[Nek5000-users] turbJet problem
nek5000-users at lists.mcs.anl.gov
nek5000-users at lists.mcs.anl.gov
Mon Dec 9 17:32:07 CST 2013
Hi Tanmoy,
Thank you for the nice reply.
Hmm, considering restart: is it possible? this could also be an
alternative considering the issue of decreasing time step.
Now how could I post my question in open format?
Thanks again
Barak
On 12/10/2013 01:23 AM, nek5000-users at lists.mcs.anl.gov wrote:
> Hi Barak,
>
> Your err-run.log clearly shows CFL number increases considerably. So, it
> is indeed a problem of time-stepping stability. So, as you suggest a
> variable time-stepping might be necessary. you could even write a small
> routine in .usr file to control your timestep DT. If you decrease your
> error of divergence, it has nothing to do with simulation time. You can
> control simulation time with NSTEPS of .rea file. However for explicit
> method the region of stability of higher accuracy methods are smaller.
> So, 3rd order accurate method is a little less stable. You could also
> try changing TORDER = 2 , when your jet develops considerably.
>
> I heard lagrangian formuation could be used in nek5000, but
> unfortunately I do not know that. It will be nice if you post this
> question of lagrangian part in an open format, so that the best person
> in the knowledge of this may answer you.
>
> Thanks,
>
> Tanmoy
>
>
> On Mon, Dec 9, 2013 at 3:59 PM, <nek5000-users at lists.mcs.anl.gov
> <mailto:nek5000-users at lists.mcs.anl.gov>> wrote:
>
> 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
> <mailto: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>
> <mailto: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
> <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.
> <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:
>
> 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.
> <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:
>
> 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
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> <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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