Originally Posted by
airfoilmod
Any idea at what point the twins uncouple? I'm getting ~.40M.
Its going to be aircraft dependent, because the shock from the LH fin has to pass aft of the Rh fin (and vice versa).
Using this nifty page:
Oblique Shock Waves there's a calculator thing for oblique shock angle. If we ignore any standing shock, and assume the fin has a leading edge wedge angle of say 10 degrees, we can get a relationship between the freestrem (upstream) MAch and the shock angle.
At M1.4 and below it's a 90 degree shock. At M1.6 it's at about 50 degrees, and at M2.0 its about 40 degrees. So in this case there's no advantage for a low Mach a/c (say a F-16 fixed intake type, perhaps) but for a M2+ aircraft there's a significant decoupling of the fins. Exactly when they fully decouple depends on the fin geometries relative to each other.