[Nek5000-users] Postprocessing

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

Mani,

It somewhat depends on what you're after.

You can use postx and compute the vorticity there --- it is
only 32 bit but it does allow you to compute the vorticity
for any existing velocity data in the (older) .fld file
output format.

Alternatively, if you're using VisIt or some other analysis
tool, or doing run-time analysis, you can compute the vorticity
at runtime.  If you wish to output the vorticity field, you can
do so, e.g., as follows:

c-----------------------------------------------------------------------
       subroutine userchk
       include 'SIZE'
       include 'TOTAL'

       parameter(lt=lx1*ly1*lz1*lelv)
       common /scrns/ vort(lt,3),w1(lt),w2(lt)

       if (mod(istep,iostep).eq.0) then
          call comp_vort3(vort,w1,w2,vx,vy,vz)
          call outpost(vort(1,1),vort(1,2),vort(1,3),pr,t,'vrt')
       endif

       return
       end
c-----------------------------------------------------------------------


This would generate an output "vrtmy_case..." if your .rea file is
my_case.rea

Any of the post-processing tools could then read the vrt.... files
and treat the vorticity as the velocity vector field.

As I say, not exactly sure what you have in mind, but this is one
possible approach.

Paul





On Wed, 24 Mar 2010, nek5000-users at lists.mcs.anl.gov wrote:

> Dear Nek devs,
>
>    I'm a bit confused regarding postprocessing. Is one supposed to run a 
> simulation and then run nek5k again to load the fld files using load_fld() 
> for postprocessing? Or can one compute the desired quantities after every 
> time step using userchk() and then output them in a file? For example, how 
> can I compute the vorticity using the differential operators defined in the 
> code? After computing the vorticity, can it be outputted using the same fld 
> files?
>
> Regards,
> Mani chandra
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