[overture] Re: False Shown Physical Boundaries

  • From: Bill Henshaw <henshaw@xxxxxxxx>
  • To: overture@xxxxxxxxxxxxx
  • Date: Sun, 12 Jul 2009 20:21:19 -0700

Dear Matt,

  At some point the plotting of mixed boundaries was broken. Here is the fix:

Change Overture/ogshow/grid.C around line 463 from

--- old:

        if( parameters.gridOptions(grid) & 
GraphicsParameters::plotInteriorBoundary )
          ISinteriorBoundaryPoint=0;
        else
          ISinteriorBoundaryPoint=MappedGrid::ISinteriorBoundaryPoint;

---- new:

        if( parameters.gridOptions(grid) & 
GraphicsParameters::plotInteriorBoundary )
          ISinteriorBoundaryPoint=MappedGrid::ISinteriorBoundaryPoint;
        else
          ISinteriorBoundaryPoint=0;
-------

After making the change just type 'make' from the main Overture directory.

As a note, to send *.cmd files just rename them to *_cmd for example.


  Convex corners are a contentious issue in my mind. I am
going to rant a bit here but don't take it personally :)
The bottom line is that you are fooling yourself if you
think you are getting an accurate answer near the sharp convex
corner.

I always recommend that the corners be rounded off slightly.
As the mesh is refined the corner can be made sharper if
desired. In this case more and more grid points are added
to resolve the corner where the solution changes rapidly.
You thus will get an accurate answer to a slightly wrong geometry
rather than the wrong answer to the right geometry.


Regards,
  Bill

matthew fuller wrote:


    Hi,
    I have a few questions about some false physical boundaries which
are plotted when using cgins. 
    To begin, i am mapping a flatback airfoil. Essentially it is an
    airfoil with the trailing edge chopped off. This in itself proved
    difficult to grid given my limited knowledge of ogen mappings and
    ogens seemingly limited ability to map around sharp corners. None
    the less i was able to get a very sharp flat trailing edge using
    shared sides, mixed boundaries, and no hole cutting. Ogen indicates
    my mappings overlap properly. But, when i read in this grid file to
    cgins the mixed boundary that i specified is still plotted as a
    physical boundary. To be clear i can tell by the flow field that
    these "false" physical boundaries are not actually recognized by
    cgins. They do however look strange and raise questions to their
    origin and significance. I have found that by disabling boundary
    plotting completely whilst in cgins gets rid them but it also gets
    rid of the airfoil boundary. This make its harder to see where the
    airfoil stops and the flow field begins.

    My question is, is there a way to change the representation of these
    mixed boundary boundaries in ogen to prevent them from showing up
when running a simulation? I have attached a screen shot to show what i mean. Unfortunately 
    the email client i am using (Gmail) will not let me send .cmd files
    (for fear of malware i suppose) so i can not send my ogen and cgins
    command files.

    I would appreciate any insight you can provide on this issue.

    Thanks!
    Matt



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