[overture] Re: Compressible flow over 2-d airfoil

  • From: Daniel Appelo <appelo@xxxxxx>
  • To: "overture@xxxxxxxxxxxxx" <overture@xxxxxxxxxxxxx>
  • Date: Fri, 17 Jul 2009 21:35:50 -0700

Dear Praven,
depending on what you want to do it might work fine to just apply grid stretching and add some artificial viscosity, the higher order the better, rather than using low-order non-reflecting bc.
You can take a look at http://www.its.caltech.edu/~appelo/preprints/HOSGS.pdf to see how it works for linear systems, you can also look at the original super-grid paper by Tim [9] which is designed for cns. Ref. [28] is also relevant. 

Daniel


On Jul 17, 2009, at 8:55 PM, Bill Henshaw wrote:


Dear Praveen,

  Unfortunately there are no characteristic boundary conditions
implemented (We have never really used cgcns very much for external
aerodynamic flows). If you enclose your airfoil in a big rectangle
(or multiple rectangles) then you may be able to use the existing
BC's

Regards,
  Bill


Praveen C wrote:

Thanks. I now understand this a little better and able to do some
computations. Are there any characteristic-based boundary conditions
available in cgcns ? What type of BC would I use for compressible flow for a curved outer (farfield) boundary. I may not know the direction of 
the velocity there since the boundary is curved.

Thanks
praveen

praveen

On Wed, Jul 15, 2009 at 9:05 AM, Bill Henshaw <henshaw@xxxxxxxx
<mailto:henshaw@xxxxxxxx>> wrote:

   Dear Praveen,
    Sorry, that error message is not very good. Try using
backGround(1,0)=subSonicOutflow mixedDerivative(1.*t +1.*t.n=300.) 

   as in cg/cns/cmd/cicSubSonic.cmd

   Regards,
    Bill

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