You might call this video afterburner theory, but we don't use any equations or math. Some cool pictures, and some real bits will be featured.
Videos mentioned, and recommended for further info:
The variable jet nozzle: https://youtu.be/6UiNCIAACnA
The howling J79: https://youtu.be/vCEhhRoJOaw
Afterburner Nozzle Actuators: https://youtu.be/FGDvTb4uMHE?si=RUcZ86yRkB6ykUcT
Diesel Thunder's engine run video: A Good Engine Run! | F-4 Phantom
( the actuator ring moving forward starts at about 19:30 )
This link works in Google, but not YouTube: https://youtu.be/ynHfJLl5V0c?si=GbpVQo-QDKkcVeGu
And a video I made about afterburners years ago.
https://youtu.be/1DdF3U2g-Ic?si=k1NTDpwP8wXYku3B
Compare to see how much I have aged !