[Nek5000-users] Problem with Genmap

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

Hi Holly,

I've posted this back to the list since it doesn't involve big
data files and the resolution of the problem might be of interest
to others.

I think I see what's going on and have a couple ideas to fix it.

Most likely, the reduction attained with 50 elements and a geomtric 
progression of 0.7 is wreaking havoc either in the .rea file or in
the tolerances within genmap.  A significant issue here is that
the file format in the .rea file is in limited precision --- I think
we can change that with little difficulty and still be compatible
with the workflow.   We'll look into that on our end.

A reasonable work-around, which is what I typically do, would be
to rescale your element coordinates inside nek, and just use a 
uniform mesh as the input.   I'll send along some code on how to
do this shortly --- along with another approach that will also
give you focused resolution at the origin without the high aspect
ratio elements that will result from the tensor-product approach
used here.

Paul



On Wed, 26 Jun 2013, Holly Johnson wrote:

> Hi Paul,
>
> My mesh is actually quite simple, I've had to reduce it from a much more 
> complicated version because Visit couldn't handle the number of elements I 
> was using.
>
> This is my .box file :
>
> linear.rea
> 2
> 1
> #
> #      linear.box
> #
> Box
> -50 -50
> -3. 0. 0.7
> -3. 0. 0.7
> SYM,   ,v  ,
> Box
> -50 -50
> -3. 0. 0.7
> 0. 3. 1.3
> SYM,   ,   ,O
> Box
> -50 -50
> 0. 3. 1.3
> -3. 0. 0.7
>   ,SYM,v  ,
> Box
> -50 -50
> 0. 3. 1.3
> 0. 3. 1.3
>   ,SYM,   ,O
>
> I get the error for any mesh tolerance value when the scaling coefficients 
> are _<_ 0.7 or _>_ 1.3. However it works fine for _>_0.8 and _<_1.2. I assume 
> therefore it is that the elements of the mesh near the center of the grid are 
> just too small?
>
> Thanks again for your help,
>
> Holly
>
> Holly Johnson
> Masters Student at ONERA - DAFE
> Département d'Aérodynamique Fondamentale et Expérimentale
> 8, Rue des Vertugadins
> 92190 - Meudon - France
>
>