[Nek5000-users] SYM boundary conditions

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

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
>>>
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