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-   -   Supersonic or subsonic BC? (http://www.cfd-online.com/Forums/main/68577-supersonic-subsonic-bc.html)

kepler September 24, 2009 06:23

Supersonic or subsonic BC?
 
In my case a turbine rotor flow is to be solved. In the absolute reference frame the inlet boundary is subsonic, while in the relative reference frame the inlet boundary is subsonic because of revolution. My question is how to specify the BC, supersonic or subsonic?

ogloth September 24, 2009 11:34

If the Mach-number normal (and relative) to the inflow boundary is supersonic, take a supersonic inflow; otherwise use subsonic inflow. The same applies for the outflow boundary. In your case it probably is subsonic, assuming that the inflow boundary lies in the rotational plane.

kepler September 24, 2009 23:23

Following your advice, because the inflow boundary plane is parallel with the rotational plane, the rotation velocity doesn't have any influence for BC specification?

ogloth September 25, 2009 04:47

Correct -- what matters is the velocity normal to your boundary.

kepler September 25, 2009 05:24

Oliver Gloth, thank you very much.


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