[Nek5000-users] ON boundary condition

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

Hi Adam,

What BC do you use for Simpson?  Can you use the same for nek?

I would assume some sort of sponge condition would be warranted.
I personally like the div > 0 condition, which works well for
turbulent outflow, but I've not tested it extensively for the
issues that you are having.  I'm guessing you might have more
luck with the std. sponge approach.  Please let me know if I
can help, though I think that most of the sponge expertise is
there in your lab.

Best regards,

Paul


On Thu, 16 Feb 2012, nek5000-users at lists.mcs.anl.gov wrote:

> Hi Paul
>
> Thank you for info. I'm using ON at the top of my box for jet in
> crossflow (it was originally in the setup I've got from Milos and I
> simply didn't change it) and it seem to work fine (I use Pn-Pn-2). My
> bigger problem is an outflow. I'm using O, but in many cases it gives
> reflections that trigger spurious oscillations, so I was looking for
> something better. To avoid this problem I run my simulations in the long
> box with an outflow 150 away from the pipe. It's a lot comparing to 60
> in simson. Every run with the distance smaller than 100 gives
> nonphysical solutions. Is there in nekton some good non reflecting
> boundary condition?
> Best regards
>
> Adam
>
> On Wed, 2012-02-15 at 08:33 -0600, nek5000-users at lists.mcs.anl.gov
> wrote:
>> Hi Adam,
>>
>> I set up ON bc some years back to support Blasius boundary layer
>> analysis in which the tangential (streamwise) velocity is
>> prescribed and the wall-normal velocity is allowed to escape
>> as the velocity boundary layer thickens.  This also implies
>> that the pressure is fixed on the upper surface.   This feature
>> was developed  for Pn-Pn-2 and hasn't been extensively tested
>> in many years.   If this is a feature that you need, we could
>> look into resurrecting it.  (Note that the "escaping" feature
>> implies that the surface is aligned with either x,y, or z, and
>> not inclined w.r.t. these principal axes.)
>>
>> Cheers,
>>
>> Paul
>>
>>
>>
>> On Tue, 14 Feb 2012, nek5000-users at lists.mcs.anl.gov wrote:
>>
>>> Hi all
>>>
>>> I try to find some information about ON boundary condition in nekton.
>>> What is the difference between O and ON?
>>> Regards
>>>
>>> Adam
>>>
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