[Nek5000-users] quasi 3D and boundary condition

Sun Jun 15 22:39:35 CDT 2014

You can find Lee Ho's MIT Ph.D. thesis online - 1989.

It's really just the variational formulation for the Stokes operator.

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 10:36 PM
To: nek5000-users at lists.mcs.anl.gov
Subject: Re: [Nek5000-users] quasi 3D and boundary condition

Hi Paul.
is there any paper of about that? I would know more math work of this implementation.
cheers
----------------------------------------------
Zhang Wei
waynezw0618 at gmail.com

On 16 Jun, 2014, at 11:34 am, nek5000-users at lists.mcs.anl.gov wrote:

>
> 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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