[Nek5000-users] Nonzero swirl velocity at the centerline

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

Dear Neks,

It turns out that an update for the latest version (r862) solved my  
problem. I am sorry for wasting your time. However, I was running r831  
(5 months old) and could not see any posts about this lately. Maybe  
this issue also was fixed at the same time as the spherical shell in  
September?

The main difference between r831 and r862 seems to be in bdry.f, line 2060:
            IF  (CB.EQ.'T  ' .OR. CB.EQ.'t  ' .OR.
      $          (CB.EQ.'A  ' .AND. IFAZIV)    .OR.
      $           CB.EQ.'MCI' .OR. CB.EQ.'MLI' .OR.
      $           CB.EQ.'KD ' .OR. CB.EQ.'kd ' .OR.
      $           CB.EQ.'ED ' .OR. CB.EQ.'ed ' .OR.
      $           CB.EQ.'KW ' .OR. CB.EQ.'KWS' .OR. CB.EQ.'EWS')
      $           CALL FACEV (TMASK(1,1,1,1,IPSCAL),
      $                       IEL,IFACE,0.0,NX1,NY1,NZ1)

In version r831, the part (CB.EQ.'A ' .AND. IFAZIV) was missing, as I  
already suspected.

In any case, this shows the importance of updating regularly, and I am  
sorry for the interruption.

Outi

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

> I have just done that.
> Thank you very much.
>
> Outi
>
> 6 Oct 2012 kl. 23:56 skrev nek5000-users at lists.mcs.anl.gov:
>
>>
>> Thanks... would you mind sending a gzip'd tarfile with
>>
>> SIZE
>> box file
>> rea file
>> usr file
>>
>> to me offline?
>>
>> Best regards,
>>
>> Paul
>>
>>
>> On Sat, 6 Oct 2012, nek5000-users at lists.mcs.anl.gov wrote:
>>
>>> Dear Paul,
>>>
>>> Thank you for the suggestion, but the prescribed profile is just  
>>> an inlet profile, and I do get a correct profile at the inlet.
>>> The nonzero swirl velocity at the centerline appears downstream.
>>>
>>> Outi
>>>
>>> 6 Oct 2012 kl. 23:42 skrev nek5000-users at lists.mcs.anl.gov:
>>>
>>>> Dear Outi,
>>>> If you are prescribing your u_theta (i.e., as temperature),
>>>> then from your formula below it should be zero on the axis.
>>>> One thing that might be of value (for small problems) is
>>>> to add to userbc the statements below
>>>>
>>>>    if (ifield.eq.2) write(6,1) x,y,temp
>>>>  1 format(1p3e13.5,' uxyz')
>>>>    if (istep.eq.2) stop
>>>> You can then grep uxyz logfile and look at what is going on.
>>>> You should see that, for y=0, you match your desired profile.
>>>> Paul
>>>> On Sat, 6 Oct 2012, nek5000-users at lists.mcs.anl.gov wrote:
>>>>> Dear Paul,
>>>>> I use the "A  " BC.
>>>>> And the new mesh generated by genbox.
>>>>> Outi
>>>>> 6 Oct 2012 kl. 23:28 skrev nek5000-users at lists.mcs.anl.gov:
>>>>>> Dear Outi,
>>>>>> Do you have the "A  " bc on your elements that touch the centerline?
>>>>>> Are you using the same mesh as vortex2? Or a new one generated with
>>>>>> genbox.
>>>>>> In principal, the A bc should set U_theta=0 on the axis.
>>>>>> Paul
>>>>>> On Sat, 6 Oct 2012, nek5000-users at lists.mcs.anl.gov wrote:
>>>>>>> Dear Neks,
>>>>>>> I have started to use the 2D axisymmetric version of Nek5000  
>>>>>>> with swirl (like the example vortex2), to get some base flows  
>>>>>>> in axisymmetric geometries.
>>>>>>> To test the code I modified the vortex2 example to simple  
>>>>>>> Grabowski vortex flow.
>>>>>>> This means setting the inlet profile:
>>>>>>> U_x=1
>>>>>>> U_r=0
>>>>>>> U_theta=0.8944r(2-r^2)
>>>>>>> The result looked good at the first sight, but a closer  
>>>>>>> inspection revealed that the swirl velocity (U_theta) is  
>>>>>>> nonzero at the centerline (up to U_theta=0.1). Also other  
>>>>>>> axisymmetric flow cases with swirl gave nonzero swirl  
>>>>>>> velocities.
>>>>>>> I wonder if it would be possible for someone to look into why  
>>>>>>> this happens? I have attached the .usr, .rea and .box files  
>>>>>>> below.
>>>>>>> Also, it would be useful if you could guide me into the  
>>>>>>> precise place in the code where the centerline condition for  
>>>>>>> swirl is set. Does OMASK have something to do with this? Or is  
>>>>>>> it TMASK?
>>>>>>> Outi
>>>>>> _______________________________________________
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