[Nek5000-users] Passive Scalar Initialization

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

Hi,

I'm deeply grateful for your help. I have another question regarding  
I/O procedure. At each time and on every grid point, I calculate some  
angles (scalar quantities) which are functions of the vorticity and  
their own values from the previous time step. I need to store the  
values of these angles at the last time step (preferably in a separate  
file) and then recall those values after restating the simulation. I  
think I should use outpost2 to store the values, but I'm not sure how  
to open a different file other than fld file and then how to read that  
file to be consistent in parallel. I wonder if you have any hint.


Regards,
Alireza





Quoting nek5000-users at lists.mcs.anl.gov:

>
> Hi Alireza,
>
> userchk() is the correct place to intervene.
>
> It is called after the end of each timestep, including "Step 0",
> which constitutes the initialization.
>
> Hence, on step 0, you have the chance to reset any variable prior
> to the start of Step 1, without worry of it being overwritten by
> some other initialization phase.
>
> So, I would do the following in userchk, for the particular
> instance of when you want to do your initialization.
>
>
>       n=nx1*ny1*nz1*nelt
>
>       if (istep.eq.0) then
>          do i=1,n
>             x=xm1(i,1,1,1)
>             y=ym1(i,1,1,1)
>             z=zm1(i,1,1,1)
>             t(i,1,1,1,1) = x*x + y-z  (or whatever...)
>          enddo
>       endif
>
> If you instead would wish to read a result in from a .fld file,
> this can also be done.  You simply modify your .rea file to
> read 2 files instead of one.  The first can have the velocity
> and the second the passive scalar, say.
>
> Cheers,
>
> Paul
>
>
> On Sun, 15 Jul 2012, nek5000-users at lists.mcs.anl.gov wrote:
>
>> Hi,
>>
>> Thanks for your hint. So, how can I reinitialize the PS after some  
>> time? Should I call useric at userchk? And as I have two passive  
>> scalars, how can I make sure that just one of them is initialized  
>> and the other one and the flow field are read from the restarting  
>> fld file?
>>
>> Thanks again.
>>
>> Regards,
>> Alireza
>>
>>
>>
>>
>>
>> Quoting nek5000-users at lists.mcs.anl.gov:
>>
>>>
>>> Hi Alireza,
>>>
>>> You can alway reinitialize any field, so either start with or without,
>>> whichever is easiest.  If it's a long and expensive run (esp. from
>>> a passive scalar standpoint, for example if you have very low Pr), then
>>> you might choose to not carry the PS along till you get to your desired
>>> background flow state.  Otherwise, PS typically costs much less than the
>>> hydro, so carrying PS along is not an excessive burden and the setup
>>> and logistics overhead is sometimes easier just to deal with it at
>>> the outset.
>>>
>>> I hope this helps.
>>>
>>> Cheers,
>>>
>>> Paul
>>>
>>>
>>> On Sun, 15 Jul 2012, nek5000-users at lists.mcs.anl.gov wrote:
>>>
>>>> Hi,
>>>>
>>>> I want to start solving the passive scalar equation after the  
>>>> background flow field has reached certain characteristics. Is it  
>>>> possible to defer the solution of the passive scalar and then  
>>>> initialize it at sometime t>0? In this case, should I include the  
>>>> passive scalar boundary condition data in the rea and usr files  
>>>> from the beginning?
>>>>
>>>> Thanks for your help.
>>>>
>>>> Regards,
>>>> Alireza
>>>>
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>>
>>
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