 PM, <nek5000-users at lists.mcs.anl.gov
> <mailto:nek5000-users at lists.mcs.anl.gov>> wrote:
>
> Hi Tanmoy,
> I have divided by 4 and again my run stopped at iteration 1200. My
> question is: does nek5000 have variable time-stepping?
> Thanks,
> Barak
>
>
> On 12/07/2013 08:37 PM, nek5000-users at lists.mcs.anl.__gov
> <mailto:nek5000-users at lists.mcs.anl.gov> wrote:
>
> Hi Barak,
>
> it is because of the fact that the generated file format is
> probably not
> readable in visit. In the *usrchk* subroutine in your .usr file
> write
>
> these 2 lines
> param(66) = 4
> param(67) = 4
>
> before the end of the routine
>
> Then compile and execute your program. Now you will get output
> files in
> the form of turbJet.fld001, turbJet.fld002, ...and so on.
> type in visnek turbJet in your terminal, and generate
> *turbJet.nek5000*.
>
> This .nek5000 file can be read by visit.
>
> Thanks,
> Tanmoy
>
>
> On Sat, Dec 7, 2013 at 10:33 AM,
> <nek5000-users at lists.mcs.anl.__gov
> <mailto:nek5000-users at lists.mcs.anl.gov>
> <mailto:nek5000-users at lists.__mcs.anl.gov
> <mailto:nek5000-users at lists.mcs.anl.gov>>> wrote:
>
> Hi Tanmoy,
> Many thanks. It seems that after dividing by 4 (dt=0.005)
> it runs
> and I get output files in the form jet0.fxxxxx .
> Now I am trying to visualize them using the precompiled
> ubuntu11
> version of visit. Unfortunately, I get the following error:
>
> VisIt could not read from the file
>
> "/home/galanti/COMPUTATION/____NEK5000/nek5_svn/TEST-____examples/turbJet/jet0.f*
>
> database".
>
> The generated error message was:
>
> There was an error opening
>
> /home/galanti/COMPUTATION/____NEK5000/nek5_svn/TEST-____examples/turbJet/jet0.f*
>
> database. It may be an invalid file. VisIt tried using the
> following file format readers to open the file: Nek5000
>
> The following error(s) may be helpful in identifying the
> problem:
> When attempting to use "Nek", the file matched the general
> format
> expected by the reader but eventually encountered this
> error: "A tag
> called filetemplate: must be specified".
>
> What's wrong?
> Many thanks again,
> Barak
>
>
>
> On 12/07/2013 12:42 AM, nek5000-users at lists.mcs.anl.____gov
>
> <mailto:nek5000-users at lists.__mcs.anl.gov
> <mailto:nek5000-users at lists.mcs.anl.gov>> wrote:
>
> Hi Barak,
>
> It is a problem with numerical Stability. Decrease DT
> in your
> .rea file
> until the simulations become stable. You could start
> with 1/2 DT to
> check if simulation is stable, other wise go for 1/4
> DT, and
> check with
> this simple test.
>
> Thanks,
> Tanmoy
>
>
> On Fri, Dec 6, 2013 at 3:31 PM,
> <nek5000-users at lists.mcs.anl.____gov
> <mailto:nek5000-users at lists.__mcs.anl.gov
> <mailto:nek5000-users at lists.mcs.anl.gov>>
> <mailto:nek5000-users at lists.
> <mailto:nek5000-users at lists.>____mcs.anl.gov <http://mcs.anl.gov>
>
> <mailto:nek5000-users at lists.__mcs.anl.gov
> <mailto:nek5000-users at lists.mcs.anl.gov>>>> wrote:
>
> Hello,
> I am testing the example turbJet, and it seems
> that I have some
> problem with output. This are the output files:
> jet0.f00001
>
> Moreover, the ran stops with emergency exit at
> time 5.64
> (CFL too
> large?):
>
>
> 282 DNORM, DIVEX 6.2789891850172769E-004
> 8.4967723454134898E-006
> 282 5.6400E+00 1.1065E+01 Fluid done
> 282 5.6400000E+00 1.1955953E-03 6.4269380E-04
> 9.9999991E-01 e2
> t max/min: 0.0000000000000000
> 0.0000000000000000
> CFL, Ctarg! 22.504301079496056
> 2.0000000000000000
> call outfld: ifpsco: T
>
> 283 5.6400E+00 Write checkpoint:
> 0 283 OPEN: jet0.f00001
>
> 283 5.6400E+00 done :: Write checkpoint
> file size =
> 55. MB
> avg data-throughput =
> 572.1MB/s
> io-nodes = 1
>
>
> 7 Emergency exit: 283 time =
> 5.6399999999999677
> Latest solution and data are dumped for
> post-processing.
> *** STOP ***
> 3 Emergency exit: 283 time =
> 5.6399999999999677
> Latest solution and data are dumped for
> post-processing.
> *** STOP ***
> 5 Emergency exit: 283 time =
> 5.6399999999999677
> Latest solution and data are dumped for
> post-processing.
> *** STOP ***
> 0 Emergency exit: 283 time =
> 5.6399999999999677
> Latest solution and data are dumped for
> post-processing.
> *** STOP ***
> 6 Emergency exit: 283 time =
> 5.6399999999999677
> Latest solution and data are dumped for
> post-processing.
> *** STOP ***
> 4 Emergency exit: 283 time =
> 5.6399999999999677
> Latest solution and data are dumped for
> post-processing.
> *** STOP ***
> 2 Emergency exit: 283 time =
> 5.6399999999999677
> Latest solution and data are dumped for
> post-processing.
> *** STOP ***
> 1 Emergency exit: 283 time =
> 5.6399999999999677
>
>
>
>
> Thank you,
> Barak
>
>
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