Does anybody knows how much did secondary nozzles bucket type on the Concorde's engines contributed to the increase of thrust during take of and sub-sonic flight? This is picture of the nozzles and here is air flow during take of all images from this link https://www.heritageconcorde.com/variable-exhaust-nozzles source states that secondary nozzles reduces noise, as well as improved engine performance. I suppose performance means thrust?
This source suggests at subsonic speeds, the secondary reduces drag but doesn't contribute significantly to thrust.
At all times below Mach 0.55 – on the ground, take-off and initial climb – the buckets are set to 21 deg., forming a ‘jet-pump’ gap at the nacelle trailing-edge. The high speed jet exiting from the primary nozzle draws-in atmosphere air from above and below the nacelle to eradicate a source of base drag that would otherwise exit between the nozzles.