PPRuNe Forums - View Single Post - Jet thrust - how long?
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Old 11th October 2005 | 08:16
  #15 (permalink)  
Mark 1
 
Joined: Aug 2000
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From: S Warwickshire
I don't understand the last reply. Thrust is the reaction to momentum change through the nozzle - jet noise is due to the turbulence and vorticity of the shear layer between the exhaust and surrounding air.

At high powers, the exhausts are just below sonic velocities (supersonic nozzles being mostly a military preserve); that is about 600 knots for the fan nozzle and 700-900 knots for the hot core exhaust.

Typically this will expand to about 3 times the diameter or 10 times the area over about 30m, so the relative velocities should be about 60-90 knots at that distance.
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