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Did David R. Davis realize that this low drag extended to high speed?from the above link (which surprised me)
The Consolidated B-24 Liberator "Davis" airfoil was also a laminar flow airfoil, which predates the Mustang's. However, the designers of the B-24 only knew that their airfoil had very low drag in the wind tunnel. They did not realize that it was a laminar flow airfoil.
If it was as easy as just how a profile looks then huge resources wouldn't have been spent on wind tunnels. A Spitfires wing looks very aerodynamic and is thinner than a P-51s so to a layman like me it would seem to be lower drag. The physics of laminar flow are complicated and in some ways counter intuitive, "laminar flow" wings were in any case just slightly better not actually true laminar flow and achieving better laminar low did compromise other areas of performance slightly.View attachment 550163
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I would say the Yak-3 wing looks quite laminar-flow-profile-like.
What do you think?
I read this three (3) times... now my head hurts.Without going too deep in the weeds, NAA crafted the 45-100 airfoil based on the planned/design pressure distribution to achieve Low Drag while still achieving:
1.) CL, CD and CMac values
2.) Stall characteristics
3.) Minimum CDo for a broad range of angle of attack 'alpha'
4.) Wing Thickness T/C 'large enough' to maintain Low Frag but also reduce structural weight of primary spars.
Beginning with a pressure distribution close to the NACA 125 Laminar Flow Airfoil, the Horkey team cranked Friden Calculators for two weeks to perform complex space conformal mapping - combining Laplace, Theodorsen and Kutta-Joukowski methods. The first cut on the Pressure distribution was one that would generate desired Lift, Drag and Moment characteristics (without knowing yet what the airfoil shape must be) as described by Millikan's principles of selecting a wing, then map the associated surface velocities to achieve the pressure distribution about a rotating cylinder in a Complex Space. The conformal mapping process begins by distributing the velocity data along a rotating Circle in Complex Space, then by transformation, map the circle to an airfoil shape with similar but not yet final desired velocity distribution in Real Space.
The primary goal for a 'Laminar' flow airfoil/wing was to develop a smooth aerodynamic shape and surface which enabled more attached flow before boundary layer separation (BL separation is the trigger to cause a 'profile increase' to the free stream, which causes increasing pressure drag losses). This was achieved to a greater degree in wind tunnel tests of the NACA-125 Laminar Flow airfoil. The NACA-125 airfoil was too thick for High Speed application. It was unique in that it gradually achieved maximum thickness at approximately 50% of chord length instead of the conventional ~25%. Another objective for laminar flow airfoils was to extend the region of peak pressure distribution across a greater percentage of the airfoil chord, to regions past the maximum thickness of the airfoil. Accompanying such shape, for same thickness to chord ratio, is a lower velocity gradient (rate of change of airflow velocity) from airfoil nose to point of maximum thickness, than the corresponding conventional airfoil which had a maximum thickness closer to 25% of the chord. The shape of the wing was also more wedge like than conventional bulbous shape.
FWIIW, the NAA/NACA 45-100 airfoil max T/C was ~ 37.5 %. The later XP-51F/G/J and H with NACA 65 and 66 series airfoils were close to 60%.
Horkey stated that there was in fact a small but definable laminar flow on the 45-100 but the primary purpose was Low Drag, which it achieved better than any US fighter. (I hesitate to state 'all' including other nations) save the series 66 on the P-63. Like the series 66 on the P-51H, both had slightly lower drag than 45-100 but the 66.2x-116 airfoil on the P-63 was a beast for low speed/stall range.
The Primary aerodynamic value for the NAA/NACA 45-100 was that the lower velocity gradient combined with the 'sharper' LE combined to delay both BL growth and Mach transition to a region further aft along the chord. Took 'longer' to reach critical mach, and when the shockwave originated further aft - the effect on the pitching moment was lower than say the P-38 or P-47 (or Bf 109 and Fw 190). The BL build up as a function of chord position was also lower - hence another reason for low drag.
I take it you meant that the location of the max T/C was at those points. An airfoil with a T/C of 60% would be rather thick.FWIIW, the NAA/NACA 45-100 airfoil max T/C was ~ 37.5 %. The later XP-51F/G/J and H with NACA 65 and 66 series airfoils were close to 60%.
Black crosses were known to disrupt airflow.View attachment 550255
View attachment 550256
Spontaneously I would say the Yakovlev's wings are less draggy than those of Me 109 and Fw 190....