So basically the surface area of the upper and lower surfaces of the wings/fuselage and so forth not counting volume inside them? Does this factor the curves of the wing's top and bottom surfaces and the curves of the fuselage and so forth?
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I'm not entirely sure what you mean here; ... picture shooting a water hose at the wing head on - a good portion of the wing will have a steady stream flowing over it and however the back section of the wing may only catch droplets of water due to dispersion as you angle the wing up then more of the wing will catch the droplets...not entirely correct as an aerodynamic analogy though...
Wait... if it can't be theoretically computed, then how come people were able to design objects that fly at hypersonic speed?
All Designs teams have designed planes w/o a full theoretical/computational analysis...there's always a difference between computed and actual flight characteristics...the base equations are themselves inexact...that's why there exist Test pilots and IIRC the first hypersonic X-plane disintegrated...although she went out FAST!!!
You mean interference effects?
(I was always under the impression that higher reynolds numbers meant more turbulence though)
Yes,...
...more turbulence =more math chaos
Does it separate more towards the front of the wing/fuselage, or more towards the rear of the wing/fuselage as the reynolds numbers go up?
low Rn numbers generally mean poor lift and drag characteristics... due to the laminar transition to turbulent against an adverse pressure ratio...flow separation may be delayed in at low Rn but the shear-effect drag is more pronounced.