jet exhaust center bodies??

[sagallacci]

I noticed there was, for a short time, any number of supersonic concepts with jet exhausts with center bodies of various styles instead of the more common nozzle. A passing fad for, presumably, non-afterburning engines? I did notice that the "Hound Dog" stand-off missile carried by B-52s for a while had a exhaust center body. Any technical/historical insights?

 

[cat-shot]

I noticed there was, for a short time, any number of supersonic concepts with jet exhausts with center bodies of various styles instead of the more common nozzle. A passing fad for, presumably, non-afterburning engines? I did notice that the "Hound Dog" stand-off missile carried by B-52s for a while had a exhaust center body. Any technical/historical insights?

the question about center body:
first of all, to avoid a fluid dynamics behavior: recirculation of hot combustion products
second a centre body by mean of translation can adjust the exit section, thus increase
the jet velocity and momentum.
Some engines designed for the US SST (SCAR or SCR) had center bodies (1978 TECH, 1985 TECH)

 

[sagallacci]

I know about the basic dynamics of a center body exhaust, just wondering how/why it has been in and out of vouge? Most of the designs I'm aware of with them date from the '50s/early '60s.
I'd wonder if the center bodies on these were fixed and the outer ring either expanded or traveled fore and aft for throttling. Or, like WWII German types, the center body moved.
As for applications, does after-burning and/or bi-pass mixing need a larger/longer post-turbine volume? And consequencially, a more conventional variable exhaust nozzel?
Or is it that the center body designs have/prefer/need less exhaust management?
Just wondering, as I think they look particularly cool.