[Nek5000-users] quasi 3D and boundary condition

Sun Jun 15 22:34:07 CDT 2014

Hi,

In that case, you need to use the stress formulation and the net result
is U.n_hat = 0 and d/dn (U.t_hat) = 0, where t_hat constitutes the two tangent
vectors.

I've not tried this myself but I assume it works - it was written by Lee W. Ho
when we were graduate students and I believe that others have used it.

If I were you I would do a small test case in 2D first. -- I just tried it and it
worked ok... you need to set ifstrs T in the .rea file and lx1m=lx1, etc. in
the SIZE file.

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: Sunday, June 15, 2014 10:13 PM
To: nek5000-users at lists.mcs.anl.gov
Subject: Re: [Nek5000-users] quasi 3D and boundary condition

Hi Paul

but for curved boundary, how you do so? I want to know the formula for what you mentioned as stress formula.

cheers
----------------------------------------------
Zhang Wei
waynezw0618 at gmail.com

On 16 Jun, 2014, at 11:09 am, nek5000-users at lists.mcs.anl.gov wrote:

>
> Assuming that the surface normal is x, y, or z, then it is simply
>
>  U.nhat = 0
>
> and Neumann on the other two boundaries.
>
> 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: Sunday, June 15, 2014 9:15 PM
> To: nek5000-users at lists.mcs.anl.gov
> Subject: Re: [Nek5000-users] quasi 3D and boundary condition
>
> Hi Paul
> what is implementation of SYM BC in NEK5000? I mean the variation formula.
>
>
> cheers
> ----------------------------------------------
> Zhang Wei
> waynezw0618 at gmail.com
>
>
>
> On 9 Jun, 2014, at 4:15 am, nek5000-users at lists.mcs.anl.gov wrote:
>
>>
>> Hi Zhang,
>>
>> There is no support for 2.5D with Fourier in z and currently no plans to move in that direction.
>>
>> If you want a slip velocity on the curved surface you should use the stress formulation (lx2=lx1-2, etc.,
>> with ifstrs T.   Then the "SYM" bc should give you the desired bc, i.e., U.nhat = 0, d/dn (U.t_hat) = 0.
>>
>> 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: Sunday, June 08, 2014 10:03 AM
>> To: nek5000-users at lists.mcs.anl.gov
>> Subject: Re: [Nek5000-users] quasi 3D and boundary condition
>>
>> Hi Paul
>> Thanks for replying.
>> for quasi-2D, I mean I wish to define the  velocity u(x,y,z) as sum(u(x,y,k)e^kz) to reduce the computational cost for really 3D case and also to avoid the long wave (which may longer then the geometry size in the z direction) in the axial direction.does nek currently support such feature?
>>
>> for prescribe the bc on curl surface, I mean something like non-immersed bc and and have velocity component in the tangential direction, like in the potential theory.
>>
>>
>>
>>
>> cheers
>> ----------------------------------------------
>> Zhang Wei
>> waynezw0618 at gmail.com
>>
>>
>>
>> On 8 Jun, 2014, at 10:44 pm, nek5000-users at lists.mcs.anl.gov wrote:
>>
>>>
>>> Hi Zhang,
>>>
>>> You can use periodic boundary conditions in the z direction, provided you have at least 3
>>> elements in z.
>>>
>>> Prescribed boundary conditions are given in Cartesian coordinates.  If you have the "mv "
>>> bc on your moving surface (i.e., the cylinder surface), along with the following things
>>>
>>>     lx2=lx1-2
>>>     ly2=ly1-2
>>>     lz2=lz1-2
>>>
>>> parameter (lx1m=lx1,ly1m=ly1,lz1m=lz1)
>>>
>>> in SIZE, and T ifstrs, T ifmvbd in the .rea file, then the mesh will move with the fluid
>>> velocity (which you prescribe as Cartesian velocity vectors, u,v,w).    Note that nek
>>> uses an ALE formulation and the mesh motion must relatively limited or the mesh
>>> becomes too distorted.   For an oscillating cylinder, this should be ok (see
>>> www.mcs.anl.gov/~fischer/ocyl.gif).    I've just added a 2D oscillating cylinder case
>>> that illustrates the basic procedure to the examples suite.
>>>
>>> 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: Sunday, June 08, 2014 8:40 AM
>>> To: nek5000-users at lists.mcs.anl.gov
>>> Subject: [Nek5000-users] quasi 3D and boundary condition
>>>
>>> Hi Everyone.
>>> I am trying to run the flow past a cylinder case. I am going to move to the 3D simulation for my study. I have two questions:
>>> 1) how to run quasi 3D simulation in nek5000 ? if there is not existing code, andy suggestion to how to implement so?
>>> 2) how to specify the normal and tangential boundary condition for a curvature boundary?
>>>
>>>
>>> cheers
>>> ----------------------------------------------
>>> Zhang Wei
>>> waynezw0618 at gmail.com
>>>
>>>
>>>
>>> _______________________________________________
>>> 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
>>
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>
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