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

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

Hi Paul and Aleks,

I wanna do it inside nek, too! The size of my data is ~comparable to the
high resolution case in "A comparison of Nek5000 and OpenFOAM for DNS of
turbulent channel flow" => E=5,...,9, N ~ 5000,...,10000.
The question however doesn't aim on how to postprocess a particular dataset
but is more a general question...

I'll try to illustrate another example with the same kind of problem to
describe what I mean:


We look at the following grid


            --> i3=1,...,5        -->i4=1,...,5
            #---+------+------+---#---+------+------+---#
jglob=9
            |                     |                     |
            +   +      +      +   +   +      +      +   +               ^
            |                     |                     |               |
            |      Element 3      |      Element 4      |               |
            +   +      +      +   +   +      +      +   +               |
            |                     |                     |               |
            |                     |                     |               |
            +   +      +      +   +   +      +      +   +               |
          ^ |                     |                     | ^             |
j3=1,...,5| #---+------+------+---#---+------+------+---# | j4=1,...,5  |
            |                     |                     |               |
            +   +      +      +   +   +      +      +   +               |
            |                     |                     |               |
            |      Element 1      |      Element 2      |               |
            +   +      +      +   +   +      +      +   +               |
            |                     |                     |               |
            |                     |                     |               |
            +   +      +      +   +   +      +      +   +               |
jglob=2
j1=1,...5 ^ |                     |                     | ^             |
          | #---+------+------+---#---+------+------+---# | j2=1,...5   |
jglob=1
           --> i1=1,...,5        -->i2=1,...,5

           ------------------------------------------>

     iglob=1   2      3      ...                       9


Now i have a list with values defined on the "global" nodes.
Lets say we have a 1d profile U(:,jglob)

     9    #   ***
          |
     8    +   ***************
          |
          |
     7    +   *********************
          |
          |
     6    +   ************************
          |
     5    #   *************************
          |
     4    +   ************************
          |
          |
     3    +   *********************
          |
          |
     2    +   ***************
          |
jglob=1   #   ***


How can I add or subtract this profile which is given on the "global nodes"
to each point of the field.
Or asked another way: how do I get the global index as a function of the
local index (jglob(j))?

Thanks in advance!
Jan F.

Am 9. März 2012 19:23 schrieb <nek5000-users at lists.mcs.anl.gov>:
>
>
> Jan,
>
> For what you want, I would do it inside nek, but it could
> also be done in VisIt or in postnek by sampling the field
> along many z-lines and then averaging these together.
>
> What is the size (E,N) of your data?
>
> Regards,
>
> Paul
>
>
>
> On Fri, 9 Mar 2012, nek5000-users at lists.mcs.anl.gov wrote:
>
>> Hi Aleks,
>>
>> thank you for posting your routines. They are certainly very useful!
>> But my point is to find an easy and quick way to check a single velocity
>> field. That can usually be done by taking the means over the full box and
>> subtracting them (as described in the first mail) from the instantaneous
>> field.
>> I don't wanna do my full postprocessing that way. It's just to have a
quick
>> look on the data (in particular the fluctuations)...
>> Do you think that is possible?
>>
>> Thanks!
>> Jan F.
>>
>> Am 9. März 2012 15:34 schrieb <nek5000-users at lists.mcs.anl.gov>:
>>
>>> Hi Jan,
>>>
>>> Here are routines that I sometimes use that call avg_all for the list
of a
>>> dump binary files given in a.list
>>>
>>> http://www.mcs.anl.gov/~obabko/avg_fld.usr
>>>
>>> Use
>>>
>>>    call avg_fld_all
>>>
>>> in post-processing mode of Nek5000 (nsteps=0 in .rea) with a created
>>> a.list file of your binary .f files (for .fld files uncomment line with
p66
>>> & p67 = 4)
>>>
>>> Best.
>>> Aleks
>>>
>>>
>>>
>>> ----- Original Message -----
>>> From: nek5000-users at lists.mcs.anl.gov
>>> To: nek5000-users at lists.mcs.anl.gov
>>> Sent: Wednesday, March 7, 2012 4:10:44 AM
>>> Subject: [Nek5000-users] Add/subtract 1d-mean profile
>>>
>>>
>>> Hi NEKs,
>>>
>>> I'm new to NEK and as a first exercise I'm calculating DNS of turbulent
>>> channel flow. So far everything is fine and works as is should.
>>>
>>> Now i wanna do some postprocessing with the (binary) files I dumped out.
>>> Let's say I wanna look at a single file:
>>>
>>> Is it possible to calc the 1d mean of u over the whole channel domain
(for
>>> example with "call planar_average_s") then take this 1d mean profile and
>>> subtract it from u at every point to get u' (=> u'(i,j,k,e) =
u(i,j,k,e) -
>>> <u>(j))?
>>>
>>> As I didn't dump the averages with "avg_all()" the hint given in
>>>
https://lists.mcs.anl.gov/mailman/htdig/nek5000-users/2010-May/000451.htmlinthis
case is not applicable.
>>>
>>>
>>> Thanks!
>>> Jan Frielinghausen
>>>
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>
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