[Nek5000-users] SYM boundary conditions

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

Is this an internal flow, or external flow?

If internal, you can use the turn_outflow() routine with sufficient divergence to ensure
that the flow is always leaving the domain.  We use this for some of our moving domain
simulations.

Paul

________________________________________
From: nek5000-users-bounces at lists.mcs.anl.gov [nek5000-users-bounces at lists.mcs.anl.gov] on behalf of nek5000-users at lists.mcs.anl.gov [nek5000-users at lists.mcs.anl.gov]
Sent: Wednesday, February 10, 2016 8:04 AM
To: nek5000-users at lists.mcs.anl.gov
Subject: Re: [Nek5000-users] SYM boundary conditions

ok, I see. If it is turbulent, then it is a bit more difficult. You can
try ON, but perhaps it will not work. But in the real case, what type of
inflow are you going to have, something turbulent? What about damping
the turbulence before it actually reaches the outflow boundary, e.g.
using a forcing? ONce it is laminar, I think that ON could work.

Philipp

On 2016-02-10 13:02, nek5000-users at lists.mcs.anl.gov wrote:
> Yes, it is turbulent...
>
> I will try to use ON. Please, could you help me to understand a bit more
> why it could work?
>
> Thanks again!
> Cheers
> SL
>
>
> El 10-02-2016 12:17, nek5000-users at lists.mcs.anl.gov escribió:
>> one initial suggestion would be to use ON at the outflow. Is the flow
>> turbulent at the outflow boundary?
>> Philipp
>>
>> On 2016-02-10 11:45, nek5000-users at lists.mcs.anl.gov wrote:
>>> Hi,
>>>
>>> Thank you. I am trying to simulate a flow whose inlet boundary condition
>>> is time periodic ux=sin(omega*time). Since there is an injection and a
>>> suction, and the mean flow is zero, I think that the boundary conditions
>>> should let the transpiration/penetration of the flow... (I have tried to
>>> run the simulation using outflow BC but it crashes). Is there any BC
>>> condition in Nek5000 that suits to this problem?
>>>
>>> Thank you for your help in advance.
>>> Best regards,
>>> SL
>>>
>>> El 10-02-2016 10:20, nek5000-users at lists.mcs.anl.gov escribió:
>>>> Hi,
>>>> SYM is essentially means that the velocity through the interface is
>>>> zero and for the inplane velocities that the normal gradients vanish.
>>>> So it does not allow transpiration/penetration through the boundary.
>>>> So I suspect that this condition is not what you are looking for.
>>>>
>>>> However, I am not exactly sure what you really mean. Perhaps you can
>>>> say a bit more about your case?
>>>>
>>>> Best regards,
>>>> Philipp
>>>>
>>>> On 2016-02-10 08:02, nek5000-users at lists.mcs.anl.gov wrote:
>>>>> Hi Neks,
>>>>>
>>>>> I am looking for a boundary condition that leads the flow to go out or
>>>>> to go into the domain.
>>>>>
>>>>> Is 'SYM' valid for this purpose?
>>>>>
>>>>>
>>>>> I think that what I am looking for is, in the outlet surface:
>>>>>
>>>>>    - If the velocity vector at the outlet points out of the domain,
>>>>> then
>>>>> the boundary condition for the velocity will be of the Neumann type
>>>>>
>>>>>    - However, if the velocity at the outlet points into the domain,
>>>>> then
>>>>> we can imagine that the outflow is no longer an outflow, but an
>>>>> inflow,
>>>>> and that we therefore would like to specify a Dirichlet boundary
>>>>> condition for velocity
>>>>>
>>>>>
>>>>> Thanks in advance
>>>>> SL
>>>>>
>>>>> _______________________________________________
>>>>> Nek5000-users mailing list
>>>>> Nek5000-users at lists.mcs.anl.gov
>>>>> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
>>>> _______________________________________________
>>>> Nek5000-users mailing list
>>>> Nek5000-users at lists.mcs.anl.gov
>>>> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
>>>
>>>
>>>
>>> _______________________________________________
>>> Nek5000-users mailing list
>>> Nek5000-users at lists.mcs.anl.gov
>>> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
>> _______________________________________________
>> Nek5000-users mailing list
>> Nek5000-users at lists.mcs.anl.gov
>> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
>
>
> _______________________________________________
> Nek5000-users mailing list
> Nek5000-users at lists.mcs.anl.gov
> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
_______________________________________________
Nek5000-users mailing list
Nek5000-users at lists.mcs.anl.gov
https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users