I am asking essentially a follow up to this very good question and answer Static Pressure in a Venturi vs a Free stream

And this Is the static gauge pressure of a free jet always atmospheric?

If I have a free jet that is subsonic, say simply the exhaust of a hair drier (operating with no heat), how does the jet pressure vary longitudinally along its axis, as it decelerates from moving to rest? It has the same ambient pressure matching requirement at the beginning and end of the jet, yet does its deceleration affect its pressure?

Also, how would this be different in an optimally expanded rocket nozzle exhaust – supersonic but pressure matched?

  • $\begingroup$ Are you talking about a jet of liquid or a jet of gas? $\endgroup$ Oct 6, 2021 at 15:29
  • $\begingroup$ I had gas in mind, but I think the question applies to both (other than the supersonic case) $\endgroup$
    – RC_23
    Oct 6, 2021 at 17:25


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