[Nek5000-users] quasi 3D and boundary condition

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

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
>
>
>
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