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Old   March 22, 2010, 04:36
Default supersonic air-jet
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Dear All,
I am trying to model a fully expanded (ambient) supersonic air-jet out of a nozzle using a 2d-axisymmetric geometry. The nozzle geometry is not included in the model, only the nozzle outlet is introduced as a mass-inlet boundary condition. I am using the pressure-based coupled solver. The operating pressure is set at 101 kPa, atmospheric. Since I want total expansion at the nozzle outlet, I specify the supersonic gauge pressure as 0 at the nozzle outlet (mass-inlet BC). In the solution I obtain however, the FLUENT solver calculates the static pressure at nozzle outlet as 54 kPa. So, I cannot get a fully expanded air-jet. Is there anyone who knows what I might be doing wrong, or how to control the nozzle exit pressure?
The velocity at the nozzle outlet is above Ma 2.5. I have quite a fine mesh and a stably converged solution.

Your help is much appreciated.
Regards,
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Old   March 25, 2010, 05:31
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a small update from my side: i kept altering the mass-inlet boundary by small increments, leading to significant increase in total. as a result, the static pressure at the nozzle outlet increases, whereas the increase in velocity isn't that significant. seems weird to me. especially since I set the supersonic gauge pressure to a definite value.

i need to control the static pressure at nozzle outlet. anyone who knows what I might be doing wrong?
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