[Nek5000-users] Transfer data from an nelx*nely*nelz array of Nth-order to an n*n*n array for FFT analysis

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

Hi Neks,
another point I'm (even more) interested in is: how do you do your FFT analysis?
I guess in a first step the grid is mapped onto a regular grid
(ifreguo = .true.) and in a second step the FFT is computed at that
grid.
Then the question arises: What is a good choice for "nrg" (with nrg as
the dimension of regular grid (nrg**ndim)...)? nrg=lx1 or lx1-1?
Regards
Jan

2012/4/13 Jan Frielinghausen <jan.frielinghausen at googlemail.com>:
> Hi Neks, Hi Can,
> I too would be very interested in getting more information about these routines.
> regards
> Jan
>
> Am 5. April 2012 18:10 schrieb  <nek5000-users at lists.mcs.anl.gov>:
>> Hi neks !
>>
>> For a given velocity field
>> (vx(1:lx1,1:ly1,1:lz1,1:lelv),vy(1:lx1,1:ly1,1:lz1,1:lelv),vz(1:lx1,1:ly1,1:lz1,1:lelv))
>> i would like to calculate the energy spectrum, this implies FFT
>> transformation on regular arrays
>> vx(1:n,1:n,1:n),vy(1:n,1:n,1:n),vz(1:n,1:n,1:n) (need
>> deltax=deltay=deltaz=cst).
>> On the emailing-list it has been said :
>> "We do have off-line serial routines
>> that can transfer data from an nelx x nely x nelz array of Nth-order
>> elements to an nxnxn array - this allows for analysis by FFTs etc"
>>
>>
>> Can you please tell me more about this ? What are these routines ??
>> B.regards
>> Can
>>
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