The Normalized Lift and Drag as Efficiencies According to the Aerodynamic Equation of State

The wetted surface of a wing induces a three-dimensional pressure distribution onto the surrounding flow field that generates lift. In a similar way, the wetted surface of an aircraft generates parasite drag. Computational fluid dynamics mimics this process by constructing a surface mesh as a grid that recreates the outer mold line (OML) or wetted surface of a wing or aircraft, and used as a geometric reference for calculating the lift and parasite drag. Once the lift and drag are obtained using these physics-based wetted surfaces as geometry references, the legacy lift and drag coefficients are calculated by resorting to the planform area of the wing, and not their aforementioned wetted surfaces. This re-referencing that results from using a planform area instead of a wetted surface results in an overestimation of the lift and drag coefficients that are devoid of a physical meaning and yield misleading results when used to compare the lift or drag of different aircraft. This paper suggests that if this re-referencing is avoided, it results in dimensionless lift and drag numbers with a physical meaning and are capable of comparing a wide variety of engineered, biomechanical, and biological systems, and furthermore, act as lift and drag efficiencies, a most useful parameter found elsewhere in science and engineering but elusive in aerodynamics.