I've seen that picture before, it was from a NASA website. What I got from that/it was that it showed the variances between zero-swept wings and higher swept back angles and their related L/D ratios through the speed of sound, concluding that the variable-sweep design, at the time, was the best of both worlds.
Concorde has a fixed variable sweep
that curves from 70-degrees to 55-degrees; the data doesn't add up. I'm not claiming that a graph from a NASA website is wrong, just it was meant to describe a specific condition.
As of the second graph, I wish there were more points available for Concorde. I could conceivably come to the same conclusion with my plot if I gave 3 points. Also, which Boeing HCST was that? Though the one from 1969 and 1999 looked similar, I doubt they were.
Besides, density to stagnation increases with Mach, rho2/rho1 = (1+0.2M2
in air. If density affects lift and drag, why the drag drop after M1.0? Even wave drag depends on velocity (mach-wise) and angle of attack of surface. What equations/methods am I missing?
It was. If I took out the Mach factor, the max points would be higher but occur at slower velocities. Plus I don't know the real TSFC, e and CD,0
of Concorde, that data I cannot find online anywhere.
I had to average the fuel consumption by dividing the total fuel used for a 3 hour flight; I get 0.5 lb/lb/hr, average. I took as much as I could into account to minimize what I don't know. The resulting CL1/2
needs to be 12.3588 to have the range of 3600 Nmi, using Burguet eqns for range. So I made a formula estimating CD,0
as a function of the wing's efficiency factor, e. Concorde has a delta wing and having that vortex kills off any elliptical load distribution, so I know it’s shotty. I came up with having e = 0.60 and CD,0
= 0.0253 which gave the highest (L/D) max subsonic. But this max value was still smaller than the data I found on Concorde at the same speed.
No doubt, this is dirty math, it isn't accurate because it makes many assumptions -- which might account for it being different than the NASA graph. I'd like an explanation.
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