An examination of the 737 airliner wing profile and that of a blue whale leads to the question of whether the high Reynolds number subsonic cruising airfoil and the low speed, high AOA airfoil are compatible.
Supercritical airfoils are designed for efficient cruising flight, relying on bottom lift and minimizing acceleration of air over the top to avoid creating drag producing transsonic shock waves.
The blue whale is designed to cruise efficiently over thousands of miles, through a viscous, non-compressible fluid (water). Their shape includes a rounded, sloping lower fore and a flatter top, very similar to a supercritical airfoil! Applying thrust to this shape would provide "lift" simply by directing water "down" (or pushing the whale "up").
Reynolds Number = Velocity×Chord/Kinematic Viscosity
Reynolds Number 20th century Type VII U Boat (submarine): speed: 4 meters/second chord length: 70 meters. Kinematic viscosity (sea water): 1.04 × 10e-6
4 × 70/1.04 × 10e-6 = 269 million
Reynolds number Blue Whale: speed: 5 meters/second, chord length: 30 meters Kinematic viscosity (sea water): 1.04 × 10e-6
5 × 30/1.04 × 10e-6 = 144 million
Reynolds number Supercritical Airfoil (approximate): speed 300 meters/second, Chord length: 4 meters Kinematic Viscosity (air): 1.46 × 10e-5
300 × 4/1.46 × 10e-5 = 82 million
Reynolds Number Cessna 172 Airfoil : speed 30 meters/second Chord length: 2 meters Kinematic Viscosity (air): 1.46 × 10e-5
30 × 2/1.46 × 10e-5 = 4 million
Reynolds Number Albatross (bird) airfoil: speed 10 meters/second Chord length: 0.2 meters Kinematic Viscosity (air): 1.46 × 10e-5
10 x 0.2/1.46 x 10e-5 = 140,000
We can see the supercritical wing is more in the range of the blue whale!
When pitched up to a higher AOA, this shape would be a very poor wing in the classic Bernoulli sense, as the significantly contributing top lift would be lost at a lower AOA than a top rounded airfoil, behaving much more like a flat plate (see polars).
There are accounts of airline pilots extending their slats at higher speeds for better performance (and getting into trouble for doing so).
So, for modern designers, would it not be important to consider a more robust low speed system that could be left on (in varying degrees) at higher speeds (V maximum flaps and slats extended airspeed) to help avoid stalling?
This could create a wider safety margin for the climb-out and landing phases of flight. Hard earned efficiency gains in cruising flight (from the supercritical wing) would be kept, when they are fully retracted, but only at safe speed and AOA conditions (for example, above 10,000 feet or at cruising flight level).