[Nek5000-users] Questions regarding avg_all

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

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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