[Nek5000-users] Nonzero swirl velocity at the centerline

[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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>>> 
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