[Nek5000-users] SYM boundary conditions

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

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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