Dutch, what you are seeing is the wave action Mach number as it exits the stinger.
The wave enters the pipe at EPO , then with a finite velocity thru the hot gas it takes until around BDC for that front to be detected at the outlet.
I must say I have never looked at that particular trace before , as I cant see it as any use to designing an optimized pipe .
So I concentrate on the Mach in the cylinder duct exit area , and the Mach in the middle of the stinger venturi.
As you can see if you plot this against Mach number , the wave action in the stinger has alot of energy and the reflections off atm bounce up and down its length with a frequency dependent upon
this length.
But with a proper nozzle , using a sharp angled step into the stinger tube , the wave action amplitude is reduced when it returns - and thus lessens the interference with the main reflection wave inside the rear cone.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
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