[Nek5000-users] Specifying boundary condition for Annulus Geometry in box file

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

Hi Ravi,

I came across this issue recently as well. I found that you are correct
about the first and second BC. However, the third and the fourth, I do not
know what they are. I tried to find it with prex, but nothing turns out.

However, when I merged it with another mesh, it played a role, which
modified the whole mesh BC, so I have a bad global BC. I do not see where
is the problem. I think there is some isssue with pretex.

Cheers,

Tubois

On Fri, Mar 14, 2014 at 2:43 AM, <nek5000-users at lists.mcs.anl.gov> wrote:

> Hi All,
>
> We are trying to build a mesh to simulate external cylinder flow, similar
> to the one given in the example "ext_cyl". Searching though the
> documentation, we understand that it is possible to generate several boxes
> of mesh using genbox and combine using pretex to get the final mesh.
>
> We are having difficulty in interpreting the boundary condition (BC)
> strings in the input to files to genbox. It is clear for a rectangular box,
> the BC string follows the order West, East, South, and North in 2D. What is
> the analogous interpretation for a circular annulus geometry? such as for
> the one defined by the box files given in "primer.pdf" (
> http://www.mcs.anl.gov/~fischer/primer.pdf), which is repeated below:
>
> x2d.rea
> 2 spatial dimension
> 1 number of fields
> #
> # comments
> #
> #
> #========================================================
> #
> Y         cYlinder
> 3 -24 1     nelr,nel_theta,nelz
> .5 .3         x0,y0 - center of cylinder
> ccbb         descriptors: c-cyl, o-oct, b-box (1 character + space)
> .5 .55 .7 .8     r0 r1 ... r_nelr
> 0 1 1         theta0/2pi theta1/2pi ratio
> v ,W ,E ,E ,     bc's (3 characters + comma)
>
>
> Does "v" corresponds to BC at r0 and W correspond to BC at r_nelr in
> r-direction and the two E's correspond to BC at theta0 and theta1?
>
> Thanks in advance for your help.
>
> Regards,
> Ravi
>
>
>
>
>
>
>
>
>
> --
> Ravi Kumar T R
>
> University of Illinois at Urbana-Champaign
> ph : +1 217 778 7538
> http://lndvl.mechse.illinois.edu/
>
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