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Supersonic or subsonic BC?

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Old   September 24, 2009, 06:23
Default Supersonic or subsonic BC?
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chung yang
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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?
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Old   September 24, 2009, 11:34
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Oliver Gloth
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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.
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Old   September 24, 2009, 23:23
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chung yang
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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?
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Old   September 25, 2009, 04:47
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Correct -- what matters is the velocity normal to your boundary.
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Old   September 25, 2009, 05:24
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Oliver Gloth, thank you very much.
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