The skin-friction drag coefficient (Cf) is a dimensionless parameter used in aerodynamics to quantify the amount of skin-friction drag generated by the frictional resistance between a solid surface and the fluid (such as air) flowing over it. It provides a standardized way to express the skin-friction drag relative to the dynamic pressure of the fluid and the size of the object’s surface area.Â
- Cf: Skin-friction drag coefficient
- Df,top: Skin-friction drag on the top surface
- q∞: Dynamic pressure of the freestream flow
- S: Reference area of the object