WOW!!

this question started off benign enough but after reviewing several patents, i am intimately convinced that almost everyone is right regarding their different thinking on this subject. your particular discipline may determine your original line of thinking. i was convinced that it had a lot (or mostly) to do with speed based on what i was told by a respected instructor (and no the info wasn't free and also, u don't need airspeeed input into the engine...there are other ways of determining that based on the prior equation).

for instance: US patent #5,676,312


Quote: "In these known designs, the external, or controlled, flaps are controlled by known actuators such that pivoting movement of the controlled flaps is imparted to the follower flaps so as to change the geometry of the nozzle.

The known exhaust nozzles may change from converging-converging configurations used for subsonic aircraft speeds to converging-diverging configurations at supersonic speeds. In addition to changing the configuration, the cross-sectional area of the throat of the nozzle may also be regulated." end quote

And then again, i have read several patents that alluded to variable geometry for noise attenuation!!!! never even thunk that...i was thinking "military and speed" and who the heck gives a hoot about noise? then again, plume pressure has been raised several times including afterburner ops!! probably a whole lot more reasons for varying the nozzle that i am yet to uncover. learned a lot indeed. thanks for the thread.


SO! for your model application, if you intend it to be practical....then you need to determine what you need it for.

over and out....