[Nek5000-users] Add/subtract 1d-mean profile

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

Works very well! Thanks a lot!

Jan

Am 12. März 2012 14:12 schrieb  <nek5000-users at lists.mcs.anl.gov>:
>
>
> Hi Jan,
>
> I've added a routine, "no_y_profile(u)" to the current version
> of the repo (navier5.f).
>
> Usage is of the form shown below.
>
> If you want the y_profile in an array, just look at the navier5.f
> source and you can see the correct calling sequence.
>
> Paul
>
>
> c-----------------------------------------------------------------------
>      subroutine userchk
>      include 'SIZE'
>      include 'TOTAL'
>
>      parameter (ll=lx1*ly1*lz1*lelt)
>      common /mystufr/ u(ll),v(ll),w(ll)
>
>      call opcopy(u,v,w,vx,vy,vz)
>      call no_y_profile(u)
>      call no_y_profile(v)
>      call no_y_profile(w)
>
>      if (istep.gt.0.and.mod(istep,iostep).eq.0)
>     $   call outpost(u,v,w,pr,t,'noy')
>
>
>      return
>      end
> c-----------------------------------------------------------------------
>
>
> Paul
>
>
>
>
> On Sun, 11 Mar 2012, nek5000-users at lists.mcs.anl.gov wrote:
>
>> Hi Paul,
>>
>> first of all thanks for the quick reply!
>>
>>
>> I guess my first question is the following.  When you say you
>> want to
>>
>> "add or subtract this profile which is given on the global nodes
>> to each point of the field"
>>
>> it seems we need to be talking in the context of some software
>> that is going to read the field in and then process the data.
>>
>> At present, I know of only 3 codes to do that: nek, VisIt, and postnek
>> (though there have been custom, one-off, codes written
>> in the past).
>>
>> I want to do the whole post-processing in nek. With VisIt I only visualize
>> my data generated with nek (the post-processed data as well as the raw
>> simulation data). With postnek I haven't worked until now and I think
>> postnek is not what I'm looking for.
>>
>>
>> Second question is --- What do you want to do with this field
>> after you have subtracted the mean profile?   Do you want to
>> write it to disk, visualize it, use it in a calculation, analyze it with
>> more statistics, or....?
>>
>> I want to analyze the statistics, calculate higher order moments of the
>> fluctuation field (to compare it with the channel data of Robert D. Moser,
>> John Kim and Nagi N. Mansour,
>> Physics of Fluids, vol 11(4), for example the skewness or the flatness of
>> the field) or the gradients of the fluctuation field du'_i/dx_j to get
>> (fluctuation based) \omega'_k or the (fluctuation based) strain rate
>> tensor
>> s'_ij = 1/2*(du'_i/dx_j + du'_j/dx_i).
>> These are only few examples on what I would like to do...
>>
>> But for all these things I need the fluctuation field and that means u' =
>> u
>> - <u>.
>> In this context <u> would be (for example if I don't have the temporal
>> avg_all() means) the spatial (y-) mean over the full channel domain.
>>
>> When I do my production run with the code I can obtain the temporal
>> averages by calling avg_all() every timestep and then write it to disk,
>> thats clear to me.
>>
>> But my question aims on how to get the fluctuation field without having
>> the
>> temporal averages. Based on only a single velocity filed (as described
>> above).
>>
>>
>> In any case, it seems likely that processing in nek is the
>> way to go because it has the ability to read the data, write
>> the data, and readily compute statistics.   In this mode, you
>> simply are using nek as a post-processor and not for timestepping.
>>
>> Please advise if that's the path you wish to take, or if you
>> had something else in mind.
>>
>> Yes, thats the way I want  to do my post-processing (and already do it
>> right now...).
>>
>> Regards
>> Jan F.
>>
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