[Nek5000-users] [*] Re: Postprocessing

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

Hi Mani,

Nek currently supports only a few output fields:

X, V, p, T, ps1, ... ,psn

X = coords
V = velocity
p = pressure
T = temperature
psj = jth passive scalar

The call

        call outpost(vort(1,1),vort(1,2),vort(1,3),pr,t,'vrt')

would generate a file "vrtmycase0.f..." with vorticity
components in place of V=(vx,vy,vz).

To view these with visit, load the vrt... file and request
to look at "velocity"  (VisIt thinks the field is a velocity
field).

Paul


On Sat, 27 Mar 2010, nek5000-users at lists.mcs.anl.gov wrote:

> On 03/24/2010 09:58 PM, nek5000-users at lists.mcs.anl.gov wrote:
>> 
>> 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
>>> _______________________________________________
>>> Nek5000-users mailing list
>>> Nek5000-users at lists.mcs.anl.gov
>>> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
>>> 
>> _______________________________________________
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>> 
> Dear Paul,
>
>    The files generated by the code in usr_chk(), vrtmy_case0.f* do not seem 
> to have vorticity in them when I view them in Visit through the database 
> file. They only seem to have pressure, x, y, z components of velocity and the 
> velocity magnitude. Could something be wrong?
>
> Mani chandra
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