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B.C. for Supersonic inlet ?

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Old   December 3, 2007, 13:47
Default B.C. for Supersonic inlet ?
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In order to use a supersonic inlet, one needs to specify : 1) either relative static pressure or total pressure 2) an inlet velocity. I am trying to get my mind around this... Because, under subsonic flow, it's either a pressure or a velocity inlet. As I understand, specifying one or the other will allow you to solve for the other.

Would anyone be able to explain why both are needed for supersonic inlet? and how would one find a suitable/reasonable combination for both (low rel. pressure + high velocity or high rel. pressure + low velocity or low rel. pressure and low velocity)?

Thanks in advance.


p/s: I know under supersonic flow, velocity tends to be > 340 m/s. I am taking that high velocity is > 1000 m/s.
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Old   December 3, 2007, 16:27
Default Re: B.C. for Supersonic inlet ?
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A subsonic bc only requires p or v and T. What you do not specify (of p or v) is solved for. if you specify v then p must be specified somwhere else (eg: at an outlet bc).

A supersonic bc requires that p, v and T are all specified because the entire flow cannot depend on the downstream values. eg: the outlet pressure cannot be felt by the inlet in this case (due to supersonic flow).

p or T can be total or static. If they are total, the static conditions are easily derived.

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