[Nek5000-users] The first time step in a Nek file must contain a mesh

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

nek5000-users at lists.mcs.anl.gov a écrit :
> Hi Can,
>
> Also note that it is better to use extention .nek5000 for your VisIt matafile instead of .nek3d where you can also drop
> the first two lines.
>
> For automatic generation of this metafile .nek5000 and running visit with it you can use the following script:
>
> http://www.mcs.anl.gov/~obabko/nekvis
>
> Best.
> Aleks
>
>
>
> ----- Original Message -----
> From: nek5000-users at lists.mcs.anl.gov
> To: nek5000-users at lists.mcs.anl.gov
> Sent: Friday, March 2, 2012 6:23:44 AM
> Subject: Re: [Nek5000-users]	The first time step in a Nek file must contain a	mesh
>
>
> Hi,
>
> Generally speaking, nek should automatically dump the geometry on step 1.
> I'm not 100% certain why that did not happen in your case.  It could be
> because your call to outpost executes on step 0 (i.e., after init. cond.
> is defined, but prior to the first step).
>
> Regarding vorticity, are you looking at a 2D case, or 3D?
>
> If 2D, for which vorticity is a scalar, I would recommend putting
> the vorticity in a temperature field and letting nek dump it.
>
>        parameter(lt=lx1*ly1*lz1*lelv)
>        common /scrns/ vort(lt*lelv,3),w1(lt),w2(lt)
>
>        call comp_vort3(vort,w1,w2,vx,vy,vz)
>
>        n=nx1*ny1*nz1*nelv
>        k=1
>        call copy(t(1,1,1,1,k),vort,n)  ! Put vorticity in temperature fld
>        ifto=.true.                     ! Tell nek to dump temperature
>
>
> ....That's all you need, because now nek will dump the other
> variables as well as vorticity, which it will put into the 
> temperature array.  If you are also doing heat transfer, you
> will need to increase k and then set ipsco(k-1) to be .true.
>
> For 3D, a separate outpost call is a good idea.  Here is a std. approach:
>
>        parameter(lt=lx1*ly1*lz1*lelv)
>        common /scrns/ vort(lt*lelv,3),w1(lt),w2(lt)
>
>
>        if (istep.gt.0.and.mod(istep,iostep.eq.0)) then
>           ifxyo=.false.
>           if (istep.eq.1) ifxyo=.true.
>           call comp_vort3(vort,w1,w2,vx,vy,vz)
>           call outpost (vort(1,1),vort(1,2),vort(1,3),pr,t,'vrt')
>        endif
>
> which puts the 3 vorticity components in the file where velocity would
> normally be.
>
> Also, it seems likely that you have param(66) and (67) set to 4 in
> your .usr file.  This is fine, but if you are using VisIt, there
> are some potential advantages to not setting these values and letting
> nek set the default (which happens automatically if you set p66 and p67
> to 0 in your .rea file and do not over-ride in the .usr file).
>
> Hope this helps,
>
> Paul
>
>
>
>
> On Fri, 2 Mar 2012, nek5000-users at lists.mcs.anl.gov wrote:
>
>   
>> Hi neks,
>>
>> I try to visualize the V.karman' vortexes by computing the vorticity field 
>> with this subroutine :
>>
>>       if(mod(istep,iostep).eq.0) then
>>       call comp_vort3(vort,work1,work2,vx,vy,vz) 
>> call outpost(vort(1,3),vort(1,2),vort(1,1),pr,t,'vrt')
>>       endif
>> Which works but, when i try to post-processes the data with Vizit i got the 
>> fallowing error message :
>>
>> "The first time step in a Nek file must contain a mesh"
>>
>>
>> i try to open my vrt[mycase].fld* files with vis.nek3D which contains
>>
>> NEK5000
>> version 1.0
>> filetemplate: vrtvkarman2.fld%02d
>> firsttimestep: 1
>> numtimesteps: 2
>>
>> Is there a way to fix this ?
>> Sorry for my poor english ..
>> B.regards
>> Can
>>
>> _______________________________________________
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>> Nek5000-users at lists.mcs.anl.gov
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>>
>>     
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>   
Thank you very much to both of you, these are really useful infos :)
But i got another question, i can visualize now the vorticity field, but 
i don't see any v.karman vortexes, i just see some vortexes around my 
circle (diameter 1) obstacle.
My bc are as follow : unit-diameter cylinder is centered at (0,0) in a 
box on [-15,35] x [-15,15]. (picked up the .rea on the ext_cyl example)
left : velocity inlet with 1m/s
right : pressure output
top and bottom , periodic
Re= 160 (>50 for the instability)
dt=0.01
End of simulation Time = 550
can this be because of the meshe not being tight enough ??
B.regards
Can