[Nek5000-users] rotating disk with periodic boundaries

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

Dear Ellinor,

Yes, there are some topological issues that arise with your
configuration.

In fact, what you would need is to zero out two velocity
components that are orthognal to the axis and leave
the 3rd component floating.

Let me look into the possibilities and see if we can resolve 
it -- no guarantees, as it tends to be a difficult problem.

I am tied up the next few days but can hopefully look at this
within a week.

Paul




On Wed, 28 Mar 2012, nek5000-users at lists.mcs.anl.gov wrote:

> Dear nek users,
> I am doing simulations over a rotating disk with nekton and would like to
> decrease my domain in order to save computational time.
>
> The mesh is currently very similar to that of a pipe, with inflow in one
> end
> (max(z)) and a rotating wall in the other end (z=0). Around the curved
> edges I use the outflow boundary condition.
>
> The way I would like to decrease the domain in is by using periodic
> boundary conditions in the rotational direction, that is cutting the
> pipe in the
> z-direction to only use a third or a quarter of the pipe.
>
> My problem is that when I try to do this, I have to make one element
> periodic
> with itself, this is since I would like to have few elements in the
> middle of
> the domain and thus not want to use the cylindrical coordinates.
>
> In some setups, I recieve an error when using genmap (when trying
> different mesh
> tolerance numbers), and in some setups I get a communication error when
> running
> the code;
>
>
> genmap error:
>
>  4   z1    0.0000E+00  1.5224E-01  1.5224E-01  0.0000E+00
>       2 3  3  1.00000005E-03  1.00000000E+00 abort: FACE MATCH FAIL
>       7 4  5  1.00000005E-03  2.54558474E-01 abort: FACE MATCH FAIL
>
>
> communication error:
>
> veryfy mesh topology ...
> ...
> ...
> WARNING1 Element mesh mismatch at:
> i,j,k,ie:    1    1    1    1
> Near X = 0.59397000    0.59397000    0.00000000    , d:    0.0000000
> -0.11313799    1.4142136
> ...
> ...
>
>
>
> The type of error seem to depend on how the elements are numbered in the
> domain.
>
> I've understood that for using the periodic boundary conditions, one
> need at
> least three elements. Is there a way around this when it comes to my setup?
> Or would there be an easy fix for this problem?
>
>
> Best regards,
> Ellinor
>