The boundary layer is a thin region of fluid that encapsulates the body; the effect of friction is dominant in this region due to surface contact with the body. This contact poses a skin friction force that acts tangent to the surface of the body. Flow outside the bound layer is dominated by the effect of pressure distribution, but physical interaction of the fluid happens in the boundary layer. Therefore, aerodynamic The study of the boundary layer has been one of the most important topics in aerodynamics.

Wing loading is defined as the ratio of aircraft weight to the reference wing area. Instead of wing area, the wing loading is a critical wing design parameter for aircrafts. Generally, a lower wing Wing loading has better aircraft performance in take-off, landing and climb; but a higher wing loading is preferred for high speed aircrafts due to a lower skin friction drag.

The aerodynamic characteristics of a body are represented in terms of aerodynamic coefficient. These coefficients are obtained by dimension reduction. Coefficients are non-dimensional; therefore, are independent of body size.