[Nek5000-users] Nonzero swirl velocity at the centerline

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

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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