[Nek5000-users] Questions regarding avg_all

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

Hi Phillip,

Thanks for the reply, that was very clear. However, I'm now facing a
problem while trying to load the avvgblah.f000* files from my case.
Currently I'm running visnek on these averaged files, generating a .nek5000
file and trying to read that using visit or paraview. This procedure
results in an error. The reader complains that the first step of a nek file
must contain a mesh which the files generated by avg_all do not seem to
have. What is the procedure for reading this data then?


Sincerely,

On Sun, Feb 4, 2018 at 5:39 AM <nek5000-users at lists.mcs.anl.gov> wrote:

> Dear Amitvikram,
>
> As far as I understand, the basic version of avg_all perform only a time
> average, i.e. the statistics are computed in 3D in every point of the
> domain. In case your flow has additional directions of homogeneity, then
> one can do an average over those directions as well; either by taking
> the output of avg_all and doing the average there, or direction during
> runtime (for the latter there is an implementation described here:
> http://www.ipd.anl.gov/anlpubs/2017/03/133610.pdf)
>
> Best regards,
> PHilipp
>
> On 2018-02-03 17:36, nek5000-users at lists.mcs.anl.gov wrote:
> > Hi all,
> >
> > I understand that a call to avg_all computes the running averages of u,
> > u^2 etc and then dumps the results after a fixed timestep as given by
> > param68.
> >
> >   What I do not understand is where in the domain does this computation
> > take place? Does it average all the points in the domain? I understand
> > how this would by useful in the turbChannel case where fully developed
> > turbulence covers essentially the entire domain. However in cases where
> > the flow develops turbulence within the domain and thus there are strong
> > regions of turbulent anisotropy, it would be imperative to calculate
> > these running averages along a specified plane or line. I did see some
> > code defining these in the turbChannel example
> > viz. common /plane/  uavg_pl(ly1*lely)
> >       $             ,  urms_pl(ly1*lely)
> >       $             ,  vrms_pl(ly1*lely)
> >       $             ,  wrms_pl(ly1*lely)
> >       $             ,  uvms_pl(ly1*lely)
> >       $             ,  yy(ly1*lely)
> >       $             ,  w1(ly1*lely),w2(ly1*lely)
> >       $             ,  ffx_avg, dragx_avg
> >
> >
> > but I'm not exactly sure how this is defining a particular section of
> > the geometry. In my particular case I'm trying to simulate a rectangular
> > jet exhausting into a cuboidal domain. How can I set avg_all to compute
> > the said average along a streamwise plane of the jet for example?
> >
> > Sincerely,
> > --
> >
> > *Amitvikram Dutta*
> >
> > Graduate Research Assistant
> >
> > Fluid Mechanics Research Lab
> >
> > Multi-Physics Interaction Lab
> >
> > University of Waterloo
> >
> >
> >
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> >
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-- 

*Amitvikram Dutta*

Graduate Research Assistant

Fluid Mechanics Research Lab

Multi-Physics Interaction Lab

University of Waterloo
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