As if the word “aerodynamics” wasn’t a misnomer enough by itself, no other field of science and technology has a worst system of naming things as aerodynamics. This simple fact is responsible for the 100-year delay in understanding lift. So what do we mean by the misnomers of aerodynamics, and how have they mislead brilliant scientific minds even like Einstein’s? … read on.
One of the most vivid examples of this bad terminology is the well known Lift-to-Drag Ratio (or L/D), used to quantify the performance of various types of airfoils. We don’t know who came up with the idea of naming this ratio and chose to use the word “Drag” in this crucial parameter. This term is the biggest culprit which has obscured scientists’ vision for so long to fully understand how lift is produced.
We all know drag is something undesirable regarding motion of any object in air, be it automobiles, projectiles, or in our case, aircraft. Drag conjures up visions of some force trying to stop the forward motion of the aircraft, and all attention focuses on ways to reduce it, for the general good 🙂 … But wait a minute … we have to be very careful here and must exercise thorough scientific thought process, to differentiate between the two types of forces resisting the forward motion of the aircraft in air.
The cardinal sin of “aerodynamicists” was to mix up the air-resistance (the real drag) with that silent and subtle de-compressive force, which produces lift. Since both forces have the same direction, i.e., opposite to thrust, someone very conveniently came up with the idea of labeling them collectively as Drag, and set out finding how planes fly ? … Thus began the century old saga of ignorance … 🙂
As the Zone-Theory has proven, the rarefying action of the airfoil over its rearward sloping inductor surface (shown in figure above) reduces the atmospheric pressure below normal, and as a consequence, the air just over this inductor pulls the wing up at a backward slanting angle to the velocity. This results in creating both lift and a backward suction or expansion force. The aerodynamic force F-aero, has two vector components. The vertical component of this force is the lift, and the horizontal component which expands the air, is F-exp. This expansion force is the same as can be experienced by pulling a fully inserted piston out of a cylinder which has no opening for air to enter in, thus creating a vacuum, that resists outward motion of the piston.
It should be clear by now that the expansion force F-exp, and drag should be kept separate, or else another century of confusion about lift will pass, unnoticed.
Other example of the misnomers of aerodynamics, regarding motion of any object in atmosphere, are the use of terms “laminar” or “streamline flow”. These are also just figment of scientific imagination, and exist only in the wind tunnels, not in the real world at all … 🙂