[Nek5000-users] Pipe example - Strange velocity/pressure signals

[nek5000-users at lists.mcs.anl.gov]

Dear Paul,

Thank you very much for looking into this. My parameters are as in the repository example, I didn't change them:
lx1=6,
lxd=10,
lx2=lx1-2
lx3=lx1

The output after the first time step (dt=2.5e-2) of hpts.out is attached below. Please note the third column (z-velocity).

  2.5000000E-02 -4.7626817E-05 -4.4872405E-05  4.8233404E-01  1.3486090E+02
  2.5000000E-02 -6.0842050E-05 -1.8870027E-02  5.9476094E-01  1.7381205E+02
  2.5000000E-02  2.0295515E-07 -1.5249089E-02  4.8242873E-01  1.3487912E+02
  2.5000000E-02 -1.5349154E-02 -1.1545977E-05  4.8241771E-01  1.3487899E+02
  2.5000000E-02  9.8682769E-03 -1.7779070E-02  5.7201214E-01  1.7367640E+02

Best regards,
Outi



On Mar 2, 2014, at 9:02 PM, nek5000-users at lists.mcs.anl.gov wrote:

> 
> Dear Outi,
> 
> What value of lx1 and lx2 were you using?
> 
> I'm not observing the phenomenon you report.
> I have:
> 
> lx1=6
> lxd=9
> lx2=lx1-2
> lx3=lx2
> 
> ...
> 
> Once I know your SIZE parameters I can retry.
> 
> Best, Paul
> 
> 
> On Sun, 2 Mar 2014, nek5000-users at lists.mcs.anl.gov wrote:
> 
>> Dear Neks,
>> We are interested to do a smoothly deformed axisymmetric geometry, much
>> like the pipe/stenosis example in the repository.
>> So, we added hpts probes in the pipe example, and modified nothing else,
>> but this turns out to give strange values initially. The first probe sits
>> 3 diameters downstream of the stenosis throat (z=3), and gives U=0.48 at
>> the first time step, despite zero initial condition. The pressure in this
>> position shoots up to very high values too, so maybe a spurious pressure
>> peak is the cause?
>> Could you please help us to understand/prevent this phenomenon? The .usr,
>> hpts.in and essential parts of .rea are attached. We are using revision
>> 1008.
>> This would be important for us as we aim to use Nek5000 to study
>> transient as well as steady state dynamics of similar flows.
>> Thank you in advance!
>> Outi
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>> Nek5000-users at lists.mcs.anl.gov
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>> 
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