Total skin-friction drag (Df) refers to the aerodynamic drag that occurs due to the frictional resistance between a solid surface (such as an aircraft’s wing or body) and the air flowing over it. Skin-friction drag is a component of the overall drag force experienced by an object moving through a fluid medium, like air. When air flows over a solid surface, it creates a thin layer of air near the surface called the “boundary layer.” This boundary layer experiences viscous effects, leading to shear stresses between adjacent layers of air. These shear stresses cause frictional resistance, which contributes to skin-friction drag.
- Df is the Total skin-friction dragÂ
- Df,bottom is the Net skin-friction drag of bottom