Flow in a nozzle : When Pe = Pb ?

aero2020

Hello every one !

We have a compressible flow in a nozzle ( convergent , CD, any way ...) . Can you tell me please in which case :

Back pressure Pb is equal to Exit pressure Pe ?

Thank you

rahkumar

Hello,

This is the condition when there is no shock wave present in the nozzle or at the nozzle exit. It's a perfectly expanded flow.

rahkumar

Yes, true! In essence, it is perfectly expanded.

rahkumar

Hello,

This is the condition when there is no shock wave present in the nozzle or at the nozzle exit. It's a perfectly expanded flow.

aero2020

Ok Thank you .

Just for information , i have found also this information :

Pb = Pe when the flow is perfectly expanded to the back pressure ( after a shock ). I mean here that the shock can exist even before the exit. Remember that to have an over expanded flow :

Pb/P0 ( Super Sonic) <Pb/P0< Pb/P0 (Normal Shock Exit)

Please check the link below ( 2:59)

https://www.youtube.com/watch?v=b0wvwkKqoVw&t=267s

rahkumar

Yes, true! In essence, it is perfectly expanded.