[Nek5000-users] Nonzero swirl velocity at the centerline

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

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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