Five cells of standing shock.
An underexpanded jet turns through a fan, overshoots, and is turned back by an oblique shock that leaves the lip at the Mach angle. It reflects off the free boundary and repeats every 1.30 D √(M²−1) — the two families cross on the centreline and print the diamonds. Move the pointer across the frame to work the throttle: right raises the pressure ratio and pulls the train apart, left compresses it.
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